CVPR Week 3: Reflex Control of Cardiovascular Function Flashcards
1
Q
Objectives
A
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)
3
Q
Identify
A
4
Q
Primary divisions of the nervous system
A
5
Q
Autonomic regulation of CV function (efferent pathways)
A
6
Q
Identify
A
7
Q
MABP equation
A
TPR x CO = MABP
TPR = Total peripheral resistance
CO = Cardiac output
MABP = Mean arterial blood pressure
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
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
10
Q
Reflex control of CV function overview
A
11
Q
Reflex control of CV function afferents
4 listed
A
Arterial baroreceptors
Pulmonary receptors
Atrial & vena caval receptors
Ventricular receptors
12
Q
Cardiopulmonary baroreceptors
4 listed
A
- Pulmonary receptors
- Atrial & vena caval receptors
- Ventricluar receptors
13
Q
Cardiopulmonary baroreceptors innervation to the central controller
2 listed
A
- Vagal afferents
- Sympathetic afferents
14
Q
Reflex control of CV function Efferents
A
- Heart
- Blood vessels
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
16
Q
Reflex control of CV function Central controller
A
Medullary Cardiovascular centers
17
Q
The arterial baroreflex function
A
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
19
Q
Sensors of the arterial baroreceptors
A
20
Q
Identify
A
21
Q
Describe the arterial baroreceptor reflex components
A
- Baroreceptors
- Baroreceptor afferent nerves
- Parasympathetic nerves
- Sympathetic nerves
- Medullary vasomotor center
- Heart
- Vasculature
22
Q
Arterial baroreceptors location
A
- Aortic arch
- Carotid sinus
&
- nearby large arteries
23
Q
Arterial baroreceptor sensitivity is impaired by?
A
- Aging
- Hypertension
- Atherosclerosis
24
Q
Carotid sinus baroreceptor innervation
A
branch of the Glossopharyngeal nerve
or
CN IX
25
Aortic arch baroreceptor innervation
Aortic nerve which is a branch of the Vagal nerves
or
CN X
26
Describe baroreceptor sensitivity
27
Don't confuse aortic bodies from aortic baroreceptors
or carotid bodies from carotid baroreceptors
* 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
28
Where are baroreceptors located histologically
in the adventitial layer of the vascular wall
29
How do baroreceptors sense changes in blood pressure?
* 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
30
If the vessel is less compliant how will this affect baroreceptors
* The vessel will be resistant to stretch and therefore produce less activation of the baroreceptors
31
Baroreceptor sensed variables
3 listed
1. MABP
2. Pulse Pressure
3. dP/dt
32
Baroreceptor firing rate is a function of?
MABP
33
Highest baroreceptor firing rate is when
during ventricular contraction, because it is the highest dP/dt
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How does the baroreceptor reflex control MABP?
Baroreceptors regulate CO and TPR
CO x TPR = MABP
35
Efferent limbs of the baroreceptor reflex
* ANS response
* Hormonal responses (slower than ANS)
36
Baroreceptor reflex: Autonomic responses
* 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
Baroreceptor reflex: Renin-angiotensin-aldosterone system
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
ACE AKA
Angiotensin converting enzyme
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Angiotensin I
relatively inactive
converted to angiotensin II by ACE
40
Angiotensin II
active metabolite of angiotensin I
inactivates AT1 receptors and causes vasoconstriction
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Baroreceptor reflex: Hormonal responses
* Renin-angiotensin-aldosterone system
* Arginine Vasopressin
* Sympathoadrenal system
42
Baroreceptor reflex: Arginine Vasopressin
Arginine Vasopressin is made and stored in the posterior pituitary
binds to V1 receptors leading to vasoconstriction
43
Arginine Vasopressin is found where
made and stored in the posterior pituitary
44
Arginine Vasopressin AKA
Anti-diuretic Hormone
These are the same molecules
45
Baroreceptor reflex: Hormonal responses efferent limbs
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
Baroreceptor reflex: Hormonal Responses: Sympathoadrenal system
* 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
α1 receptor stimulation sensitivity
* high affinity to NE over E
* high concentrations of E will cause α1 activation
48
Baroreceptors reflex: Regulation of CO: Autonomics
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
Afferent and sympathetic efferent limbs of the baroreflex
50
Central controller
Medullary cardiovascular centers
51
Medullary cardiovascular centers pathways: Sympathetics
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
Medullary cardiovascular centers pathways: Parasympathetics
* 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
Summary of Baroreceptor reflex effects
54
Summary of Baroreceptor reflex arterial components
55
Question
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
Question
57
Question
58
Volume receptor-mediated reflex: Regulation of blood volume/arterial pressure
59
Volume receptor-mediated reflex Sensors
Cardiopulmonary stretch receptors
60
Volume receptor-mediated reflex afferents
Run in vagus
61
Volume receptor-mediated reflex: Elevating blood volume
increases vagal nerve activity
62
Volume receptor-mediated reflex: Central controller
Medullary CV centers
63
Volume receptor-mediated reflex: Efferent Limbs
* ANS
* Hormones
Which function to?
1. Regulate TPR
2. Regulate renal function to control blood volume
64
Volume receptor-mediated reflex: Autonomic responses
65
Volume receptor-mediated reflex: Hormonal responses
66
Volume receptor-mediated reflex: Hormonal responses that regulate TPR
67
Volume receptor-mediated reflex: Hormonal responses that regulate renal function to control blood volume
Renin-angiotensin-aldosterone System (RAS)
And
Arginine Vasopressin
68
Volume receptor-mediated reflex: Hormonal responses that regulate TPR RAS
69
Volume receptor-mediated reflex: Hormonal responses that regulate TPR (AVP or ADH)
70
Volume receptor-mediated reflex: renal response to reduced blood volume
71
Volume receptor-mediated reflex: renal response to increased blood volume
72
Summary of blood volume regulation
73
Question
74
Question and explanation
