control of heart rate Flashcards
why is the cardiac muscle myogenic?
can contract/relax without receiving signals from nerves but pattern controlled in regular heartbeat
describe how a heartbeat is initiated and coordinated
- SAN sends a wave of electrical impulses across atria causing atrial contraction
- non-conducting tissues prevents the immediate contraction of the ventricles.
- AVN delays impulse whilst blood leaves atria.
- AVN sends a wave of electrical impulses down bundle of His.
- causing ventricles to contract from the base up.
Name the two types of receptors in the heart
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
what is the coordinator of the heart?
medulla oblongata
what does an increase in the impulses to the SAN through the sympathetic and parasympathetic nervous system do to the heart rate?
S=increases heart rate
P=decreases heart rate
what does increasing the conc. of acetylcholine or noradrenaline do to the heart rate?
A=slower heart rate
N=faster heart rate
how does the heart respond to high blood pressure?
- 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
how does the heart respond to low blood pressure?
- 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
how does the heart respond to high blood O2/low CO2/high pH?
- 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
how does the heart respond to low blood O2/high CO2/low pH?
- 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