2- Cardiovascular system Heart2

Question 1

A cardiac action potential is initiated by..?

Answer 1

The autorhythmic fibres of the SA nodes

Question 2

An action potential in a contractile fibre is characterised by..?

Answer 2

Rapid depolarisation, an extended plateau, and then repolarisation

Question 3

What is an electrocardiogram (ECG)?

Answer 3

A recording of the electrical changes that accompany each cardiac cycle (heartbeat)

Question 4

In a Lead II record, what are the three clearly visible waves that accompany each heartbeat?

Answer 4

P wave: atrial depolarisation - spread of impulse from SA node over atria

QRS complex: ventricular depolarisation - spread of impulse through ventricles

T wave: ventricular repolarisation

Question 5

Name the three phases of a cardiac cycle

Answer 5

Atrial systole
Ventricular systole
Relaxation period

Question 6

What is the the end diastolic volume (EDV)?

Answer 6

The amount of blood (20-25ml) in the ventricles at the end of diastol

Question 7

Explain contraction of the ventricles in 3 stages

Answer 7

Isovolumetric contraction: AV and SL valves are all closed. Ventricular volume remains the same.​

Ventricular ejection: Pressure continues to rise opening the SL valves leading to ejection of blood from heart. ​

End Systolic Volume (ESV): The amount of blood in the left ventricle at the end of systole.

Question 8

Which is faster.. depolarisation or repolarisation?

Answer 8

depolarisation

Question 9

Explain the relaxation period in 3 stages

Answer 9

Ventricular diastole: ventricles are relaxed. Pressure in the ventricles fall and the SL valves close. At the same time, the atria are relaxed. ​

Isovolumetric relaxation: A brief time when all four valves are closed and ventricular blood volume does not change.​

Ventricular filling: Pressure in the ventricles continues to fall, so the AV valves open, and ventricular filling begins

Question 10

Name the steps in a cardiac cycle

Answer 10

1- P wave
2- QRS complex
3- T wave
4- Relaxation period

Question 11

How many BPM is normal?

Answer 11

75bpm

Question 12

End diastolic volume (EDV)​:

Answer 12

Volume in ventricle at end of diastole, about 130ml​

Question 13

End systolic volume (ESV)​:

Answer 13

Volume in ventricle at end of systole, about 60ml​

Question 14

Stroke volume (SV)​:

Answer 14

The volume of blood ejected per beat from each ventricle each contraction is about 70ml

Question 15

Cardiac output equals..?

Answer 15

the stroke volume multiplied by the heart rate: CO = SV x HR

Question 16

3 influences on stroke volume?

Answer 16

1- preload (more volume in=more forceful out)
2- contractility (calcium/potassium)
3- afterload (pressure buildup for a semilunar valve to open)

Question 17

CO = SV x HR

Answer 17

cardiac output = stroke volume x heart rate

Question 18

nervous control for the cardiovascular centre is where in the brain?

Answer 18

the medulla oblongata

Question 19

Hormones and ions that affect HR..?

Answer 19

Epinephrine, norepinephrine, thyroid hormones.

Cations (Na+, K+, Ca2+).