Biology, Eighth Edition (Raven)

Chapter 49: The Circulatory and Respiratory Systems

Baroreceptor Reflex Control of Blood Pressure

What causes abnormal blood pressure? Blood pressure is determined by the force of the blood acting on the walls of the blood vessels. Two factors determine the size of this force. One is the volume of blood being pumped through the vessel. The other is the size of the vessels. Changes in blood pressure can be caused by either a change in the amount of blood being pumped or by a change in the size of the blood vessels. Feedback mechanisms, described in this animation, will alter heart rate and blood vessel dilation to maintain blood pressure at appropriate levels. Abnormal blood pressure results from a failure to regulate blood pressure. A common cause of high blood pressure is the build up of cholesterol on the surfaces of the blood vessels reducing the volume.

View the animation below, then complete the quiz to test your knowledge of the concept.


1.	Baroreceptors are located...

		A)	in the aorta and subclavian arteries.
		B)	in the aorta and carotid arteries.
		C)	aorta and carotid veins.
		D)	aorta and subclavian veins.
		E)	aorta and common iliac arteries.

2.	Action potentials are conducted from the baroreceptors to the brain via...

		A)	the vagus nerve.
		B)	the vagus and glossopharyngeal nerves.
		C)	the vagus and phrenic nerves.
		D)	the phrenic and glossopharyngeal nerves.
		E)	the phrenic nerve.

3.	The action potential from the brain to the heart travels along...

		A)	the vagus nerve.
		B)	the vagus and glossopharyngeal nerves.
		C)	the vagus and phrenic nerves.
		D)	the phrenic and glossopharyngeal nerves.
		E)	the phrenic nerve.

4.	Heart rate and stroke volume decrease under decreased parasympathetic stimulation.

		A)	True
		B)	False

5.	Increased sympathetic stimulation causes vasodilation, bringing elevated blood pressure back to normal.

		A)	True
		B)	False