Upgrade to remove ads
Nervous Control of Circulation
Terms in this set (36)
Pa= CO x TPR
an increase in cardiac output (CO) or total peripheral resistance (TPR) can _________ MSAP (Pa)
CO= SV x HR
an increase in stroke volume (SV) or heart rate (HR) _______ cardiac output (CO)
what is the major factor affecting cardiac output (CO)?
what is the major factor affecting total peripheral resistance (TPR)?
-acute, short-term: fast-responding, CNS-mediated baroreceptor reflex response
-chronic, long-term: slower-responding, hormonally/renally-mediated renin-angiotensin-aldosterone system
what are the 2 mechanisms for regulating arterial pressure (Pa)?
-neurons secrete NE; fibers distributed throughout cord
-nerve impulses from the pressor area stimulate sympathetic vasoconstrictor nerves and cardiac nerves
what are the impulses of the vasoconstrictor area of the medullary vasomotor center?
-increased heart rate
what are the physiologic responses resulting from nerve impulses originating in the vasoconstrictor area of the medullary vasomotor center?
continuous, slow firing maintaining a partial state of contraction in vascular smooth muscle
adjusted by variations in the rate of tonic discharge; inhibition of tonic activity causes vasodilation
Medullary cardioinhibitory center
located in the nucleus ambiguous and dorsal nucleus of vagus nerve
-parasympathetic output: stimulation of the vagus nerves decreases heart rate and cardiac output
-little to no effect on TPR
what are the physiologic responses resulting from nerve impulses originating at the medullary cardioinhibitory center?
-the most important mechanism for responding to changes in MSAP
-an acute, short-term control mechanism for regulating arterial pressure
100 mm Hg
what is the set point of the baroreceptor reflex?
negative feedback system
what kind of feedback control does the baroreceptor reflex have?
-The baroreceptor reflex is initiated by stretch receptors located in the walls of the carotid sinus and aortic arch
-From the carotid sinus, signals in response to stretch travel through Hering's nerve to the glossopharyngeal nerve (CN IX) to the nucleus of the tractus solitarius (NTS) in the medullary area of the brain stem
-From the aortic arch, signals in response to stretch travel through the vagus nerves to the NTS
describe the location of baroreceptors and pathways for nerve impulse transmission to the medullary area of the brainstem
-An increased Pa stretches the walls of the carotid sinus and aorta and stimulates "sensor" cells mediating the baroreceptor response
-Baroreceptor stimulation results in increased frequency of firing of afferent signals from the carotid sinus and the aortic arch to the medulla area
how does an increased arterial pressure (Pa) affect the baroreceptor reflex?
A decreased Pa results in a decreased stretch on carotid sinus baroreceptors causing decreased afferent firing of carotid sinus nerve
how does a decreased arterial pressure (Pa) affect the baroreceptor reflex?
For an increased Pa, the baroreceptor reflex increases the firing frequency of the afferent signals
for an increased Pa, explain the changes in firing frequency of afferent signals:
For a decreased Pa, the baroreceptor reflex decreases the afferent firing of the carotid sinus nerve
for a decreased Pa, explain the changes in firing frequency of afferent signals:
the vasoconstrictor area is inhibited which results in a decreased sympathetic outflow
for an increased Pa, explain the response of the vasoconstrictor area:
The cardioinhibitory center is excited which increases parasympathetic outflow
for an increased Pa, explain the response of the cardioinhibitory center:
the vasoconstrictor area has increased activity which increases sympathetic outflow to heart and vessels
for a decreased Pa, explain the response of the vasoconstrictor area:
The cardioinhibitory center is inhibited which decreases parasympathetic outflow to the heart
for a decreased Pa, explain the response of the cardioinhibitory center:
-there is a decreased sympathetic tone resulting in the peripheral vasodilation of arterioles and veins to lower TPR
-There is also an increased vagal stimulation resulting in decreased heart rate that decreases CO
-The net response is decreased Pa
for an increased Pa, describe the reflex responses (efferent signals) of heart & vasculature:
there is an increased:
-heart rate and contractility
-and increased venoconstriction that causes increased VR
-The net effect is an increase in Pa
for a decreased Pa, describe the reflex responses (efferent signals) of heart & vasculature:
postural (orthostatic) hypotension
-may occur if the baroreceptor reflex is impaired
-If body position is changed from lying down to standing up, hydrostatic forces will cause pooling of blood in the extremities, decreased systemic Pa, and decreased cerebral perfusion
-The decreased Pa in the brain can cause unconsciousness
-Baroreceptors do not participate in long-term Pa regulation, and they will reset in 1-2 days to whatever Pa to which they are constantly exposed
-This prevents baroreceptors from controlling changes in Pa that last longer than a few days at a time
-involved in the mechanism for essential hypertension
explain the resetting of baroreceptors:
location of arterial chemoreceptors?
-excess carbon dioxide
-excess hydrogen ion (low pH)
what do arterial chemoreceptors respond to?
reflexively excite the vasoconstrictor center
what are arterial chemoreceptor effects of stimulation on the vasomotor center?
in the walls of the atria and pulmonary artery
where are low pressure stretch receptors located?
-stimulated by increased blood volume, increased VR, increased CO, and increased Pa
-response is a decreased Pa by two mechanisms
explain the activation & response of low pressure stretch receptors:
A decreased activity of the pressor area inhibits sympathetic outflow and decreases TPR
what are low pressure stretch receptor effects of stimulation on the vasomotor center?
-inhibition of vasopressin release that causes decreased water reabsorption in the kidney helping to restore blood volume to normal
what are low pressure stretch receptor effects on vasopressin secretion?
-The CNS ischemic response can cause total constriction of some peripheral vessels (renal shutdown may occur)
-greatly increased sympathetic activity elevates Pa to as high a value as can be achieved by the pumping action of the heart (may reach 250 mm Hg)
how does the CNS ischemic response affect peripheral circulation?
-increased intracranial pressure (ICP) compresses the cerebral arteries resulting in cerebral ischemia
-sympathetic stimulation (due to CNS ischemic response as above) raises the Pa above the ICP to restore cerebral blood flow
-increased Pa is detected by the baroreceptors; stimulation of the cardioinhibitory center results in parasympathetic-mediated lowering of the heart rate
-increased Pa with decreased heart rate is called the Cushing reaction (indicative of elevated ICP)
explain the Cushing Reaction:
THIS SET IS OFTEN IN FOLDERS WITH...
Cardiac Output & Venous Return
OTHER SETS BY THIS CREATOR
Prostate TBL Questions
Benign Prostatic Hyperplasia