6.4 Homeostasis

Question 1

What is homeostasis?

Answer 1

involves phsyiological control systems that maintain the internal environment within restricted limits

Question 2

Why is it important to maintain core body temperature and pH?

Answer 2

enzymes will denature in extreme pHs and in high temps
in low temps - eznzyme activity is slowed

Question 3

Why is it important to maintain blood glucose levels?

Answer 3

to maintain water potential of blood and supply glucose to cells as a respiratory substrate
water potential needs to be maintained in order to prevent cells loosing or gaining water by osmosis

Question 4

What is negative feedback?

Answer 4

when deviations from the optimum level are detected by receptors, corrective mechanisms bring the factor back to optimum

Question 5

What is positive feedback?

Answer 5

when a stimulus detected by a receptor brings about a response that enhances the effect further - so there is greater deviation from the optimum

Question 6

What is the benefit of having separate mechanisms for different deviations from the optimum?

Answer 6

there is greater control over the system when a factor becomes too high or too low

Question 7

What are the 3 ways glucose can enter the bloodstream?

Answer 7

absorption from the gut after digestion
hydrolysis of stored glucose
conversion of non carbohydrates into glucose

Question 8

How do hormones bring about a response?

Answer 8

produced by glands which secrete hormones directly into the blood
carried in blood plasms to target cells with specific receptors

Question 9

What are all the strcutures of the pancreas?

Answer 9

the pancreatic duct
the pancreas
acinar glands
islet of langerhans:
- alpha and beta cells
-capillary

Question 10

What is the role of beta cells?

Answer 10

secrete insulin in response to increased glucose concentrations

Question 11

What is the role of alpha cells?

Answer 11

secrete glucagon in response to lowered glucose concentrations

Question 12

What is glycogenesis?

Answer 12

the formation of glycogen from glucose

Question 13

What is glycogenolysis?

Answer 13

the hydrolysis of glycogen into glucose

Question 14

What is gluconeogenesis?

Answer 14

the synthesis of glucose from molecules that are not carbohydrates - amino acids and fatty acids, glycerol

Question 15

What triggers the release of insulin?

Answer 15

increased glucose levels detected by beta cells
vesicles containing insulin move to the cell surface membrane and release insulin into surrounding capillaires

Question 16

How does insulin lower blood glucose concentrations?

Answer 16

1. insulin binds to receptor proteins on the surface membrane of target cells
2. glucose carrier proteins on the membrane allow for facilitated diffusion of glucose
3. insulin changes the shape of carriers and causes more carrier proteins to join the cell surface membrane of target cell = increase rate of glucose uptake
4. insulin activates an enzyme for glycogenesis
5. also activates enzymes that manufactures fatty acids and glycerol which are stored as fat
   negative feedback

Question 17

What triggers the release of glucagon?

Answer 17

decreased glucose levels are detected by the alpha cells
vesicles fuse with membrane to release glucagon into surrounding capillaries

Question 18

How does glucagon raise blood glucose concentration?

Answer 18

1. binds to transmembrane protein of hepatocytes
2. activates enzymes involved in glycogenolysis and gluconeogenesis