PSIO 532 Study Guide - Midterm Guide: Vascular Resistance, Vasomotor Center, Smooth Muscle Tissue
PSL – Cardiovascular System
Baroreceptor – Sympathetic & Vagal Activity
In this graph, we are measuring the activity of 3 different
neurons as a function of transmural pressure. The
baroreceptors afferents have a tonic level of activity for
normal pressure; if pressure falls, baroreceptor nerve
activity falls, if the pressure rises, then the baroreceptor
nerve activity rises. Due this rise and fall in pressure, the
activity of vagal and sympathetic efferents is affected.
Based on the graph, we are able to tell that there is a
tonic level of sympathetic and parasympathetic activity.
With no afferent input, the
vasomotor center would induce a high sympathetic activity and low parasympathetic activity.
Increases in baroreceptor nerve activity inhibits the vasomotor center and thus sympathetic
activity decreases and parasympathetic activity increases.
A rise in pressure would lead to a rise in baroreceptor activity, and this causes reflex increase of
PNS and reflex decrease of SNS to bring the blood pressure back to normal. If we decrease
sympathetic activity, you get vasodilation, so the total peripheral resistance goes down, drop in
HR, drop in cardiac output → all in the attempts to bring blood pressure back down to normal.
This is called the proportional negative feedback system → sympathetic and parasympathetic
do’t just go to axiu or iiu if there is a hage i lood pressure. The hage i PNS
and SNS is proportional and reflects the blood pressure change. Magnitude in change of the
effectors in PNS and SNS is dependent on the change of the baroreceptor nerve activity.
Example: Picture above shows the short term compensatory responses to rapid blood loss
(hemorrhage). Rapid blood loss causes a decrease in venous return to the heart therefore
decreases cardiac preload. A decrease in preload will decrease stroke volume. A decrease in
stroke volume will decrease cardiac output (remember CO = SV x HR). A decrease in CO will
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Document Summary
In this graph, we are measuring the activity of 3 different neurons as a function of transmural pressure. The baroreceptors afferents have a tonic level of activity for normal pressure; if pressure falls, baroreceptor nerve activity falls, if the pressure rises, then the baroreceptor nerve activity rises. Due this rise and fall in pressure, the activity of vagal and sympathetic efferents is affected. Based on the graph, we are able to tell that there is a tonic level of sympathetic and parasympathetic activity. With no afferent input, the vasomotor center would induce a high sympathetic activity and low parasympathetic activity. Increases in baroreceptor nerve activity inhibits the vasomotor center and thus sympathetic activity decreases and parasympathetic activity increases. A rise in pressure would lead to a rise in baroreceptor activity, and this causes reflex increase of. Pns and reflex decrease of sns to bring the blood pressure back to normal.
