Physiology and Pharmacology 14: (Evans) Vascular phys and pharm

Question 1

General structure of a blood vessel? 4 classes of vessel properties?

Answer 1

3 layers
outer - connective tissue
middle - smooth muscle
inner - endothelium

Large arteries like aorta highly elastic to respond to high pressure generated by heart

Arterioles less elastic, more smooth muscle, major site of resistance to flow

Capillaries made from single cell wall of endothelial cells

Veins and venules -> little smooth muscle, walls only slightly thicker than capillaries

Question 2

Purpose of valves in veins?

Answer 2

Assure single direction of flow -> prevent backflow

- movement of blood back to the heart may be facilitated by muscular movements (pressure opens valves)

Question 3

Methods of transport from capillaries to interstitial fluid?

Answer 3

Diffusion of lipid-soluble substances through plasma membranes

Diffusion of soluble substances through tiny gaps between endothelium cells (endothelial pores)

Bulk flow of water and dissolved substances

Endo -> Exo cytosis

Question 4

What is the blood brain barrier?

Answer 4

Brain is part of a separate circulatory system -> edothelial pores are replaced with tight junctions (much harder to pass through)

Only lipid-soluble substances, water, O2 and CO2 can pass with ease

Question 5

What are lymph and lymphatics?

Answer 5

Lymph = Formed when interstitial fluid is collected through lymph capillaries

Lymphatics = Thin walled vessels that carry lymph, act as filter at lymph nodes which remove foreign particles and bacteria (packed with lymphocytes and phagocytes)

Question 6

What is oedema?

Answer 6

block of lymph flow -> results in protein from capillaries building up in interstitial spaces
-> leads to water retension

Question 7

Describe method of taking blood pressure measurement

Answer 7

Inflatable cuff inflated to point where blood flow of arm arteries is completely restricted (no sound can be heard through stethoscope)

Cuff slowly deflated until heart can force blood through gap and sound can be heard generated by pulsatile flow -> (Korotkoff sound) -> systolic pressure

Blood flow silent again at basal -> (diastolic) pressure

Question 8

What is hypertension? 2 types and causes/risks associated?

Answer 8

High blood pressure, defined by diastolic arterial blood pressure > 90mmHg

1) Primary (essential HT) 90-95% of cases
- no apparent (obvious) cause
- risk factors for High blood pressure include alcohol, genetic predisposition, lack of excercise, smoking, overweight (synergistic effect)

2) Secondary HT 5-10% of cases
- renovascular disease or endocrine disease e.g. tumour of adrenal gland, secretes excessive adrenaline

Question 9

Main classes non-cardiac drugs / mechanisms regulating blood pressure?

Answer 9

Non-cardiac

• Drugs that affect the SNS / muscle contraction
• Endothelium / local regulation
• Renin-angiotensin system
• Changes in blood volume

Question 10

Where are baroreceptors located? Function and interactions with SNS?

Answer 10

In aortic arch and carotid sinus -> detection of blood pressure via stretch

When increase of blood pressure detected,

• Baroreceptor output stimulates APs in inhibitory interneuron
• Inhibitory signals sent to sympathetic nerves -> inhibited vasocontriction, blood pressure lowered

i.e increased baroreceptor activity, decreased sympathetic activity