Lec8 - Physi - baroreceptor and chemoreceptor regulation

Vascular reflexes

internal sensory feedback systems that “sense” changes in important circulatory parameters and respond via feedback pathways that alter tonic autonomic control of heart/vasculature

Vascular reflexes work to maintain and optimize ____ in ______

cardiovascular performance in rapidly changing physiological situations

Types of vascular reflexes

peripheral baroreceptors and chemoreceptors, central chemoreceptors, pulmonary stretch receptors and hypothalamus

The arterial baroreceptors play a key role in _____ adjustments of blood pressure when abrupt changes in blood volume, cardiac output or peripheral resistance occur

short-term

key triggers for arterial baroreceptors

posture changes, exercise and hemorrhage

Baroreceptors will sense

pressure (blood pressure)

Arterial baroreceptors are stretch receptors located in the

carotid sinuses and aortic arch

Arterial baroreceptors detect physical deformation in the vessel wall due to

blood pressure changes

Arterial baroreceptors relay changes to the ___ in the medulla via afferent nerve fibers

nucleus tractus solitarius (NTS)

Carotid baroreceptor afferents travel the ____ to the glossopharyngeal nerve to the NTS

sinus nerve

Aortic arch baroreceptor afferents travel along the ____ to the NTS

vagus nerve

Carotid sinus afferent firing ____ with increased blood pressure

increases

Carotid sinus afferent firing occurs mainly during

systole

Baroreceptor stimulation decreases _____ activity and increases ____ activity

sympathetic; parasympathetic

Afferents from the baroreceptors stimulate the NTS, inhibiting

the tonic sympathetic impulses to the peripheral resistance blood vessels

Reduction in sympathetic firing is paralleled by an increase in

parasympathetic outflow that slows the heart rate

An increased baroreceptor firing rate leads to

vasodilation and bradycardia

Increase in sinus pressure will result in

decrease in sympathetic pressure

In sympathetic pathway, an increase in blood pressure and baroreceptor firing leads to

decreased sympathetic discharge, vasoconstriction and in result lowered blood pressure

In the sympathetic pathway, a decrease in blood pressure ad baroreceptor leads to

increase in sympathetic discharge, vasoconstriction and in result increase in blood pressure

In parasympathetic pathway, all firing is

excitatory

in sympathetic pathway firing, it can be

excitatory or inhibitory

In parasympathetic pathway, an increase in blood pressure and baroreceptor firing leads to

increased vagal discharge, decreased heart rate and ultimately a decrease in blood pressure

Adaptation of the baroreceptors occurs during the long term changes in mean arterial blood pressure, have a

decreased sensitivity to pressure changes

Low pressure baroreceptors are located in

atria and pulmonary vessels

“low pressure” baroreceptors will detect

blood volumes changes (preload)

Atrial baroreceptors are

atrial mechanoreceptors

atrial baroreceptros are afferent fibers that run the

vagus to the medulla

Increased stimulation (stretch) of atrial baroreceptors leads to increased

stimulation of the medullary centers

Increased stimulation of the medullary center causes

decreases parasympathetic output to the heart (increase HR) and increased sympathetic output to the heart (increase HR)

Atrial baroreceptors have negative feedback to

reduce preload by increasing cardiac output

Peripheral chemoreceptor two main types

aortic bodies and carotid bodies

Peripheral chemoreceptors are highly ____ cells in the aortic arch and carotid sinus that are sensitive to blood ___, ___, and ____

vascularized; O2; CO2; and pH

Peripheral chemoreceptors are mostly involved in

respiratory regulation (but have minor effect on vasomotor centers)

Peripheral chemoreceptors are more sensitive to ___ rather than CO2 or pH

O2 changes

Central chemoreceptors have a primary role in

respiratory regulation

Increased blood CO2 levels stimulate the ______ located in the medulla, causing ____

central chemoreceptors; increased sympathetic outflow and vasoconstriction

Increased ventilation causes decreased blood CO2 levels, which will ____ resulting in ______

reduce stimulation of the central chemoreceptors; vasodilation

Oxygen tension has _____ effect on the central chemoreceptors

little to no

Central chemoreceptors are most sensitive to

change in CO2 levels that leads to change in pH

Long-term control of blood pressure involves regulating _____, largely by the kidneys

systemic blood volume

Long term blood pressure regulation main mechanisms are

hormonal (ADH secretion, the renin-angiotensin-aldosterone system and atrial natriuretic peptides)

Hormones of the long-term blood pressure regulation will affect blood volume by

regulating salt and water retention/excretion from the kidneys

Vascular reflexes

detect changes and measure parameters in the circulatory system and respond via feedback pathways

Vascualr reflexes help to optimize/maintain

cardiovascualt performance in rapid change situation

Parameters of vascular reflexes

blood pressure, O2, CO2, pH and temperature

Types of vascular reflexes

Peripheral (arterial) baroreceptors, peripheral chemoreceptors, central chemoreceptors, pulmonary stretch receptors, and hypothalamus

Aterial baroreceptors are triggered by sitatuion such as

posture changes, exercise, and hemorrhage

Arterial baroreceptors are ____ receptors located in high pressure areas in the ____ and _____

stretch; carotid sinuses and aortic arch

Arterial baroreceptors innervation is with carotid which is ____ and aortic which is ____

afferent nerves trvel to the glossopharyngeal nerve; afferent nerves travel tot he vagus nerve

Arterial baroreceptors are stretch receptors that measure the

mechanical stretch at the cellular/molecular level on the vessel wall due to BP change

BP changes are sent as neuronal impulses that travel to _____ in the _____ via nerve fibers

nucleus tractus soliarius (NTS); medulla

increased afferent firing of Carotid sinus increases with

increased BP

At normal BP, the afferent firing of carotid sinus occurs mainly during

systole

When there is an increase in BP, the nerve afferents from baroreceptros stimulate the ____ and this leads to inhibition of ___ and ____ to slow heart rate

NTS; sympthatetic nerve impulses and an increase in parasympathetic nerve outflow to

Increased baroreceptor firing rate leads to

vasodilation and bradychardia

A decrease in BP leads to a decrease in _____ firing

baroreceptor

Less baroreceptor firing leads to less ____ stimulation and increase in ____ drive

glutamate; sympathetic drive

The parasympathetic pathway is full of ____ neurons

excitatory

Parasympathetic control is only in the

heart

The parasympathetic activity is done through the

vagus nerve

Adaptation of the baroreceptors occurs during ____ changes in mean arterial blood pressure such as ____

long-term; hypertension

Low pressure baroreceptors are located in the

atria and pulmonary vessels

When low pressure baroreceptors sense too much stretch/load they trigger the _____ system to reduce the preload

parasympathetic nervous system

In the atria, afferent fibers travel up the ____ to the medulla

vagus nerve

In the atria, increased stimulation increases stimulation causing negative feed back to ____ preload by ____ CO2

reduce; increasing

The carotid and aortic arch baroreceptors are considered _____ baroreceptors

high pressure

In the atria, increased stimulation leads to _____ Parasympathetic NS to heart to ___ HR

decrease; increase

In the atria, increased stimulation leads to ____ Sympathetic NS to the heart and ___ HR

increase; increase

Peripheral chemoreceptors are

aortic bodies and carotid bodies

Aortic bodies and carotid bodies are highly ____ cells in the aortic arch and carotid sinus

vascularized

Peripheral chemoreceptors are sensitive to

blood O2, CO2, and pH

Peripheral chemoreceptros are extremely involved with

respiratory regulation

Two classes of chemoreceptors

peripheral and central

Central chemoreceptors have the primary role in

respiratory regulation

Central chemoreceptors are more sensitive to

CO2

Oxygen levels have little to no effect on

Central chemoreceptors

increased blood CO2 levels cause a drop in pH, which stimulates _____ and increased the ____ outflow

Central chemoreceptors; sympathetic

If there was decreased ventilation, we would see an increase of ____ in blood which would then increase

CO2; stimulation sympathetic outflow and vasoconstriction

Long term control of BP involves

regualting systemic blood volume, largely by the kidneys

Long term BP regulation amin mechanism and examples

hormonal; ADH, RAAS, and atrial natriuretic peptides

Long term BP regualtion hormones affect blood volume by

regulating salt and water excretion/retention from kidneys

Normal individual at rest mean arterial BP

90 mm Hg

Hypertensive individual mean arterial BP

>110 mm HG

Hypertensive individual Systolic/diastolic

>135 and >90

Sever hypertension mean arterial BP

150-170 mm Hg

Severe hypertension systolic/diastolic pressure

250/130

In essential hypertension, the MBP is

elevated but cardiac output is still normal

With those with essential hypertension, the high BP is

essential