23- Regulation of Arterial BP & CPR Endocrinology Flashcards
What is the equation for MAP (Mean Arterial Pressure)?
MAP = CO x TPR
***Can also be MAP = HR x SV x TPR
What is a normal MAP?
93.3 mmHg
***Usually about 100 mmHg
MAP is composed of 2/3 ______ and 1/3 ______.
DBP
SBP
What are the 3 major systems that regulate the MAP?
– Baroreceptor reflex (rapid)
– Endocrinologically via Renin-Angiotensin-Aldosterone System (RAAS) (slower)
– Some input from ADH (vasopressin) and ANP (slower)
The MAP uses the baroreceptor reflex, which uses a classical reflex arc. Describe this.
1) Detector – detects deviation from set point
2) Afferent neural pathway
3) Coordinator center – brainstem
4) Efferent neural pathway
5) Effectors – correct deviation from set point
What are the locations of the Baroreceptors for the MAP, and what nerves do they utilize?
Carotid Sinus – Glossopharyngeal N. and Sinus nerve of Hering
Aortic Sinus – Vagus N. and Aortic N.
Baroreceptors are a type of ___________ that respond to changes in arterial pressure to return to “normal”. __________ are also present and responds to PO2, PCO2, and pH.
Mechanoreceptors
Chemoreceptors
Baroreceptors can make changes in pressure through stretch receptors on vessel walls. They can (INCREASE/DECREASE) firing rate to increased stretch, and (INCREASE/DECREASE) firing rate when pressure falls. They can act within seconds and these changes can last indefinitely.
Increase
Decrease
***Most responsive to change in pressure, not just magnitude of change
This can be reset for Baroreceptors to create a new “normal”, especially for hypertensive patients.
Basal set point
Baroreceptors send signals to the ________ ________ in the medulla.
Vasomotor Center
If there is decreased stretch of Baroreceptors, there is decreased firing rate of _________ neurons (i.e., TRP channels).
Afferent
For Baroreceptors, Efferents are both __________ and _________. Efferents travel into the Cerebral Cortex and _________.
Parasympathetic
Sympathetic
Hypothalamus
This area of the brain/brainstem receives and coordinates peripheral signals, specifically for Baroreceptors in this case.
Nucleus of Tractus Solitarius (NTS)
This area of the brain/brainstem consists of Parasympathetic activity associated with CV function.
Dorsal Motor Nucleus of the Vagus
Nucleus Ambiguus
This area of the brain/brainstem consists of Sympathetic activity associated with CV function.
Rostral Ventrolateral Medulla
The Baroreceptors from the Carotid Sinus and Aortic Sinus lead to what?
Nucleus Tractus Solitarius (NTS)
***Via Afferent Neurons – use Glutamate
Briefly explain how the Carotid Sinus baroreceptors can decrease BP.
Carotid Sinus baroreceptors — Travel to NTS via CN IX — Activate Cardiac Decelerator — SA Node is inhibited/slowed
***This is Parasympathetic!
Briefly explain how the Aortic Sinus baroreceptors can decrease BP.
Aortic Sinus baroreceptors — Travel to NTS via CN X — Inhibit Cardiac Accelerator and Vasoconstrictor
- **This is Parasympathetic!
- **Cardiac Accelerator and Vasoconstrictor are components of Sympathetics (so they have to be inhibited)
For Baroreceptors, (AORTIC/CAROTID) has a higher threshold for activation and continues to respond above saturation. It’s less sensitive to rate and less effected by decreases.
Aortic
The Sympathetic nervous system is stimulated by an (INCREASED/DECREASED) baroreceptor firing rate.
Decreased
For Sympathetics, the preganglionic fibers are below T1, and it influences heart muscles and the SA Node directly, as well as vessels and Adrenal Gland via Splanchnic N. What do the Sympathetics do for these?
– Constriction of arterioles and veins (alpha-receptors)
– Increases HR and contractility (B1 receptors)
– Fluid retention by kidney due to afferent arteriole constriction and renin secretion
The Parasympathetic nervous system is stimulated by an (INCREASED/DECREASED) baroreceptor firing rate.
Increased
What influence does Parasympathetics have?
– Decreased HR - Muscarinic receptors (via Vagus N. signal to SA Node)
– Indirect vasodilation on blood vessels (i.e., stimulate NO release)
Briefly explain what happens when there is decreased MAP and you need to increase it?
Decreased MAP — Decreased Baroreceptor Firing — Increased SNS Activity and Decreased PSNS Activity — Leads to Increased CO and the Decreased PSNS will cause increased TPR
***This leads to increased arterial pressure!