heart

Question 1

Explain how atrioventricular valve in the left atrium maintains a unidirectional flow of blood.

Answer 1

when the left atrium pressure is higher than the left ventricle the valves open
when the left ventricle pressure is HIGHER than the left atrium the ventricles shut

Question 2

Exercise causes an increase in heart rate.
Describe the role of receptors and of the nervous system in this process.

Answer 2

Chemoreceptors detect / fall in pH
Send more impulses to medulla;
sends more impulses to SAN via sympathetic nervous system

Question 3

When the heart beats, both ventricles contract at the same time.
Explain how this is coordinated in the heart after initiation of the heartbeat
by the SAN.

Answer 3

Electrical activity only through Bundle of His / AVN;
Wave of electrical activity passes over / through both ventricles at the
same time;

Question 4

Damage to the myelin sheath of neurones can cause muscular paralysis

Answer 4

less saltatory conduction
2. (Nerve) impulses slowed/stopped;
1. Slower/fewer impulse(s) along sympathetic/parasympathetic

(pathway/neurones);

Question 5

(b) Sometimes Guillain–Barré syndrome causes heart rate irregularities

Answer 5

(b) 1. Slower/fewer impulse(s) along sympathetic/parasympathetic
(Impulses) from medulla;
3. To SAN;