Cardiac Output Flashcards
what is cardiac output, CO
the RATE at which a ventricle pumps blood out (L/min)
what is heart rate
the NUMBER of contractions per min
what is the equation for CO
CO= HR X SV
what affects CO
intrinsic (affecting SV)= ventricular contractility, EDV, ESV, afterload
extrinsic (affecting HR)= hormones, autonomic innervation
where is the autonomic headquarter for cardiac control
medulla oblongata
what cardiac structures/ tissues do the para/symp divisions of the autonomic nervous system innervate
- SAN/ AVN
- atrial muscle cells
- ventricular muscle cells
what is another word for parasympathetic fibres and why
cranio-sacral
they are innervated by cranial nerves 3,7,9,10
why is another word for sympathetic fibres and why
thoracolumbar
ganglia are located on either side of spine
describe the effect of parasympathetic activity on the HR
parasympathetic neurones release Ach, opens chemically gated Na+ channels, decrease rate of depolarisation, increase length of repolarisation= decrease HR
describe the effect of sympathetic activity on the HR
sympathetic neurones release NE, bind to beta 1 receptors, open na/cl ion channels, influx of +ve ions, decrease rate of depolarisation, shorten length of repolarisation= increase HR
what is the affect of parasympathetic activity on the conducting system
decrease SPEED OF CONDUCTION, ventricles contract a longer while after atria contract, systole is longer
what is the affect of sympathetic activity on the conducting system
increase the SPEED OF CONDUCTION, ventricles contract ASAP after atria, systole is shorter
which hormones affect the HR
adrenaline
thyroid hormones: insulin, glucagon
what is the affect of adrenaline on the HR
increase HR because….
- increases AP at SAN
- increases speed/ velocity of AP since its linked with sympathetic NS
what is the affect of the thyroid hormones on the HR
increase HR because…
- increase the force of contraction
what factors are affecting the HR
autonomic nervous system (para/sympathetic nerve fibres)
hormones (adrenaline and thyroid hormones)
what factors affect the SV
ventricular contractility
EDV
afterload
what is ventricular contractility
how forcefully the ventricle contracts
what is afterload
the pressure the ventricle is contracting against (atrial pressure)
which factors influence ventricular contractility
- adrenaline
- sympathetic NS
- Ca2+ (linked with sympathetic NS stimulating alpha/beta receptors of cardiac cell membrane)
which factors influence EDV
starlings law of heart
what is the starling’s law of heart
when the RATE of which blood flows INTO the heart from the veins changes, the heart automatically ADJUSTS its OUTPUT to match INFLOW
(adjust the SV, so that CO matches the venous return)
what are the affects of a high EDV on the cardiac muscle cell
- increase in troponin affinity for ca2+, increases cross-bridges
- a high EDV increases the length of cardiac muscle cells to optimum length for contraction
what is the affect of sympathetic activity on the starlings curve
moves upwards, at any EDV
what influences the EDV
pre-load aka end-diastolic-pressure
EDV is directly proportional to pre-load
what is pre-load/ end-diastolic pressure
the pressure of blood inside the heart before a contraction
which determines the pre-load/ end - diastolic pressure
- filling time
- atrial pressure (which is determined by atrial contraction, venous return)
