Homeostasis

Question 1

How does sweating or panting help control temperature?

Answer 1

Evaporation of water from skin or mouth lining.

Question 2

What happens to heat during sweating or panting?

Answer 2

Heat is transferred from the blood to the water.

Question 3

Why is evaporation effective for heat loss?

Answer 3

Because of the high latent heat of vaporisation of water.

Question 4

What detects changes in blood CO₂ or pressure?

Answer 4

Chemoreceptors detect CO₂/pH; baroreceptors detect pressure.

Question 5

Which part of the brain processes this information?

Answer 5

The medulla/cardiac centre.

Question 6

What happens after detection of low pH or high CO₂?

Answer 6

More impulses sent to SAN along sympathetic nerves.

Question 7

Where are the chemoreceptors detecting pH located?

Answer 7

Carotid artery and aorta.

Question 8

How does less CO₂ in blood affect heart rate?

Answer 8

Detected by chemoreceptors → fewer impulses to cardiac centre.

Question 9

What nervous system activity changes to reduce heart rate?

Answer 9

More impulses along parasympathetic nerve or fewer along sympathetic nerve to SAN.

Question 10

How does insulin affect target cells?

Answer 10

Binds to receptors on all body cells.

Question 11

What does insulin stimulate?

Answer 11

Uptake of glucose by GLUT transport proteins.

Question 12

What does insulin activate in liver and muscle?

Answer 12

Enzymes converting glucose to glycogen.

Question 13

What does glucagon do at target cells?

Answer 13

Attaches to receptors and activates enzymes.

Question 14

What processes does glucagon stimulate?

Answer 14

Glycogenolysis (glycogen to glucose) and gluconeogenesis.

Question 15

What happens to glucose concentration inside cells during glycogen formation?

Answer 15

Falls below blood/plasma glucose concentration.

Question 16

How does this affect glucose movement?

Answer 16

Creates a diffusion gradient for glucose to enter cells via facilitated diffusion.

Question 17

How can blood glucose levels be increased hormonally?

Answer 17

By release of glucagon.

Question 18

What does glucagon cause in the liver?

Answer 18

Formation of glucose from non-carbohydrates (amino acids, fatty acids).

Question 19

What enzyme is activated in the secondary messenger model?

Answer 19

Adenylate cyclase.

Question 20

What is produced as a second messenger?

Answer 20

cAMP (cyclic AMP).

Question 21

What does cAMP activate?

Answer 21

Protein kinase enzymes.

Question 22

What are the effects on glucose metabolism?

Answer 22

Glycogenolysis and gluconeogenesis occur; glycogenesis is inhibited.

Question 23

What causes ultrafiltration in the glomerulus?

Answer 23

High blood/hydrostatic pressure.

Question 24

Name some small substances that pass through during ultrafiltration.

Answer 24

Water, glucose, ions, urea.

Question 25

Through what structures do these substances pass?

Answer 25

Gaps/pores/fenestrations in capillary endothelium and basement membrane.

Question 26

What feature increases surface area for reabsorption?

Answer 26

Microvilli or folded cell surface membrane.

Question 27

What proteins help reabsorb glucose?

Answer 27

Channel and carrier proteins for facilitated diffusion, active transport, and co-transport.

Question 28

What provides energy for active transport?

Answer 28

Many mitochondria producing ATP.

Question 29

What helps produce the carrier/channel proteins?

Answer 29

Many ribosomes.

Question 30

Why does a thicker medulla lead to more concentrated urine?

Answer 30

It means a longer loop of Henle.

Question 31

What does a longer loop of Henle maintain?

Answer 31

A higher sodium ion concentration gradient in the medulla.

Question 32

How does this affect water reabsorption?

Answer 32

Water potential gradient is maintained longer, so more water is reabsorbed by osmosis.

Question 33

Where does ADH bind in the kidney?

Answer 33

To receptor proteins on cells lining the distal convoluted tubule (DCT) and collecting duct (CD).

Question 34

What effect does ADH have on these cells?

Answer 34

Increases permeability to water.

Question 35

What is the result for urine?

Answer 35

More water is reabsorbed by osmosis, producing smaller volume and more concentrated urine.

Question 36

Why is glucose found in urine of someone with untreated diabetes?

Answer 36

High blood glucose leads to high filtrate glucose concentration.

Question 37

Why isn’t all glucose reabsorbed?

Answer 37

Carrier/co-transport proteins in proximal tubule are saturated and working at max rate.