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Physiology > Autonomic Nervous System > Flashcards

Autonomic Nervous System Flashcards

1
Q

3 sympathetic nervous system activations

  • chronotropic
  • dromotropic
  • inotropic
A

all positive effects via beta1-adrenergic receptors (usually norepinephrine)

  • stimulate heart via SA node
  • stimulate AV nodal condunction
  • stimulate myocardial (ventricular) contractility
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2
Q

3 parasympathetic nervous system activations

  • chronotropic
  • dromotropic
  • inotropic
A

all negative effects via muscarinic cholinergic receptors (usually ACh)

  • inhibit heart rate at SA node
  • inhibit AV nodal conduction
  • inhibit atrial contractility (mild compared to sympathetic ventricular stimulation)
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3
Q

sympathetic VS parasympathetic in regards to preganglionic VS postganglionic fibers

A

symp: pre are short, post are long
para: pre are long, post are short and close to target tissues

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4
Q

locations of pre VS postganglionic fibers

A

pre: lie in CNS in columns in brain stem and spinal cord; exit to make synapses
post: in peripheral ganglia that project to target tissues

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5
Q

A, B, and C fibers

A

A: large-diameter, fast conducting myelinated motor neurons of skeletal muscle
B: small diameter, slow conducting myelinated preganglionic axons
C: small diameter, slow conducting unmyelinated postganglionic axons

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6
Q

divergence in SNS VS PNS

A

SNS: one preganglionic axon can contact ~100 postganglionic neurons by collateral branching
PNS: one preganglionic axon contacts 15-20 postganglionic
-enables widespread responses to numerous effectors when necessary

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7
Q

varicosities (in passing synapses)

A

characteristic of autonomic nervous system, with single axon having broad actions in target tissues

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8
Q

somatic nervous system origin, ganglia, and target organs

A

central nervous system, w/o ganglia, to skeletal muscle

-N1 nicotinic acetylcholine receptor on muscle

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9
Q

parasympathetic axon system origin, ganglia, and target organ

A

autonomic nervous system, w/ ganglia, to smooth muscle, cardiac muscle, or glands

  • ganglion has N2 nicotinic cholinergic (ACh) receptor
  • release ACh to muscarinic ACh receptor on organ (M1-5)
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10
Q

sympathetic axon system origin, ganglia, and target organ

A

autonomic nervous system, w/ ganglia, to smooth muscle, cardiac muscle, and glands, including adrenal glands

  • ganglion has N2 nicotinic cholinergic (ACh) receptors
  • all except adrenals and sweat have alpha/beta-adrenergic receptors (NE>E)
  • adrenal “ganglion” Chromaffin cell has N2 receptor for ACh, and releases E to alpha/beta adrenergic receptors all over body
  • sweat glands have mjuscarinic ACh receptors
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11
Q

Chromaffin cells

A

in adrenal medulla, and directly innervated by SNS

  • release mostly epinephrine (80%), and carried in body to various tissues
  • last 5-10 times longer b/c inactivated slowly, and reach tissues not innervated by sympathetic
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12
Q

mechanism of action of alpha1-adrenoreceptors (active VS inactive); GPCR metabotropic

A

inactive: alpha-q subunit of Gq is bound to GDP
active: NE bound to receptor, so alpha-q bound to GTP
- active to phospholipase C, which releases PIP2 that breaks into DAG and IP3
- IP3 releases Ca++, which acts on PRO kinase C with DAG

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13
Q

mechanism of action of beta-adrenoreceptors (active VS inactive); GPCR metabotropic

A

inactive: alpha-s subunit of Gs is bound to GDP
active: NE bound to receptor, so alpha-s bound to GTP
- active to adenylyl cyclase, which converts ATP to cAMP

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14
Q

mechanism of nicotonic cholinergic receptors; odds VS evens; GPCR metabotropic

A

M1, 3, 5: PLC leads to generation of IP3 and DAG (like alpha1 adrenergic receptors)
M2, 4: inhibition of adenylate cyclase causes decreased cAMP (opposite of B1/2)

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15
Q 
antagonists of
N1 (nicotinic ACh)
N2 (nicotinic ACh)
M1/3/5 (muscarinic ACh)
M2/4 (muscarnic ACh)
beta1 (adrenergic)
A

N1 - d-Tubocuraine
N2 - hexa-methonium
M1-5 - atropine (less selective for 2/4)
beta1 - propranolol

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16
Q

alpha 1 metabotropic adrenoreceptor effects in SNS

A

mydriasis (pupil dilation) and eyelid retraction
vasoconstriction
sphincter contraction
alpha+beta: epinephrine from adrenal medulla, smooth muscle wall contraction

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17
Q

beta metatropic adrenoreceptor effects in SNS

A

1: increased heart rate and force of contraction
2: bronchial dilation
alpha+beta: epinephrine from adrenal medulla, smooth muscle wall contraction

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18
Q

muscarinic cholinergic metatropic effects on SNS

A

sweating

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19
Q

epinephrine VS norepinephrine targets

A

E: beta-adrenergic receptors (CO, BMR, bronchiodilation, inhibit intestines)
NE: alpha-adrenergic receptors (BP elevation, urinary excretion)

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20
Q

pheochromocytoma cause, effect, treatment

A

tumor of the adrenal medulla (rarely extramedullary sites) secretes excessive amounts of NE, and less so E (since not enough cortisol); rarely increase dopamine

  • sustained (rarely episodic) HTN
  • in all ages/genders, esp. 40-50 yrs
  • treat by excising well-circumscribed tumors (1 gram to kilograms)
  • treat symptoms with alpha1 and beta1-adrenergic antagonists
21
Q

Horner syndrome effects, types of lesions

A

injuries to SNS make ipsilateral lesions causing miosis (constricted pupil), ptosis (drooping eyelid), anhydrosis (lack of sweating)

  • 1st order lesion: brainstem interrupting descending tracts (stroke)
  • 2nd order lesion: preganglionic sympathetic cell bodies or fibers supplying eye synapse in superior cervical ganglion
  • 3rd order lesion: postganglionic sympathetic cell bodies or fibers
22
Q

pupillary constriction/miosis is controlled by?

A

CN III (pupillary light reflex); occulomotor

23
Q

gland secretion is controlled by?

A

CN VII - nasal/lacrimal/submandibular
CN IX - parotid (glossopharyngeal)
CN X - gastric, pancreatic

24
Q

GI peristalsis is controlled by?

A

CN X - increased motility and sphincter relaxation

25
Q

bronchial constriction and decreased heart rate is controlled by?

A

CN X (heart is beta1 receptors; chonotropic and inotropic; lung is beta2 receptors)

26
Q

what does a cardiac vagotomy do?

A

cut the vagus nerve

-increases heart rate to 160 bpm, and compensatory mechanisms take many months to restore HR to normal

27
Q

where does the vagus nerve originate?

A

from dorsal motor nucleus of vagal nerve in the medulla

28
Q

what controls more than 75% of the PNS?

A

the 2 vagal nerves

29
Q

what are supraspinal nuclei containing neurons part of?

A

the ANS; contain cell bodies of pregnanglionic parasympathetic neurons (efferent)

30
Q

Edinger-Westphal nucleus

A

contains cell bodies of preganglionic parasympathetic fibers that travel with CN III to ciliary ganglion

31
Q

superior salivatory nucleus

A

contains cell bodies of preganglionic fibers that travel with CN VII to pterygopalatine and submandibular ganglia

32
Q

inferior salivatory nucleus

A

contains cell bodies of preganglionic fibers that travel with CN IX to otic ganglion

33
Q

nucleus ambiguus (rostral portion and the rest)

A

rostral: contains preganglionic cell bodies that distribute with CN IX
the rest: along with dorsal motor nucleus of vagus, contains cell bodies of preganglionic fibers that travel with CN X to host of terminal ganglia in viscera of thorax and abdomen

34
Q

nucleus trachus soltarius (NTS)

A

not part of the ANS

  • receives visceral afferents and is part of the larger visceral control system
  • major regulator of MAP that tells ANS what to do
35
Q

enteric nervous system

A

distinct division of ANS, contains more neurons than spinal cord
-includes myenteric and submucosal plexues of gut (diffuse interconnected series of neuronal cell bodies, axons, and dendrites)

36
Q

myenteric (Auerbach’s) plexus

A

controls motility

37
Q

submucosal plexus

A

controls secretions

38
Q

what in the gut is activated by distention and food?

A

mechanoreceptors and chemoreceptors in the epithelial lumen that innervate central control centers to activate PNS and inhibit SNS to promote digestion via enhanced motility and secretions

39
Q

what happens when you cut the parasympathetic fibers innervating the gut?

A

decrease in GI muscle tone, increase in sphincter tone, showing that PNS exerts a tonic effect on GI motility

40
Q

where are postganglionic neurons of PNS primarily located?

A

in myenteric and submucosal plexuses

41
Q

where is PNS innervation of the GI system particularly extensive?

A

in the oral cavity and the anus

  • smell/presence of food initiates nose/mouth to brain stem to salivate and secrete digestive juices
  • distention in rectum initiates mechanoreceptors to sacral region of spinal cord to activate PNS defecation
42
Q

PNS effect on myenteric plexus

A

activation is depolarizing, and generates APs leading to contractions of smooth muscle of gut

43
Q

SNS effect on myenteric plexus

A

NE is released, which is hyperpolarizing and relaxing the smooth muscle, and increasing sphincter constriction
-too strong, can inhibit motility so much that movement of food is blocked (ileus)

44
Q

actions of detrussor muscle, internal, and external sphincters in bladder filling

A

detrusor: relaxed via beta2 sympathetics
internal: contracted via alpha1 sympathetics
external: contracted via voluntary somatic

45
Q

actions of detrussor muscle, internal, and external sphincters in bladder emptying

A

detrusor: contracted via muscarinic parasympathetics
internal: relaxed via muscarinic parasympathetics
external: relaxed via voluntary somatic

46
Q

what are descending cortical pathways regulating through ANS?

A

fear, panic, stress and related responses

-may be via direct connections in spinal cord, or indirect through hypothalamus

47
Q

examples in which visceral afferents overwhelm cortical function

A

nothing else seems to matter

  • hunger
  • nausea
  • dyspnea
  • visceral pain
  • bladder, bowel distention
  • hypothermia, hyperthermia
48
Q

vasovagal syncope

A

emotional fainting begins with disturbing thoughts in cortex

  • activates vasodilator centers in hypothalamus and heart via vagus nerves, slowing heart
  • signals through spinal cord to SNS vasodilator nerves in muscles (rapidly increasing flow to muscles)
  • resultant fall in arterial pressure reduces blood flow to brain and causes person to lose consciousness

Physiology (60 decks)

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