Topic E - Cardiovascular system, cardiovascular diseases and the eye P1-2

Question 1

what are the 9 important components of the heart?

Answer 1

1. sup. vena cava
2. inf. vena cava
3. right atrium
4. right ventricles
5. pulmonary artery
6. pulmonary vein
7. left atrium
8. left ventricles
9. aorta

Question 2

what is the function of the cardiac conduction system?

Answer 2

It stimulates the heart to contract and sets the basic rhythm of heartbeat

Question 3

How do cardiac muscle cells work to bring about heart contraction?

Answer 3

• Cardiac muscle is auto-rhythmic, meaning it does not
need to be stimulated by the brain to contract

• The cardiac muscle cells initiate and carry the electrical impulses as part of the conduction system that stimulates heart contraction

• Nerve impulses are not needed to initiate a heart
contraction

Question 4

what are the 5 Components of the Cardiac Conduction System?

Answer 4

1. SA node
2. AV node
3. AV bundle
4. bundle branches
5. purkinje fibres

Question 5

What is ECG (electrocardiogram)? what do the P wave, QRS complex and T wave represent?

Answer 5

A graph showing the electrical activity in the heart

• P wave – shows atrium depolarization (contract)
• Q, R, S waves/complex – represents ventricular
depolarizing (contract)
• T wave – represents ventricular repolarizing (relax)

Question 6

what are the 4 phases of the cardiac cycle? briefly describe what happens in each cycle.

Answer 6

1. Atrial systole – atrium contract &
   depolarize, Blood push into ventricles.
2. Ventricular diastole – ventricle
   relax & repolarize, Blood flow from
   atrium to ventricle passively
3. Atrial diastole – relax & repolarize,
   blood flow back to atrium.
4. Ventricular systole– contract &
   depolarize. Blood pump out & pushed
   through the pulmonary & aortic valves
   into pulmonary trunk & aorta.

**When atrium contract, ventricle relax and vice versa
Contract=depolarize
Relax=repolarize

Question 7

what is the avg heart rate? What are the terms used for too fast and too slow heart rates?

Answer 7

75 bpm
(males and athletes have lower heart rate than females)

too fast: tachycardia
too slow: bradycardia

Question 8

What does the lub dup sound correspond to?

Answer 8

Lubb (S1) – closure of mitral & tricuspid valves

Dupp (S2) – closure of pulmonary & aortic valves

**The pause corresponds to the heart beats/heart
rate

Question 9

What is cardiac output and how is it calculated? what is the norm?

Answer 9

Cardiac Output (CO) = amount of blood pumped by each ventricle of the heart in one minute
CO = (heart rate [HR]) x (stroke volume [SV])

e.g CO = 75 beats/min x 70ml/beat = 5,250 ml/min

**Stroke volume = volume of blood pumped by each ventricle in one contraction

Normal CO ~ 4-6 litres/min

Question 10

How is heart rate (HR) regulated?

Answer 10

• Primarily regulated by the autonomic nervous system:
the cardiac control center (CCC) in the brain

• It has sympathetic & parasympathetic components

• Sympathetic: impulses transmit to heart – increase HR
• Parasympathetic: impulse transmit away from heart –
decrease HR
• The CCC – regulate the impulses and control the HR

Question 11

Why the heart does not fatigue?

Answer 11

• Cardiac muscle cells has the following adaptations
the enable them to use aerobic respiration almost
exclusively:-

• 1. have many very large mitochondria to perform
aerobic respiration.

• 2. rich in myoglobin (protein for storing oxygen)

• 3. rich in glycogen (a starch that can be converted
to glucose to be used as fuel)

• 4. can use a variety of fuels as energy source
(glucose, fatty acids, amino acids, and ketones).