Module 5 revision

Why is coordination needed? Organisms have to coordinate all their different cells and organs to make sure they're operating effectively overall Have to be able to respond to changes in their internal and external environments Neuronal communication Neurones have: cell body --> contains the nucleus with a cytoplasm full of endoplasmic reticulum and mitochondria which are involved in the production of neurotransmitters dendrons --> responsible for transmitting the impulse TOWARDS the cell body axons --> transmit the impulse AWAY from the cell body Three types of neurone: sensory --> transmit impulses from receptor to the relay neurone, motor neurone or the brain --> have one dendron and one axon relay --> transmit impulses between sensory and motor neurones --> short dendrons and axons motor --> transmit the impulse to the effector --> one long axon and many short dendrites Myelination: Schwann cells produce layers of plasma membranes around the axon The layers of plasma membrane act as an insulating layer which makes the impulse faster than non-myelinated as it has to "jump" between the gaps (aka the nodes of Ranvier) This "jumping" = saltatory conduction Sensory receptors Specific to a single type of stimulus Act as transducer --> convert stimulus into a nerve impulse by generating a generator potential Four types: mechanoreceptor = pressure and movement chemoreceptor = chemicals thermoreceptor = heat photoreceptors = light Pacinian corpuscle is a type of mechanoreceptor has special sodium ion channels in its plasma membranes --> stretch-mediated channels when these channels change shape / stretch the permeability to sodium ions changes too Resting potential Resting potential = no impulse in the neurone -70mV Generated by: sodium-potassium ion pump actively pumps 3 sodium ions OUT for 2 potassiums IN the sodium ion channels are mostly closed so they can't diffuse in the potassium ion channels are open so they diffuse back out of the axon ^^ this combines to give an overall resting potential of -70mV Action potential The neurone has a resting potential (some K ion channels are open but the Na voltage-gated channels are closed) Energy of the stimulus triggers some of the voltage-gated Na channels to open so Na ions diffuse into the axon down their electrochemical gradient This change in charge triggers more of the voltage-gated Na channels to open (positive feedback) When the potential difference reaches +40mV the voltage-gated Na channels close and the voltage-gated K channels open K ions diffuse out the axon, down their electrochemical gradient to make the axon more negative Lots of K ions move out, making the axon super negative (-90mV) so the voltage-gated K channels close The Na-K pump takes over again to restore the resting potential of -70mV This is followed by a refractory period where another impulse cannot be fired -70mV = resting potential -70mV --> +40mV = depolarisation +40mV --> -70mV = repolarisation -70mV --> -90mV = hyperpolarisation -90mV --> -70mV = restoration of resting potential Propagation of action potentials The depolarisation of one region on the membrane of an axon acts as a stimulus for the next region along ^^ this continues along the length of the axon  Refractory period prevents the propagation of the action potential BACKWARDS down the membrane --> makes sure the impulse is unidirectional ^ also ensures the action potentials don't overlap Action potentials are sped up by: axon diameter --> the bigger the diameter, the faster the impulse because there is less resistance to the flow of ions temperature --> higher the temperature, the faster the impulse because the ions have more kinetic energy All or nothing principle A certain level of stimulus must be achieved before a response is triggered (threshold value) No matter how large the stimulus, the same action potential is always triggered The size of the stimulus effects the number of...

Endocrine system is made of endocrine glands which are a group of cells specialised to secrete chemicals (hormones) directly into the bloodstream Pituitary gland = growth hormone, ADH, FSH, LH Thyroid gland = thyroxine Adrenal gland = adrenaline, noradrenaline, aldosterone Testis = testosterone Ovaries = oestrogen Pancreas = insulin, glucagon Thymus = thymosin Hormones Secreted directly into the blood They then diffuse to bind to specific receptors on target cells or organs Once bound they cause the organ to produce a response Steroid hormones --> lipid soluble so pass through the cell membrane of the cell and bind to receptors in the cytoplasm or nucleus --> forms a hormone-receptor complex which has a transcription factor attached so a gene is either activated or inhibited as a result Non-steroid hormone --> hydrophillic so bind to specific receptors on the cell surface membrane --> triggers cascade reaction in cell involving secondary messengers like cAMP Adrenal glands Adrenal cortex --> outer region of the glands where cortisol and aldosterone are made controlled by hormones released from the pituitary gland Glucocorticoids (release controlled by hypothalamus) --> cortisol which regulates metabolism and corticosterone which works with cortisol to regulate the immune response and suppress inflammatory reactions Mineralcorticoids (release controlled by signals from the kidneys) --> aldosterone which helps control blood pressure and maintain water and mineral balances in the blood  Andorgens --> small amounts of sex hormones  Adrenal medulla --> inner region of the gland where adrenaline and noradrenaline are made released when the sympathetic nervous system is stimulated adrenaline --> increases heart rate, raises blood glucose levels (glycogenolysis and gluconeogenesis) noradrenaline --> works with adrenaline to increase the heart rate, dilate the pupils, widen air passages and narrow blood vessels to non-vital organs Fight or flight response Once a threat is detected by the autonomic nervous system, the hypothalamus is stimulated Hypothalamus stimulates sympathetic nervous system The sympathetic nervous system stimulates the adrenal medulla and smooth muscles to secrete adrenaline and noradrenaline Hypothalamus stimulates the pit. gland to release ACTH ACTH travels to the adrenal cortex and activates the release of about 30 hormones to help with the response  heart rate increases to pump more oxygenated blood to the muscles for respiration pupils dilate to take in as much light as possible for better vision aterioles near skin constrict  to send more blood to major muscle groups blood glucose rises to increase glucose available for respiration  smooth muscle in airways relaxes to let the most amount of air into the lungs non-essential systems shut down to focus energy to muscles Action of adrenaline Adrenaline is non-steroid based so binds to specific receptors in the cell membrane When it has bound, the enzyme adenylyl cyclase inside the cell is activated Adenylyl cyclase triggers the conversion of ATP to cyclic AMP or cAMP on the inner surface of the membrane in the cytoplasm The increase in cAMP activates protein kinases which phosphorylate and in turn activate other enzymes (e.g. enzymes that break down stored glycogen to glucose) The pancreas Endocrine gland --> produces hormones (insulin and glucagon) that are released into the bloodstream Exocrine gland --> produces enzymes (amylases, proteases and lipases) which are released into the duodenum  Islets of Langerhans have alpha and beta cells Alpha cells produce glucagon Beta cells produce insulin Alpha cells are bigger and more numerous in the islets than the beta cells Beta cells are usually stained blue and alpha cells are pink Controlling blood glucose Example of negative feedback loop Increased via diet, glycogenolysis and gluconeogenesis Decreased via respiration and glycogenesis Role of...

Endotherms and ectotherms Ectotherms --> use their surroundings to warm their bodies (reptiles and amphibians) behavioural responses --> they bask in the sun, orientating as much surface area toward the sun to absorb the most head by radiation or they can increase their body heat by conduction by pressing their bodies against warm ground or can use some exothermic metabolic reactions they shelter from the sun or dig burrows to cool down or they press their bodies against cool rocks or stones or they orientate their bodies so that a small surface area is in the sun physiological responses --> they use the fact that dark colours absorb more heat radiation than light and some increase or decrease their heart rate to effect their metabolic activity Endotherms --> rely on metabolic processes to heat themselves, usually maintain a steady body temperature regardless of their environment (mammals and birds) behavioural responses --> basking in the sun, pressing themselves to warm surfaces, wallowing in water and mud or digging burrows --> humans wear clothes and build houses physiological responses --> peripheral temperature receptors, thermoregulatory centres in the hypothalamus, the skin and muscles anatomical adaptations --> animals in hot climates have large SA:Vol to increase heat loss (big ears) and pale fur or feathers to reflect the sun but animals in cold climates do the opposite often having a thick insulating layer of blubber cooling down vasodilation --> vessels near the skin dilate so more heat is lost via radiation through the skin increased sweating --> as sweat evaporates from the surface of the skin, heat is lost and the blood below is cooled reducing the insulating effect of hair --> erector pili muscles in the skin relax and hairs lay flat to remove the insulating layer of air warming up vasoconstriction --> vessels near the skin constrict so less heat is lost via radiation through the skin decreased sweating --> reduces the cooling provided by the evaporation of water from the surface of the skin raising of body hairs or feathers --> erector pili muscles contract to lift the hairs or feathers which traps a layer of air to insulate the body and reduce heat loss shivering --> rapid and ivoluntary contracting and relaxing od the large voluntary muscles to increase respiration which releases heat  Changes to the temperature of the blood are detected in the hypothalamus which sends impulses along motor neurones and the autonomic nervous system to effectors in the skin and muscles to create these ^^^^ responses The Liver Has a very rich blood supply Blood supplied by hepatic artery Blood removed by hepatic vein Blood loaded with products from digestion supplied by the hepatic portal vein Hepatocytes (liver cells) have large nuclei, prominent Golgi apparatus and lots of mitochondria Blood from hepatic artery and portal vein mixed together in spaces aka sinusoids which are surrounded by hepatocytes  Mixing increases the oxygen content to satisfy the needs of the hepatocytes Sinusoids contain Kupffer cells which act as macrophages Hepatocytes secrete bile which drain into the canaliculi that drain into the bile duct to the gall bladder   Functions of the liver carbohydrate metabolism  hepatocytes are particularly responsive to insulin and glucagon they convert glucose to glycogen and store it and reverse this when glucagon is about deamination of excess amino acids hepatocytes synthesise most of the plasma proteins hepatocytes carry out transamination where one amino acid is converted to another hepatocytes carry out deamination where the amine group is removed from the molecule the amine group is converted to ammonia and then to urea to be removed  the rest of the amino acid can be used in respiration or the formation of lipids ammonia is converted to urea through the ornithine cycle (ornithine --> ammonia added, CO2 added, water produced...

Auxins cell elongation, prevent leaf abscission, apical dominance, stimulate release of ethene IAA --> growth stimulant made in cells at tips of roots and shoots and meristems move in the transport tissues and cell to cell high concentrations inhibit gibberellins --> supports apical dominance bind to specific receptors in the cell membrane, cause pH to fall to 5 which makes the cell walls flexible and plastic which enables elongation, as the cell matures hormone levels fall and the cell walls become more fixed in shape and inflexible low concentrations promote root growth --> produced in the tips and they get some from the shoot when its little --> less auxin means less growth Gibberellins cause stem elongation of lateral shoots, trigger seed germination, stimulate pollen tube growth in fertilisation add water to seed --> embryo produces gibberellins --> gibberellins + water = gibberellic acid -->activates the transcription of amylase --> amylase breaks the stored starch to maltose --> maltase breaks the maltose to glucose --> glucose is respired for ATP to build materials for growth they effect the length of the internodes (regions between the leaves the stem) and can make them long and spindly Ethene causes fruit ripening, promotes abscission lengthening of the dark period of the day triggers abscission and a period of dormancy --> falling light = falling auxin to which the leaves respond my making ethene --> the base of the leaf has an abscission layer with two layers of ethene sensitive cells --> these cells produce enzymes that digest and weaken the cell walls of the abscission layer when ethene is present --> vascular bundles are sealed off and fatty material is deposited to form a protective scar when the leaf falls --> hormones made cells retain water and put more pressure on the separation layer --> abiotic factors like the wind make the break ABA (abscisic acid) maintains dormancy of seeds and buds, stimulates cold protective responses, stimulates stomatal closure leaf cells release ABA under abiotic stress --> ABA binds to receptors in the plasma membranes --> this changes the ionic concentrations of the cell so water leaves the vacuoles and the stomata are closed Chemical defences to herbivory Tannins --> bitter taste and put animals off eating the plant Alkaloids --> bitter tasting, nitrogenous compounds which act as drugs affecting the metabolism of the animals that take them in or even poisoning them Terpenoids --> form essential oils and act as toxins to insects and fungi Pheremones --> communication between groups of the same species ("I'm being attacked, protect yourselves!") or they attract parasites to eat their attackers rather than let their attackers eat them (wasps lay eggs in over larvae so that the baby wasps eat the larvae but leave the plant alone) How're they used? Ethene used commercially to make fruit perfect ripeness for sale Auxin is used in rooting powder Synthetic auxins can act as weedkillers that only kill broad-leafed plants (their growth rate increases to a point where its unsustainable and it dies) Auxins can be used in the production of seedless fruit Ethene is used to promote early abscission Cytokinins are used to prevent aging of ripened fruit Gibberellins are used to delay ageing and ripening in fruit