Unit 9- Heart

Question 1

What initiates the heart beat?

Answer 1

The sinoatrial node

Question 2

What is cardiac output?

Answer 2

Volume of blood flowing in a given time

Cardiac output=heart rate x stroke volume

Question 3

How can the CNS regulate cardiac output?

Answer 3

By controlling heart rate and stroke volume

Question 4

What controls the heart rate?

Answer 4

Part of the Medulla oblongata called the cardiac centre

Question 5

Brief summary of how the cardiac centre controls heart rate:

Answer 5

Cardiac centre sends an impulse to the SAN either through sympathetic or parasympathetic neurones

Question 6

What is the phrase linked to the sympathetic neurones

Answer 6

Fight or flight

Question 7

What is the phrase linked to the parasympathetic neurones?

Answer 7

Rest and digest

Question 8

What occurs in the sympathetic neurones to increase heart rate?

Answer 8

The sympathetic neurones release the neurotransmitter noradrenaline at SAN increasing the heart rate

Question 9

What occurs at parasympathetic neurones to slow down heart rate?

Answer 9

Parasympathetic neurones release neurotransmitter acetyl choline at SAN reducing heart rate

Question 10

Summary of what happens when there is a change in O2/CO2 levels in the blood?

Answer 10

Stimulus: O2 levels
Receptor: chemoreceptors in aortic and carotid bodies detect pH change
Coordinator: cardiac centre in medulla receives the impulse
Effector: SAN receives impulse through either parasympathetic or sympathetic nerve
Response: change in heart rate

Question 11

Summary of what happens when there is a change in blood pressure:

Answer 11

Stimulus: change in blood pressure
Receptors: baroreceptors in aortic or carotid bodies sense stretch
Coordinator: receives impulse at cardiac centre in the medulla
Effector: SAN receives impulse through sympathetic or parasympathetic nerve
Response: change in heart rate

Question 12

How is arterial blood pressure measured?

Answer 12

By stretch receptors (baroreceptors) in the wall of the aortic arch and walls of the carotid arteries

Question 13

How does a the body reduce a high blood pressure?

Answer 13

• artery walls are stretched at a high blood pressure so baroreceptors detect this
• baroreceptors send more frequent impulses through sensory neurone to cardiac centre
• cardiac centre sends impulses through parasympathetic nerve to SAN to reduce heart rate
• cardiac centre also sends impulses through parasympathetic neurones to arterioles to dilate
• this reduces blood pressure

Question 14

What is baroreflex?

Answer 14

When the body responds to a high blood pressure by slowing down the heart rate and dilating arterioles through the parasympathetic nerve to reduce blood pressure (homeostasis)

Question 15

How does the body measure the bloods pH?

Answer 15

Chemoreceptors in the aortic and carotid bodies

Question 16

When exercising the blood pH decreases, how does the body respond to this?

Answer 16

• Chemoreceptors in the aortic/carotid bodies detect the low pH
• high frequent impulses are sent to cardiac centre via sensory neurones
• cardiac centre sends impulses through the sympathetic nerve to SAN to increase heart rate
• cardiac centre also sends impulses through sympathetic nerve to arterioles to vasoconstrict, increasing blood pressure
• more oxygenated blood fills the heart in diastole to be pumped to the muscles, increasing the pH