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53 Cards in this Set
- Front
- Back
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The most powerful short-term regulator of MAP
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Arterial Baroreflex.
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Resting Tone of the Heart is
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VAGAL TONE
You can speed it up by either removing the vagal tone or by adding SNS tone. |
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SNS branches out from the ______ spine.
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Thoracolumbar.
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Components of a Control System (Negative Feedback Loop)
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A) SENSOR - Detects magnitude of variable that is controlled.
B) AFFERENT PATHWAY - Pathway for detected signal to go to the integrator. C) INTEGRATOR - Compares detected value with homeostatic range. Makes changes if necessary. D) EFFERENT PATHWAY - Pathway to effector E) EFFECTOR - Evokes changes to return the controlled variable to homeostatic value. |
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PNS review
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Vagus Nerve releases ACh to M2 receptors on heart.
Decreases inotropy, chronotropy, dromatropy, lucidotropy. No innervation of vasculature (except penis). Decreases BP by decreasing HR. |
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T/F
Basal Tone to heart is at zero. |
False.
The resting basal tone of the heart is VAGAL. Therefore you can increase heartrate by decreasing PNS. Or by adding SNS. |
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Extrinsic Regulation of Blood Flow will affect what vascular beds?
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Extrinsic Regulation of UPSTREAM PRESSURE will cut off blood supply to the
Renal, GI Skeletal Muscle Skin/ Cutaneous (Team ball players). Perfusion to Heart and Brain are maintained. |
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SNS review
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Releases Epi, NE to Alpha 1 receptors causes vasoconstriction.
Epi, NE to Beta 1 receptors causes positive iontropy, chronotropy, dromotrophy, and Lucitropy. Epi to Beta 2 receptors causes Vasodilation of skeletal muscle |
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Venoconstriction reduces vein
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compliance.
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Only the baroreceptor responses to ______ pressure will occur during diastole.
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static
(if the static pressure/ stretch is large enough). |
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Arterial Baroreceptors are located where?
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Carotid Sinus
Aortic Arch. |
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What afferent nerve carries the carotid sinus baroreceptor signal to the brain?
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Sinus nerve, part of the GLOSSOPHARYNGEAL NERVE.
Cranial Nerve # 9. |
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What afferent nerve carries the Aortic Arch baroreceptor signal to the brain?
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aortic nerve, part of the VAGUS NERVE
Cranial nerve 10 |
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Arterial baroreceptors respond to the ______ and _______ aspects of stretch/ pressure.
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Arterial baroreceptors respond to the PHASIC and STATIC aspects of stretch/ pressure.
PHASIC RESPONSE - firing rate related to rate of change in receptor stretch STATIC RESPONSE - firing rate related to degree of receptor stretch There is a threshold pressure level. There is also a saturation pressure level (200). |
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What MAP level will saturate arterial baroreceptors so that you have no response to increased BP?
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200
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True or false
Anything that changes BP will evoke a baroreflex? |
TRUE
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The "Integrator" of BP feedback loops is the
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The integrator of BP feedback loops is the Medulla of the Brainstem.
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Arterial Baroreceptors
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Mechanoreceptors that respond to stretch to detect changes in blood pressure. (respond to stretch by blood in the aorta or carotid artery).
Located in the carotid sinus and the aortic arch. CAROTID SINUS - responds to increases and decreases in BP AORTIC ARCH - responds to increases in BP. These act to increased BP by stimulating NTS via the Glossopharyngeal Nerve and the Vagus Nerve respectively. |
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Caudal Ventrolateral Medulla (CVLM)
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Located at about the same ventrolateral coordinates as the RVLM, except just caudal (about middle third of medulla).
-When stimulated by the NTS (nucleus of the tractus soliltarus), it INHIBITS THE RVLM, causing DECREASED BP, and LOSS OF BASAL VASCULAR TONE!! |
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The CVLM is stimulated by
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the NTS (Nucleus of the tractus solitarus).
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If BP goes up, what happens to baroreceptor afferent activity? What happens to HR and BP?
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Afferent activity goes UP!!
*Baroreceptors afferents increase stimulation of NTS, which stimulates CVLM, NA and DVM, *NA and DVM (via vagus nerve) stimulate heart to decrease HR. *CVLM inihibits RVLM and causes a drop in blood pressure. |
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If BP goes down, what happens to baroreceptor afferent activity? What happens to HR and BP?
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Afferent Activity goes DOWN!!
*Baroreceptor afferents DECREASE stimulation of NTS, which decreases stimulation of NA, DVM, and CVLM. * Less NA and DVM stimulation will cause HR to go up. *Less CVLM causes less inhibition of RVLM. Increased RVLM activity increases BP. |
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Nucleus Ambiguios (NA)
and Dorsal Motor Nucleus of the Vagus (DMV) |
Source of efferent VAGAL neurons (preganglionic parasympathetic) to the heart.
Stimulated by NTS. Stimulate the heart to decrease HR. |
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What are all the parts of the integrator in the medulla?
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RVLM - tonic excitatory activity to SPN in spinal cord, causing vasoconstriction.
CVLM - Inhibits RVLM NTS - Stimulated by Baroreceptor Afferents. Stimulates CVLM, NA, and DMV NA/ DVM - axon is the vagus nerve. Stimulation causes decreased HR. |
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Increased BP will cause what changes via the baroreflex?
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1) Increased baroreceptor afferent activity (Cranial nerves 9 and 10), which stimulate NTS
2) Decreased HR via NA, DVM stimulation 3) Decreased BP via CVLM inhibition of RVLM |
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Decreased BP will cause what changes via the baroreflex?
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1) Decreased baroreceptor afferent activity (Cranial nerves 9 and 10), which decrease stimulation of NTS
2) Increased HR via decreased NA, DVM stimulation 3) Increased BP via decreased CVLM inhibition of RVLM |
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Nucleus of the tractus solitarius (NTS)
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Recieves a tremendous amount of input from cranial nerves IX (Glossopharyngeal) and X (Vagus) (baroreceptor afferents).
(Also receives input Vagus nerve as a cardiopulmonary mechanoreceptor afferent) Sends EXCITATORY projections to: 1) CVLM 2) Nucleus Ambiguus (NA) 3) Dorsal Motor Nucleus of the Vagus (DMV). 4) Hypothalamus (Hypothalamus then inhibits the release of vasopressin (ADH).Lowering BP). (Part of the CB reflex). |
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NTS is stimulated by
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baroreceptor afferents
Cranial Nerve IX - Glossopharyngeal from Carotid Sinus. Cranial Nerve X - Vagus from Aortic Arch. CP Mechanoreceptors Afferent.: Vagus Nerve |
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What is the source of the vagus nerve in the medulla?
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NA and DMV
Nucleus Ambiguus and Dorsal Motor Nucleus of the Vagus (DMV). (Stimulated by NTS). |
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Control of heart rate during the baroreflex is done by mediation of the
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Parasympathetic NS.
Decreased Afferent Activity, decreased stimulation of NTS, decreased stimulation of NA and DMV, Increased HR. |
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What are the two effector organs of the baroreflex?
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Heart
Blood Vessels. |
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A Shift in the baroreflex curve will be seen with what disease?
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Hypertension.
The MAP set range is increased. (Not good). Body adapts to new set range, will be dangerous to have BP below this. |
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Do Baroreceptors saturate?
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Yes. At an MAP> 200.
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Baroreceptors are very powerful ____ _____ regulators of BP
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Short Term.
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Why are baroreceptors not long term regulators of BP?
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Because long term HTN will cause the baroreflex to shift to the right and create a new set point (ie, they ADAPT).
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An increase in MAP causes a(n) _________ in cranial nerve afferent activity and a __________ in PNS vagal activity via the barorecptor reflex.
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An increase in MAP causes a(n) increase in cranial nerve afferent activity and a increase in PNS vagal activity via the barorecptor reflex.
Also causes RVLM inihibiition by CVLM |
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Cardiopulmonary Mechanoreceptors
(Cardiopulmonary Baroreflex) |
These receptors are located in the Vena Cava, Pulmonary Artery and the Heart.
Respond to stretch. Do not respond to phasic and static stretch like arterial baroreceptors because these areas are much more compliant. They only respond to changes in volume. MONITOR CENTRAL BLOOD VOLUME. *Increased CBV, increased stretch, sends signal via vagus nerve to the NTS. *NTS stimulates CVLM, which inhibits RVLM, decreasing BP. *NTS stimulates NA, DMV, which send a signal via the vagus to the heart to DECREASE HR. * NTS stimuates the hypothalamus to inhibit the release of vasopressin, decreasing BP. Bainbridge Reflex - increase in HR when you get a rapid filling of the ventricle. Big influx in volume can cause an increase in HR. (not prominent in humans.....more in dogs). |
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Bainbridge Reflex
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Increase in HR when you have a rapid filling of the ventricle.
Only happens when you RAPIDLY fill the ventricle with a LARGE amt of volume. Not common in humans. More common in dogs. |
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If a person is not spontaneously breathing, and they develop bradycardia and increased BP, what do you do?
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Ventilate them.
Lung Mechanoreceptors will cause tachycardia and decreased vasoconstriction, overiding the chemoreceptor response. |
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Arterial chemoreceptor response of bradycardia and vasoconstriciton only occurs in patients who....
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are not spontaneously breathing.
(no lung mechanoreceptor response). |
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The ultimate CV response from visceral nociceptors depends on...
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which NS gets activated the most.
PNS (vagus) - bradycardia and decreased MAP SNS (Spinal) - tachycardia and increased MAP |
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Visceral Nociceptors with Spinal (SNS) Afferents
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LOCATION - Heart, GI
STIMULUS - Pain from pressure (mechanical) or chemical (capsaicin, serotonin, histamine, bradykinin). EFFECT - Tachycardia and Increased SNA (SNS outflow). - VASOCONSTRICTION. Increased MAP and HR. |
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Bezold - Jarisch Reflex
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Name given to reflex when cardiac nociceptor afferents are chemically stimulated. (capsaicin, serotonin, histamine, bradykinin)
Get to brain via VAGUS: Causes Bradycardia and decreased MAP |
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Vasovagal Syncope
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Visceral pain caused from touching ventricle wall (when they don't have enough blood). Drive visceral nociceptors to the brain via VAGUS. Cause syncope from the bradycardia and decreased MAP.
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Diving Reflex
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RECEPTOR LOCATION: face and nasopharynx
STIMULUS: Fluid on face, face in water EFFECT: *PNS to heart --> BRADYCARDIA. *SNS to vasculature -->VASOCONSTRICTON |
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Ice to the face during SVT demonstrate what reflex?
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The diving reflex
Bradycardia and vasoconstriciton. |
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The diving reflex is greatly enhanced with
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apnea.
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MAP is regulated by reflexes that change ________ and __________.
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TPR and CO.
MAP = TPR * CO |
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The basal tone of the vascular beds is
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sympathetic.
Can vasoconstrict by increasing sympathetic tone. Can vasodilate by decreasing sympathetic tone. (This is true for the skeletal muscle, GI, and skin, but don't forget that NO also has a basal tone on the vasculature due to shear stress.) Also, the kidneys autoregulate. So does the brain. The heart depends on O2 comsumtion only. The brain also depends on CO2 levels in the body. Also don't forget that sympathetic cholinergics vasodilate the skin.). |
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What are the two ways HR is increased?
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1) Increase SNS outflow to the heart (Beta 1 receptor) (RVLM stimulation)
2) Decreased PNS outflow to the heart (M2) receptors (DECREASED NA and DMV stimulation via vagus nerve). These both happen at once. |
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Arterial Chemoreceptors
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LOCATION: carotid and aortic bodies.
STIMULUS: Increases in PCO2, H+, decrease in O2 of arterial blood. FUNCTION: To regulate RR depending on the the levels of the above gases in arterial blood. HOWEVER, stimulation will also cause BRADYCARDIA and increased VASOCONSTRICTION to the periphery. This will most likely increase BP. IF THE PT IS SPONTANEOUSLY BREATHING WILL YOU SEE THIS EFFECT? No. Why? Lung Mechanoreceptors (from breathing) cause the opposite: Tachycardia and decreased SNS vasoconstriction. Lung mechanoreceptors override the chemoreceptors. |
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Visceral nociceptors with VAGAL afferents.
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LOCATION - Heart, J-receptors on interstitium of lung, GI
STIMULUS - Pain from pressure (mechanical) or chemical (capsaicin, serotonin, histamine, bradykinin). EFFECT - Bradycardia and decreased SNS outflow (SNA) (vasodilation). Bezold-Jarisch Reflex: Name given to reflex when cardiac afferents are chemically stimulated. (capsaicin, serotonin, histamine, bradykinin) Vasovagal Syncope: Visceral pain caused from touching ventricle wall (when they don't have enough blood). Drive visceral nociceptors to the brain via vagus. Cause syncope from the bradycardia and decreased MAP. |
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A decrease in MAP causes an ______ in SNS afferent activity (cranial nerves 9 and 10) and a ________ in PNS vagal activity via the baroreceptor reflex.
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A decrease in MAP causes an decrease in cranial nerve afferent activity and a decrease in PNS vagal activity via the baroreceptor reflex.
This will cause less RVLM inihibition by CVLM, increasing vasoconstriction. This will cause increased HR via removal of NA and DMV. |
