UNIT 3

Página 1

Objective Sheet 1

Explain what is meant by the term homeostasis.

Maintaining a stable environment

Explain the need for homeostasis and how it is achieved.

Essential as the external and internal environment is constantly changing

E.G. body temperature, blood sugar levels

Name the two systems of the body that control homeostasis.

Hormone & Endocrine

Distinguish between endocrine and exocrine glands.

Exocrine glands – secrete into a duct that carries the secretion to the body surface to one of the body cavities. Sweat glands, mucous glands, salivary glands and glands of the alimentary canal are examples of exocrine glands.

Endocrine glands – secrete hormones into the extracellular fluid that surrounds the cells that make up the gland. The secretion then usually passes into capillaries to be transported by the blood. Endocrine glands are sometimes called ductless glands.

Describe the location of the main endocrine glands in the body and label a diagram showing their location.

Describe the characteristics of hormones.

Hormones – chemicals secreted by endocrine glands that are transported throughout the body in the blood. They change the functioning of cells by changing the type, activities or quantities of proteins produced.

Explain what is meant by saturation and how this affects the functioning of hormones.

When all receptor molecules are occupied by a hormone molecule

Addition of more hormones does not produce any greater effect

List the three different types of hormones.

Steroid, protein, amine

Describe how protein and amine hormones act upon target cells.

Water soluble, they are unable to diffuse across the cell membrane. Instead, they work by attaching to RECEPTOR proteins in the membrane of the target cell. The combination of the hormone with the receptor causes a secondary messenger substance to diffuse through the cell and activate particular enzymes.

Protein and Amine hormones tend to be quick to cause a response, however, the effect is short lasting.

Protein attaches/binds to the specific receptor molecules on the cell membrane of the target cell

This causes a secondary messenger substance to diffuse through the cell membrane

This substance activates an enzyme within the cell, to perform the cell’s function

Describe how steroid hormones act upon target cells

Lipid soluble, meaning they do not dissolve in water. Once released into the blood, the hormones bind to transport proteins, enabling them to travel into the bloodstream. When they reach target cells, the steroid hormones sperate from the transport proteins and diffuse across the cell membrane. Inside the cell they work by combining with a receptor protein in the cytoplasm or nucleus.

The hormone-receptor complex activates the genes controlling the formation of particular proteins. It does this by binding to the promoter section of a certain gene, stimulating (or inhibiting) transcription and, therefore, protein synthesis.

Steroid hormones are SLOW to have an effect, but the effect is LONG LASTING.

Hormones move through the cell membrane of target cell

Hormones combine with a receptor protein inside cell

This new molecule diffuses into the nucleus

This then activates a specific gene/section of DNA required for forming a particular enzyme

Describe how hormones affect target cells/organs (i.e. how do they change the function of cells.)

Hormones may:

Activate certain genes in the nucleus so that a particular enzyme or structural protein is produced

Change the shape or structure of an enzyme so that it is turned “on” or “off”

Change the rate of production of an enzyme or structural protein by changing the rate of transcription or translation during protein production.

Describe how negative feedback systems regulate hormonal secretions.

The response produced by the secretion of the hormone is the opposite of the stimulus that caused the secretion

Some involve the nervous system through the release of regulating factors from the hypothalamus

Whatever caused the secretion will be opposite of what is produced

Distinguish between releasing factors and inhibiting factors.

Inhibiting factors

Releasing factors

Stop the secretion of a hormone

Come from hypothalamus

Target anterior pituitary

Simulate the release of a hormone

Come from hypothalamus

Target anterior pituitary

Describe the structural relationship between the hypothalamus and the anterior and posterior lobes of the pituitary gland.

Hypothalamus

Anterior and Posterior lobes

Located at base of brain

Stalk called infundibulum

Functions of the hypothalamus are carried out through the pituitary gland

Attached to the infundibulum

Allows the functions of the hypothalamus to be carried out

Anterior

Posterior

Connected to hypothalamus by a network of blood vessels

Hormones are self-made in anterior lobe

Has inhibiting factors

Joined to the hypothalamus by nerve fibres

Direct connection

Hormones made in hypothalamus

Does not have inhibiting factors

State where the hormones that are released from the anterior and posterior lobes of the pituitary, are made.

Hormone

Target organ

Main effects

ANTERIOR LOBE OF PITUITARY GLAND

Follicle stimulating hormone (FSH)

Ovaries (females)

Growth of follicles

Testes (males)

Production of sperm

Luteinising hormone (LH)

Ovaries (females)

Ovulation and maintenance of corpus luteum

Testes (males)

Secretion of testosterone

Growth hormone (GH)

All cells

Growth + Protein synthesis

Thyroid-stimulating hormone (TSH)

Thyroid gland

Secretion of hormones from the thyroid

Adrenocorticotropic hormone (ACTH)

Adrenal cortex

Secretion of hormones from adrenal cortex

Prolactin (PRL)

Mammary glands

Milk production

POSTERIOR LOBE OF PITUITARY GLAND

Antidiuretic hormone (ADH)

Kidney

Reabsorption of water

Oxytocin (OT)

Uterus

Contractions of uterus during childbirth

Mammary glands

Release of milk

Describe what stimulates the release of the hormones from the anterior and posterior lobes of the pituitary gland.

Secretions of ANTERIOR lobe are in turn controlled by releasing and inhibiting factors secreted by hypothalamus

The release of hormones from POSTERIOR lobe is triggered by nerve impulses initiated in the hypothalamus and conducted along the cell extensions.

List the hormones produced by the following endocrine glands, identify the target cells/organs and describe their effect(s):

Gland

Hormone

Target cells

Main effects

Thyroid

Thyroxine

Most body cells

Increases metabolic rate and therefore oxygen consumption and heat production

Calcitonin

Bones, Kidney

Decreases calcium and phosphate levels in the blood

Parathyroid

Parathyroid hormone

Bones, Kidneys

Increases level of calcium in blood

Thymus

Thymosin

T-lymphocytes

Stimulates development and maturation of T-lymphocytes

Adrenal Cortex

Corticosteroids:

Aldosterone

Kidneys

Increase reabsorption of sodium ions and excretion of potassium ions

Cortisol

Most body cells

Promotes normal metabolism; helps the body deal with stress; promotes repair of damaged tissues

Adrenal Medulla

Adrenaline and Noradrenaline

Most body tissues

Prepares the body for fight-or-flight responses; reinforces the effects of the sympathetic nervous system

Pancreas

Insulin

Most body cells

Stimulates the uptake of glucose. Lowers blood glucose levels

Glucagon

Liver and fat storage tissues

Stimulates the breakdown of glycogen and fat. Increases blood glucose levels.

Testes

Androgens;

e.g. testosterone

Many tissues

Stimulate sperm production, growth of skeleton and muscles, and development of male sexual characteristics

Ovaries

Oestrogen

Many tissues

Stimulate development of female sexual characteristics; regulate menstrual cycle.

Progesterone

Uterus + mammary glands

Regulates menstrual cycle and pregnancy; prepared mammary glands for milk secretion.

Explain why the pituitary gland is sometimes referred to as the ‘master gland’.

The hypothalamus and pituitary gland work together to control the functioning of many of the other glands.

Describe the effects of an excess and a deficiency of thyroid hormones.

Hypo = LOW Hyper = HIGH

Disorder of the thyroid, thyroxine controls metabolism (chemical reactions)

Symptoms –

Hyper

Rapid heart rate

More energy (anxiety)

Weightless (high metabolism)

Excessive hunger

Hypo

Tired

Weight gain

Depression

Mood swings

Slow heart rate

Página 2

Objective sheet 2

State that neurons/nerve cells are the structural and functional unit of the nervous system.

Label a diagram of a neuron + describe the functions of the structures

Cell body – contains the nucleus which directs cell activities also containing cytoplasm and organelles. Dendrites – receives nerve impulses from other nerve cells and sends them to cell body, picks up impulses.

Axon – sends nerve impulses away from cell body

Synoptic Knob/Axon terminal – pass nerve impulses onto next neuron.

Myelin Sheath – insulating layer

Nodes of Ranvier – gaps in between the myelin sheath

Schwann Cells – myelinates the axon

Describe the pathway that the nerve impulse takes along a neuron.

Travels along the neuron pathways as an electrical message to move along each neural cell membrane

Begins in the dendrite  cell body  axon  axon terminal  synapse

Distinguish between sensory (receptor/afferent), motor (effector/efferent) and inter (connector/associative/relay) neurons both structurally and functionally.

Sensory neurons – carry nerve impulses into the CNS

Motor neurons – carry nerve impulses away from CNS

Inter neurons – found in the CNS, they are the link in between the sensory and motor neurons.

Multipolar

Motor neurons and interneurons

Many dendrites and one axon

Bipolar

Only found in the eyes, ears and nose

One dendrite and one axon

Pseudo unipolar

Sensory neurons

One axon that can divide into two

Describe the role of synapses and state where they occur.

End of the nerve/synaptic knobs

Neurons do not make direct contact with each other

Small gap in between neurons = synapse

Neurotransmitters carry the nerve impulses across the synapse to the adjacent nerve  simple diffusion

Distinguish between the central nervous system (CNS) and peripheral nervous system (PNS).

CNS

PNS

Structurally just the brain and spinal cord

12 pairs of cranial nerves

31 pairs of spinal nerves

All the nerve that branch off of the brain and spinal cord

Describe the relationship between the CNS and the PNS.

Describe where cranial nerves and spinal nerves are found.

Cranial Nerves – nerves that emerge directly from the brain, including the brainstem

Spinal Nerves – emerge from segments of the spinal cord, attached to vertebrae

Describe the structure of the spinal cord - white matter, grey matter, ventral root, dorsal root, dorsal root ganglion, central canal, ascending and descending tracts

White matter – myelinated, located on the outside of the spinal cord

Grey matter – unmyelinated, located on the inside of the spinal cord

Dorsal root – contains axons of sensory nerves

Dorsal root ganglion – contains cell bodies of the sensory neurons

Ventral root – contains axons of motor nerves

Distinguish between the afferent and efferent divisions of the PNS and the somatic and autonomic divisions of the PNS.

Sensory (afferent) division

Carrying info INTO the CNS

Conducts impulses from the receptors to the CNS

Motor (efferent) division

Carrying info AWAY from CNS

Conducts impulses from the CNS to the effectors

Understand the relationships between the various divisions of the PNS.

Distinguish between the actions of the sympathetic and parasympathetic divisions of the autonomic nervous system.

Sympathetic – mobilizes body systems during activity. (fight or flight)

Parasympathetic – Conserves energy (rest and digest)

Both involuntary divisions and actions become involuntary.

Label a diagram of the brain and describe the functions of the major regions – cerebrum, cerebellum, hypothalamus, medulla, corpus callosum, meninges and cerebrospinal fluid.

Cerebrum

Thinking and reasoning

Intelligence  learning and speech

Perception of senses

Cerebellum

Posture and balance

Fine motor coordination

Subconscious movements

Hypothalamus

Homeostasis

Heart rate

Sleep and wake patterns

Regulates metabolism, growth and reproduction  pituitary gland

Medulla

Swallowing

Sneezing

Vomiting

Coughing

Regulates heart rate

Corpus Callosum

Communication between left and right hemispheres of the brain

Meninges

Layer of connecting tissue forming membranes around the surface of the brain and spinal cord

Cerebrospinal fluid

Clear watery fluid, containing few cells, glucose, proteins and salt

Describe the function of the spinal cord

Describe the role of receptors and identify where they may be found.

The role of a receptor is to detect stimuli and any change in the bodies external/internal environment. Receptors can be located throughout the body in places such as skin, brains, nose, mouth

Identify the main types of receptors found in the body

Thermoreceptors –

Detect heat or cold

Hypothalamus acts as modulator

Osmoreceptors –

Detects osmotic pressure (water concentration)

Hypothalamus acts as modulator

Chemoreceptors –

Stimulus detects odours, taste and PH of blood

Medulla oblongata acts as modulator

Touchreceptors –

Responds to touch

Found in the lips, fingernails and eyelids

Nociereceptors (pain) –

Detects damage to tissue, poor blood flow, excessive stimulation

Found in skin and mucous membrane

Describe where each of the receptors listed in objective 17 are found, what they respond to and their role.

Describe reflex actions – their function and some examples.

A reflex is a rapid automatic response to a change in the internal and external environment

Most reflexes are coordinated from the spinal cord.

Some examples of reflexes are sneezing, coughing, blinking and restriction of the pupil

Describe the four important properties that all reflexes have.

A stimulus is required to trigger a reflex

A reflex is involuntary

It provides a rapid response

The response is stereotyped – occurs in the same way every time

List the main components of a reflex arc and describe how the neurons are arranged.

stimulus  receptor  sensory neuron  CNS (interneuron)  motor neuron  effector  response

A reflex arc is when a response travels from a receptor to an effector

The reflex arc works quickly to withdraw from a painful stimulus to protect the body from injury

Describe the role of each component of a reflex arc

Receptor – detects stimulus

Sensory Neuron – carries nerve impulse towards CNS

Dorsal Root Ganglion – contains cell bodies of sensory neurons

Dorsal Root – contains axons of sensory neurons

Synapses – small gap in between neurons

Interneuron – link between sensory and motor neurons

Ventral Root – contains axons of motor neurons

Motor Neuron – carries nerve impulses away from CNS

Effector – stimulates the response

Describe how nerve impulses are generated and propagated

Nerve impulses are generated through a series of action potentials that take place along the axon of a neuron.

The resting membrane potential is maintained by a difference in the number of leakage channels for sodium and potassium ions. Resting nerve cell is always at -70mV.

The membrane being impermeable to large organic negative ions and the sodium-potassium pump

This results in the intracellular fluid being less positively charged than the extracellular fluid

Resting membrane potential - Plasma membrane in polarised. Polarised = positive charges outside, negative charge inside. Inside the cell positive ions are potassium. Outside the cell are sodium ions.

Depolarisation – generation of the action potential – Na gates open and Na rushes in. Inside is now positively charged and outside negatively charged. The inwards rush of Na causes depolarisation of the cell membrane.

Propagation of the Action Potential – This activates the neuron to transmit an action potential or nerve impulse which stimulates the next section of the membrane to depolarise, passing the impulse along the neuron.

Repolarisation – after the Na ions enter the neuron the membrane permeability changes becoming impermeable to Na ions. Now K ions diffuse out of the neuron rapidly, becoming repolarised again and returning to its resting state.

After repolarisation the initial concentrations of sodium and potassium ions are restored due to the sodium-potassium pump which uses ATP energy to pump excess Na out and excess K into the cell.

Refractory period – ions return to their normal state

Compare the transmission of nerve impulses along unmyelinated fibres and myelinated fibres

If nerve fibres are myelinated the impulse is conducted faster rather than an unmyelinated nerve fibre.

Describe how nerve impulses are transmitted across a synapse or neuromuscular junction.

The junction between the axon terminals of one neuron and the dendrites or cell body of the next neuron is called a synapse.

The junction between the axon terminals of one neuron and a skeletal muscle is called a neuromuscular junction.

The synaptic bulb at the end of the axon contains mitochondria and numerous vesicles that contains neurotransmitters

When the nerve impulse (action potential) reaches the synaptic knob calcium ions surround and enter the bulb. This causes the vesicles to move to the presynaptic membrane and fuse with it in the process of exocytosis discharging the neurotransmitter substance.

This neurotransmitter diffuses across the synapse and attaches to the receptor sites or postsynaptic membrane of the adjacent structure

Compare nervous and hormonal action/control – speed of action, duration of action, transmission and specificity of message.

Nervous

Hormonal

Cells / Structures involved

Neurons

Endocrine glands

Types of stimulus

Varied (light, sound touch, pain and pressure)

Change in internal environment

Transport of message

Along nerves and across synapse

In the blood

Mode of transmission

Electrochemical (electricity and chemical)

Chemical (hormones)

Speed of transmission

Rapid

Slower

Effector (cells affected)

Muscles or glands (other neurons)

All body cells

Specificity of response

Very specific and usually local

Usually more widespread effects many parts

Response time

Rapid / immediate (milliseconds)

Slower acting (seconds  days)

Duration of response

Short duration

Long duration

Short- or long-term adjustments

Short term adjustments

Long term adjustments

Voluntary or involuntary

Involuntary or voluntary

Involuntary

Parkinson’s Disease and Alzheimer’s Disease – symptoms, cause and treatment.

Página 3

Objective Sheet 3

Describe the components of a feedback system:

Stimulus – detects a change in environment

Receptor – detects the stimulus by sensory cells

Modulator – (control centre) determines the appropriate response

Effector – muscle/glands receive messages from the modulator

Response – appropriate reaction produced by effector group

Feedback – (USUALLY NEGATIVE) response reacts / changes to the stimulus

THERMOREGULATION (Chapter 5)

Describe how heat is generated in the body

Body processes – metabolism (cell respiration and exercise)

Heat gained from the environment – by conduction and or radiation

Illness

Stress/ emotions

Increased thyroxin levels

Describe how heat can be lost from the body

Evaporation of water from skin and lungs

Warm air breathed out

Voiding warm urine and faeces

radiation of body heat to the cooler surroundings

conduction and convection

State the normal body temp for humans = 36.7°C

Describe the location of the thermoreceptors in the body

PERIPHERAL = Skin and mucous membrane – detects temperature changes in the external environment and sends this information to the hypothalamus

CENTRAL = in the hypothalamus (thermoregulatory centre) – detect the temperature of internal environment

Describe how heat can be transferred by radiation, conduction and convection

RADIATION = transfer of heat without contact (physical)

CONDUCTION = transfer of heat from one object to another by direct physical contact

CONVECTION = transfer of heat by convection currents (liquid and gas)

Explain how evaporation of sweat can lead to cooling of the body

Sweating is the active secretion of fluid by the sweat glands and the periodic contraction of cells surrounding the ducts to pump the sweat to the skin surface. The production and transport of sweat to the skin surface is stimulated by sympathetic nerves.

Evaporation of sweat from the skin has a cooling effect; heat is removed from the skin when liquid sweat changes into vapour. Vapour leaves as HOT water, which takes the heat OUT of the body. Cooling of the skin results in cooling of the blood flowing through the skin. This evaporation accounts for a considerable proportion of the daily heat loss from the body.

Describe how the body responds to a fall in body temperature

constriction of blood vessels in the skin – this decreases heat loss to the surroundings via radiation

wear warm clothes, hot shower

decrease surface area by curling up

shivering – involuntary contraction of skeletal muscle. This activity produces heat

increase thyroxine secretion

increase voluntary activity (running on the spot, rubbing hands together)

Describe how the body responds to a rise in body temperature

Dilation of blood vessels – increases heat loss via radiation (in the skin). Blood vessels don’t move closer to the skin, rather they bring blood closer to the surface of the skin

Sweat production - increases heat loss by evaporative cooling

Lighter clothing, sitting in the shade

Increase surface area of the body – by spreading your limbs

Reduce voluntary activity - (Less exercise/ more rest)

Decrease thyroxine secretion – this is seasonal

Explain the terms vasodilation and vasoconstriction

VASODIALATION = A widening of blood vessels, usually near the surface of the skin, leading to increased blood flow with flushing or warmth.

VASOCONSTRICTION = Vasoconstriction is the narrowing (constriction) of blood vessels by small muscles in their walls. When blood vessels constrict, blood flow is slowed or blocked

Describe the relationship between the level of thyroxine and body temperature

Thyroxin is produced in the thyroid stimulated by the hypothalamus, when thyroxine levels increase so does body temp as it regulates metabolism and HR

Explain why piloerection is ineffective in humans as a means of preventing body temperature from falling.

Is ineffective in humans because the arm hairs on our bodies are too thin and don’t hold any heat in

TEMPERATURE TOLERANCE – core body temp over 42C and under 33C is dangerous and can lead to heat stroke or hypothermia.

GLUCOSE (BLOOD SUGAR) REGULATION (Chapter 5 & 8)

Explain the relationship between glucose and glycogen

Glucose is stored as glycogen. Excess glucose is converted to glycogen for storage.

Glucose = simple carbohydrate (basic carbohydrate building block) & main source for cell respiration. *NO STORAGE

Glycogen = complex carbohydrate, consists of long chains of glucose molecules

*STORED IN LIVER & MUSCLES

Explain the role of the liver in the regulation of blood sugar

Is able to convert glucose to glucose into glycogen for storage, or glycogen to glucose for release into the blood.

The breakdown of products, mainly glucose, are absorbed into the blood capillaries which is then carried to the liver through the hepatic portal vein.

Describe the possible fate of glucose absorbed in the small intestine

Once in the liver glucose may:

Be removed from the blood by the liver to provide energy for liver functioning

Be removed by the liver and/or muscles and converted into glycogen for storage

Continue to circulate in the blood, available for body cells to absorb and use as a source of energy

Be converted into fat for long – term storage if it is in excess of that required to maintain both normal blood sugar and tissue glycogen levels.

Describe the regulation of blood sugar levels by the hormone’s insulin and glucagon

Insulin = (BETA CELLS) When glucose is converted into glycogen for muscle activity, as there is an excess of glucose. Hormone that lowers blood glucose levels when too much glucose (glucogenesis)

Glucagon = (ALPHA CELLS) When glucose levels drop below normal, the glycogen stores in the liver and muscle cells can be broken down into glucose. Converting glycogen back into glucose. Pancreatic hormone that raises blood glucose levels when too little glucose (glycogenolysis)

Define the following terms: glycogenesis, glycogenolysis, glucogenesis

GLYCOGENESIS – glucose molecules chemically joining together to form glycogen molecules

GLUCOGENOLYSIS – breakdown of glycogen to glucose

GLUCOGENESIS – conversion of fats or proteins into glucose

Describe the effects of adrenaline and cortisol (a glucocorticoid) on blood sugar concentration.

Explain the term hyperglycaemia and the possible causes

high blood sugar, can be from just eating or underlying diseases

Distinguish between diabetes type 1 and type 2

Type Diabetes 1:

Insulin dependent diabetes

Usually begins in childhood and therefore can be called juvenile diabetes

Caused by a fault in the patient’s immune system causes the destruction of beta cells in the islet of Langerhans of the pancreas

beta cells produce insulin, therefore someone with type 1 doesn’t produce insulin

the disease can be managed by giving the person insulin injections

can’t be taken as tablets as it will be digested in the alimentary canal

it can’t be cured, but injections fulfil a role to make sure the body functions right.

Long term effects; kidney failure, heart attack, stroke, blindness, nerve damage, amputations

Type 2 diabetes:

A disease affecting older, overweight people, who’s cells develop the resistance to insulin uptake.

Incurable btu treatments consist of:

BGL checks

Management of diet

Reduce weight and blood pressure

Exercise

Stop smoking

Managed through dieting, exercise

Body cells don’t respond appropriately to the insulin that is present and blood glucose levels increase

Symptoms:

increased appetite which can increase weight

urine production increases to rid the body of excess glucose, excess glucose creates a thirst

inability to use glucose leads to muscle weakness and fatigue, irritability, frequent infection and poorly healing wounds

Explain how gene therapy and synthetic hormones can be used to treat diabetes mellitus.

OSMOREGULATION (Chapter 6)

Distinguish between intracellular fluid, blood plasma and intercellular fluid (tissue fluid / interstitial fluid)

Intracellular fluid: fluid found inside the cell

Can be referred to as the cytosol

Blood plasma:

found inside the blood vessels

also called intravascular fluid

Intercellular fluid (interstitial fluid):

Fluid between cells

Or called intercellular, tissue, interstitial fluid

Extracellular fluid: outside the cell

Blood plasma in the plasma

Explain how nutrients, wastes and water movement between the cytoplasm and vascular fluids.

Movement between the cytoplasm and vascular fluids:

Diffusion: movement of a substance from an area of high concentration to low concentration. Diffusion happens in liquids and gases.

Movement of water: BY OSMOSIS

Water is consumed in fluids and foods is absorbed into the blood from the alimentary canal.

There is a constant exchange of water between the blood, the extracellular fluid and the intracellular fluid

Any excess fluid in the extracellular fluid is collected by the lymph system and returned to the blood by lymph vessels that join veins in the upper chest

Movement of nutrients (glucose): DIFFUSION

Glucose diffuses through the blood into tissue

Movement of waste: DIFFUSION

Movement of waste: OSMOSIS

Due to pressure changes

Define excretion and list the excretory structure and their products

The removal of waste products of metabolism from the body, they must be removed before they reach harmful concentrations

Organs of excretion:

Lungs: removes carbon dioxide from the body. Produces carbon dioxide and water during cellular respiration and the body can’t use it so it must be removed by exhalation. It is carried in the blood until it reaches the lungs where it is excreted. The lungs also remove water in the form of vapour

Sweat glands of the skin: secrete water containing by-products of metabolism such as salts, urea and lactic acid.

Alimentary canal: passes out bile pigments from the small intestine. These pigments are the breakdown of haemoglobin from red blood cells. They leave the body by faeces (poo).

Kidney: principal excretory organ. Responsible for maintaining a concentration of all body fluids. It removes urea, which is from the breakdown of proteins.

Define the structure of the nephron

Nephron = functional unit of the kidney, carry out the kidney’s role in excretion and water regulation.

Outline very briefly the processes involved in the formation of urine – filtration, selective reabsorption and tubular secretion

FILTRATION = the high blood pressure forces water and small dissolved molecules out of the blood and into the capsule. Large molecules and blood cells are retained in the blood. The filtrate is collected by the glomerular capsule.

SELECTIVE REABSORPTION = The filtrate passes through the proximal convoluted tubule and the collecting duct. Water and other useful substances are reabsorbed into the peritubular capillaries.

TUBULAR SECRETION = some materials that need to be removed from the body are secreted into the kidney tubule from the peritubular capillaries.

Describe where in the nephron water reabsorption occurs

In distal convoluted tubules and collecting duct.

Describe the role of ADH (antidiuretic hormone) in maintaining the water balance

ADH controls the active levels of reabsorption (from hypothalamus, stored in PPG), the permeability of the DCT walls and collecting duct is controlled by ADH, when ADH conc is up the tubules become more permeable

Describe the role of the thirst reflex in maintaining water balance

The water level of the body can be increased by taking in more fluid. Osmoreceptors are able to stimulate the thirst centre in the hypothalamus, prompting the person to drink water. This fluid is absorbed across the wall of the alimentary canal into the blood, decreasing osmotic pressure.

Explain the causes and consequences of dehydration

Dehydration: when water loss exceeds water intake and there is not enough water int eh body to carry out normal functions

Causes: thirst reflex Is less effective as we age,

Symptoms: low blood pressure, thirst, headache, dizziness

Consequences: person can become delirious, lose consciousness and die

Explain the consequences of water intoxication

Water intoxication: when body fluids become diluted, and cells take in extra water by osmosis.

Causes: if a person loses a lot of water and salts through sweating and replaces it with normal water. Instead, they should consume water with dissolved substances to replenish their salts

Symptoms: light headedness

Consequences: headache, vomiting, collapsing

Role of Aldosterone on water balance

Aldosterone is secreted from the adrenal cortex

Aldosterone acts on the DCT and collecting ducts to increase the concentration of sodium ions (Na+) in the blood

It also decreases the concentration of potassium ions (K+) excreted in urine

Water is also reabsorbed from the filtrate with the sodium ions; hence aldosterone causes water content and blood volume to increase

As a result, aldosterone indirectly increases blood pressure due to the increase in blood volume

The stimulus for aldosterone would be a drop in sodium levels in the blood

GASREGULATION (Chapter 6)

Write a word equation for cellular respiration.

When carbon dioxide dissolves in water it forms carbonic acid (H2CO3).

H2CO3 readily breaks down to form hydrogen ions (H+) and bicarbonate ions (HCO3-).

Name the muscles that are responsible for ventilation and name the nerves that stimulate them.

The muscles that cause air to move into and out of the lungs are the diaphragm and the intercostal muscles.

The phrenic nerve stimulates the diaphragm

The intercostal nerve stimulates the intercostal muscles.

*The respiratory center in the medulla controls the nerve impulses travelling to the diaphragm and intercostal muscles.

*There is inspiratory center that controls inspiration and an expiratory center that controls expiration.

Describe the relationship that exists between the concentration of CO2 in the plasma and the concentration of hydrogen ions (pH) - see equation page 140.

CO2 in plasma affects the concentration of H+ ions. When CO2 dissolves in water, it forms a carbonic acid (H2CO3) which breaks down readily to form hydrogen ions and bicarbonate ions (HCO-3)

O2 / CO2 / H+ all have effects on the regulation of breathing activity.

As hydrogen ion concentration of the blood increases, the pH decreases. (MORE ACIDIC) A decrease in pH directly stimulates chemoreceptors in the aortic and carotid bodies (Central AND Peripheral), which then transmit impulses to the respiratory centre in the medulla oblongata, resulting in an increase of breathing rate and depth.

Name the chemoreceptors that are stimulated when the oxygen concentration decreases dramatically.

There are two types of chemoreceptors: Peripheral and central chemoreceptors.

Peripheral – groups of cells within the walls of the aorta and carotid arteries that are sensitive to changes in the concentration of oxygen, carbon dioxide and hydrogen ions in the blood plasma. Known as the aortic and carotid bodies.

Central – located in the medulla oblongata. There are sensitive to changes in the concentration of carbon dioxide in the blood and hydrogen ions in the cerebrospinal fluid. When chemoreceptors are stimulated, they send a nerve impulse to the area of the respiratory centre that regulates breathing.

Describe how a very low concentration of oxygen in the blood can affect the breathing rate.

As oxygen is consumed by the cells, its concentration in the blood begins to fall. If the O2 concentration falls below normal while other factors are held constant, breathing rate increases. However, within the normal range of blood oxygen concentration, effect on breathing is only slight.

Because of this, O2 plays little part in the regulation of breathing.

The concentration of oxygen must fall VERY LOW before it affects the breathing rate.

A large decrease in O2 conc stimulates the peripheral chemoreceptors, and nerve impulses are transmitted to the respiratory centre. These nerve impulses stimulate the transmission of messages to the diaphragm and intercostal muscles, and so the breathing rate AND depth increases.

Describe the regulation of carbon dioxide in the blood (and pH of blood plasma) *.

The concentration of carbon dioxide in the blood plasma is a major factor in the regulation of breathing rate. A relatively small increase in the concentration of carbon dioxide is enough to cause a MARKED increase in the rate and depth of breathing.

Any increase in carbon dioxide results in an associated increase in hydrogen ion concentration. This increase of chemicals in the blood stimulates the CENTRAL and PERIPHERAL chemoreceptors. These in turn transmit nerve impulses to the respiratory system, resulting in an increase in breathing rate and depth. Responsible for 80% of the increase in breathing rate that results from an increase in the carbon dioxide concentration of the blood.

*NONE of the three factors (Oxygen, Carbon dioxide and hydrogen ion concentration) is independent on the regulation of breathing. Each factor interacts with the others.

Describe the difference between quiet and active breathing.

Normal Breathing (Quiet Breathing)

This is the kind of breathing you use when you’re awake and sitting quietly, like you are now.

Normal breathing consists of:

an active inspiratory phase, involving the contraction of the diaphragm and intercostal muscles, and

a passive expiratory phase, during which these muscles relax.

Breathing is controlled by the respiratory centre located in the medulla oblongata.

There are two regions within the respiratory centre: one that controls expiration and one that controls inspiration.

To coordinate breathing, information needs to pass back and forth between the neurons in these two regions.

During the inspiratory phase, the inspiratory centre in the medulla oblongata is active and sends out nerve impulses along the phrenic and intercostal nerves to the diaphragm and external intercostal muscles respectively. (See Fig 8.12 page 108)

We inhale when these two muscles contract.

During this phase the expiratory centre is suppressed.

The inspiratory circuit remains active for about two seconds, after which it shuts down and the respiratory muscles relax, causing us to breath out.

This sequence takes around five seconds, creating a normal breathing rate of 12 – 15 breaths per minute.

The inspiratory centre is then switched on again and the cycle is repeated.

Active Breathing

Active breathing occurs, for example, when we are panting after vigorous exercise.

The expiratory centre is involved in active breathing.

At the completing of the inspiratory phase, the expiratory centre is activated, sending nerve impulses to the internal intercostal muscles and to the abdominal muscles.

The combined effect of these two sets of muscles contracting is to expel air from the lungs with considerable force.

Explain why it is dangerous to hyperventilate before swimming under water.

Hyperventilation – rapid, deep breathing. Provides more oxygen than required and remove more carbon dioxide than necessary. Can occur voluntary or stimulated by physical stress – severe pain, emotional stress (anxiety)

Dangerous when swimming:

Allows the person to hold their breath for longer (stay underwater for a longer period of time)

Not caused by the EXTRA oxygen in the blood; it is due to the loss of carbon dioxide.

Can caused somoni to lose consciousness from LACK of oxygen to the brain, then feeling the urge to breathe. DROWNS!

Exercise and breathing:

During exercise the contracting muscle cells require MORE O2 and produce LARGE amount of CO2.

The rate and depth of breathing increases to allow for more gas exchange

During HEAVY exercise the air going into and out of the lungs can increase up to 20 times

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Objective Sheet 4

Pathogens and their transmission

Describe the characteristics of communicable/infectious diseases.

Communicable diseases – are known as ‘infectious’ or ‘transmissible’ diseases.

Characteristics = caused by pathogens

Communicabls = contagious

Explain the relationship between pathogens and communicable diseases.

A communicable disease is SPREAD by the transmission of pathogens

Define the term pathogen and briefly describe the structure of the two most common pathogens – bacteria and viruses and give some examples of each.

Pathogens – an organism capable of causing disease.

Commonly, bacteria + viruses.

BACTERIA

Single-celled

Classified by cell shape (circular, rod-shaped, curved, other)

Many non-pathogenic bacteria

Diseases caused by bacteria

Cholera = bacteria infect intestine; produce cholera toxin causes severe diarrhea + dehydration

Diphtheria = bacteria cause a toxin that affects mucous membranes of the mouth and nose. General flu-like symptoms (fever, chills, swollen glands, cough, sore throat)

Whooping cough = respiratory tract infection; cold-like symptoms, persistent dry cough. Bacteria attach to cilia lining the upper part of respiratory tracts; cilia and airways swell.

VIRUSES

Only visible with an electron microscope

Contain EITHER DNA or RN (Never both)

Surrounded by a protein coat

Diseases caused by viruses

HIV/AIDS (RNA) = virus attacks CD4 helper (immune) lymphocytes. The body is unable to fight off infection

Ebola (RNA) = virus targets liver, immune and endothelial cells lining blood vessels. Disrupts cell adhesion, leading to haemorrhaging and internal bleeding

Measles (RNA)­ = virus infects macrophages and dendritic cells, then B & T cells in lymph nodes. Causes inflammation throughout the entire body.

BACTERIA

VIRUS

Surrounded by plasma membrane, cell wall and slime capsule

Enclosed by protein coat

No nucleus or membrane bound organelles

Contain both DNA and RNA

Contain either DNA or RNA

Cytoplasm containing ribosomes

No ribosomes

Comparatively larger; can be seen under a light microscope

Comparatively smaller; can only be seen under electron microscope

Describe how pathogens can be transmitted: transmission by contact (direct and indirect

Contact – (indirect or direct) involves the spread of the pathogen by actual physical contact. Can be direct, actually touching an infected person, or indirect, touching an object that has been touched by an infected individual. Skin infections and sexually transmitted infections are spread by contact.

Transfer of body fluids – (saliva, mucus, blood, semen) when blood or other body fluid from an infected person comes into contact with the mucous membranes, such as in the mouth, nose, throat and genitals, or the bloodstream of an unaffected individual (needle / open wound)

Infection by droplets – may occur when tiny droplets of moisture containing pathogenic organisms are emitted when breathing, talking, sneezing or coughing. The droplets may be breathed in by others or may settle on food or utensils to be later ingested with food. Many viral infections (COVID + Ebola) are spread by droplets.

Ingestion – (contaminated food or water) When an individual ingests food or drink that has been contaminated with pathogens.

Airborne transmission – when the moisture in exhaled droplets evaporates, many bacteria are killed, but viruses and some bacteria remain viable and can cause infection when inhaled. As these particles are lighter, they remain viable for a greater distance than those transmitted by droplets.

Vectors – transfer of pathogens by other animals such as insects, ticks or mites. Some vectors transfer pathogen directly or to food/water. Many vector-borne diseases are spread by a specific vector.

Describe and give an example of a disease transmitted by each method listed in Objective

Transmission

Example

Contact

Skin infections (Chickenpox)

Sexually transmitted diseases (i.e. Genital warts)

Body Fluids

HIV

Hepatitis

Droplets

Colds

Influenza

Ingestion

Dysentery

Salmonella

Airborne

Many viruses, some bacteria (those that can remain viable once moisture has evaporated)

Vectors

Malaria and dengue fever – spread by mosquitoes

Trypanosomiasis – spread by tsete fly

Lyme disease – spread by ticks

Non-specific defences to infection

Distinguish between non-specific and specific defences.

Specific = directed at a particular pathogen. The immune system produces antibodies to the target pathogen

Non-Specific = work against all pathogens. Body’s ‘first line’ of defence. External defences, internal defences and protective reflexes.

Describe the external defences that prevent pathogens from invading the following tissues/organs of the body

SKIN

Barrier; prevents entry of micro-organisms

A large number of bacteria lives on the skin – occupying bacteria make it difficult for new (pathogenic) establishments

Sebum (oily secretion) – substance that kills some pathogenic bacteria.

Sweat – salts and fatty acids prevent the growth of many microorganisms

MUCOUS MEMBRANE

Found in; digestive, urinary, respiratory and urogenital tracts.

Lines body cavities (that open to the exterior)

Secrete mucus – inhibits entry of micro-organisms

HAIRS

Found in, the nasal cavity, ears

Traps micro-organisms

CILIA

Found in; the respiratory tract (line nasal cavity, trachea etc)

Tiny hair-like projections from cells

‘Beating motion’

Moves mucus up towards the throat (coughed out/swallowed)

ACIDS

Found in; stomach, vagina, sweat

Kills micro-organisms that are ingested with food or in mucus (stomach)

Reduces growth of micro-organisms (vagina/sweat)

LYSOZYMES

Found in; tears, saliva, sweat, nasal secretions, tissue fluid

Contain enzymes that kill bacteria

CERUMEN (EAR WAX)

Found in; the outer ear

Slightly acidic

Contains lysozymes

FLUSHING ACTION

Occurs in; urine flowing through the urethra; tears, sweat, saliva

Cleansing action – prevents bacterial growth/travel through ducts/tracts

Describe the four reflexes that help to protect against infection.

SNEEZING

Stimulus; irritation of walls of the nasal cavity – noxious fumes/dust particles

Forceful expulsion of air from lungs

Carries mucus/foreign particles/irritating gases out through the nose and mouth

COUGHING

Stimulus; irritation in lower respiratory tracts (bronchi/bronchioles)

Air forced from lungs

Carries mucus / foreign particles up towards the throat and mouth

VOMITING

Stimulus; psychological, excessive stretching of the stomach; bacterial toxins

Muscles of the abdomen and diaphragm contract

Stomach contents expelled

DIARRHOEA

Stimulus; irritation of small / large intestines by bacteria / virus / protozoans

Increases peristalsis to quickly remove the irritant

Materials spend less time in the intestine – faeces watery

Describe the non-specific external defences the body has against pathogens.

INFLAMMATORY RESPONSE

Response to tissue damage (mechanical damage / local chemical changes, i.e. pollen, bee, allergies)

Why inflammatory response?

Reduce the spread of pathogens / destroy pathogens / prevent the entry of further pathogens

Repair damaged tissue (pus) / cell debris

Repair of damaged tissue

Signs of inflammation – redness, swelling, heat, pain

FEVER

Elevation of body temp

Inhibits the growth of some bacteria/viruses

An increased rate of metabolism; helps body cells repair themselves more quickly

Fever is harmful; fatal if reaches 44.4/44.5C

PHAGOCYTES

Cells that engulf and digest micro-organisms & cell debris (PHAGOCYTOSIS)

Leucocytes + macrophages

Describe the role played by leucocytes (including lymphocytes) and macrophages in defending the body against pathogens.

Leucocytes – white blood cells. Able to leave blood capillaries; migrate through tissues to place of injury/infection. Some can secrete substances to destroy bacteria (before engulfing them)

Macrophages – large; develop from monocytes (TYPE OF WBC).

Some move through tissues; look for pathogens, destroy them.

Some are fixed in place; deal with pathogens that come to them.

Engulf pathogens, or release substances to destroy.

Explain the term inflammation and outline its purpose.

INFLAMMATORY RESPONSE

Response to tissue damage (mechanical damage / local chemical changes, i.e. pollen, bee, allergies)

Why inflammatory response?

Reduce the spread of pathogens / destroy pathogens / prevent the entry of further pathogens

Repair damaged tissue (pus) / cell debris

Repair of damaged tissue

Signs of inflammation – redness, swelling, heat, pain

List the four signs of inflammation.

Redness (increased blood flow)

Swelling (movement of fluid from the blood into tissue)

Heat (increased blood flow)

Pain (abnormal conditions stimulate pain receptors [nociceptors])

Describe the series of steps involved in the inflammatory response.

NON-SPECIFIC

Mechanical damage/local chemical changes – stimulates mast cells to release histamine and heparin

Histamine increased blood flow (dilation of ARTERIOLES); also causes increased permeability of blood capillary walls (more fluid filtered out of blood) *IMPORTANT

Heparin prevents clotting in the immediate area of injury; clot forms around damage (slows spread of pathogen into healthy tissue)

Mast Cells release chemicals (chemokine) – attract phagocytes, mainly macrophages + neutrophils (consume pathogens and debris via phagocytosis)

Abnormal conditions stimulate pain receptors

Phagocytes (filled with bacteria/debris / dead cells) begin to die; combines with tissue fluid to form pus (yellow liquid)

Mitosis (chemokine) in tissue produces new cells (repair occurs)

Define the term fever and explain the purpose of the change in body temperature.

An elevation of body temperature (usually 37.5)

Hypothalamus resets the body’s thermostat (core temp) in response to infection.

WBC release pyrogens during an inflammatory response (e.g., interleukin-1, released by macrophages)

Pyrogens act on the hypothalamus and raise the setpoint. Thermoreceptors detect the body temperature, and the hypothalamus recognizes it is lower than the new setpoint, therefore thinks you are cold.

At crisis the fever breaks, the setpoint lowers, and the hypothalamus recognizes that you are too hot.

Describe how fever may assist in defending the body against pathogens.

High body temp may inhibit the growth of some pathogens

Heat increases metabolism – increase the rate of repair

*HARMFUL IF TOO HIGH (ABOVE 44.4C)

The immune response – anti-body mediated and cell-mediated immunity

1st line of defence – skin, reflexes

2nd line of defence – phagocytosis, fever, inflammatory response

3rd line of defence – immune response

Explain what is meant by the immune response.

Homeostatic mechanism

Micro-organisms / foreign substances enter the body – immune response deals with invasion (of pathogens) and restores the internal environment to normal conditions.

Identify the two different types of specific immune responses (antibody-mediated and cell-mediated) and distinguish between them.

ANTIBODY-MEDIATED IMMUNITY = production of antibodies; circulate body and attack invading agents (extracellular/outside cell) B cells

CELL-MEDIATED RESPONSE = formation of special lymphocytes that destroy invading agents (cells have been invaded/inside the cell) T cells

B & T cells are both leucocytes (WHITE BLOOD CELLS)

Both responses are directed at specific invading pathogen

Both responses involve lymphoid tissue

Describe where lymphoid tissue is found in the body.

Most in lymph nodes; also, spleen, thymus gland, tonsils

Compose of TWO types of lymphocytes

B Cells

T Cells

Describe the lifecycle of T and B cells – where they are made, where they mature and where they end up.

B CELLS – lymphocyte (antibody-mediated/ humoral immunity).

Produced in BONE MARROW

Mature in BONE MARROW

Become part of lymphoid tissue

*ATTACK INVADERS OUTSIDE OF THE CELL

T CELLS – lymphocyte (cell-mediated immunity)

(Lots of different types of T cells)

Produced in BONE MARROW

Mature in THYMUS

Become part of lymphoid tissue

*ATTACK INVADERS INSIDE OF CELL

Define the terms antigen, self-antigen, non-self-antigen, antibody plasma cells and memory cells.

ANTIGEN

Any substance capable of causing a specific immune response

Causes the body to produce antibodies

large molecules; proteins, carbohydrates, lipids, or nucleic acids

Not just associated with pathogens (i.e., blood groups, transplanted tissue, pollen grains, egg whites)

SELF-ANTIGEN

Large molecules; produced by own body

Do NOT cause an immune response

NON-SELF-ANTIGEN

‘foreign’ compounds

DOES cause an immune response

ANTIBODY PLASMA CELLS

B-cells produced from specific cloned B-cells

Produces specific antibodies which will act as non-specific antigens

MEMORY CELLS

Cells that remain in the body for a long time (sometimes > 20 years)

Enable immune response to be activated quickly should pathogen enter the body again.

Explain the main events that occur in antibody-mediated immunity (humoral response).

HUMORAL RESPONSE (the process of antibody-mediated immunity)

Summary:

Production and release of antibodies into blood and lymph

Protection against viruses/bacteria/bacterial toxins before they enter the body’s cells (extracellular)

Antigen-presenting cells (antibody-mediated + cellular-mediated)

When a non-self-antigen enters a body, specific cells recognize this and respond, these cells are called ANTIGEN presenting cells and include:

Dendrite cells

Macrophages

Undifferentiated B cells

These cells detect the presence of a non-self-antigen

Engulf the pathogen

Digest pathogen, producing small fragments that move to the surface of the cell

Present the antigen to the LYMPHOCYTES to initiate an ANTIBODY- MEDIATED IMMUNE RESPONSE

The humoral response involves the production of and release of antibodies into the blood and lymph. This antibody-mediated immunity

It provides resistance to viruses, bacteria before these enter the body’s cells

Process of antibody-mediated immunity

Antigen-presenting cell presents the non-self-antigen to a specific B lymphocyte (Also presents helper t cells which produce a chemical [cytokine – chemical messenger] which activates specific B-cells)

Lymphoid tissue contains a thousand types of B cells.

The antigen activates specific B-cell – becomes sensitized; it enlarges and divides (By mitosis = CLONES)

Clones become specialised – specialised or B memory cells (spread to all body tissues and allow response to occur more rapidly)

Antibodies circulate in the blood, lymph, and extracellular fluid to reach the infection site.

HOW DO ANTIBODIES WORK

Inactivate antigens = antibodies combine with antigens to form an antigen-antibody complex

Antibody combines with foreign enzymes/bacterial toxins. Inactivate them by inhibiting reaction with other cells or compounds (neutralisation)

Bind to the surface of the virus; prevent entry into the cell

Coat pathogens (on the surface); enhances consumption by phagocytes (phagocytosis)

Causes agglutination (when antibodies make pathogens clump together, making them easy for phagocytes to capture and destroy,

Dissolve organisms – bacteria (lysis)

React with soluble substances to make them insoluble (TOXINS) more easily consumed by phagocytes

Describe the six ways antibodies may render an antigen inactive.

Antibodies combine with antigens to form an antigen-antibody complex

Antibody has a specific active site – this combines with antibody

‘Lock and key’; each antibody can only bind with one particular antigen

6 ways antibodies render an inactive antigen

Antibody combines with foreign enzymes / bacterial toxins – inactivate them by inhibiting reaction with other cells or compounds (neutralisation)

Bind to the surface of virus; prevent entry into cell

Coat pathogens; enhances consumption by phagocytes

Cause agglutination

Dissolve organisms (lysis)

React with soluble substances to make them insoluble – more easily consumed. By phagocytes

Explain what is meant by the primary response and describe the characteristics of this response.

Response upon FIRST EXPOSURE to non-self-antigen (pathogen)

The body responds slow; takes several days to build up large amounts of antibodies

Why? B cells need to multiply, differentiate then make antibodies (B memories)

SICK

Explain what is meant by the secondary response and describe the characteristics of this response.

Second/subsequent exposure to same pathogen/antigen

Memory cells recognise non-self-antigen much quicker

Plasma cells form more quickly – antibodies rise more quickly

WON’T GET SICK (no symptoms)

Explain the main events that occur in cell-mediated immunity.

Only involved with T cells (T lymphocytes made in bone marrow, mature in thymus gland) that destroy invaded cells

Provides resistance to the intracellular phase of pathogens. Is important in fighting whole cells as well as fighting cancer cells.

Lead to organ rejection after transplantation

When a foreign non-self-antigen (virus) enters the body, the antigen-presenting cells present the antigen to a particular type of T lymphocyte

This causes this type of T-cell to sensitise, enlarge and divide (mitosis) giving rise to a clone. Those cloned can become differentiated (specialised) – t killer, t suppressor, t helper, t memory cell

Describe how killer T cells may deal with an invading antigen.

Also known as cytotoxic T cells.

Migrate to the infection site

Attaches to cells with foreign antigen

Secrete substances that destroy infected cells and then go search for more antigens

Describe the role played by helper T cells and suppressor T cells

Helper

Bind to the antigen on the antigen-presenting cells and secrete cytokines

Cytokines – attract lymphocytes to the infection which becomes sensitized and activated = intensifying the response

Attract macrophages to the infection site

Intensify phagocytic activity of macrophages

Promote action of killer T-cells

Suppressor

Act when immune activity is excessive /infection is gone or infection has been dealt with successfully

Release substances that inhibit B-cell & T-cell activity

Explain the role played by the memory cells (in both antibody-mediated immunity and cell-mediated immunity).

Both B and T memory cells formed during an immune response

Remain in lymphoid tissue

Able to quickly recognise antigen = faster response to subsequent infections

TABLE 7.2 TXT BOOK – compares 2 systems

Define the term immunity.

Protection an individual develops against an antigen. Resistance to infection.

Distinguish between the four different types of immunity – passive natural, passive artificial, active natural and active artificial. Give an example of each type of immunity.

Natural

Define the term vaccine.

Vaccine – antigen preparation used in artificial immunisation

Describe the concept of ‘herd’ immunity

Occurs when high proportion of population are immunised so that those who are not immune are protected

Reduces chance of disease in susceptible individuals

Reduces transmission of pathogen between individuals in population

Distinguish between the four different types of vaccines that are available.

Living attenuated micro-organisms

Reduced virulence (ability to produce disease symptoms)

Often by exposing micro-organisms to high temps

E.g., polio, tuberculosis, rubella, measles, mumps

Inactivated vaccine

Dead pathogen; unable to produce disease symptoms

Immunity is not as prolonged as living attenuated vaccine

E.g., cholera, typhoid, whooping cough

Toxoids

Filtrate of bacterial cultures containing toxins

Bacteria is not necessary as it is a toxin that causes symptoms

Toxins inactivated (now called toxoids)

E.g., diphtheria, tetanus

Sub-unit

Fragment of micro-organisms either whole or attenuated

E.g., HPV, hepatitis B

Outline some of the risks and ethical concerns associated with the production and use of vaccines

RISKS

allergic reaction (often from culture rather than vaccine)

rick of cross-species disease introduction

some claim that preservatives can affect nervous system

ETHICAL CONCERNS

treatment of animals used in production of vaccines

source of human tissue (foetuses) used in production

testing of vaccines on individuals in developing countries

testing of vaccines on animals

parents may consider risk that child may suffer permanent damage from faulty vaccine/allergic reaction

Describe how antibiotics and antiviral drugs differ in their actions and effectiveness.

Antibiotics – drugs that fight bacterial infection i.e., penicillin. Effectiveness decreases as bacteria develops resistance.

Bacterial antibiotics – kill bacteria by changing cell wall/membrane structure, or disrupt enzyme action

Bacteriostatic antibiotics – stop bacteria reproducing by disrupting protein synthesis

Broad-spectrum: effective against a wide range of bacteria

Narrow-spectrum: effective against specific types of bacteria

Evolution of ‘super bugs’ due to overuse/misuse of antibiotics

Antivirals – target viral infections; inhibit development of virus. Research aims to identify viral proteins that can be disables by specifically designed chemicals.