the heart
the heart consists of two muscular pumps
what the different parts do
the cardiac cycle pumps blood around the body
control of heart rate involves the brain and nervous system
cardiac muscle controls the regular heart beat
right side = deoxygenated blood to lungs
left side = oxygenated blood to body
left ventricle = thicker
needs to pump blood all around body
ventricles = thicker than atria
have to push blood from heart to body
atrioventricualr (AV) valves link the atria to ventricles
this prevents backflow
semi-lunar (SL) valves link ventricles to the pulmonary artery and aorta
prevent backflow after ventricle contraction
it is a sequence of contraction and relaxation
the volume of the atria and ventricles change as they contract/relax
3 stages of cardiac cycle
1) ventricles relax, atria contract
2) ventricles contract, atria relax
3) ventricles relax, atria relax
ventricular pressure increases
AV valves shut, SL valves open
SL valves shut, atria begin to fill again
cardiac muscle is myogenic
can contract/relax without signals from nerves
process begins in sinoatrial node (SAN)
in the wall of right atrium
SAN acts like pacemaker
sends elecrical waves to atrial walls
causes atria to contract at same time
non-coding collagen tissue prevents waves being passes from atria to ventricles
electrical activity transferred to AV node
then AV node passes electrical activity to the bundle of His
bundle of His = muscle fibres
conducts waves between ventricles and bottom of heart
split into finer fibres called purkyne tissue
they cause ventricle walls to contract
SAN generates electrical impulses
causes cardiac muscles to contract
rate of fire controlled by medulla oblongata
stimuli are detected by pressure and chemical receptors
pressure receptors = baroreceptors
in the aorta and carotid arteries
stimulated by high\low pressure
chemical receptors = chemoreceptors
in the aorta, carotid arteries and medulla
measure blood oxygen levels