L19. Physiology - Regulation of BP & BV

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Questions and Answers

What happens to baroreceptor nerve activity as blood pressure rises to high levels?

It decreases gradually.

It continues to increase indefinitely.

It ceases to increase further. (correct)

It increases linearly with blood pressure.

Which characteristic describes the relationship between baroreceptor whole nerve activity and arterial blood pressure?

Linear

Sigmoidal (correct)

Exponential

Quadratic

In the midrange of blood pressure, what aspect of baroreceptors is at its highest?

Threshold for activation

Saturation level

Slope of whole nerve activity (correct)

Overall nerve activity

Which of the following nerves carry baroreceptor afferents from the carotid sinus to the central nervous system?

Glossopharyngeal nerve Signup and view all the answers

What is the main integrator of information from various baroreceptor afferents?

The vasomotor center Signup and view all the answers

Which of the following factors does NOT affect baroreceptor nerve activity?

Heart rate Signup and view all the answers

What occurs as more afferents reach saturation during an increase in blood pressure?

The slope of whole nerve activity decreases. Signup and view all the answers

What is designated as the area of maximal sensitivity in baroreceptors?

The midrange around normal levels Signup and view all the answers

What happens to sympathetic activity when arterial pressure falls?

It increases. Signup and view all the answers

How does rapid blood loss affect cardiac output?

It decreases stroke volume. Signup and view all the answers

What is the primary response of the body when mean arterial pressure (MAP) decreases?

Increase in total peripheral resistance. Signup and view all the answers

What role do baroreceptors play when arterial pressure rises above normal levels?

They increase parasympathetic activity. Signup and view all the answers

What happens to the heart rate during a hemorrhage?

It increases. Signup and view all the answers

What is the relationship between stroke volume and cardiac output?

Cardiac output is the product of stroke volume and heart rate. Signup and view all the answers

In response to decreased venous return, what is the effect on vasomotor center inhibition?

Inhibition of the vasomotor center decreases. Signup and view all the answers

Which statement accurately describes the effect of sympathetic activity on peripheral blood vessels in hemorrhage?

It leads to vasoconstriction, increasing total peripheral resistance. Signup and view all the answers

When does tonic activity of the parasympathetic nerves prevail?

When arterial pressure is stable at normal levels. Signup and view all the answers

What physiological response can result from the activation of cardiac afferents during prolonged orthostasis?

Reflex bradycardia and decreased sympathetic vasoconstrictor activity Signup and view all the answers

What condition can lead to orthostatic intolerance after prolonged bed rest?

Decreased blood volume making subjects more susceptible Signup and view all the answers

Why might highly trained athletes be more susceptible to orthostatic intolerance?

Larger hearts and increased activation of ventricular afferents Signup and view all the answers

What effect does prolonged orthostasis have on arterial pressure and brain perfusion?

Decreased arterial pressure and reduced brain perfusion Signup and view all the answers

What mechanism contributes to fainting during prolonged orthostasis?

Peripheral vasodilation and decreased cardiac output Signup and view all the answers

What effect does an increase in sympathetic activity to the kidney have during hemorrhage?

Increases renin release Signup and view all the answers

What role does vasopressin play in response to decreases in blood volume?

Reduces H2O loss in urine Signup and view all the answers

Which receptor primarily responds to changes in blood pO2 and pCO2?

Peripheral chemoreceptors Signup and view all the answers

What happens during the Cushing Reflex in severe hemorrhage?

Marked increase in sympathetic activity Signup and view all the answers

What is the immediate response to decreased blood volume according to the content?

Release of vasopressin Signup and view all the answers

How do capillaries respond to vasoconstriction during hemorrhage?

Favors fluid reabsorption from interstitium Signup and view all the answers

What is a long-term response to blood volume reduction?

Fluid reabsorption from the interstitium Signup and view all the answers

What is the relationship between pO2 and vascular resistance according to the findings?

High pCO2 leads to significant resistance changes Signup and view all the answers

Which hormone's release is influenced by decreased inhibition to the vasomotor center?

Vasopressin Signup and view all the answers

What is the effect of a decrease in peripheral venous volume on cardiac preload?

Increases cardiac preload Signup and view all the answers

What physiological role do Atrial Natriuretic Peptide (ANP) and Brain Natriuretic Peptide (BNP) most likely play during an increase in blood volume?

Act to decrease blood volume Signup and view all the answers

How do cardiopulmonary baroreceptors differ from arterial baroreceptors in terms of pressure sensitivity?

They are more sensitive to small changes in pressure. Signup and view all the answers

What occurs in patients with head injuries related to systemic pressure?

Increased systemic pressure to maintain brain perfusion. Signup and view all the answers

Which peptide is released in response to stretching of ventricular walls?

Brain Natriuretic Peptide (BNP) Signup and view all the answers

During hemorrhage, which of the following is expected regarding the release of ANP and BNP?

Decreased ANP and BNP release to conserve fluids. Signup and view all the answers

What potential negative effect can occur from severe stimulation of ventricular receptors?

Induction of a 'vicious cycle'. Signup and view all the answers

What is the primary action of baroreceptors in relation to pressure changes?

They modulate sympathetic nervous system response. Signup and view all the answers

What happens to Atrial and Central Venous Pressure during hemorrhage?

They decrease, reinforcing sympathetic drive. Signup and view all the answers

Which statement accurately describes the role of baroreceptors during hemorrhage?

They help regulate blood pressure through signaling. Signup and view all the answers

What is the effect of stretching the atrial walls in terms of peptide release?

Release of ANP and BNP. Signup and view all the answers

Study Notes

Baroreceptor Function

Baroreceptors monitor blood pressure changes and adjust heart rate and vascular resistance to maintain blood pressure.
Baroreceptors have a sigmoidal relationship with blood pressure:
- At low blood pressure, baroreceptor activity is low.
- As pressure rises, the slope of the relationship increases rapidly, reaching maximum sensitivity at normal blood pressure levels.
- At high blood pressure, the slope flattens as baroreceptors become saturated.
Different baroreceptors have different sensitivity thresholds and saturation points.
Carotid sinus baroreceptors send signals through the glossopharyngeal nerve to the CNS.
Aortic arch and cardiopulmonary baroreceptors send signals through the vagus nerve to the CNS.
The vasomotor center in the medulla integrates baroreceptor input and controls autonomic nervous system activity for blood pressure regulation.

Blood Pressure Regulation

At normal blood pressure, baroreceptors maintain tonic activity, influencing the parasympathetic and sympathetic nervous systems.
When blood pressure falls, baroreceptors decrease activity, inhibiting parasympathetic activity and increasing sympathetic activity to increase heart rate and vasoconstriction.
When blood pressure rises, baroreceptors increase activity, increasing parasympathetic activity and inhibiting sympathetic activity to decrease heart rate and vasodilation.

Hemorrhage Response

Hemorrhage leads to a decrease in preload, stroke volume, cardiac output, and mean arterial pressure (MAP).
Reduced MAP decreases baroreceptor activity, leading to a decrease in parasympathetic activity and an increase in sympathetic activity.
This sympathetic activation increases heart rate, contractility, and peripheral vasoconstriction, helping to restore MAP towards normal levels.
Long-term hormonal responses include increased release of renin, angiotensin II, aldosterone, and vasopressin to further compensate for blood loss.
These hormonal responses contribute to vasoconstriction, fluid retention, and blood volume restoration.

Chemoreceptors

Carotid and aortic chemoreceptors respond to changes in blood oxygen (pO2) and carbon dioxide (pCO2) levels.
They are particularly sensitive to changes in pCO2, triggering vascular resistance adjustments.
Central chemoreceptors monitor brain perfusion pressure and trigger the Cushing Reflex in severe hemorrhage or head injuries.
The Cushing Reflex involves intense vasoconstriction to redirect blood flow to the brain, leading to hypertension.

Cardiopulmonary Baroreceptors

These receptors act in a similar way to arterial baroreceptors, but are more sensitive to pressure changes.
Located in atria and ventricles, they release natriuretic peptides (ANP and BNP) in response to stretch.
ANP and BNP contribute to long-term blood volume regulation by promoting sodium and water excretion in the kidneys.
Ventricular receptors reinforce the arterial baroreflex, but can contribute to a "vicious cycle" during prolonged orthostasis (standing upright).
This "vicious cycle" can lead to orthostatic intolerance, characterized by decreased cardiac output, vasodilation, and fainting due to reduced brain perfusion pressure.
- Prolonged bed rest or spaceflight can increase susceptibility to orthostatic intolerance.
- Highly trained athletes may also be at increased risk due to larger hearts and potential changes in baroreflex sensitivity.

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Description

This quiz explores the role of baroreceptors in monitoring and regulating blood pressure. It covers their sensitivity, signal pathways, and the overall integration of blood pressure control within the autonomic nervous system. Test your understanding of these crucial physiological mechanisms.