6.4 Homeostasis

Question 1

What is homeostasis?

Answer 1

A self-regulating process in which a constant internal environment is maintained and regulated

Question 2

What is negative feedback?

Answer 2

Change which counteracts changes back to normal limits

Question 3

What is positive feedback?

Answer 3

Effectors respond to amplify a change away from the normal level

Question 4

Why are multiple negative feedback systems more efficient?

Answer 4

• Gives more control as you can actively increase or decrease a level
• As opposed to simply switching on or off/ waiting for hormones to break down etc.

Question 5

Factors that can influence blood glucose

Answer 5

• Eating
• Exercise
• Age

Question 6

Usual blood glucose concentration

Answer 6

0.9 g/dm3

Question 7

Where is insulin produced?

Answer 7

beta cells in the Islets of Langerhans in the pancreas

Question 8

What processes does insulin promote?

Answer 8

Glycogenesis

Question 9

What process does glucagon promote?

Answer 9

Glycogenolysis + Gluconeogenesis

Question 10

Insulin actions

Answer 10

• Increases glucose permeability of muscle cells
• Activates enzymes in the liver
• Increases rate of respiration

Question 11

Glucagon actions

Answer 11

• Activates liver enzymes

- Decreases rate of respiration

Question 12

Adrenaline processes

Answer 12

• Activates glycogenolysis and inhibits glycogenesis

- Activates glucagon production and inhibits insulin production

Question 13

Which cells does insulin bind to?

Answer 13

Muscle cells + liver cells

Question 14

Which cells does glucagon bind to?

Answer 14

Liver cells

Question 15

Which cells detect changes in glucose blood conc. ?

Answer 15

Pancreas cells

Question 16

What is GLUT4?

Answer 16

Glucose channel protein

Question 17

Where is GLUT4 found?

Answer 17

Skeletal and cardiac muscle cells, stored in vesicles in cytoplasm

Question 18

Describe the action of adrenaline and glucagon

Answer 18

• Secondary messenger = cAMP
  1) Bind to protein receptors on cell membrane
  2) Activates attached enzyme = adenylate cyclase
  3) Activated enzymes converts ATP into cAMP = a chemical signal
  4) cAMP activates protein kinase A
  5) Activates a cascade which breaks down glycogen

Question 19

What is type 1 diabetes?

Answer 19

• Inability to produce insulin

After eating blood glucose remains high

Question 20

How can type 1 diabetes be treated?

Answer 20

Eating regularly and eat simple carbohydrates - avoid sudden rise in glucose conc.
Insulin pump - regular insulin injections

Question 21

What is type 2 diabetes?

Answer 21

• Insulin insensitivity
  beta cells don’t produce enough or no response to insulin
  resting blood glucose conc. too high

Question 22

How can type 2 diabetes be treated?

Answer 22

Healthy exercise, lose weight, regulate carbohydrate intake

Question 23

What reagent is used in colorimetry of glucose solutions?

Answer 23

Quantitative Benedict’s reagent

- Doesn’t produce yellow or green intermediate colours but uses shades of blue which can be detected

Question 24

How is water potential monitored and acted upon?

Answer 24

Osmoreceptors in the hypothalamus which send a signal to the posterior pituitary gland which secretes ADH into the blood stream

Question 25

Where does ADH act on?

Answer 25

DCT and collecting duct

Question 26

What three layers must filtrate pass through in the Bowmans capsule?

Answer 26

Blood endothelium
Basement membrane
Bowman’s capsule epithelium