Chapter 16 - Homeostasis

Question 1

Define homeostasis

Answer 1

A set of physiological systems that maintain a stable and constant internal environment

Question 2

Why is temperature maintained in the body

Answer 2

• Metabolism controlled by enzymes which have an optimum temperature
• Too hot causes denaturation
• Too cold slows reaction

Question 3

Why is pH maintained in the body?

Answer 3

• Metabolism controlled by enzymes which have an optimum pH

- Too extreme causes denaturation and slows reaction

Question 4

Why is glucose maintained in the body?

Answer 4

• Minimum amount of glucose needed
• Too much decreases water potential so water leaves by osmosis
• Cells shrivel up

Question 5

Define negative feedback system

Answer 5

When the product of a reaction leads to a decrease in that reaction. In this way, a negative feedback loop brings a system closer to a target of stability or homeostasis

Question 6

How does a negative feedback system operate?

Answer 6

• Receptors detect change away from normal

- Effectors activate mechanisms to return to normal

Question 7

Why does the body have separate negative feedback systems?

Answer 7

• More control

Question 8

What is a positive feedback system?

Answer 8

A system that results in effectors amplifying the change away from the normal more produces more

Question 9

What is the point of a positive feedback system?

Answer 9

• Rapid changes and responses

Question 10

Give two examples of positive feedback systems

Answer 10

Action potentials and blood clotting

Question 11

How is high blood glucose controlled?

Answer 11

• Concentration increases
• Receptors in the pancreas detect this
• Beta cells in the isle of langerhans secrete insulin
• Binds to receptors in the liver and muscle
• Increases permeability to glucose
• More glucose absorbed by facilitated diffusion
• Glycogenesis occurs
• Increase in rate of respiration
• Blood glucose concentration decreases

Question 12

How is low blood glucose controlled?

Answer 12

• Concentration decreases
• Receptors in the pancreas detect this
• Alpha cells in the isle of langerhans secrete glucagon
• Glucagon binds to receptors on the liver cells
• Rate of respiration decreases
• Glycogenolysis occurs
• Gluconeogenesis occurs

Question 13

What is glycogenolysis

Answer 13

The breaking down of glycogen to produce glucose molecules promoted by glucagon and adreanline

Question 14

Define gluconeogensis

Answer 14

The production of glucose from non carbohydrate respiratory substrates promoted by glucagon

Question 15

Define glycogensis

Answer 15

The production of glycogen from glucose promoted by insulin

Question 16

Summarise the glucagon hormone

Answer 16

• Secreted by alpha cells
• When blood glucose low
• Attached to liver receptors
• Increases blood glucose
• Decreases rate of respiration, causes glycogenolysis and gluconeogensis

Question 17

Summarise the adrenaline hormone

Answer 17

• Secreted by alpha cells
• When blood glucose low
• Attached to liver receptors
• Increases blood glucose
• Activates glycogenolysis and inhibits glycogenesis

Question 18

Summarise the insulin hormone

Answer 18

• Secreted by B cells
• When blood glucose high
• Attaches to liver and muscle receptors
• Decrease blood glucose
• Increases rate of respiration, causes glycogenesis and increases permeability to glucose

Question 19

How does insulin increase permeability to glucose?

Answer 19

• Glucose carrier proteins stored in vesicles inside the cells
• Insulin binds to receptors and vesicles fuse with cell membrane
• Carrier proteins join membrane and glucose absorbed by facilitated diffusion

Question 20

Define diabetes

Answer 20

Illness where the body fails to control blood glucose levels

Question 21

Distinguish between hyperglycaemia and hypoglycaemia

Answer 21

Hyper = too much glucose and hypo = too little glucose

Question 22

Summarise type I diabetes

Answer 22

• Caused by immune system destroying B cells that produce insulin
• Hyperglycaemia so glucose in urine
• Inject insulin/pump
• However this can cause low glucose (hypoglycaemia) so avoid carbs, eat regularly and exercise

Question 23

Summarise type II diabetes

Answer 23

• Obesity, lack of exercise and poor diet so lack of production/stop responding
• Hyperglycaemia so glucose in urine
• Eat healthy, lose weight, regular exercise and use drugs to increase sensitivity to insulin, produce more insulin and reduce glucose released