Topic 7B : Exercise Flashcards
state the name and location of the two 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 two atria
cardiac muscle as myogenic
it can contract and relax without receiving signals from neuroens
explain how heartbeats are initiated and coordinated
SAN sets the rhythm of the heartbeat by sending out regular waves of electrical activity to the atrial walls causing both atria to contract at the same time.
A band of non conducting collagen tissues prevents the waves of electrical impulses being passed directly from the atria to the ventricles so the eaves are transferred from SAN to AVN instead.
AVN passes waves of electrical activity to the bundle of his, but there is a slight delay before AVN reacts to make sure ventricles contract after the atria have emptied.
the bundle of his is a group of muscle fibres responsible for conducting the waves of electrical activity to the finer muscle fibres in the right and left ventricles walls called purkyne fibres.
they carry out the waves of electrical activity into muscular walls of the right and left ventricles causing them to contract simultaneously from the bottom up.
electrocardiograph
a machine that records the electrical activity of the heart
formula for cardiac output
stroke volume (V) x heart rate (R)
tachycardia
heartbeat too fast (120 beats per minute)
its okay during exercise but at rest it shows that the heart is not pumping blood efficiently.
bradycardia
heartbeat too slow (60 beats per minute) at rest
ectopic heartbeat
extra heartbeat caused by earlier contraction of atria or ventricles than in previous heartbeats
fibrillation
irregular heartbeat due to atria/ventricles completely loosing their rhythm and stop contracting properly.
it can result in anything from chest pain and fainting to lack of pulse and death.
what happens to your heart and breathing rate when you exercise
heart rate increases to deliver oxygen and glucose to the muscles faster and remove extra carbon dioxide produced by increased rate of respiration in the muscle cells.
breathing rate increases to obtain more oxygen and to get rid of more carbon dioxide.
what controls rate of breathing in medulla oblongata
two ventilation centres called inspiratory and the expiratory
how does the inspiratory centre control breathing rate
inspiratory centre in medulla oblongata sends nerve impulses to the intercostal and diaphragm muscles to make them contract.
this increases the volume of the lungs lowering the pressure in the lungs.
air enters the lungs due to pressure differences between lungs and outside.
as lungs inflate, stretch receptors in the lungs are stimulated, stretch receptors send nerve impulses back to medulla oblongata which inhibit the action of the inspiratory centre.
how does the expiratory centre control breathing rate
it sends impulses to the diaphragm and intercostal muscles to relax which causes lungs to deflate expelling air.
stretch receptors become inactive
inspiratory centre is not longer inhibited so cycle starts again.
how does exercise trigger an increase in breathing rate by decreasing blood pH
level of carbon dioxide in blood increases which decreases blood pH.
chemoreceptors in medulla oblongata, apetic bodies and carotid bodies are sensitive to changes in blood pH.
if chemoreceptors detect decrease in blood pH they send nerve impulses to medulla oblongata which sends more frequent nerve impulses to the intercostal muscles and diaphragm and this increases the rate and depth of breathing.
this causes gaseous exchange to speed up, carbon dioxide level drops and extra carbon dioxide is supplied for muscles and the pH returns to normal and breathing rate decreases.
aortic bodies
clusters of cells in the aorta
carotid bodies
clusters of cells in the carotid arteries
carotid artery
carries blood to brain
ventilation rate
volume of air breathed in or out in a period of time eg a minute
how does exercise affect ventilation rate
it increases because breathing rate and depth increase
baroreceptors
pressure receptors in the aortic and carotid bodies which are stimulated by high and low blood pressure.
what effect do neurotransmitters released from sympathetic neurones have on heart rate
they get the body ready for action and increase the heart rate during exercise
what effect do neurotransmitters released from parasympathetic neurones have on heart rate
they calm the body down and decrease the heart rate after exercise
stroke volume
volume of blood pumped by one ventricle each time it contracts
cardiac output
total volume of blood pumped by a ventricle every minute
how does the heart responds to high blood pressure
baroreceptors detect high blood pressure
impulses are send to cardiovascular control centre which sends impulses along parasympathetic neurones which secrete acetylcholine that would bind to receptors on the SAN.
the SAN fires impulses less frequently to slow heart rate and reduce blood pressure back to normal
how does the heart responds to low blood pressure
baroreceptors detect low blood pressure
impulses sent to cardiovascular control centre which sends impulses along sympathetic neurones which secrete noradrenaline that would bind on receptors of SAN.
the SAN fires impulses more frequently to increase heart rate and bring blood pressure back to normal.
how does the heart respond to high blood oxygen, low carbon dioxide or high pH levels
chemoreceptors detect chemical changes in the blood.
impulses are sent to the cardiovascular control centre which sends impulses along parasympathetic neurones which secrete acetylcholine that binds to receptors on SAN.
SAN fires impulses less frequently to decrease heart rate and return all of these to normal levels.
