The heart Flashcards
the autonomic nervous system controls involuntary activities of
internal muscles and glands
function of the sympathetic nervous system
stimulates effects and so speeds up activity
it heightens our awareness and preparing us for activity flight or flight
function of parasympathetic nervous system
inhibits effectors and slows down any activity
controls activities under normal resting conditions
what does it mean when it says the cardiac muscle is myogenic
it can contract and relax without receiving signals from the nervous system
function of the SAN
sends out regular waves of electrical activity to the left and right atrial wall causing contraction
when an electrical wave is sent from SAN where is it then passed on to
AVN then to the bundle of His with a slight delay. The bundle of his splits into the purine tissue causing contraction of the left and right ventricles
changes to the heart rate are controlled by a region of the brain called the
medulla oblongata
a centre that increases heart rate
sympathetic nervous system
a centre that decrease heart rate
parasympathetic nervous system
where are chemoreceptors found
wall of carotid arteries
chemoreceptors are sensitive to the changes in ph of blood this may result in
changes in CO2 Conc.
when wave of electrical activity reaches AVN there is a short delay before a new wave leaves AVN. Explain importance of this short delay
it allows atria to empty and ventricle to fill before ventricle contacts
describe how a heartbeat is initiated and coordinated (5M)
SAN sends wave of electrical activity/ impulse across atria causing atrial contraction
non conducting tissues prevent immediate contraction of ventricles
AVN delays (impulse) whilst blood leaves atria
AVN sends wave of electrical activity down bundle of His
causing ventricle o contract
explain how the heart muscle and the heart valve maintain a one-way flow of blood from the left atrium to the aorta (5M)
atrium has higher than ventricle due to contraction
causing atrioventricular valves to open
ventricle has higher pressure than atrium due to contraction causing atrioventricular valve to close
ventricle has higher pressure than aorta causing semilunar valve to open
higher pressure in aorta than ventricle causing semilunar valve to close
muscle contraction causes increase in pressure
how the nervous control in a human can cause increased cardiac output during exercise
coordination via medulla
increased impulses along sympathetic nerve
increased heart rate/ increased stroke volume
more impulses sent from the sinoatrial node
