Control of heartrate Flashcards
what does the cardiac muscle being myogenic mean?
it contracts on its own, but the rate of contraction is controlled by a wave of electrical activity
where is the SAN located?
the right atrium
what does SAN stand for?
sinoatrial node
what is the SAN?
a tissue which can release a wave of electricity, to act as a pacemaker. when this hits the cardiac muscle, it causes contraction
what does AVN stand for?
atrioventricular node
where is the AVN located?
in between the right and left ventricle, whilst still in the atria
what is the bundle of His?
conductive tissues
where is the bundle of His located?
running through the septum
where are the purkyne fibres located?
walls of the ventricles
explain the process of controlling the heart (6)
-SAN releases a wave of depolarisation across the atria, causing contraction.
-AVN releases a wave of depolarisation, but this doesn’t travel to the ventricles due to a non-conductive layer.
-instead, the bundle of His conducts and passes the wave of depolarisation down the septum and purkyne fibres in the ventricle walls.
-as a result, the apex then the ventricle walls contract. there is a short delay before this whilst the AVN transmits the second wave.
-this allows time to pump all blood into the ventricles, so they are full. the cells then repolarise and the cardiac muscle relaxes.
what part of the brain controls heart rate and via what part of the nervous system?
the medulla oblongata, via the autonomic nervous system
what are the 2 parts of controlling heart rate?
-the centre linked to the SAN which increases heart rate via the sympathetic nervous system
-the centre that decreases heart rate vis the parasympathetic nervous system
what are the receptors to pH called?
chemoreceptors
what are the receptors to blood pressure called?
baroreceptors
where are chemoreceptors and baroreceptors located?
the aorta and carotid artery
what can happen if blood pressure is too high or too low?
artery walls may be damaged or there could be insufficient oxygen supplied to respiring cells
what happens to pH and heart rate when there’s a high respiratory rate?
pH will decrease in the blood due to CO2 or lactic acid production. excess acid is removed so that enzymes won’t denature. this is achieved by an increased heart rate, so that CO2 diffuses out the alveoli quicker.
describe the process when increased blood pressure is detected
the stimulus of increased pressure is detected by baroreceptors in the wall of the aorta and carotid artery, which are stretched due to high pressure.
more electrical impulses get sent to the medulla oblongata, which are then sent to the parasympathetic nervous system to the SAN to decrease the frequency.
the cardiac muscle and SAN tissues then reduce the heart rate.
describe the process when decreased blood pressure is detected
the stimulus of decreased pressure is detected by baroreceptors in the wall of the aorta and carotid artery, which are not stretched due to low pressure.
more electrical impulses get sent to the medulla oblongata, which are then sent to the sympathetic nervous system to the SAN to increase the frequency.
the cardiac muscle and SAN tissues then increase the heart rate.
describe the process when decreased pH is detected
the stimulus of decreased pH is detected by the chemoreceptors in the walls of the aorta and carotid artery.
more electrical impulses are sent to the medulla oblongata, which are then sent via the sympathetic nervous system to the SAN to increase the frequency.
the cardiac muscle and SAN tissues then increase the heart rate to deliver blood to the lungs rapidly to remove CO2.
describe the process when increased pH is detected
the stimulus of increased pH is detected by the chemoreceptors in the walls of the aorta and carotid artery.
more electrical impulses are sent to the medulla oblongata, which are then sent via the parasympathetic nervous system to the SAN to decrease the frequency.
the cardiac muscle and SAN tissues then decrease the heart rate.
