Baroreceptor and Chemoreceptor Reflexes

There are times when blood flow doesn't change, but the amount of oxygen delivered to the tissues decreases. This would happen if the oxygen content of the blood were to change and carbon dioxide levels increase.

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What do chemoreceptors respond to?

changes in oxygen, increases in carbon dioxide, or increases in hydrogen ions.

The __________ reflex works to ensure sufficient delivery of oxygen when blood gas levels change.

chemoreceptor

stimulation of chemoreceptors results in a(n) __________ in cardiac output which delivers more blood to the tissues to provide for adequate gas exchange.

increase.

where are chemoreceptors for the heart located?

near the baroreceptors in the carotid and aortic bodies.

The ultimate role of the heart is to create sufficient ________ to ensure that blood flow to the body's tissues is maintained.

pressure

The baroreceptor reflex plays a key roll in the ______ -term regulation of blood pressure.

short term

When we stand, blood flow decreases due to gravity. Venous return decreases, cardiac output decreases and blood pressure decreases. This is immediately sensed by baroreceptors since they are stretched less. reduced stretch=lower frequency of action potentials transmitted to cardiovascular centers, which is interpreted as a drop in blood pressure. Cardiovascular centers will then decrease parasympathetic activity and increase sympathetic activity. This results in increased rate of contraction as well as an increase in the strength of contraction, which increases cardiac output and restores blood flow to the brain.

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5 components to the baroreceptor reflex:

1. the receptors: baroreceptors. Reside in arch of aorta and in carotid sinuses. Stretch receptors. Increase B.P.=increased stretch and increase a.p.... drop in bp=decrease stretch and decrease ap. 2. Afferent pathway: Cranial nerve 9 transmits A.P's from carotid sinus receptors to the brainstem. Cranial nerve 10 transmits A.P.'s from aortic arch to brain. 3. Control Center: cardiovascular centers that regulate rate and strength of contraction of heart and diameter of systemic blood vessels. 4. Efferent Pathway: parasympathetic fibers travel to the heart via the vagus nerve. Sympathetic fibers travel through cardiac sympathetic nerves to heart and to adrenal medulla. 5. Effector Organ: the heart. Can increase or decrease cardiac output through changes in heart rate and strength of contraction.

How could you maintain oxygen delivery to tissues even if the blood oxygen content is decreased?

Increase blood flow to the tissues.