CNS And Hormonal Control Of The Heart

Question 1

Sympathetic system

Answer 1

A part of the autonomic nervous system that speeds up the heart rate

Question 2

Parasympathetic system

Answer 2

A part of the autonomic nervous system that decreases the heart rate

Question 3

Medulla oblongata

Answer 3

The most important part of the brain as it regulates processes that keep us alive such as breathing and heart rate

Question 4

How does the sympathetic nervous system speed up the heart?

Answer 4

-Increases HR by releasing adrenaline.

-Adrenaline increases the strength of ventricular contraction which then increases stroke volume

-Noradrenaline aids the spread of electrical impulse throughout the heart increasing HR.

-Increased metabolic activity causes increased concentration of CO2 and lactic acid, decreasing pH of blood.

-These changes are picked up by chemoreceptors and inform the sympathetic centre to increase HR to flush out the waste products.

-This results in an INCREASED CARDIAC OUTPUT.

Question 5

How does the parasympathetic nervous system slow down the heart?

Answer 5

-Releases acetylcholine which slows the spread of impulses throughout the heart.

-This results in lower a heart rate!

Question 6

What do chemoreceptors sense?

Answer 6

-Increase in CO2 levels

-Increase in heart rate

Question 7

What do baroreceptors sense?

Answer 7

-Increase in blood pressure

-Decrease in heart rate

Question 8

What do proprioceptors sense?

Answer 8

-Increase in muscle movement

-Increase in heart rate

Question 9

What does hormonal control mechanism do?

Answer 9

-Hormones can also have an effect on heart rate

-The release of adrenaline during exercise is known as hormonal control

-Adrenaline is a stress hormone that is release by sympathetic nerves and cardiac nerve during exercise.

-This stimulates the SAN (pacemaker) which increases the speed and force of contraction in the heart

-Therefore increasing cardiac output allowing more oxygenated blood being pumped to the muscles for the energy they need to work.

Question 10

What is adrenaline?

Answer 10

Adrenaline is a stress hormone that is released by the sympathetic nerves and cardiac nerves during exercise which causes and increased heart rate

Question 11

What is stroke volume?

Answer 11

The volume of blood pumped out by the heart ventricles in each contraction

Question 12

What is the diastole phase?

Answer 12

When the heart relaxes to fill with blood

Question 13

What is ejection fraction?

Answer 13

The percentage of blood pumped out by the
left ventricle per beat

Question 14

What is the neural control mechanism?

Answer 14

The mechanism which involves the sympathetic nervous system which stimulates the heart to beat faster, and the parasympathetic nervous system which returns the heart to the resting level

Question 15

What is the cardiac conduction system?

Answer 15

A network of specialised muscle cells found in the heart’s walls. These muscle cells send signals to the rest of the heart muscle causing contraction

Question 16

What are the 4 steps to the cardiac conduction system?

Answer 16

1. Impulse generation which is when the SA node contracts generating nerve implodes that travel through the heart wall, causing both atria to contract
2. AV node impulse conduction which is when the impulses from the SA node reach the AV node being delayed for a 10th of a second which will allow the atria to contract and empty out their contents into ventricles prior to ventricle contraction

3.AV bundle impulse conduction which allows impulses to be sent down the atrioventricular bundle allowing bundle of branches off into two bundles and the impulses are carried down the left and right ventricles

4.Purkinje fibres impulse conduction which is when the atrioventricular bundles start to divide further into purkinje fibres, meaning when the impulses reaches the fibres they trigger the muscle fibres in ventricles to contract allowing the right ventricle to send blood to the lungs and the left ventricle pumping blood to the aorta