Many people experience orthostatic hypotension upon standing from a seated or la
ID: 3481431 • Letter: M
Question
Many people experience orthostatic hypotension upon standing from a seated or laying position. This means that their blood pressure decreases rapidly. During this event they quickly activate short term (so not the RAA pathway) mechanisms for blood pressure control. Please explain the following: a. Where are receptors located in the body for measuring blood pressure and how do they sense a change in blood pressure. b. Where do the above sensors send their signals? C. part b respond (which part of the nervous system is activated)? d. Activation of the nervous system in part c would produce what change in blood pressure and why (for the why part of this question you should be talking about the definition of blood pressure)?Explanation / Answer
Ans-) Orthostatic or postural hypotension is a sudden drop in blood pressure that occurs with change of posture be it from sitting to standing or sometimes in patients it can occur in any postural change. This postural change causes a gravitational blood pooling in the lower extremity veins , as a result venous return and cardiac output are reduced causing CEREBRAL HYPOPERFUSION.
a-) The receptors for measuring the blood pressure in the body are called as BARORECEPTORS , these are special receptors that detect changes in blood pressure. Baroreceptors are found within the walls of the blood vessels. The AORTA and Carotid sinus contains important baroreceptors that constantly monitors fluctuations in blood pressure. If blood pressure within the Aorta or Carotid sinus increases the walls of these arteries stretches and get stimulated the increased activity of baroreceptors.
b-) Baroreceptors after reciving the signals send them to the central nervous system more often the cardio regulatory center of the medulla oblongata via nerves.
c-) In orthostatic hypotension the drop in blood pressure is experienced by receptors causing a reflex called as BARORECEPTOR REFLEX. which is a homeostatic mechanism to maintain blood pressure. The beroreceptor information transmitted to the Medulla and thus stimulates SYMPATHETIC NERVOUS SYSTEM resulting in increased heart rate and increased stroke volume and thus increased Vasoconstriction.
d-) The decrease in blood pressure causes decrease in Action potentials sent to the cardio regulatory center of medulla. With activation of the sympathetic nervous system the SA node or the SINUS node and the natural pacemaker of heart get activated causing an increase in the Heart rate , resulting in more blood pumping from the Heart muscles increasing the STROKE VOLUME. CARDIAC output is increased with increase in heart rate and stroke volume . Increased cardiac output results into increased blood pressure and thus restoring blood pressure to normal.
Secondly this increased blood pressure causes an increased SYMPATHETIC input to the Blood vessels causing VASOCONSTRICTION which increases total peripheral resistance and thus increases Blood pressure and regulation occurs to normal.
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