control of heart rate Flashcards
what is myogenic
contraction of heart is initiated within the muscle itself rather than by nerve impulses
state the name and location of the 2 nodes involved in heart contraction
SINOATRIAL NODE - within the wall of the right atrium
ATRIOVENTRICULAR NODE - near lower end of right atrium in the wall that separates the 2 atria
describe how heartbeats are initiated and coordinated
sinoatrial node initiates waves of electrical activity which travel down the heart
waves of electrical activity spread across both atria = atrial systole
layer of fibrous, non-conducting tissue delays impulse while ventricle fill and valves close
atrioventricular node conveys waves of electrical activity down septum via bundle of His, which branches into purkinje fibres along ventricles
causes ventricles to contract from apex upwards
formula for cardiac output
cardiac output = stroke volume x heart rate
what is the autonomic nervous system
system that controls involuntary actions of glands and muscles
2 subdivisions - sympathetic and parasympathetic
state the difference between the sympathetic and parasympathetic nervous system
sympathetic involved in fight or flight response - stimulates effectors to speed up activity
parasympathetic involved in normal resting conditions - inhibits effectors to slow down activity
name the receptors involved in changing heart rate and state their location
baroreceptors - detect changes in blood pressure - carotid body
chemoreceptors - detect changes in pH due to increase in CO2 concentration - carotid body and aortic body
how does the body respond to an increase in blood pressure
baroreceptors send more waves of electrical activity a to cardioinhibitory centre in the medulla oblongata
more waves of electrical activity to SAN down vagus nerve via parasympathetic nervous system
stimulates release of acetylcholine, which decreases heart rate
how does the body respond to a decrease in blood pressure
baroreceptors send more waves of electrical activity to cardioacceleratory centre in the medulla oblongata
more waves of electrical activity to SAN via sympathetic nervous system
stimulates release of noradrenaline, which increases heart rate and strength of contraction
how does the body respond to an increase in CO2 concentration
chemoreceptors detect pH decrease and send more waves of electrical activity to cardioacceleratory centre of medulla oblongata
more waves of electrical activity to SAN via sympathetic nervous system
heart rate increases, so rate of blood flow to lungs increases = rate of gas exchange and ventilation rate increases
sympathetic nerve
releases the neurotransmitter noradrenalin onto the heart surface
picked up by adrenergic receptors
causes the SAN to send out waves of electrical activity
heart rate increases
parasympathetic nerve
releases the neurotransmitter acetylcholine onto the heart surface
picked up by cholinergic receptors
causes the SAN to send out waves of electrical activity less often
heart rate decreases
