Homeostasis Flashcards
What is the definition of homeostasis?
The maintenance of a constant internal environment by maintaining volume, blood factors and tissue fluid within restricted limits
Why is homeostasis important?
1) Enzymes are sensitive to change in temperature and pH
2) Independent of the external environment
3) Maintaining a constant blood glucose
4) Maintaining of water potential of blood and tissue fluid
How is the set point monitored?
1) Receptor
2) Controller
3) Effector
4) Feedback loop
What are the mechanisms of heat gain?
1) Metabolism of food during respiration
2) Environmental gain of heat
i) conduction, convection, radiation
What are the mechanisms of heat loss?
1) Evaporation of water
2) Conduction from solid to solid
3) Convection (air con/ cold pool)
4) Radiation
What are endotherms and ectotherms?
Endotherm- derives most heat energy from metabolic activities
Ectotherm- obtains most heat energy from the external environment
How do ectotherms regulate body temperature?
1) Mainly controlled by exposure to the sun
2) Obtains heat from the ground by burrowing
3) Can change colour to alter heat that is radiated
How do endotherms regulate body temperature?
1) Altering enzyme activity
What are the long term and short term adaptations in conserving heat in a cold environment?
Long term 1) Small surface area to volume ratio 2) Physical properties (smaller ears, dark fur) Short term 1) Decreased sweating 2) Raising hair to trap a layer of air 3) Shivering 4) Vasoconstriction 5) Changing behaviour (going to heat)
What are the long term and short term adaptations in conserving heat in a hot environment?
Long term 1) Large surface area to volume ratio 2) Physical properties (larger ears, light fur) Short term 1) Increased sweating 2) Less hair 3) Vasodilation 4) Changing behaviour (going to cold)
What structure coordinates the control of body temperature?
Hypothalamus
Which part of the hypothalamus regulates body temperature?
Heat gain and heat loss centres in the thermoregulatory centre
How does the hypothalamus measure blood temperature?
Thermoreceptors and temperature receptors in the skin
Which system do the impulses to the hypothalamus travel on?
Autonomic nervous system
What is the secondary messenger model?
1) Hormone binds to receptor on the cell membrane form hormone-receptor complexes
2) H-RC activates an enzyme inside the cell which produces a secondary messenger
3) Secondary messenger acts within the cell and produces changes
How does adrenaline act as a secondary messenger?
1) H-RC activates an enzyme inside the cell membrane
2) Enzyme converts ATP to Cyclic AMP which acts as a secondary messenger
3) Cyclic AMP activates other enzymes which convert glycogen to glucose
What are the group of hormone producing cells in the pancreas called?
Islets of Langerhans
Which cells secrete which hormones in the pancreas?
Alpha- glucagon
Beta- Insulin
What are the 3 main sources of blood glucose?
1) Gluconeogenises- production of new glucose from sources other than carbohydrate or glycogen
2) Glycogenolysis- break down of glycogen in the liver and muscle cells
3) Diet- mainly from carbohydrates
What stimulates beta cells to secrete insulin?
Increase in blood glucose concentration
What happens when insulin binds to receptors?
1) Change in the tertiary structure of the glucose transport channel
2) Increase of glucose into the cell (by increasing permeability of liver/muscle/tissue cells)
3) Increased number of carrier molecules in the membrane
4) Enzymes activated which convert glucose to fat or glycogen
What stimulates alpha cells to secrete glucagon?
Decrease in blood glucose concentration
What is the result of releasing glucagon?
1) An enzyme is activated which converts glycogen to glucose
2) Increasing the conversion of amino acids and glycerol to glucose
What are the types of diabetes and how are they managed?
1) Type 1- insulin dependent- dose of insulin must match blood glucose concentration when injecting to prevent hypoglycaemia
2) Type 2- insulin independent- diet (carbohydrates) and exercise
What are the symptoms of diabetes?
1) Increased Drinking
2) Excess Urination
3) Tiredness
4) Blurred vision
5) Glucose in the urine
What is negative feedback?
The process which causes the corrective measures to be switched off which returns the system to a set point
What is positive feedback?
The process which causes the corrective measure to remain on
Give an example of positive feedback relating to neurones.
Influx of Na+ ions to increase permeability of the neurone
