Control of the Heart Rate Flashcards
1
Q
define myogenic
A
- a muscle that can beat with it own rhythm (without an external impulse)
2
Q
describe how a heartbeat is initiated and coordinated
A
- the SAN in the wall of the right atrium sends impulses through the walls of the atria causing them to contract
- the impulses reach the AVN between the atria and ventricles however don’t pass directly to the ventricles as they are blocked by a layer of non-conducting collagen tissue
- this causes a delay of 0.15 seconds allowing the atria to fully empty
- impulses are then sent from the AVN through the Purkyne tissue in the Bundle of His to all parts of the ventricles
- the ventricles are stimulated to contract together from the base upwards to push blood up and out into the arteries
3
Q
how is heartrate increased by the nervous system
A
- heart rate is sped up by the medulla sending more impulses along sympathetic neurones to the SAN (noradrenaline is released by sympathetic neurones which stimulates the SAN)
4
Q
how is heartrate decreased by the nervous system
A
- heart rate is slowed down by the medulla sending more impulses along parasympathetic neurones to the SAN (acetylcholine is released by parasympathetic neurones which inhibits the SAN)
5
Q
how is a high blood pressure detected and returned to normal
A
- increase in blood pressure is detected by baroreceptors in the wall of the aorta and carotid artery
- baroreceptors send more impulses to the cardiac centre in the medulla and therefore more impulses are sent from the cc along parasympathetic neurones to the SAN causing a decrease in heart rate
6
Q
how is a change in blood pH detected and returned to normal
A
- decrease in the pH is detected by chemoreceptors in the aortic and carotid bodies
- chemoreceptors in the aortic and carotid bodies transmit more impulses to the cardiac centre in the medulla and therefore more impulses are sent from the cc to the SAN along the sympathetic neuron causing an increase in heart rate (to remove carbonic acid quicker)
