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Autonomic Nervous System > ANS Reflexes > Flashcards

ANS Reflexes Flashcards

1
Q

Key points of integrations between the ANS and endocrine system

A

Renin-angiotensin-aldosterone system (RAAS)

Vasopressin

Glucocorticoids

Insulin

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2
Q

Five components of the biological feedback loop (arc)

A

Sensor
Afferent pathway
Control center
Efferent pathway
Effector organ or tissue

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3
Q

Component of the biological feedback loop that monitors the environment

A

Sensor

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4
Q

Component of the biological feedback loop that detects and change in a variable

A

Sensor

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5
Q

Component of the biological feedback loop that conducts the action potential towards the control center

A

Afferent pathway

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6
Q

Most common location of control center

A

CNS

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7
Q

Component of the biological feedback loop that links the sensor and control center

A

Afferent pathway

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8
Q

Component of the biological feedback loop that modifies output to effector

A

Control center

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9
Q

Component of the biological feedback loop that maintains a set point

A

Control center

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10
Q

Component of the biological feedback loop that links the control center to the effector organ/ tissue

A

Efferent pathway

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11
Q

Pathway that is almost alway a 2- neuron pathway (pre- and post- ganglionic)

A

Efferent pathway

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12
Q

Component of the biological feedback loop that elicits a physiologic change to restor homeostasis

A

Effector

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13
Q

Effector tissues/ organs in autonomic (visceral) reflex arcs

A

Smooth muscle
Cardiac muscle
Glands

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14
Q

Fast- acting reflex loops between the cardiovascular system and CNS

A

Cardiovascular reflexes

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15
Q

Short term BP control takes place via what mechanism?

A

Neural (ANS reflexes–> mechanoreceptors)

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16
Q

Longer term BP control takes place via what mechanism

A

Hormonal (RAAS, vasopressin, natriuretic peptides)

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17
Q

List the cardiac reflexes

A

Baroreceptor
Bainbridge
Bezold- Jarisch
Chemoreceptor
Vasovagal
Oculocardiac

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18
Q

Reflex that aims at maintaining BP around a setpoint

A

Baroreceptor reflex

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19
Q

Reflex that is responsible for maintaining BP during position changes

A

Baroreceptor reflex

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20
Q

Why do patients with chronic hypertension not tolerate hypotension well?

A

Baroreceptors have adapted to the higher BP and increased the set point for autoregulation

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21
Q

Location of high-pressure baroreceptors

A

Transverse aortic arch
Bifurcations of the carotid arteries

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22
Q

Afferent pathway of baroreceptor reflex

A

Transverse aortic arch > Vagus n (CN 10)

Carotid bifurcation > carotid sinus n (Hering’s n) > glossopharyngeal n (CN 9)

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23
Q

Where is the control center for the baroreceptor reflex?

A

Nucleus tractus solitarius (NTS) in the medulla

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24
Q

The spinal cord origin of cardioaccelerator fibers

A

T1-T4

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25
Q

Effect on baroreceptor reflex: volatile anesthetics

A

Impair in a dose-dependent fashion

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26
Q

Volatile anesthetic associated with the least impairment of the baroreceptor reflex

A

Isoflurane (has mild B1 agonist properties)

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27
Q

Effect on baroreceptor reflex: Propofol

A

Usually impairs

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28
Q

Effect on baroreceptor reflex: Ketamine

A

Activates SNS = increased HR with minimal change in SVR

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29
Q

Effect on baroreceptor reflex: Etomidate

A

Usually unchanged HR with small decrease in SVR

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30
Q

Effect on baroreceptor reflex: Thiopental

A

Preserves reflex

Decrease SVR with compensatory increase in HR

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31
Q

Effect on baroreceptor reflex: hydralazine

A

Preserves reflex

Decrease SVR d/t vasodilation and increase HR

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32
Q

Effect on baroreceptor reflex: nitroglycerine and nitroprusside

A

Preserved reflex

33
Q

Effect on baroreceptor reflex: beta blockers

A

Impair reflex

Prevent compensatory increase in HR depending on extent of B1 blockade

Labetolol also blocks alpha-1 receptor and may increase the risk of orthostatic hypotension

34
Q

Effect on baroreceptor reflex: phenylephrine

A

Preserves

35
Q

Effect on baroreceptor reflex: norepinephrine

A

Lower doses = B1 chronotropic effects prevail

As dose increases, alpha-1 vasoconstriciton overshadows and reflex is preserved

36
Q

Reflex that slows HR in the setting of profound hypovolemia

A

Bezold-Jarisch reflex

37
Q

Bezold-Jarisch triad

A

Bradycardia
Hypotension
Coronary artery dilation

38
Q

Reflex that prevents sludging of the blood in the veins, atria, and pulmonary circulation

A

Bainbridge reflex

39
Q

Reflex that increases HR and inotropy in the setting of persistent hypoxemia

A

Chemoreceptor reflex

40
Q

Bainbridge reflex: stimulus

A

Increased blood volume

41
Q

Bainbridge reflex: sensor

A

Increased firing of low-pressure stretch receptors during atrial firing

42
Q

Bainbridge reflex: afferent pathway

A

Vagus (CN 10) to the nucleus tractus solitarius

43
Q

Location of low-pressure baroreceptors

A

Atria
Lung vasculature

44
Q

Bainbridge reflex: control center

A

Nucleus tractus soltarius and its projections to CV centers in medulla

45
Q

Bainbridge reflex: efferent pathway

A

PNS and SNS pathways to SA node

46
Q

Bainbridge reflex: effector and response

A

SA node > increase HR

47
Q

Bainbridge reflex: effects on contractility and stroke volume

A

Insignificant

48
Q

Counterbalances the baroreceptor reflex

A

Bainbridge reflex

49
Q

Cardio-inhibitory reflex that may play a prominent role in cardioprotective reflexes in response to noxious stimuli

A

Bezold-Jarisch

50
Q

Chemical triggers for the Bezold-Jarisch reflex

A

Veratrum alkaloids, nicotine, capsaicin, histamine, sertonin, snake/ insect venoms

51
Q

Bezold-Jarisch reflex: stimulus

A

Noxious ventricular stimuli (MI, low venous return, thrombolysis)

52
Q

Bezold-Jarisch reflex: sensor

A

Chemo- and mechanoreceptors in the LV wall

53
Q

Bezold-Jarisch reflex: afferent pathway

A

Nonmyelinated C fibers in the vagus (CN 10) to the nucleus tractus solarius

54
Q

Bezold-Jarisch reflex: control center

A

Nucleus tractus solarius and medullary cardiovascular nuclei and centers

55
Q

Bezold-Jarisch reflex: efferent pathway

A

Vagus (CN 10)

56
Q

Bezold-Jarisch reflex: effector and response

A

SA node > decrease HR/ AV node > decrease dromotropy

57
Q

Strongest stimulus at peripheral chemoreceptors

A

Hypoxia

58
Q

Afferent pathway of peripheral chemoreceptors

A

Hypoxia> afferent impulse from carotid and aortic bodies > hering n (branch of CN 9) > vagus (CN 10) > nucleus tractus soliatrius

59
Q

Effector response to hypoxia

A

Increased RR
Increased Vt
= Increased minute ventilation

60
Q

Acute cardiovascular response to hypoxemia

A

Activation of PNS > decreased HR and decreased inotropy

61
Q

Cardiovascular response to persistent hypoxemia

A

SNS activation > increased HR and increased inotropy = increased cardiac output

62
Q

What drugs blunt the chemoreceptor reflex?

A

Subanesthetic concentrations of most volatile anesthetics (<0.1 MAC)

Opioids

Nitrous oxide

63
Q

Vasovagal reflex triggers

A

Psychological stress
Periotoneal stretching or distension

64
Q

When is fainting more likely to occur due to vasovagal reflex?

A

In a warm room
After a volume loss
Upon standing up

65
Q

Afferent limb of oculocardiac reflex

A

Long and short ciliary nerves > ciliary ganglion > ophthalmic division (V1) of trigeminal (CN 5) > trigeminal ganglion

66
Q

Efferent limb of oculocardiac reflex

A

Vagus (CN 10)

67
Q

Oculocardiac reflex: stimulus

A

Traction on the extraocular muscles (especially the medial rectus)

Strabismus surgery

Pressure on the globe

Pressure on the conjunctiva

Ocular trauma

Pressure on the orbital tissue following enucleation

Retrobulbar block (can cause or prevent)

68
Q

Oculocardiac reflex: Sensor

A

Mechanoreceptors in the ocular tissues

69
Q

Oculocardiac reflex: Control center

A

Nucleus soltarius tractus and medullary cardiovascular nuclei and centers

70
Q

Oculocardiac reflex: effector and response

A

Decreased activity of the SA and AV nodes

71
Q

Oculocardiac reflex: clinical presentation

A

Bradycardia
Hypotension
Junctional rhythm
AV block
Asystole

72
Q

Oculocardiac reflex: factors that worsen the severity

A

Hypoxemia
Hypercarbia
Light anesthesia

73
Q

Oculocardiac reflex: treatment options

A

Remove stimulus

Administer 100% O2, ensure adequate ventilation, and deepen anesthetic

Administer anticholinergic (atropine, glycopyrrolate)

74
Q

Massive SNS activation due to profound decrease in medullary vasomotor centers

A

CNS ischemic reflex

75
Q

Result of CNS ischemic reflex trigger

A

Immense vasoconstriction

Profound increase in BP, often as high as the heart can create

76
Q

Type of CNS ischemic response that results from increased intracranial pressure

A

Cushing Reflex

77
Q

Cushing’s Triad

A

Hypertension
Bradycardia
Irregular respirations

78
Q

Control center for temperature maintenance

A

Preoptic area of the hypothalamus

Autonomic Nervous System (13 decks)

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