Resistance and Exchange

Question 1

What mechanism of action leads to changes in resistance in arterioles?

Answer 1

• Vasodilation
• Vasoconstriction

Question 2

What are the three things that influence arteriole resistance?

Answer 2

• Metabolic requirements
• Sympathetic reflexes
• Hormonal control

Question 3

In what state is smooth muscle in most blood vessels?

Answer 3

It is in a state of partial constriction at all time known as muscle tone

Question 4

What three things influence the contraction of smooth muscle in blood vessels?

Answer 4

• Neurotransmitters
• Hormones
• Paracrine signals

Question 5

What is local control of blood vessels?

Answer 5

Signal produced by both the blood vessels and underlying tissues to alter the arteriolar diameter

Question 6

What happens during sympathetic control of resistance in arterioles?

Answer 6

Norepinephrine binds to alpha receptors causing vasoconstriction

Question 7

How is surface area and diffusion distance organised in capillaries?

Answer 7

• Maximised surface area
• Minimised diffusion distance

Question 8

What determines the leakiness of capillaries?

Answer 8

Cell junctions

Question 9

What are continuous capillaries?

Answer 9

The least leaky capillary which is in most organs

Question 10

What are fenestrated capillaries?

Answer 10

The second least leaky capillary which is in the kidney and endocrine glands

Question 11

What are sinusoids?

Answer 11

The most leaky capillary which is in blood marrow to allow blood cells to enter

Question 12

What are the three main mechanisms of capillary exchange?

Answer 12

• Diffusion
• Transcytosis
• Bulk flow

Question 13

What is bulk flow?

Answer 13

The mass movement of water and dissolved solutes between blood and the interstitial fluid

Question 14

What is filtration?

Answer 14

Flow out of capillary

Question 15

What reabsorption?

Answer 15

Flow into the capillary

Question 16

What is occurring at the arterial end of capillaries?

Answer 16

Net filtration

Question 17

What is occurring at the venous end of capillaries?

Answer 17

Net reabsorption

Question 18

When does net filtration occur?

Answer 18

When hydrostatic pressure (PH) is greater than colloid osmotic pressure (π)

Question 19

When does net absorption occur?

Answer 19

When colloid osmotic pressure (π) is greater than hydrostatic pressure (PH)

Question 20

What is hydrostatic pressure?

Answer 20

Pressure inside the capillary which forces fluid out of the capillary

Question 21

What is colloid osmotic pressure?

Answer 21

Pressure of proteins within the capillary that pulls fluid into the capillary

Question 22

Overall is there a net flow in or flow out of capillaries?

Answer 22

Net flow out

Question 23

What are the two forces that regulate capillary bulk flow?

Answer 23

• Hydrostatic pressure
• Osmotic pressure

Question 24

How do you calculate net pressure?

Answer 24

Outward pressure - inward pressure

Question 25

What are the three functions of the lymphatic system?

Answer 25

- Return of fluid and proteins - Picks up absorbed fat from the small intestine - Filter, capture and destroys foreign pathogens

Question 26

What is lymph?

Answer 26

Interstitial fluid that enters a lymphatic vessel

Question 27

What are initial lymphatics?

Answer 27

Lymph capillaries that are small blind ended terminal lymph vessels that permeate almost every tissue of the body

Question 28

What are lymph vessle?

Answer 28

Lymphatics which empty into the venous system near where blood enters the right atrium

Question 29

What does lymph flow rely on?

Answer 29

Waves of contraction of smooth muscle in large lymph vessels

Question 30

What aids waves of contraction of smooth muscle in large lymph nodes?

Answer 30

- Contractile fibres in endothelial cells - Valves - Skeletal muscle compression

Question 31

What is oedema?

Answer 31

Swelling of tissue when too much interstitial fluid accumulates

Question 32

What are the four main causes of oedema?

Answer 32

- Reduced concentration of plasma proteins - Increased permeability of capillary wall - Increased venous pressure - Blockage of lymph vessels