Homeostasis

Question 1

What is the definition of homeostasis?

Answer 1

The maintenance of a constant internal environment by maintaining volume, blood factors and tissue fluid within restricted limits

Question 2

Why is homeostasis important?

Answer 2

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

Question 3

How is the set point monitored?

Answer 3

1) Receptor
2) Controller
3) Effector
4) Feedback loop

Question 4

What are the mechanisms of heat gain?

Answer 4

1) Metabolism of food during respiration
2) Environmental gain of heat
i) conduction, convection, radiation

Question 5

What are the mechanisms of heat loss?

Answer 5

1) Evaporation of water
2) Conduction from solid to solid
3) Convection (air con/ cold pool)
4) Radiation

Question 6

What are endotherms and ectotherms?

Answer 6

Endotherm- derives most heat energy from metabolic activities
Ectotherm- obtains most heat energy from the external environment

Question 7

How do ectotherms regulate body temperature?

Answer 7

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

Question 8

How do endotherms regulate body temperature?

Answer 8

1) Altering enzyme activity

Question 9

What are the long term and short term adaptations in conserving heat in a cold environment?

Answer 9

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)

Question 10

What are the long term and short term adaptations in conserving heat in a hot environment?

Answer 10

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)

Question 11

What structure coordinates the control of body temperature?

Answer 11

Hypothalamus

Question 12

Which part of the hypothalamus regulates body temperature?

Answer 12

Heat gain and heat loss centres in the thermoregulatory centre

Question 13

How does the hypothalamus measure blood temperature?

Answer 13

Thermoreceptors and temperature receptors in the skin

Question 14

Which system do the impulses to the hypothalamus travel on?

Answer 14

Autonomic nervous system

Question 15

What is the secondary messenger model?

Answer 15

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

Question 16

How does adrenaline act as a secondary messenger?

Answer 16

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

Question 17

What are the group of hormone producing cells in the pancreas called?

Answer 17

Islets of Langerhans

Question 18

Which cells secrete which hormones in the pancreas?

Answer 18

Alpha- glucagon

Beta- Insulin

Question 19

What are the 3 main sources of blood glucose?

Answer 19

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

Question 20

What stimulates beta cells to secrete insulin?

Answer 20

Increase in blood glucose concentration

Question 21

What happens when insulin binds to receptors?

Answer 21

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

Question 22

What stimulates alpha cells to secrete glucagon?

Answer 22

Decrease in blood glucose concentration

Question 23

What is the result of releasing glucagon?

Answer 23

1) An enzyme is activated which converts glycogen to glucose
2) Increasing the conversion of amino acids and glycerol to glucose

Question 24

What are the types of diabetes and how are they managed?

Answer 24

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

Question 25

What are the symptoms of diabetes?

Answer 25

1) Increased Drinking
2) Excess Urination
3) Tiredness
4) Blurred vision
5) Glucose in the urine

Question 26

What is negative feedback?

Answer 26

The process which causes the corrective measures to be switched off which returns the system to a set point

Question 27

What is positive feedback?

Answer 27

The process which causes the corrective measure to remain on

Question 28

Give an example of positive feedback relating to neurones.

Answer 28

Influx of Na+ ions to increase permeability of the neurone