Homeostasis

Homeostasis

Ectotherms
1. An organism that relies an external sources of heat to regulate its body temperature.
2. Methods of Heat Loss/Gain
  1. When cold/hot ectotherm changes its behaviour or physiology to increase/decrease absorption of heat.
  2. Expose/orientate body to sun, hide in burrow, alter body shape, increase breathing movements
3. Use less of their food in respiration, need to find less food & may be able to survive for long periods without eating. Greater proportion of energy obtained from food can be used for growth.
4. Less active in cooler temps and may need to warm up in the morning before they can be active (puts them at greater risk of predation. May not be capable of activity during the winter as they never warm up sufficiently, meaning they must have sufficient stores of energy to survive the winter without eating.
Endotherms
1. An organism that uses internally generated sources of heat from metabolism to maintain body temperture
2. Temperature Regulation
  1. Thermoregulatory centre in the hypothalamus monitors core body temperature
    1. Neuronal system initially. Sends impulses to glands, skin, liver and muscles. (rate of metabolism, muscle contraction, heat loss to environment).
  2. Peripheral temperature receptors are found in the skin of the bodies extremities send information to the thermoregulatory centre to indicate behavioural changes.
  3. Core temp dropping below optimum results in increased rate of metabolism in order to release more heat from exergonic reactions. Release of heat through extra muscular contraction, decreased loss of heat to the environment. Opposite happens if core temp too high (negative feedback.
    1. Metabolic reactions are increased by thyroxine and adrenaline.
3. Fairly consistent body temperature whatever the temperature is externally. Activity possible when external temperature is cool. Ability to inhabit colder parts of the planet.
4. Significant part of energy intake is used to maintain body temperature in the cold. More food is required. Less of the energy from food is used for growth, or more food is needed in order to grow.
5. Sweat glands in skin, lung nose & mouth, hairs on skin, arterioles leading to capillaries in skin.
Exergonic= reactions that release heat energy e.g. respiration.
Latent heat of vapourisation: heat loss through evaporation
Insulation: still air prevents loss
Hormones
1. Adrenaline
  1. Medulla - Nor/Adrenaline (catecholamines)- increase heart rate and force of heart contraction. Relax smooth muscle, conversion of glycogen to glucose.
  2. Cortex- androgens e.g. testosterone- create & maintain differences between males and females- affect bodes metabolism, minimal effect on development of make characteristics.
  3. Cortex- aldosterone- inhibits level of sodium excreted in urine
  4. Effects: Smooth muscle in bronchioles relaxes (intake air quicker, supply enough to keep up with increased metabolism, fuel fight/flight). Increased heart rate (increased blood flow around body to supply oxygen and glucose for respiration). Glycogen forms glucose (glucose used in respiration to supply energy in the form of ATP for flight or flight. Mental Awareness increases (throughout process so a response is quick. Helps us focus on the stimuli/respond to the external stimuli). Body Hair erects (reduces heat loss, increase speed of movement). Vasoconstriction of blood vessels (reduced heat loss so you don't slow down, less energy used trying to warm up, metabolism would drop if cold as not at optimum temp for enzyme activity). Gut action inhibited (energy focused on muscles/metabolism rather than wasted digesting food). STROKE VOL OF HEART INCREASES
2. Slower and longer lasting than nervous responses although some can be released quickly e.g. adrenaline and can have a short life span. Secreted from glands. Made from protein or steroid. Transmitted around the body of an organism by diffusing into and travelling through blood. They act on specific target tissues with cells having specific membrane receptors. Roles in stabilising organs and have roles in growth and development.
Pancreas
1. Has a dual function as an endocrine and exocrine gland.
2. Islet of Langerhans- contains two types of cells: alpha cells (secrete glucagon), beta cells (secrete insulin)
3. Regulation of Insulin
  1. Glucagon initiates gluconeogenesis and glycogenolysis so glucose leaks into the blood stream. Glucagon acts on (binds to receptor cells) liver cells, causing conversion of glycogen into glucose (glycogenolysis). More fatty acids are used in respiration. Fats and proteins are converted into glucose (gluconeogensis).
  2. DIABETES
    1. Type 1
      1. Symptoms/STE: Thirst, fatigue, weight loss, blurred vision, skin infections, body unable to produce insulin.
      2. LTE: eye problems, kidney damage, heart disease, stroke
      3. Current Treatments: Pancreas transplants, insulin injections, islet cell transplant, insulin pump therapy
      4. Future treatments: genetic engineering
      5. Diagnosis: urine sample test, blood test confirms
    2. Type 2
      1. Symptoms/ STE: urinating more often, blurred vision caused by lens drying out, unexplained weight loss, fatigue, thirst, cuts/wounds don't heal as quickly, genital itching, frequent episodes of thrush
      2. LTE: eye problems, kidney damage, heart disease, stroke
      3. Current treatments: medicines: insulin, biguanide, sulpherylurea, nareglinide, rapaglinide (all stimulate release of insulin), islet cell transplant, treatment for hypoglycaemia
      4. Future treatments: weight loss surgery, new drugs being researched- look set to alter management of the condition and are radically giving more treatment options.
      5. Diagnosis: Diagnosed through blood and urine tests. Urine sample tested for glucose (urine doesn't usually contain glucose). If urine contains glucose, glycated haemoglobin (HbA1C) blood test is used to determine if you have diabetes.
4. Order of Events in Insulin Secretion
  1. 1. Glucose levels rise. 2. Facilitated diffusion of glucose in. 3. ATP produced. 4. This closes potassium channels. 5. This leads to a change in p.d. 6. Voltage-gated calcium channels open. 7. Calcium diffuses in. 8. Vesicles of insulin fuse with the membrane and are released outside (exocytosis).
Exocrine grand:secrete substance including enzymes (NOT hormones) into a duct.
Endocrine gland: secretes hormones into the blood
Control of Blood Glucose
1. Glucose: sugar needed to be controlled in the body
2. Gluconeogenesis: production of glucose from fat and proteins
3. Glucogenesis: formation of glycogen from glucose
4. Glycogenolysis: formation of glucose form glycogen
5. Glucagon: hormone secreted from alpha cells
6. Glycogen: storage molecule in animals with alpha glucose monomers
7. Hormones are regulated by native feedback. Regulation of blood sugar is a good example of this. Blood glucose is kept at 90mg 100cm-3 of blood between 4-6mol dm-3. Controlled and maintained by hormones released in the islet of Langerhans

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	Created by Hannah Wood over 10 years ago