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CVPR > CVPR Week 3: Reflex Control of Cardiovascular Function > Flashcards

CVPR Week 3: Reflex Control of Cardiovascular Function Flashcards

1
Q

Objectives

A
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2
Q

Blood pressure control system theory

A
  • the controlled variable (arterial pressure/blood volume) is measured by a sensor (blood pressure)
  • (receptors) sensor relays information to the controller (brain stem)
  • the controller uses (through efferent nerves/hormones) an effector (vessels/heart/kidney) to modify the controlled variable (arterial pressure/blood volume)
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3
Q

Identify

A
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4
Q

Primary divisions of the nervous system

A
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5
Q

Autonomic regulation of CV function (efferent pathways)

A
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6
Q

Identify

A
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7
Q

MABP equation

A

TPR x CO = MABP

TPR = Total peripheral resistance

CO = Cardiac output

MABP = Mean arterial blood pressure

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8
Q

How would an increase in blood volume impact MABP?

A

↑

because of ↑ CO from increasing preload and Starling’s Law through ↑End-diastolic volume

If the volume is increased in a closed system the pressure is also increased so ↑ Pressure

Blood volume and blood pressure an directly proportional

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9
Q

Question

A
  • there are sensors that detect blood pressure and blood volume
  • sends info to the central nervous system
  • sent to autonomic efferent pathways to constitute the reflex control of CV function
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10
Q

Reflex control of CV function overview

A
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11
Q

Reflex control of CV function afferents

4 listed

A

Arterial baroreceptors

Pulmonary receptors

Atrial & vena caval receptors

Ventricular receptors

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12
Q

Cardiopulmonary baroreceptors

4 listed

A
  • Pulmonary receptors
  • Atrial & vena caval receptors
  • Ventricluar receptors
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13
Q

Cardiopulmonary baroreceptors innervation to the central controller

2 listed

A
  • Vagal afferents
  • Sympathetic afferents
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14
Q

Reflex control of CV function Efferents

A
  • Heart
  • Blood vessels
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15
Q

Reflex control of CV function efferents innervation

2 listed

A
  • Vagal efferents to the heart
  • Sympathetic efferents to the heart and blood vessels
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16
Q

Reflex control of CV function Central controller

A

Medullary Cardiovascular centers

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17
Q

The arterial baroreflex function

A
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18
Q

Describe the arterial baroreceptor reflex Stimulus and responses

A

Stimulus: Acute change in blood pressure

Responses: Changes in heart rate, contractility & vascular resistance

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19
Q

Sensors of the arterial baroreceptors

A
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20
Q

Identify

A
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21
Q

Describe the arterial baroreceptor reflex components

A
  • Baroreceptors
  • Baroreceptor afferent nerves
  • Parasympathetic nerves
  • Sympathetic nerves
  • Medullary vasomotor center
  • Heart
  • Vasculature
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22
Q

Arterial baroreceptors location

A
  • Aortic arch
  • Carotid sinus

&

  • nearby large arteries
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23
Q

Arterial baroreceptor sensitivity is impaired by?

A
  • Aging
  • Hypertension
  • Atherosclerosis
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24
Q

Carotid sinus baroreceptor innervation

A

branch of the Glossopharyngeal nerve

or

CN IX

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25
Q

Aortic arch baroreceptor innervation

A

Aortic nerve which is a branch of the Vagal nerves

or

CN X

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26
Q

Describe baroreceptor sensitivity

A
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27
Q

Don’t confuse aortic bodies from aortic baroreceptors

or carotid bodies from carotid baroreceptors

A
  • Carotid and aortic bodies are chemoreceptors which sense things like blood oxygen saturation (partial pressure of blood gasses) and function in the regulation of ventilation
  • in the same general location and have the same afferent innervation
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28
Q

Where are baroreceptors located histologically

A

in the adventitial layer of the vascular wall

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29
Q

How do baroreceptors sense changes in blood pressure?

A
  • They are mechanoreceptors which sense stretching of the adventitial layer of the vascular wall
  • An increase in BP will stretch the arterial wall and activate the baroreceptors and increases action potential firing back to the central controller
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30
Q

If the vessel is less compliant how will this affect baroreceptors

A
  • The vessel will be resistant to stretch and therefore produce less activation of the baroreceptors
31
Q

Baroreceptor sensed variables

3 listed

A
  1. MABP
  2. Pulse Pressure
  3. dP/dt
32
Q

Baroreceptor firing rate is a function of?

33
Q

Highest baroreceptor firing rate is when

A

during ventricular contraction, because it is the highest dP/dt

34
Q

How does the baroreceptor reflex control MABP?

A

Baroreceptors regulate CO and TPR

CO x TPR = MABP

35
Q

Efferent limbs of the baroreceptor reflex

A
  • ANS response
  • Hormonal responses (slower than ANS)
36
Q

Baroreceptor reflex: Autonomic responses

A
  • Imagine an increase in MABP sensed by the carotid sinus or aortic baroreceptors by an increased stretch
  • This enhances the Carotid sinus or aortic baroreceptor firing rate to the vasomotor center of the medulla which is determined to be either above or below the set point
  • The vasomotor center through sympathetic vasomotor nerves decrease firing rate
  • Arterioles and veins dilate and TPR is ↓
37
Q

Baroreceptor reflex: Renin-angiotensin-aldosterone system

A

Renin-Angiotensin-Aldosterone System

increase in sympathetic nerve activity causes the kidney to release Renin into the renal circulation

Renal juxtaglomerular cells (modified vascular smooth muscle cells that don’t contract but have an endocrine function and have β1 receptors)

Renin converts angiotensinogen → angiotensin I —-(ACE)→ Angiotensin II → causes vasoconstriction by inactivating AT1 receptors

ACE AKA Angiotensin-converting enzyme

Angiotensin II binds to angiotensin receptors inactivating them and causes vasoconstriction

38
Q

ACE AKA

A

Angiotensin converting enzyme

39
Q

Angiotensin I

A

relatively inactive

converted to angiotensin II by ACE

40
Q

Angiotensin II

A

active metabolite of angiotensin I

inactivates AT1 receptors and causes vasoconstriction

41
Q

Baroreceptor reflex: Hormonal responses

A
  • Renin-angiotensin-aldosterone system
  • Arginine Vasopressin
  • Sympathoadrenal system
42
Q

Baroreceptor reflex: Arginine Vasopressin

A

Arginine Vasopressin is made and stored in the posterior pituitary

binds to V1 receptors leading to vasoconstriction

43
Q

Arginine Vasopressin is found where

A

made and stored in the posterior pituitary

44
Q

Arginine Vasopressin AKA

A

Anti-diuretic Hormone

These are the same molecules

45
Q

Baroreceptor reflex: Hormonal responses efferent limbs

A
  1. imagine a fall in blood pressure
  2. ↓MABP
  3. ↓Baroreceptor stretch
  4. ↑Renin SNA and ↑AVP (ADH)
  5. causes vasoconstriction
  6. ↑MABP = CO x ↑TPR
46
Q

Baroreceptor reflex: Hormonal Responses: Sympathoadrenal system

A
  • increased sympathetic preganglionics that innervate adrenal medulla
  • chromaffin cells in the adrenal medulla are stimulated and they release catecholamines (80% epinephrine and 20% norepinephrine)

causes

  1. vasoconstriction (α1 receptors) NE and E
  2. ↑HR and contractility (β1 receptors) NE and E
  3. Vasodilation of skeletal and coronary circulations (β2 receptors) {epinephrine}
  4. ↑MABP = ↑CO x ↑TPR
47
Q

α1 receptor stimulation sensitivity

A
  • high affinity to NE over E
  • high concentrations of E will cause α1 activation
48
Q

Baroreceptors reflex: Regulation of CO: Autonomics

A
  1. ↑ MABP
  2. activates by stretch and increases firing rate of baroreceptors
  3. Vasomotor center evaluating vs set point
  4. ↑Vagal firing rate and ↓Cardiac sympathetic firing rate
  5. Heart responds by (↓Rate and ↓Contractility)
49
Q

Afferent and sympathetic efferent limbs of the baroreflex

50
Q

Central controller

A

Medullary cardiovascular centers

51
Q

Medullary cardiovascular centers pathways: Sympathetics

A

afferent lobs of the baroreceptors to the NTS (Nucleus tractus solitarius)

NTS to CVLM (caudal ventral lateral medulla)

CVLM releases GABA to inhibit RVLM (Rostral ventral lateral medulla)

RVLM activity is decreased so the IML activity is reduced and less adrenal, arterial and heart sympathetic activity

↓HR, ↓CO and ↓MABP

A decrease in MABP would decrease the release of GABA and would result in more sympathetic activation

52
Q

Medullary cardiovascular centers pathways: Parasympathetics

A
  • afferent lobs of the baroreceptors to the NTS (Nucleus tractus solitarius)
  • NTS to Nucleus ambiguous
  • nucleus ambiguous to parasympathetic post ganglionics to ↓HR and CO
53
Q

Summary of Baroreceptor reflex effects

54
Q

Summary of Baroreceptor reflex arterial components

55
Q

Question

A

Because the baroreceptor reflex very quickly resets to long-term changes in BP around a new set-point

A good example of this is in chronic hypertension

56
Q

Question

57
Q

Question

58
Q

Volume receptor-mediated reflex: Regulation of blood volume/arterial pressure

59
Q

Volume receptor-mediated reflex Sensors

A

Cardiopulmonary stretch receptors

60
Q

Volume receptor-mediated reflex afferents

A

Run in vagus

61
Q

Volume receptor-mediated reflex: Elevating blood volume

A

increases vagal nerve activity

62
Q

Volume receptor-mediated reflex: Central controller

A

Medullary CV centers

63
Q

Volume receptor-mediated reflex: Efferent Limbs

A
  • ANS
  • Hormones

Which function to?

  1. Regulate TPR
  2. Regulate renal function to control blood volume
64
Q

Volume receptor-mediated reflex: Autonomic responses

65
Q

Volume receptor-mediated reflex: Hormonal responses

66
Q

Volume receptor-mediated reflex: Hormonal responses that regulate TPR

67
Q

Volume receptor-mediated reflex: Hormonal responses that regulate renal function to control blood volume

A

Renin-angiotensin-aldosterone System (RAS)

And

Arginine Vasopressin

68
Q

Volume receptor-mediated reflex: Hormonal responses that regulate TPR RAS

69
Q

Volume receptor-mediated reflex: Hormonal responses that regulate TPR (AVP or ADH)

70
Q

Volume receptor-mediated reflex: renal response to reduced blood volume

71
Q

Volume receptor-mediated reflex: renal response to increased blood volume

72
Q

Summary of blood volume regulation

73
Q

Question

74
Q

Question and explanation

CVPR (93 decks)

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