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Baroreceptor Reflexes

Terms in this set (21)

Baroreceptors
Cells that are sensitive to blood pressure changes.
Locations of baroreceptors
carotid sinus and aortic arch
vagus nerve
this Xth cranial nerve carries most baroreceptor impulses to the brainstem
baroreceptor activity in high blood pressure
More action potentials are fired by baroreceptors in this situation (more pressure = more action potentials)
baroreceptor activity in low blood pressure
Fewer action potentials are fired by baroreceptors in this situation.
Baroreceptor Purpose
Communicate to brain current blood pressure; brainstem then alters nervous input to the heart and blood vessels to bring blood pressure back to normal.
Baroreceptor reflex - showing sympathetic and parasympathetic response to either low or high blood pressure
Low blood pressure causes the brainstem to....
increase sympathetic neuron activity to the heart
high blood pressure causes the brainstem to .....
increase parasympathetic neuron activity to the heart
sinoatrial node (SA node)
cluster of electric pulse-generating cells that serves as a natural pacemaker for the heart - modified by sympathetic or parasympathetic stimulation
Sympathetic stimulation of the heart
Increases heart rate and increases force of contraction - contributes to RAISING blood pressure
Parasympathetic stimulation of the heart
decreases heart rate and decreases force of contraction - contributes to LOWER blood pressure.
Norepinephrine (NE)
the neurotransmitter used by the sympathetic division of the autonomic nervous system - speeds up heart rate, increases blood pressure
Acetylcholine (ACh)
the neurotransmitter used by the parasympathetic division of the autonomic nervous system - slows down heart rate, decreases blood pressure
NOTE - also many other functions, including skeletal muscle contraction, but in this flashcard set we are focusing on the baroreceptor reflex only
Low blood pressure reflex
*baroreceptors fire FEWER APs up vagus
*brainstem responds by stimulating sympathetic neurons down spinal cord and out to the SA node of the heart.
*NE is released from sympathetic neuron axon terminals onto the SA node heart muscle cells.
*NE binds to Beta-1 adrenergic receptors on the heart muscle.
*B-1 adrenergic receptors, when stimulated, open Ca++ channels on the heart muscle.
*Ca++ increases contraction rate and force of contraction.
*CO increases and BP goes up.
High Blood Pressure reflex
*baroreceptors fire MORE APs up vagus
*brainstem responds by stimulating parasympathetic neurons back down the vagus and out to the SA node of the heart.
*ACh is released from parasympathetic neuron axon terminals onto the SA node heart muscle cells.
*ACh binds to muscarinic cholinergic receptors on the heart muscle.
*muscarinic cholinergic receptors, when stimulated, open K+ channels on the heart muscle.
*K+ leaves the cells, hyperpolarizing them which decreases contraction rate and force of contraction.
*CO decreases and BP goes down.
orthostatic hypotension (postural hypotension)
abnormally low blood pressure when the person suddenly stands up
Familial Dysautonomia
--ineffective baroreceptor reflexes can lead to frequent fainting.
Incomplete development of autonomic system neurons and/or sensory neurons:
GI dysfunction, altered sensitivity to pain and temperature, autonomic crises
vasovagal response
Fainting because the body overreacts to certain triggers (the sight of blood, extreme emotional distress)
****typically caused when there is an initial STRONG sympathetic drive followed by a too-rapid WITHDRAWAL of SYMPTATHETIC drive. Blood pressure goes TOO low.
fainting during labor
caused by bearing down which overstimulates the vagus nerve parasympathetic stimulation of the heart. Blood pressure drops too low.
fainting during bowel movement
caused by bearing caused by bearing down which overstimulates the vagus nerve parasympathetic stimulation of the heart. Blood pressure drops too low.
Elderly people begin to lose their autonomic baroreceptor control and are more prone to this.
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