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35 Cards in this Set

  • Front
  • Back
What is the difference between primary and secondary MAP reflexes and regulatory mechanisms?
Primary reflexes maintain MAP constant; secondary reflexes acutely alter MAP.
Where are the arterial baroreceptors located?
In the carotid sinus bodies and the arch of the aorta.
How is the firing rate of arterial baroreceptors related to MAP?
They fire constantly in a rate that is directly related to vessel tension, and thus MAP. Increase in MAP increases firing, and a decrease in MAP decreases firing.
How do afferent nerves arising from the arterial baroreceptors travel to the medulla?
From the aortic arch they travel with the vagus (CN X), from the carotid sinus bodies they travel with the glossopharyngeal (CN IX)
What does the medulla do when an increase in MAP is sensed?
Decrease SNS stimulation, increase parasympathetic stimulation.
What does the medulla do when a decrease in MAP is sensed?
Increase SNS stimulation, decrease parasympathetic stim.
What is the effective range of control for the baroreceptor reflex?
What are 5 things that SNS stimulation will do to increase MAP? What is the end result of each?
1.Decrease venous CPL
2.Increase HR
3.Increase LV CTY
4.Increase release of angiotensin II
5.Increase Starling forces
After a disturbance occurs, how long does it take for the baroreceptor to kick in? How long until compensation to nearly normal happens?
Seconds to onset, 95% of normal by 30 seconds.
What are the immediate and long effects of vasopressin? Under what MAP conditions is it released?
It immediately increases SVR and lowers CPL. Over time it promotes retention in the kidney and increases volume. It is released when MAP is low.
What parameter is the cardiopulmonary reflex based on?
Indirectly on CVP.
Where are the sensors for the cardiopulmonary reflex located?
At the point where the IVC and SVC enter the RA and where the pulmonary veins enter the LA.
How do afferent nerves from the cardiopulmonary sensors travel to the medulla?
With the vagus (CN X)
How do the cardiopulmonary sensors work?
They fire with increasing frequency during atrial filling; rate of firing is thus proportional to CVP.
What two factors determining CVP are most important to the cardiopulmonary reflex?
*total blood volume
*venous CPL
How would a decrease in CVP due to venous hemorrhage by corrected by the cardiopulmonary reflex?
A decrease in sensor firing would be detected by the medulla which would increase SNS and decrease parasympathetic stim. Vasopressin and angiotensin II would be released.
When does CVP pooling occur?
In space and during prolonged bed rest.
What occurs in CVP pooling?
The lack of gravitational pressure causes blood to move from the periphery into the thorax, thus increasing CVP.
How does the body react to CVP pooling?
Cardiopulmonary sensors trigger decreased SNS and parasympathetic stim, and less release of angiotensin II and vasopressin. Output increases and volume decreases.
What are the dangers of CVP pooling?
The decrease in volume can accentuate orthostatic disturbances.
What is cold diuresis?
Low temp causes blood to be diverted from the periphery and results in CVP pooling.
Describe a situation where the cardiopulmonary and baroreceptor reflexes might be antagonistic.
In CHF, where MAP is low but CVP is high. The baroreceptors are generally the more powerful.
What is the goal of the baroreceptor reflex? Of the cardiopulmonary reflex?
Baroreceptor: maintain MAP.
Cardiopulmonary reflex: maintain CVP
What is the primary function of the arterial chemoreceptor reflex?
To control resp rate and depth - seeks to maintain arterial blood gases and pH.
Where are the peripheral chemoreceptors located?
In aortic and carotid bodies.
What about the arterial chemoreceptors makes them particularly sensitive to ABG?
They have the highest metabolic rate in the body.
Specifically, what do peripheral chemoreceptors sense?
Disturbances that lower PO2, raise PCO2, and lower pH.
Where are the central chemoreceptors located? To what are they most sensitive?
In the ventral medulla. They are most sensitive to PCO2 and pH in the interstitial fluid.
Arterial chemoreceptors can trigger an increase in sympathetic or parasympthetic stimulation.
False: these are one-way receptors that stimulate only a rise in SNS stim. They are only active in times of low PO2, hi PCO2, and lo pH
At what MAP does the cerebral ischemic reflex kick in?
When MAP is no longer maintained by the baroreceptor reflex and falls below 50mmHg
What is the action of the cerebral ischemic reflex? When does it stop?
It causes a "super SNS stim". It stops if MAP and CBF continue to fall and cell death occurs in control centers.
What are the hallmark signs of the cerebral ischemic reflex?
Tachycardia (>200bpm) and low BP.
When does the Cushing reflex occur?
When ICP is sharply increased and CBF occluded (e.g. intracranial hemorrhage). The ensuing rise in PCO2 is sensed by central chemoreceptors.
What is the action of the Cushing reflex?
A "super SNS stim" which greatly increases MAP and HR.
What are the hallmark signs of the Cushing reflex?
Brachycardia, profound HTN, likely unconsciousness.