Physiology Objectives 15



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Physiology Objectives 15

1. Baroreceptor reflex: baroreceptors located in the aortic arch and carotid sinus monitor blood pressure. The aortic baroreceptors relay through the vagus nerve; the carotid sinus baroreceptors relay through the glossopharyngeal nerve. Afferent input enters into the tract of the solitary nucleus and can then be sent to cardiovascular control center in the brainstem (vasoconstrictor center, cardiac accelerator center, cardiac decelerator center)



MAP regulation on a beat to beat basis: because the baroreceptors monitor pressure on a beat to beat basis, the baroreceptor reflex is responsible for beat to beat MAP regulation
2. Functional components of cardiovascular control center:

  1. Vasoconstrictor center: works to constrict vessels and increase TPR

  2. Cardiac accelerator center: works on the SA/AV nodes to increase heart rate and contractility

  3. Cardiac decelerator center: works on the SA/AV nodes to decrease heart rate and contractility

3. Blood pressure and the Renin-Angiotensin system: decreased blood pressure is sensed by renal mechanoreceptors causing juxtaglomerular cells to convert prorenin into renin. Renin then works in the plasma to convert angiotensinogen into angiotensin I, followed by angiotensin I conversion to angiotensin II in the kidneys and lungs.



Angiotensin II: angiotensin II is a powerful vasoconstrictor, stimulates the production of aldosterone, and acts on the renal proximal tubule to increase reabsorption of Na+ and HCO3-
4. Influence on MAP:

  1. ADH: ADH acts on two receptors to increase MAP

    1. V1: V1 receptors are located in vascular smooth muscle cells and cause vasoconstriction when stimulated by ADH

    2. V2: V2 receptors are located in the renal collecting ducts and cause water reabsorption when stimulated by ADH

  2. Chemoreceptors:

    1. Central: in the medulla, chemoreceptors sense pH and PCO2 changes and cause MAP to increase if pH decreases or PCO2 increases

    2. Peripheral: in the carotid body, chemoreceptors sense PO2 changes and relays information to the cardiovascular control centers



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