Mean Arterial Pressure Control - Usmle CVS Physiology animated lecture

Video Description

Mean Arterial Pressure Control

2 mechanisms exist to monitor and regulate changes in MAP (mean arterial pressure):

1) Baroreceptor reflex—more important for short-term control of blood pressure
- Arterial baroreceptors in the carotid sinus sense and respond to acute increases or decreases in arterial pressures
- Arterial baroreceptors in the aortic arch respond to acute increases, but not decreases in arterial pressure.

2) RAA (renin angiotensin aldosterone) system—more important for long-term control of blood pressure.
For example, how would the body respond to an acute hypotensive episode?
1) Baroreceptor reflex responds within seconds:
Acute ? in MAP ?? afferent signals sent from the carotid sinus baroreceptors via glossopharyngeal nerve (CN IX) to the brain stem medulla ?? in parasympathetic activity via the efferent vagus nerve to the heart, with a simultaneous ? in sympathetic outflow from the nucleus of the solitary tract to the heart and vasculature ?
- ? Heart rate (chronotropic effect)
- ?Myocardial contractility (inotropic effect) ?? stroke volume
- ? AV conduction velocity (dromotropic effect)
- ? TPR (total peripheral resistance)
?compensatory? of mean arterial pressure toward normal
Recall: MAP = CO*TPR, and CO = HR * SV
CO=cardiac output, HR=heart rate, SV=stroke volume
2) RAA (renin angiotensin aldosterone) system senses the the acute drop in blood pressure but takes minutes-hours-days to kick into gear:

? MAP ?? renal blood flow is sensed by the juxtaglomerular apparatus ?? renin ?? angiotensin II ?
- Angiotensin II is a potent vasoconstrictor that increases total peripheral resistance.

- Angiotensin II also stimulates release of aldosterone ? stimulates renal sodium retention and subsequent renal fluid reabsorption to help maintain total blood volume in an attempt to preserve stroke volume, cardiac output, and mean arterial pressure.