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Neuropsych > 4,5 - Autonomic Nervous System > Flashcards

4,5 - Autonomic Nervous System Flashcards

1
Q

Divisions of the nervous system (diagram)

A
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2
Q

Background and purpose of the autonomic nervous system (ANS)

A
  • The purpose of the ANS is to regulate the body’s internal environment
    -Prepare the body for perceived stress
    -Promote recovery and routine maintenance
  • Visceral motor neurons innervates non-skeletal
    (non-somatic) muscles
    -Cardiac muscle
    -Smooth muscle (blood vessels, walls of viscera)
    -Glands
    -Skin
  • Generally not under conscious control
  • Modulatory:
    -End organ effectors do not depend entirely on the ANS for proper function, but serve to adjust their activity in accordance with needs of the body
    →ex: heart can function if nerves are severed
  • Homeostasis
    -Provides the optimal internal environment during normal and stressful periods
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3
Q

Sympathetic Division of the ANS

A
  • Extreme responses referred to as “fight or flight”
    -Responses involved in stress, anger, fear
    -Increase in heart rate, breathing rate, increased blood pressure
  • Ordinary responses may be subtle and hardly noticed
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4
Q

Motor neuron vs. Sympathetic neuron:

A
  • Somatic Nervous System
    -One neuron pathway
    -Originates in ventral horn
    -Heavily myelinated
    →Fast conduction
  • Sympathetic division of ANS
    -Two neuron pathway
    →First preganglionic neuron originates in lateral horn
    →T1-T12; L1-L2 (also called thoracolumbar division)
    →Second ganglionic neuron synapses outside of CNS
    -Lightly myelinated or unmyelinated → slow
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5
Q

Sympathetic neurons

A

Pre- and post-ganglionic fibers both demonstrate
convergence and divergence
* No 1-1 relationship between pre and post ganglionic neurons
* Neuronal convergence: each postganglionic cell may receive synapses from multiple preganglionic cells
* Divergence: each preganglionic fiber branches and synapses with multiple postganglionic fibers
* Sympathetic division → widespread effect!

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6
Q

Sympathetic preganglionic fibers

A
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7
Q

Ganglion in sympathetic division

A
  • Sympathetic chain
    -Located on each anterolateral
    side of vertebral column
    -Extend from base of skull to
    coccyx
    -~22 ganglia
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8
Q

Sympathetic chain/sympathethic trunk

A
  • Sympathetic chain
    -Located on each anterolateral
    side of vertebral column
    -Extend from base of skull to
    coccyx
    -~22 ganglia
  • Neuron enters through white
    ramus communicans
  1. Synapse in chain ganglion and follow to skin
  2. Ascend/descend to superior/inferior ganglion and synapse
  3. Pass through the chain without synapsing
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9
Q

Ganglion in sympathetic division

A
  • Sympathetic ganglion outside of chain
  • Input from the splanchnic nerves
  • Collateral ganglia (prevertebral ganglia)
    -Celiac ganglion
    →stomach, liver, gallbladder, spleen
    -Superior mesenteric ganglion
    →small intestine, ascending and transverse colon
    -Inferior mesenteric ganglion
    →descending colon, kidney, bladder
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10
Q

Sympathetic Division: pre and post-ganglionic

A
  • Preganglionic
    -Short in length
    -Synapse with postganglionic neuron near cord
    -Cholinergic: Release acetylcholine (ACh) to activate nicotinic receptors on postganglionic neuron
  • Postganglionic
    -Long
    -Synapse on target viscera, etc.
    -Adrenergic: Release norepinephrine (NE) on adrenergic receptors on neuroeffector junction
    -Exception: Postganglionic neurons innervating sweat glands (thermoregulation) release ACh
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11
Q

cholinergic receptors

A
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12
Q

Noradrenergic Junction

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NE synthesis/release
* Adrenergic neurons transport precursor amino acid tyrosine into nerve ending
* Tyrosine is converted to dopamine and
transported into vesicle by vesicular monoamine transporter (VMAT)
* Dopamine converted to NE
* Opening of voltage-sensitive Ca2+ channels causes physiologic release of transmitter

Fate of NE after release
* Reabsorbed by nerve terminal by NE transporter and either reused or broken down by the enzyme monoamine oxidase (MAO)
* Diffuse into surrounding tissue
* Some picked up by the bloodstream, circulates through body

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13
Q

Adrenergic receptors

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Alpha (⍺) receptors (⍺1, ⍺2) are generally excitatory (i.e. constriction/contraction) except in gut

Beta (β) receptors (β1, β2, β3) are inhibitory (e.g. relaxation in lung) or excitatory (e.g. heart, liver and fat cells)

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14
Q

⍺-Adrenergic receptors

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15
Q

β-Adrenergic receptors

A
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16
Q

Autonomic Neuroeffector Junctions

A
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17
Q

overview of the sympathetic division of the autonomic nervous system (diagram)

A
18
Q

Adrenal medulla

A
  • Middle (medulla) of gland
  • Postganglionic cells have lost their axons
  • Nicotinic receptors
  • Contains phenylethanolamine-N-methyltransferase
  • Systemic release of epinephrine and norepinephrine in extreme cases
  • 80% epinephrine/20% norepi
19
Q

Overview of the Autonomic Nervous System (sympathetic and parasympathetic divisions and innervations diagram)

A
20
Q

Parasympathetic division background and key features

A
  • Key features
    -Recovery, routine maintenance, digestion and waste elimination
    -“Rest and Digest”
    -Originates in cranium and sacral cord (S2-4) (para = “around”)
    →Also called Craniosacral division
    -Cholinergic
  • Similarities w/ sympathetic division
    -Two neuron pathway, preganglionic and postganglionic
    -Use nicotinic receptors in ganglionic synapse
    -Varicosity at effector organ
  • Differences
    -Craniosacral origin
    -No parasympathetic innervation of skin/extremities
    -Muscarinic receptors at target organ
    -Long preganglionic fibers, short postganglionic fibers
    -Minimal convergence and divergence → more direct effects
  • Neural divergence
    -There is some neural divergence, but much less than in sympathetic division
    -Relatively selective in its stimulation of target organs
21
Q

Cranial nerves (background)

A
  • Nerves that emerge directly from the brain
  • 12 pairs of cranial nerves, numbered I to XII, from rostral to caudal
  • The names of the cranial nerves reflect their general distribution and function
  • Bundles of sensory and motor neurons that transmit information from sensory receptors and innervate muscles or glands
22
Q

cranial nerves (list)

A
23
Q

Cranial nerves in the parasympathetic division

A

Cranial Nerves
* III – pupils constrict (near vision); ciliary muscles contract (spherical lens)
* VII – glands of face (tears, nasal mucus, submandibular and sublingual salivary glands) increase secretion
* IX – increased secretion of parotid salivary gland
* X – visceral organs of thorax and abdomen
-Decreases heart rate
-Causes bronchial constriction
-Stimulates digestive glands (e.g. in liver, pancreas)
-Increases smooth muscle motility of digestive tract

24
Q

CN III: Oculomotor

A
  • Eye muscles including ciliary and sphincter pupillae
  • ANS nucleus: Edinger-Westphal in the midbrain (mesencephalon)
25
Q

CN VII: Facial

A
  • Muscles/glands of face, taste
  • ANS nucleus: Superior salivatory nucleus (pons)
  • Two branches:
    -sphenopalatine ganglion
    -submandibular (submaxillary) ganglion
26
Q

CN IX: Glossopharyngeal

A
  • Sensory fibers, parasympathetic fibers to the
    parotid gland via the otic ganglion
  • ANS nucleus: Inferior salivatory nucleus (medulla)
27
Q

CN X: Vagus

A
  • Muscles of the larynx, pharynx, palate
  • Motor/sensory from the gut tube, heart and lungs
  • ANS nucleus: Dorsal motor nucleus (medulla)
  • Ganglia near viscera
28
Q

Parasympathethic division (diagram)

A
29
Q

Parasympathetic division

  • Sacral Cord (S2-S4)
A

Sacral Cord (S2-S4)
* Pelvic splanchnic nerves
* Smooth muscle and glands of the pelvis
-Promotes digestion and waste elimination via the descending colon
-Contracts bladder wall
-Preparation for sexual activity (e.g. erection of penis)

30
Q

Sympathetic vs. Parasympathetic:
Neurotransmitters

A

Sympathetic Division
* Preganglionic – Cholinergic (nicotinic)
* Postganglionic – Adrenergic (a and b)

Parasympathetic Division
* Preganglionic – Cholinergic (nicotinic)
* Postganglionic – Cholinergic (muscarinic)

31
Q

Cholinergic Synapse

A
32
Q

Muscarinic receptor subtypes

A
  • G-protein (Gi, Gq)
  • Inhibitory in the heart
    -K+ channels, Inhibition of adenylate cyclase
  • Excitatory in smooth muscle and glands
    -Increased intracellular calcium
  • 5 different subtypes (M1-M5)
33
Q

Muscarinic receptors

A
34
Q

Muscarinic M2

A
35
Q

Muscarinic M3

A
36
Q

End Organ Innervation

A
37
Q

Dual Innervation

A

Antagonistic
* Effects oppose each other
* e.g. sympathetic activation speeds up heart while
parasympathetic activation slows down the heart

Cooperative
* Divisions produce a unified overall effect
* e.g. male sexual response → parasympathetic: mediates erection while sympathetic mediates ejaculation

Dominant tone
* Even though both divisions innervate a single organ, one may have greater tonic activity

Dual Innervation is not always necessary to produce opposite effects
* e.g. in some instances this occurs with the control of blood pressure (extremities and body wall)
* The sympathetic fibers of blood vessels have a baseline sympathetic tone which keeps the blood vessel in a state of partial constriction – vasomotor tone
* increase in firing rate causes vasoconstriction
* decrease in firing rate causes vasodilation (allowing smooth muscle to relax)

38
Q

Diagramatic overview of the ANS (sympathetic, parasympathetic)

A
39
Q

Horner’s Syndrome

A
  • Primarily an acquired pathologic condition, but may also be congenital:
    →Interruption of central pathway, preganglionic neurons, and postganglionic neurons can result in Horner’s Syndrome
  • Ipsilateral loss of sympathetic innervation to:
    -smooth muscle of upper eyelid – drooping (ptosis)
    -dilator pupillae muscle – pupillary constriction (miosis)
    -sweat glands of face – causing anhidrosis
    -smooth muscle of blood vessels – vasodialation (skin becomes flush and warm to the touch)
  • Preganglionic neuron axons are anatomically related to: (symptoms can include)
  • spine
  • apex of lung
  • cervical pleura
  • subclavian artery
  • common carotid
  • internal jugular
  • thyroid gland
  • upper ribs
40
Q

Denervation Hypersensitivity

A
  • Autonomic lesion eliminates the release of neurotransmitter at ganglion or on effector
  • Denervated structures show an increase in sensitivity to their neurotransmitters, which at times may be found in circulation
  • e.g. pupillary response (dilation) in Horner’s Syndrome following adrenal medulla activation
41
Q

Raynaud’s Disease

A
  • Disease of peripheral vascular innervation, possibly from enhanced NE sensitivity
  • Initially affects the fingers and toes, but may also spread to involve larger areas
  • Treatment: sympathetic pharmacologic blockers or sympathectomy

Neuropsych (15 decks)

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