control of heart rate

Question 1

why is the cardiac muscle myogenic?

Answer 1

can contract/relax without receiving signals from nerves but pattern controlled in regular heartbeat

Question 2

describe how a heartbeat is initiated and coordinated

Answer 2

1. SAN sends a wave of electrical impulses across atria causing atrial contraction
2. non-conducting tissues prevents the immediate contraction of the ventricles.
3. AVN delays impulse whilst blood leaves atria.
4. AVN sends a wave of electrical impulses down bundle of His.
5. causing ventricles to contract from the base up.

Question 3

Name the two types of receptors in the heart

Answer 3

Baroreceptors-in aorta and carotid arteries detect changes in blood pressure
Chemoreceptors-in aorta, carotid arteries and medulla detects change in O2/CO2 conc. and pH of the blood

Question 4

what is the coordinator of the heart?

Answer 4

medulla oblongata

Question 5

what does an increase in the impulses to the SAN through the sympathetic and parasympathetic nervous system do to the heart rate?

Answer 5

S=increases heart rate

P=decreases heart rate

Question 6

what does increasing the conc. of acetylcholine or noradrenaline do to the heart rate?

Answer 6

A=slower heart rate

N=faster heart rate

Question 7

how does the heart respond to high blood pressure?

Answer 7

• baroreceptors in aorta detect increase and send impulses to the medulla
• increased impulses to the SAN via parasympathetic nerves
• release of ACh decreases impulses from SAN

Question 8

how does the heart respond to low blood pressure?

Answer 8

• baroreceptors in aorta detect decrease and send impulses to the medulla
• increased impulses to SAN via sympathetic nerves
• release of noradrenaline increases impulses from SAN/heart rate

Question 9

how does the heart respond to high blood O2/low CO2/high pH?

Answer 9

• chemoreceptors in aorta detect change and send impulses to the medulla
• increased impulses to SAN via parasympathetic nerves
• release of ACh decreases impulses from SAN/heart rate slows

Question 10

how does the heart respond to low blood O2/high CO2/low pH?

Answer 10

• chemoreceptors in aorta detect change and send impulses to the medulla
• increased impulses to SAN via sympathetic nerves
• release of noradrenaline increases impulses from SAN/faster heart rate