Cardiovascular [Heart Beat]

Question 1

What does a long plateau phase ensure?

Answer 1

Unidirectional excitation of the myocardium

Question 2

How long is a cardiac AP

Answer 2

0.3s

Question 3

Max and min membrane potential during cardiac AP

Answer 3

Max 20mV

Min -100mV

Question 4

Name the 3 parts of the ECG and what they represent

Answer 4

P wave: atrial depolarisation
QRS complex: onset of ventricular depolarisation.
T wave: ventricular repolarisation

Question 5

First 3 stages of ECG in correlation with atrial / ventricular contraction

Answer 5

1. Depol of atrial fibres —> Start of P wave.
2. Atrial contraction (after lump).
3. Depol of ventricular fibres —> QRS spike

Question 6

Last 3 stages of ECG in correlation with atrial / ventricular contraction (last QRS)

Answer 6

4. Ventricular contraction (line after spike).
5. Repol of ventricular fibres —> T wave (start of hump)
6. Ventricular relaxation (last line).

Question 7

3 types of nerves that go from CV centre to effectors and their functions

Answer 7

Para vagus: decrease HR.
Sym Cardiac accelerator: increase HR + contractility.
Sym vasomotor: vasoconstriction.

Question 8

What 3 things increase SV

Answer 8

Increased preload
Increased contractility
Decreased afterload

Question 9

What 3 things increase HR

Answer 9

Nervous system (low para high sym)
Chemicals (thyroid / catecholamine)
Other factors (personal, age)

Question 10

Location of cardiac centre

Answer 10

Medulla olongata

Question 11

Cause and result of decreased afterload

Answer 11

Decreased Blood pressure of artery during relaxation.

Semilunar valves open sooner when BP in aorta and pul artery is lower.