T551:  Answers to Quiz 3--Regulation of MAP & CV System in Stress and Disease

REGULATION OF SYSTEMIC ARTERIAL PRESSURE  & CV SYSTEM IN STRESS AND DISEASE

1.  heart rate, stroke volume

2.  cardiac output, total peripheral resistance

3.  increase, decrease, increase

4.  Complete the table below to indicate the direct effect  of an increase in parasympathetic nerve activity (>PSNA), a decrease in sympathetic nerve activity (¯SNA), and an increase in circulating epinephrine (>Epi) on each of the cardiovascular parameters listed.  Use > to represent an increase, ¯ for a decrease, and -- when no direct effect would be expected.

5.  Angiotensin II is very important in the regulation of arterial pressures.  An increase in circulating levels of angiotensin can result in elevated blood pressure through three separate mechanisms.  First, it is one of the most potent vasoconstrictors.  Its direct action on vascular smooth muscle causes arteriolar constriction resulting in an increase in total peripheral resistance.  Angiotensin II indirectly increases total blood volume by stimulating the release of antidiuretic hormone (ADH) from the hypothalamus and aldosterone from the adrenal cortex.  ADH and aldosterone increase the reabsorption of water and sodium in the kidney and thereby elevate total blood volume.   

6.  While heart rate and cardiac contractility are increased in response to both exercise and hemorrhage, cardiac output is elevated above normal only during exercise.  The primary reason is that the end diastolic volume of the heart is reduced in hemorrhage, so stroke volume is decreased even though cardiac contractility is elevated.   

7.  Hemorrhage: the escape of blood from the vessels, bleeding; if significant blood loss occurs, hemorrhagic shock occurs.

     Circulatory shock:  progressive deterioration of cardiovascular function, if not reversed quickly will lead to tissue damage and ultimately death.

     Orthostatic hypotension:  A decrease in blood pressure by 20 mm Hg upon standing abruptly; associated with dizziness, syncope, and blurred vision..

     Essential hypertension:  Persistently elevated blood pressure (diastolic >90 mm Hg, systolic > 140 mmHg)  due to a primary disturbance of the cardiovascular system (i.e. not secondary to other pathologies such as renal disease).

     Congestive heart failure:  Inability of the heart to maintain adequate cardiac output resulting in pooling of blood (congestion) in the systemic (right ventricle failure) or pulmonary (left ventricle).

8.  Common types of drugs used for treating hypertension are:

                diuretics which primarily act to decrease total blood volume by reducing the renal reabsorption of sodium

                anti-adrenergic agents:  These include both alpha- and beta-adrenergic blockers.  Alpha blockers act primarily on the peripheral               circulation to reduce total peripheral resistance; Beta blockers act to depress cardiac function.

                vasodilators:  act on the peripheral circulation to reduce total peripheral resistance

                Angiotensin-converting enzyme inhibitors:  Inhibit the synthesis of angiotensin II and the vasodilator, bradykinin.

                Calcium channel antagonists:  Inhibit slow or voltage-dependent calcium channels, clinical effect is primarily due to action depressing cardiac function

9.  Diuretics and digitalis-like drugs are used to improve cardiac output in congestive heart failure.  Digitalis-type drugs act to improve cardiac contractility by increasing intracellular calcium concentrations.  With advanced heart failure, diuretics can be used to reverse excess fluid accumulation and return the heart to the ascending limb of the stroke volume/EDV curve (see Fig. 19-33, p. 609).

Copyright © 1999 Joseph L. Unthank

URL: http:www.iuvascular.com/Unthank/Teach/Quiz3Answers.html