Cardiovascular system

Question 1

Name the valve between right atrium and right ventricle

Answer 1

Tricuspid valve (AV)

Question 2

Name the valve between the left atrium and left ventricle

Answer 2

Mitral / bicuspid

Question 3

Name the two valves between right and left ventricles and the respective veins/arteries

Answer 3

Pulmonary semilunar valve RHS

Aortic semilunar valve LHS

Question 4

Two types of cardiac myocytes

Answer 4

Contractile (majority)

Autorhythmic (pacemaker)

Question 5

Describe action potentia in myocardic cells

Answer 5

4. Relaxed cells
5. Depolarization due to entering of Na ions arrives at threshold
6. Na channels close and instead Potassium voltage gated channels open up causing a brief repolarization
7. Voltage gated calcium channels open up . They tend to depolarize the cell but the potassium ones are still open so the two ions balance out to give a stable line called plateau.
8. Calcium channels close and just potassium channels are open. This results in a depolarization of the cell back to the normal relaxed state in stage 4.

Question 6

Explain why refractory period in cardiac myocytes is longer than muscles

Answer 6

Because the myocytes need to be fully relaxed before undergoing another contraction otherwise we would have muscle twitches which are a result of summation of contractions

Question 7

Explain process of propagation of electrical conduction in the heart

Answer 7

1. Sinoatrial node depolarizes
2. Electrical activity spreads rapidly to Atrioventricular node via the internodal pathways
3. Depolarization spreads across the atria leading to their contraction
4. Depolarization spreads rapidly through the Bundle of His which branches in two
5. Electrical signal finally arrives at Purkinje Fibres which go upwards and surround the ventricles

Question 8

ECG Waves

Answer 8

1. P wave ( depol. of atria)
2. QRS comples (depol. of ventricles)
3. T wave ( repo. of ventricles)

Question 9

What is Diastole?

Answer 9

Time during when cardiac muscle relaxes and the chamber fills with blood

Question 10

What is systole ?

Answer 10

Time during when cardiac muscle contracts and blood is pushed out of the chamber

Question 11

What is the End Diastolic Volume? (EDV)

Answer 11

Maximum volume of blood left in a ventricle at the end of contraction

Question 12

What is the End Systolic Volume?

Answer 12

Amount of blood left in the ventricle after contraction

Question 13

What is the Stroke volume?

Answer 13

Amount of blood pumped by one ventricle during one contraction

Question 14

What are perycites?

Answer 14

Contractile cells around capillaries

Question 15

What are capillaries made of?

Answer 15

Endothelium layer one cell thick supported on basal lamina (ECM)

Question 16

Do capillaries contain muscle?

Answer 16

No

Question 17

What are precapillary sphincters?

Answer 17

Muscles with a ring-like structure that surround metaarterioles and control if blood has to go into capillary bed (open) or go straight to venous circulation(closed)

Question 18

What are metarterioles?

Answer 18

Branches of arterioles

Question 19

What 3 forces help venous return?

Answer 19

1. Muscoloskeletal pump
2. Respiratory pump (inspiration)
3. Constriction of veins by sympathetic activity

Question 20

Formula for Mean Arterial Pressure

Answer 20

diastolic pressure + 1/3 (systolic- diastolic)

Question 21

What part of the brain controls blood pressure?

Answer 21

The CardioVascular Control Centre (CVCC) in Medulla oblongata

Question 22

What are baroreceptors and where are they located

Answer 22

Baroreceptors are stretch receptors located in the walls of carotid arteries and aorta. They continously trigger action potentials and when pressure changes, they increase or decrease the frequency. Response within two heartbeats.

Question 23

What does atherosclerosis lead to ?

Answer 23

• Ischaemic heart disease
• Angina pectoris
• Myocardial infarction
• Stroke

Question 24

What type of cholesterol causes atherosclerosis?

Answer 24

LDL (low density lipoprotein) because cells in the endothelium of arteries have receptors for it so they can intake it. Whereas they don’t have receptors for HDL so it doesn’t accumulate in arteries.

Question 25

Phases of atherosclerosis

Answer 25

1. NORMAL ARTERIAL WALL
2. FATTY STREAK ( LDL accumulates in ecs between endothelium and connective tissue. Eaten up by macrophages which become lipid filled foam cells. Cytokines from macrophages make smooth muscle cells migrate to lipid deposit.
3. STABLE FIBROUS PLAQUE : Fibrous scar tissue forms to wall the lipid core. Muscle cells thicken the arterial wall. Dying muscle cells become calcified
4. VULNERABLE PLAQUE: enzymes released by macrophages make the fibrous wall more thin till it eventually ruptures exposing collagen to platelets and giving rise to blood clot.

Question 26

What is Angina Pectoris?

Answer 26

Blood clot that block blood flow in the arteries. Cells switch to anaerobic metabolism which creates lactic acid that leads to chest pain.

Question 27

Congestive heart failure

Answer 27

When one half of the heart works more than the other so the other tries to compensate. Congestive because of accumulation of liquid in the lungs (pulmonary edema) because capillary filtration exceeds the capacity of the lymph system to drain liquids out of the lungs.

Question 28

What causes Mitral stenosis and what is it?

Answer 28

• Rheumatic fever
• Mitral valve becomes calcified and thickened: blood leaks from left atrium to left ventricle. Left ventricle pressure increases and so hypertension in lungs: left ventricle increases to compensate for lungs hypertension