3.6.1.3. control of heart rate

Question 1

what does myogenic mean?

Answer 1

can contract and relax without recieving electrical impulses from the nerves.

Question 2

Describe myogenic stimulation of the heart.

Answer 2

1.) sinoatrial nerve (SAN/pacemaker) releases regular waves of electrical activity across atria causing atria to contract
2.) non conducting tissue between atria & ventricles prevent impulse passing directly into ventricles.
3.) Waves of electrical activity reaches AVN which delays impulse allowing atria to fully contract and empty before ventricles contract.
4.) AVN sends wave of electrical activity down Bundle of His, conducting wave between ventricles to apex where it branches to purkyne tissue causing ventricles to contract simultaneously from base up.

Question 3

where are chemoreceptors and pressure receptors located?

Answer 3

aorta and carotid arteries.

Question 4

how do baroreceptors and chemoreceptors increase in heart rate.

Answer 4

baroreceptors detect the fall in blood pressure.
chemoreceptors detect the rise in blood CO2 conc or fall in blood ph.
Send impulses to cardiac control centre in medulla.
which send more frequent impulses to SAN along sympathetic neurones . (para= parachute, slows heart rate)
so more/ less frequent impulses are sent from SAN to AVN
Cardiac muscle contracts more/less
heart rate increases/ decreases.

Question 5

how do baroreceptors and chemoreceptors decrease the heart rate

Answer 5

1. baroreceptors detect rise in blood pressure and chemoreceptors detect fall in blood co2 or rise in blood ph.
2. sends impulses to cardiac control centre in the medulla.
3. which sends more frequent impulses to SAN along parasympathetic neurones
4. so less frequent impulses from SAN
   so heart rate decreases.

Question 6

what do sympathetic nerves in the autonomic nervous system do?

Answer 6

sympathetic nerves increase heart rate

Question 7

what do parasympathetic nerves do in autonomic nervous system.

Answer 7

parasympathetic nerves decrease heart rate