Describe baroreceptors and their role in the control of blood pressure.
This is a core topic and a detailed knowledge was expected. Baroreceptors are stretch receptors
located in the walls of the heart and blood vessels and are important in the short term control of
blood pressure. Those in the carotid sinus and aortic arch monitor the arterial circulation. Others,
the cardiopulmonary baroreceptors, are located in the walls of the right and left atria, the
pulmonary veins and the pulmonary circulation. They are all stimulated by distention and
discharge at an increased rate when the pressure in these structures rises. Better answers
provided some detail on the innervation for these receptors. It was expected candidates would
describe that increased baroreceptor discharge inhibits the tonic discharge of sympathetic
nerves and excites the vagal innervation of the heart. This results in vasodilation, venodilation, a
drop in blood pressure, bradycardia and a decreased cardiac output.
Some candidates had a major misunderstanding around the purpose of "low pressure
baroreceptors" with many believing that these are the ones that respond to lower blood
pressures, while the "high pressure baroreceptors" respond to higher blood pressures
The precise focus of the quetion is somewhat unclear here, as the college clearly mention the atrial stretch receptors (suaully associated with the Bainbridge reflex), but spend most of their time discussing the conventional arterial baroreceptor function. Echoing this confusion, the following suggested answer mentions these "low pressure" receptors once, and never returns to them.
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