Control of Heart Rate

Question 1

What does ‘myogenic’ cardiac muscle mean?

Answer 1

Cardiac muscle contracts/relaxes without receiving electrical impulses from nerves

Question 2

Where is the sinoatrial node found and what does it do to the atria?

Answer 2

A group of cells in the right atrium that initiate a wave of depolarisation and cause the atria to contract. Acts as a pacemaker.

Question 3

How are electrical impulses prevented from passing from atria to ventricles.
What does this prevent from happening in the ventricles?

Answer 3

Non conducting tissue stops conduction of the electrical impulse.
This prevents immediate contraction of the ventricles.

Question 4

4

In the atria, where do electrical impulses now reach after being prevented from being transmitted by non conducting tissue? What happens to the impulse?
What does this structure cause the atria to do before the ventricles contract?

Answer 4

The atrioventricular node (AVN) which delays the electrical impulse.
It allows atria to fully contract and empty before the ventricles contract.

Question 5

What is the bundle of his?

Answer 5

Muscle tissue connecting the atria and ventricles.

Question 6

After the impulse has reached the AVN, where does it travel down?

Answer 6

The bundle of his.

Question 7

The bundle of his carries electrical impulses to which part of the heart?

Answer 7

Ventricles

Question 8

The bundle of his extends to which tissue?

Answer 8

Purkyne tissue.

Question 9

Electrical impulses now in the Purkyne tissue now cause which part of the heart to contract?

Answer 9

Ventricles.

Question 10

What are chemoreceptors?
Give an example of what chemoreceptors might detect.

Answer 10

Nerve cells that detect changes in the chemical composition of the blood.
For example, they detect changes in pH caused by CO2 concentrations.

Question 11

What are pressure receptors?

Answer 11

Receptors in the heart that detect a change in blood volume and pressure as it is returned to the heart.

Question 12

The medulla oblongata in the brain controls heart rate via which part of the nervous system?

Answer 12

Autonomic.

Question 13

How does the parasympathetic nervous system affect heart rate?

Answer 13

Decreases heart rate.

Question 14

How does the sympathetic nervous system affect heart rate?

Answer 14

Increases heart rate.

Question 15

Where are pressure and chemo receptors located? (2 arteries).

Answer 15

In the aorta and carotid arteries

Question 16

If blood pressure rises or falls, or if blood PH rises or falls, impulses are sent to where?

Answer 16

The cardiac control centre (in the medulla).

Question 17

In response to changes in blood pH or pressure, what does the cardiac control centre do to counter this?

Answer 17

It sends more frequent impulses to the SAN via the parasympathetic or sympathetic nervous system (depending on whether the change led to a rise or fall), which causes cardiac muscle to contract more or less frequently.

Question 18

Changes in blood pressure or pH ultimately lead to changes in…

Answer 18

Heart rate.