Vascular Physiology

Question 1

How much blood is in the veins?

Answer 1

42%

Question 2

What is capillary diameter controlled by?

Answer 2

Actin and myosin in the epithelial cells

Question 3

What are the three layers of blood vessels?

Answer 3

Connective tissue adventitia - Elastic
Smooth Muscle
Endothelium

Question 4

What acts like a reservoir of blood?

Answer 4

The veins

Question 5

What is the blood brain barrier composed of?

Answer 5

The endothelial cells of the cerebral capillaries and the choroids plexus epithelium.

Question 6

What substances can pass easily through the blood brain barrier?

Answer 6

Carbon dioxide
Water
Oxygen

Question 7

What is the main function of the lymphatic system?

Answer 7

Return plasma to the circulatory system

Question 8

Where does the lymphatic system drain?

Answer 8

Jugular and subclavian veins

Question 9

What is a normal BP for a young adult?

Answer 9

120/70 mmHg

Question 10

When measuring blood pressure what do Korotkoff sounds signal?

Answer 10

Systole

Question 11

What equation is blood flow given by?

Answer 11

Pressure/Resistance

Question 12

State Pouiselle’s Law

Answer 12

Resistance is proportional to 1/r to the power of 4

Question 13

What is blood velocity proportional to?

Answer 13

1/Cross sectional area

Question 14

Where is the biggest drop in blood pressure and why?

Answer 14

From the arterioles to the capillaries due a large increase in cross sectional area

Question 15

What is hypertension defined as?

Answer 15

Diastolic arterial BP > 90mmHg

Question 16

What are the two types of hypertension?

Answer 16

Primary Hypertension - No known cause it is due to super additive risk factors
Secondary Hypertension - Has a known cause

Question 17

What systems regulate blood pressure?

Answer 17

Sympathetic Nervous System
Endothelium
Renin-Angiotensin system
Changes in blood volume

Question 18

Where are baroreceptors located?

Answer 18

The carotid sinus and the aortic arch

Question 19

What are varicosities?

Answer 19

Thickenings at the end of the axon which release NA

Question 20

What are the methods we can regulate BP via the sympathetic nervous system?

Answer 20

At adrenoceptors e.g. Clonidine
Block NA release e.g. Reserpine
Calcium effects - Dihydropyridines

Question 21

What are dihydropyridines?

Answer 21

L-type calcium blockers which lower blood pressure

Question 22

Outline the 3 mode calcium channel model

Answer 22

Calcium channels can be in one of three states:
Mode 0 - Can’t open on depolarization
Mode 1 -Unlikely to open on depolarization
Mode 2- Likely to open on depolarization
Normally most channels are in mode 1, drugs act to stabilise the varying modes for example Nifedipine stabilizes mode 0 and BayK8644 stabilizes mode 2

Question 23

What do endothelins do?

Answer 23

Increase blood pressure by causing vasoconstriction

Question 24

What are the types of endothelins?

Answer 24

Endothelin I - Endothelium
Endothelin II - kidney
Endothelin III - brain, lungs and adrenal gland

Question 25

Outline Endotheline I synthesis

Answer 25

Pre-pro ET –> Big ET-1 –> ET-1

Question 26

What are the receptors for endothelins?

Answer 26

ETA and ETB

Question 27

How does ETA cause vasoconstriction?

Answer 27

Through Gq

Question 28

What do prostacyclins do?

Answer 28

Decrease blood pressure by raising cAMP and inhibiting platelet aggregation, adherence and vasodilation

Question 29

What does EDRF do?

Answer 29

Cause vasodilation therefore decreases BP

Question 30

Outline the mechanism by which EDRF works

Answer 30

L-arginine -(NOS)–> Citrulline and NO –(Diffuse into arterial smooth muscle)–> NO –(stimulates)–> Guanylate Cyclase causing GTP –> cGMP –> PKG activation –> Relaxation

Question 31

What is the rate determining step in the renin-angiotensin system?

Answer 31

Renin release

Question 32

What does renin do?

Answer 32

Cleave angiotensinogen –> Angiotensin I

Question 33

Where is renin synthesised and stored?

Answer 33

Granular juxtaglomerular cells

Question 34

What causes renin secretion?

Answer 34

Renal B1 adrenoceptor stimulation
Decrease in [NaCl] sensed by the macula densa cells
A fall in juxtaglomerular BP

Question 35

What does Angiontensin converting enzyme (ACE) do?

Answer 35

Converts Angiotensin I to Angiontensin II

Question 36

What are the angiotensin receptors and where are they located?

Answer 36

AT1 - Vascular, myocardial tissue and smooth muscle

AT2- Adrenal medulla

Question 37

What does angiotensin II do?

Answer 37

Increase BP

Question 38

How can we inhibit the Renin-angiotensin system?

Answer 38

ACE inhibitors e.g. Captopril

AT2 antagonists e.g. Losartan

Question 39

What do diuretics do?

Answer 39

Primary effect is to decrease NaCl reabsorption

Secondary effect is to decrease water reabsorption

Question 40

Where do loop acting diuretics work and give an example?

Answer 40

They inhibit the Na-K-2Cl symporter in the luminal membrane of the ascending loop of henle.
Furosemide

Question 41

What is the main side effect of loop acting diuretics?

Answer 41

Hypokalemia

Question 42

What is so bad about hypokalemia?

Answer 42

It causes tachycardia as there is a shorter refractory period as Ek is reduced

Question 43

Where do early distal tubules act and give an example?

Answer 43

Inhibit the Na/Cl transporter in the distal convoluted tubule.
Bendrofluazide

Question 44

What do potassium sparring diuretics act on?

Answer 44

The K ATPase in the distal convoluted tubule

Amiloride

Question 45

How do osmotic diuretics work? Give an example

Answer 45

They are pharmacologically inert substances that increase the osmolarity of the filtrate therefore increase water loss
Mannitol