Physiology - Intro to the heart

Question 1

What is compliance?

Answer 1

Measure of expandibility of a vessel

Question 2

Describe the compliance of a vein

Answer 2

More compliant than arteries => act as a reservoir

Have much lower venous pressure

Question 3

What is Darcy’s law?

Answer 3

Arterial pressure = Cardiac output * total peripheral resistance

Question 4

What are the two phases of the cardiac cycle?

Answer 4

Diastole = chambers are relaxed and filling

Systole = ventricles are contracting and ejecting

Question 5

Which valves are open and close during diastole and why?

Answer 5

Tricuspid and mitral valves open

Pulmonary and aortic valves are close

• Atrial pressure > ventricular pressure

Question 6

Which valves are open and closed during systole and why?

Answer 6

Tricuspid and mitral = closed

Pulmonary and aortic = open

• Ventriculuar pressure > atrial pressure

Question 7

What is the purpose of valves?

Answer 7

To ensure unidirectional flow

Question 8

What is the end-diastolic volume?

Answer 8

The volume filling a ventricle before contraction

Question 9

What is stroke volume?

Answer 9

The blood volume ejected by a ventricle on contraction

Question 10

What is end-systolic volume?

Answer 10

Volume of blood remaining in ventricle after systole

Question 11

What is the general concept of the baroreceptor reflex?

Answer 11

Short term response occuring when:

Increased stretch felt by baroreceptors => increased impulse

Question 12

Where are the four main baroreceptors located and which nerve innervates them?

Answer 12

Vagus nerve

• Atrial stretch receptors
• Left ventricle/coronary artery
• Arch of aorta

Glossopharyngeal
- Carotid sinus

Question 13

Describe the pathway of the baroceptor reflex?

Answer 13

Baroceptors -> medulla -> ANS -> SA node

Question 14

Describe the effect of the baroreceptors in response to increased and decreased pressures?

Answer 14

Increased pressure => increased impulses => increased medullary stimulation => increased parasymp activity through vagus nerve => reduced HR through action on SAN => vasodilation

Decreased pressure => decreased impulses => decreased medullary stimulation => increased sympathetic activity through sympathetic chain => increased HR through SAN => increased contraction + vasoconstriction

Question 15

What is the long term control of blood pressure?

Answer 15

Osmoregulation

Pressure natriuresis

Renin-Angiotensin-Aldosterone system

Question 16

What are the three layers of the wall in larger blood vessels?

Answer 16

Tunica intima

Tunica media

Tunica adventitia

Question 17

Describe the tunica intima

Answer 17

A layer of flat endothelial cells overlying thin connective tissue

Endothelial cells in direct contact with blood

Seperated from the tunica media by the internal elastic lamina

Question 18

Describe the tunica media

Answer 18

A circular layer of smooth muscle containing elastin and collagen

Innervated by sympathetic nerve fibres

Provides mechanical strength to vessel

Question 19

Describe the tunica adventitia

Answer 19

Loosely formed layer of elastin and collagen fibres

Anchors blood vessel in place

Seperated from tunica media by the external elastic lamina

Question 20

What are the different types of blood vessels?

Answer 20

Elastic (Windkessel) arteries
- aorta, pulm artery, main branches of these

Muscular arteries
- large/medium arteries with high prop. of smooth muscle

Arterioles
- resistance vessels

Capillaries
- exchange vessels

Veins
- reservoir/capacitance vessels