Respoding To Change

Question 1

What is the role of the SAN? and where is it found?

Answer 1

Found in the right atrium
Acts as a pace maker
Releases waves of depolarisation to cause contraction in the atria.

Question 2

What is the role of the AVN?

Answer 2

Electrical impulses arrive at the AVN which delays the impulse so atria can fully contract and empty. The AVN then passes the electrical impulse to the bundle of His which conducts waves between ventricles to the purkyne tissue contracting the ventricles simultaneously.

Question 3

What does the medulla oblongata control the HR by?

Answer 3

Autonomic nervous system

Question 4

If the HR decreases is it the sympathetic or parasympathetic nervous system?

Answer 4

Parasympathetic

Question 5

What do chemoreceptors detect?

Answer 5

Changes in pH

Question 6

Describe what happens when pH is too high. (Low CO2)

Answer 6

Chemoreceptors detect change in pH
Send impulses along sensory neurone to medulla oblongata
The medulla then sends impulses along the parasympathetic nervous system.
Neurotransmitter is then released which binds to receptors on SAN causing it to decrease the rate at which it sends impulses - cardiac muscle contracts less frequently
Decreasing the HR

Question 7

What do the baroreceptors detect?

Answer 7

Changes in blood pressure

Question 8

Describe what happens when blood pressure is too low.

Answer 8

Baroreceptors in the aorta detect low blood pressure
Impulses sent along a sensory neurone to medulla oblongata which sends impulses along sympathetic nervous system to SAN
More frequent impulses sent from SAN - cardiac muscle contracts more frequently
HR increases