Lecture 6: Autonomic Nervous System Flashcards

1
Q

Nervous system divisions

A

NS = CNS + PNS
PNS = somatic + autonomic
Autonomic = sympathetic + parasympathetic + enteric

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2
Q

What does the autonomic nervous system do?

A

Involuntary innervation of tissues other than skeletal muscle/GI tract (enteric)

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3
Q

How do autonomic nerves connect to the CNS?

A

2 neurons in series synapsing at the autonomic ganglion outside the CNS. Pre-ganglionic cell body is in the CNS.

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4
Q

How are sympathetic neurons/ganglia placed?

A

Sympathetic ganglia run in 2 chains close alongside the length of spinal cord in sympathetic trunks or are closer to organs in the abdominal cavity (collateral ganglia). Sympathetic nerves leave CNS at thoracic/lumbar spinal cord.

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5
Q

Sympathetic trunks (paravertebral ganglia)

A

Bundled nerve fibers running alongside the vertebral column containing the sympathetic ganglia. Allows pre-ganglionic sympathetic nerves to travel up/down before synapsing

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6
Q

How are parasympathetic nerves/ganglia placed?

A

Parasympathetic ganglia are placed very close to or within innervated organs. Parasympathetic nerves leave CNS at brain stem/sacral spinal cord.

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7
Q

Collateral (pre-vertebral) ganglia

A

Sympathetic ganglia in the abdominal cavity placed closer to innervated organs compared to other sympathetic ganglia. Specifically the celiac and superior/inferior mesenteric ganglia.

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8
Q

Autonomic nervous divisions

A

-Sympathetic (AKA thoracolumbar) division
-Parasympathetic (AKA craniosacral) division
-Enteric NS

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9
Q

Pattern of sympathetic innervation

A

Sympathetic NS typically affects targets in concert due to higher pre-ganglionic divergence and circulating epi/norepi.

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10
Q

Pattern of parasympathetic innervation

A

Parasympathetic NS typically affects targets individually in a finely-tailored pattern due to less pre-ganglionic divergence.

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11
Q

General somatic NS efferent pathway

A

Large diameter, myelinated axons of motor neurons directly innervate skeletal muscle with ACh; faster transmission

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12
Q

General autonomic NS efferent pathway

A

Medium diameter, myelinated pre-ganglionic neurons release ACh onto small, unmyelinated post-ganglionic neurons which innervate targets with NE (symp.) or ACh (parasymp.), or synapse onto adrenals. Apparently no evolutionary need for faster transmission.

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13
Q

Autonomic innervation of the adrenal medulla

A

The adrenal medulla acts like a ganglion. Chromaffin cells receive ACh from pre-ganglionic fibers and then release NE and epi into circulation.

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14
Q

Primary autonomic neurotransmitters

A

In general, pre-ganglionic fibers release ACh and post-ganglionic release NE (sympathetic/adrenal medulla) or ACh (parasympathetic).

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15
Q

Cholinergic receptor types

A

Named for agonists.
Nicotinic: skeletal muscle, autonomic post-ganglionic dendrites
Muscarinic: parasympathetic targets + sweat glands/blood vessels (sympathetic)

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16
Q

Antagonists for cholinergic receptors

A

Curare = somatic nicotinic antagonist
Hexamethonium = autonomic ganglia nicotinic antagonist
Atropine = muscarinic antagonist

17
Q

Adrenergic receptor types

A

Adrenergic receptors are not named for agonists.

α1, α2, β1, β2 on smooth/cardiac muscle and glands (autonomic)

18
Q

Agonist

A

Substance that binds a receptor and activates it

19
Q

Inverse agonist

A

Substance that binds a receptor and decreases its (basal) activity in the absence of ligands

20
Q

Antagonist

A

Substance that reduces the efficacy of agonists/inverse agonists

21
Q

Reciprocal innervation

A

Most autonomic targets are innervated in opposition by both sympathetic and parasympathetic nerves. Exceptions include skin hair, sweat glands, adrenal medulla, some blood vessels

22
Q

Reciprocal innervation exceptions

A

Likely allows separate regulation separate from circulating NE/epi. Piloerectors, sweat glands, adrenals, some blood vessels receive ACh and NE from sympathetic post-ganglionic nerves.

23
Q

Nonadrenergic, noncholinergic neurons

A

Many autonomic post-ganglionic neurons use other NTs/factors like NO for many functions.

24
Q

Sympathetic and parasympathetic purposes

A

Sympathetic = fight or flight, gas pedal
Parasympathetic = rest and digest, brakes
(in general)

25
Varicosities
AKA "en passant" synapses. Swellings along axon branches form many autonomic synaptic junctions (rather than axon terminals)
26
Patterns of somatic innervation
Somatic motor neurons are inactive until stimulated, and initiate activity in otherwise inactive muscle
27
Patterns of autonomic innervation
Autonomic neurons typically maintain a basal tonic activity and modulate targets that have autogenic activity.
28
Horner's syndrome
Caused by a sympathetic defect -> inactivating several muscles, resulting in partial eyelid droop (ptosis) and uneven pupils (miosis)