negative feedback control of MAP by baroreceptor reflex Flashcards
what are the sensor, control centre and effector(s) for this short- term negative feedback system
sensors = baroreceptor
control centre = medulla
effector(s) = heart and blood vessels
where are baroreceptors found and how do they signal the medulla to report a change
they are found wrapped around the aorta and carotid arteries, they sense stretch and so when the blood vessels stretch too little or too much it signals the medulla. They can only sense acute changes, not a maintained change in MAP
describe how the firing rate in baroreceptor afferent neurons changes as MAP changes
firing rate increases as MAP increases, and vice versa
what is cardiac output and how do you calculate it
cardiac output is the volume of blood pumped by the ventricles of the heart every minute
CO = SV x HR
what is stroke volume
the volume of blood pumped by the ventricles of the heart per heart beat
what is systemic vascular resistance and how can it be used to calculate MAP
SVR is the sum of resistance of all vasculature in the circulation
MAP = SVR x CO
what 3 things could be regulated in order to regulate MAP
CO, SVR and SV
what is meant when saying the heart has autorhythmicity
it is able to beat in the absence of external stimuli, the electrical impulse used to beat the heart comes from within it
explain how heart rate is regulated by the Autonomic Nervous System (ANS)
the sympatheticNS increases heart rate (noradrenaline)
the parasympatheticNS decreases heart rate (acetylcholine)
explain how stroke volume is controlled by the ANS
the SNS can increase the SV because it supplies the myocardium in the ventricles with nerves and so can increase contraction strength and therefore SV
explain how SVR is regulated by the ANS
vasodilation and constriction decrease and increase SVR and MAP respectively, this is controlled by the SNS. the PNS makes no significant impact on SVR
explain what is meant by the vasomotor tone
this refers to the smooth muscles in arteries being partially constricted at rest, caused by continuous release of noradrenaline by SNS
summarise the negative feedback response to increased MAP
increased baroreceptor firing rate to medulla, decreased cardiac sympathetic activity>(decreased HR>decreased SV)> decreased CO
decreased sympathetic vasomotor tone>(veno and vasodilation)> decreased SVR
summarise the negative feedback response to decreased MAP
decreased baroreceptor firing rate to medulla, increased cardiac sympathetic activity>(increased HR> increased SV)> increased CO
increased sympathetic vasomotor tone>(veno and vasoconstriction)> increased SVR
