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Block 2 Week 3 > Integrated CV Responses > Flashcards

Integrated CV Responses Flashcards

1
Q

What is the Valsalva Maneuver?

A
  • forced expiration against a closed glottis, occurs during defecation, coughing, lifting weight
  • decreases venous return
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2
Q

How does the valsalva maneuver decrease venous return?

A
  • when forcefully expire against a close glottis, your diaphragm pushed upward increasing the intrathorasic pressure (usually have negative intrathroasic pressure to suck blood into ventricles and increase preload) so now have less venous return
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3
Q

What are the 4 phases of the valsulva maneuver ?

A

1) forced expiration
2) sustained forced expiration
3) release
4) rebound

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4
Q

What occurs in valsulva maneuver forced expiration?

A
  • MAP increases as thoracic aorta compressed

- intrathroacic pressure increases

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5
Q

What occurs in valsulva maneuver sustained forced expiration?

A
  • MAP and PP decrease as the high intrathroacic pressure decreases venous return
  • baroreflex (Symp. augmentation occurs)
  • increase HR, vasodilation/veno constriction, stabilize MAP
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6
Q

What occurs in valsulva maneuver release phase?

A
  • brief increase in MAP due to release of pressure on thoracic aorta
  • surge in venous return
  • increase stroke volume
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7
Q

What occurs in valsulva maneuver rebound phase? What is the clinical test for baroreflex competence?

A
  • increase MAP
  • activation of baroreceptors
  • reflex bradycardia, (is the clinical test to see baroreflex competence)
  • increased PP
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8
Q

What happens in valsulva maneuver if don’t have functioning autonomic nervous system?

A
  • SNS and PNS can’t activate
  • BP will drop during valsulva & can’t be restored since no SNS response, brain under perfused and they faint- SYNCOPY
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9
Q

What is vasovagal syncope?

A
  • sudden withdrawal of sympathetic vascular tone (dilation) along w/ vaguely mediated bradycardia causing hypotension & inadequate brain perfusion
  • you faint
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10
Q

How do you withdraw sympathetic vagal tone?

A

a) loose SVR due to arteriolar vasodilation

b) loose CVP (preload) due to venodilation

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11
Q

what are the vagal effects in vasovagal syncopy?

A

-vagal nerve (from PNS) decreases HR, contractility and CO which significantly drops MAP and contributes to low brain perfusion

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12
Q

What can trigger vasovagal syncopy?

A

a) reduction in central blood volume (hemmorage, prolonged standing (peripheral venous pooling)
b) painful/unpleasant stimuli
c) prolonged exposure to heat, intense emotions, hunger, nausea/vomiting

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13
Q

Why do you wake up once collapse after vasovagal syncopy?

A
  • when hit ground the effects of gravity on your blood is eliminated, so it allows easier blood flow back to the heart/ throax so brain can be perfused rapidly
  • increases preload, restores MAP and CO rapidly
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14
Q

What is the Bezold-Jarisch Reflex?

A

1) peripheral pooling of blood decreases CVP, preload, and causes hypotension
2) activates baroreceptors, get SNS augmentation to heart
3) increase HR, contractility, but heart & LV empty due to peripheral pooling
4) causes distortion/defomration of myocardium as contracts around unfilled chamber & C-fibers activated
5) C-fibers tell medullary of NTS that heart too full so withdraw SNS and activate PNS & slow HR
6) powerful vagal discharge, worsens hypotension, loose brain perfusion and faint

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15
Q

what are the c-fibers in myocardium?

A
  • the cardiopulmonary baroreceptors (volume receptors)
  • when stretched, tell the brain heart has too much volume and to slow heart rate down
  • send info to medullary command center of NTS to increase PNS
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16
Q

How prevent Bezold-Jarisch Reflex?

A
  • drink more H20 to increase venous reservoir
  • compression socks
  • dont use diuretics
17
Q

what is syncope?

A
  • transient loss of consciousness accompanied by loss of postural tone (fall down)
  • when hit ground Bezold-Jarisch Reflex stoped and SVR along with decreases in gravity effect is easier to push blood to thorax
  • life legs help to use gravity to push blood to thorax
18
Q

What are the components of blood pressure?

A

-2 components, hemodynamic pressure
-hemodynamic pressure: pressure generated by the heart
-hydrostatic pressure: pressure generate day gravity, density & length of the blood column
BP= Pa + pgh

19
Q

How does gravity effect our BP?

A
  • gravity has greatest effects when standing upright (orthostasis) decreases when lying down (supine)
  • humans hold ~70% of blood below heart so need extra pressure to pump against gravity to get blood to heart
  • quadrapeds lack this issue so require less BP
20
Q

How do giraffes combat gravity?

A
  • griaffess require 200mmHG of extra BP to get blood up to heart they adapted by:
    1) large, muscular heart
    2) rapid resting HR (~150)
    4) have system to prevent the 200mmHG from falling into brain when drop heads to drink
    5) have tight sheaths of thick skin around lower limbs that maintains high extravascular pressure to push blood up to heart like pilot G-suits have
21
Q

What happens when go from supine to orthostatic (lying down to standing up?

A
  • lay down have ~600mL of blood in thoracic compartment, large veins of chest swell w/ extra blood, pre-load, SV, and CVP increase
  • when stand upright gravity add ~75mmHG of hydrostatic pressure and the 600mL falls into lower limbs
  • SNS & baroreceptors help push blood up to thorax but you get postural hypotension briefly (head rush)
22
Q

How does gravity affect MAP, CVP, and perfusion pressure?

A
  • gravity has no effect on perfusion pressure and since is such a transient issue (unless have issues with SNS/ baroreceptor) won’t have affect on CVP/MAP since a transient situation
23
Q

What are the effects of rising? and which are the W baroreflex compensations?

A 
baroreflex compensations
- increase HR
-increase SVR
-increase vasotone (constriction)
other effects of rising?
-decrease central blood volume 
-increase blood volume in legs 
-decrease SV 
-decrease CVP
24
Q

How does do we counter peripheral venous pooling in extremities?

A
  • activating skeletal muscle pump and respiratory pump
  • both help milk blood up to the thorax and prevent venous pooling
  • throughout day if have healthy valves the venous pressure in legs rises and falls rhythmically as move around
25
Q

What happens if have leaky valves?

A

-as your sk. muscle and respiratory pumps milk blood up to the thorax, some blood slips back through valves down to legs due to pressure of gravity (hydrostatic pressure)
-can develop varicose veins and prone to venous ulcerations
-

26
Q

what is pedal edema?

A
  • swelling of the feet if have leaky valves or prolonged standing w/o moving around
  • gravity increases venous pressure since pushing blood into feet, causes distention of the veins
  • pressure transmitted back into arteries causing them to push fluid out into the interstitum and get edema
27
Q

What is postural hypotension cause and mechanisms?

A
  • postural hypotension= a decrease in BP within 1-3 min of standing from being supine, mostly in elderly pop*
  • this is due to lapse in venous return on standing resulting in inadequate perfusion of brain
  • if have blunted baroreflex can be severe
  • mechanism is gravitational shift in thoracic blood to the lower extremities
28
Q

What is postural hypotension precipitating factors? and principle defense?

A
  • precipitating factors= hypovolumia, peripheral venous pooling, venous valve insufficiency
  • principle denies: baroreflex, sk muscle pump activity

Block 2 Week 3 (6 decks)

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