Intro to PNS Flashcards

1
Q

Describe pathway of somatic nerves

A

Single neuron efferent pathway

Directly innervates skeletal muscle

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2
Q

Describe pathway of sympathetic nerves

A

Two neuron efferent pathway (preganglionic and postganglionic)
Preganglionic neuron - short
Postganglionic neuron - long
Ganglia are paravertebral (sympathetic chain) or prevertebral (celiac, s. & i. mesenteric)

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3
Q

Describe pathway of parasympathetic nerves

A

Two neuron efferent pathway (preganglionic and postganglionic)
Preganglionic neuron - long
Postganglionic neuron - short
Ganglia are in/near the structures innervated

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4
Q

Where does the sympathetic division originate?

A

T1-L2 (thoraco-lumbar division)

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5
Q

Where does the parasympathetic division originate?

A

Cranial nerves 3, 7, 9, 10 and sacral (cranio-sacral division)

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6
Q

What is the neurotransmitter of somatic nervous system?

A

ACh

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7
Q

What is the preganglionic neurotransmitter of parasympathetic nervous system?

A

ACh

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8
Q

What is the postganglionic neurotransmitter of parasympathetic nervous system?

A

ACh

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9
Q

What is the preganglionic neurotransmitter of sympathetic nervous system?

A

ACh

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10
Q

What is the postganglionic neurotransmitter of sympathetic nervous system?

A

NE

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11
Q

What are the exceptions to postganglionic neurotransmitter of sympathetic nervous system?

A

Normally NE
ACh - sweat glands
Dopamine - renal vascular smooth muscle

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12
Q

Describe synthesis and packaging of ACh

A
ACh synthesized from choline and acetyl-CoA by choline acetyltransferase (ChAT)
ACh transported into vesicles by H+-coupled countertransporter (VAT)
ACh released (with ATP and cotransmitters) in Calcium dependent process
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13
Q

Describe termination of ACh action

A

ACh rapidly degraded into choline and acetate by AChE

Choline is taken back up and recycled by Na-coupled choline cotransporter

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14
Q

Describe synthesis and packaging of NE

A
Tyrosine transported into nerve terminal by Na-coupled cotransporter
Tyr converted to DOPA by tyrosine hydroxylase (rate limiting step)
DOPA converted to dopamine
Dopamine transported into vesicles by H+-coupled countertransporter (VMAT)
Dopamine converted to NE by dopamine-beta-hydroxylase (DBH)
NE released (with ATP, DBH, and cotransmitters) in Calcium dependent process
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15
Q

Describe termination of NE action

A

NE reuptake into nerve terminal by NET

NE diffuses from the site of action

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16
Q

How is epinephrine formed?

A

NE converted to EPI by phenylethanolamine-N-methyltransferase in the adrenal medulla

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17
Q

What are metabolic products of catecholamines?

A

Normetanephrine and metanephrine
MHPG (MOPEG)
VMA

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18
Q

What are the general categories of cholinergic receptors?

A

Nicotinic

Muscarinic

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19
Q

What are the general categories of adrenergic receptors?

A

Alpha

Beta

20
Q

What type of receptor are nicotinic receptors?

A

Ionotropic

21
Q

What type of receptor are muscarinic receptors?

A

G protein coupled receptors

22
Q

What are the types of nicotinic receptors and where are they located?

A

Nm (neuromuscular junction)

Nn (autonomic ganglia, adrenal medulla)

23
Q

What are the types of muscarinic receptors, where are they located, and which G protein is used?

A

M1 - autonomic ganglia, Gq
M2 - heart, Gi
M3 - smooth muscle, glands, endothelium, Gq

24
Q

What is the response of M1 activation?

A

Late EPSP in ganglia

25
Q

What is the response of M2 activation?

A

Decreased heart rate and contractility, slows spontaneous depolarization

26
Q

What is the response of M3 activation?

A

Contraction of smooth muscle

Secretion

27
Q

What type of receptor are adrenergic receptors?

A

G protein coupled receptors

28
Q

What are the types of alpha receptors, where are they located, and which G protein is used?

A

Alpha1 - smooth muscle in vasculature, Gi and Go

Alpha2 - pancreatic beta cells, platelets, nerve endings, Gi and Go

29
Q

What are the types of beta receptors, where are they located, and which G protein is used?

A

Beta1 - cardiac muscle, Gs
Beta2 - smooth muscle pulmonary, liver, skeletal muscle, Gs
Beta3 - adipose cells, Gs

30
Q

What is the response of Alpha1 activation?

A

Vasoconstriction
GU relaxation
Glycogenolysis and gluconeogenesis

31
Q

What is the response of Alpha2 activation?

A

Decreased transmitter release, causes contraction

32
Q

What is the response of Beta1 activation?

A

Increased heart rate, force of contraction, and renin release

33
Q

What is the response of Beta2 activation?

A

Relax smooth muscle

Increase glycogenolysis and K uptake

34
Q

What is the response of Beta3 activation?

A

Increased lipolysis

35
Q

What is the response of dopaminergic receptor activation by NE?

A

Relaxation of renal vascular smooth muscle

36
Q

What is the predominant tone of bronchiole smooth muscle?

A

Parasympathetic (no sympathetic innervation)
M3 receptors - constriction
No sympathetic but B2 receptors can be activated by circulating epinephrine, causing dilation

37
Q

What is the predominant tone of arterioles?

A

Sympathetic

Alpha receptors - constriction

38
Q

What is the predominant tone of veins?

A

Sympathetic

Alpha receptors - constriction

39
Q

What is the predominant tone of the iris?

A

Parasympathetic

M2 receptors - constriction

40
Q

What are the two negative feedback loops involved in regulation of MAP?

A
Hormonal loops (renin/angiotensin)
ANS loop (Baroreceptor reflex)
41
Q

What are the 4 variables that the sympathetic system directly influences that controls blood pressure?

A

Increased TPR
Heart rate
Contractile force
Increased venous tone

42
Q

What variable does the parasympathetic system influence that controls blood pressure?

A

Decreased heart rate

43
Q

Describe the autonomic functions in the eye

A

Sympathetic - Alpha1 receptor, mydriasis (dilation)

Parasympathetic - M3 receptor, miosis (constriction)

44
Q

What are the symptoms of Horner’s syndrome?

A

Anhydrosis
Miosis (constriction)
Ptosis

45
Q

Describe test for Horner’s syndrome and the rationale of each step

A

Cocaine - inhibits NE reuptake, should cause mydriasis (dilation)
- If no dilation, indicates a problem at either pre or postganglionic neuron

Hydroxyamphetamine - causes release of NE from presynaptic vesicles, should cause mydriasis (dilation) and requires intact postganglionic nerve with some NE in vesicles.
- If no dilation, indicates a problem with the postganglionic neuron

46
Q

What drug inhibits uptake of choline by Na+-coupled cotransporter?

A

Hemicholinium

Reduced uptake of choline = neuromuscular dysfunction

47
Q

What drug activates alpha 2 receptors, thereby inhibiting NE release?

A

Clonidine