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Neuromuscular junction and dz Flashcards

1
Q

Anatomy of Neuromuscular junction

A
  1. Nerve
    - Root (within spinal canal)
    - Peripheral nerve
  2. Junction
    - presynaptic endplate
    - synaptic cleft
    - post-synaptic membrane
  3. Muscle
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2
Q

Lower motor neuron reflex arc

A
  1. Afferent nerve to
  2. Synapse in dorsal root ganglion to
  3. Dorsal horn to
  4. Synapse in ventral horn to
  5. Two pathways from there
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3
Q

Resting membrane potential for a large nerve fiber

A

~-90 millivolts

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4
Q

Depolarization

A
  1. inc Na+ permeability, influx of positive

2. Potential may approach zero or….?

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5
Q

Repolarization

A
  1. Na+ channels begin to close
  2. K+ channels open more
  3. Re-establishment of RMP
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6
Q

Defecit in Ca

A

Causes Na+ channels to become activated with little increases in membrane potential -> tetany (exciteability)

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7
Q

High extracellular Ca+

A

Decreases membrane permeability to Na+ and reduces exciteability

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8
Q

Local anesthetics (3)

A
  1. Na+ channel blockers
  2. Act on sodium channel activation gates
  3. Reduce excitability
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9
Q

When Action Potential strength to excitability threshold is < 1

A

Nerve impulses are not conducted

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10
Q

Anatomy of the neuron (5)

A
  1. Dendrites (receptor endings)
  2. Perikaryon (cell body)
  3. Axon
  4. Collateral branches
  5. Axon terminals
  6. Synaptic bulb
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11
Q

Myelin sheath

A

On CNS nerves I think

-Oligodendroglial cell processes

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12
Q

Schwann cells on

A

PNS nerves I think

-Rolled up Schwann cell membrane

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13
Q

Things with no myelination (4)

A
  1. Initial segment
  2. Axon hillock
  3. Nodes of Ranvier
  4. Axon terminals
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14
Q

Larger nerves have faster

A

conduction

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15
Q

Saltatory conduction (2)

A
  1. Increases velocity

2. Conserves energy with only nodes depolarizing

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16
Q

Presynaptic terminal elements (2)

A
  1. Transmitter vesicles
    - excitatory or inhibitory
  2. Mitochondria
    - Provide ATP for transmitter synthesis
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17
Q

Depolarization of presynaptic membrane (3)

A
  1. Depolarized by Action potential
  2. Opens voltage-gated Ca channels
  3. Amount of Ca inflow is directly related to transmitter released
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18
Q

Postsynaptic receptor proteins (2)

A
  1. Binding component protruding into cleft

2. Ionophore component

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19
Q

Ionophore component (2)

A
  1. Ion Channel-rapid

2. Second messenger activator-slow, I think

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20
Q

Ion channel (2)

A
  1. Cation channels: allow entrance of Ca ->excitatory

2. Anion channels: allow entrance of Cl- -> inhibitory

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21
Q

‘second messenger’ activator (2)

A
  1. For prolonged postsynaptic neuronal changes

2. G-proteins

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22
Q

Neurotransmitters (2)

A
  1. Small molecules (rapidly action)

2. Neuropeptides (slowly acting or growth factors)

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23
Q

Small, rapidly acting neurotransmitters (4)

A
  1. Class I (ACh)
  2. Class II: Amines
    - norepi, epi, dopamine, serotonin, histamine
  3. Class III: Amino Acids
    - GABA, Gly, Glutamate, Aspartate
  4. Class IV (NO)
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24
Q

Neuropeptides, slow neurotransmitters (4)

A
  1. Hypothalamic-RH
    - TRH, LHRH, Somatostatin
  2. Pituitary peptides
    - ACTH, GH, ADH
  3. Peptides GI, Brain
    - Enkephalins, gastrin, VIP, insulin, glucagon
  4. Other
    - Bradykinin, Angiotensin II
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25
Things affecting synaptic transmission (4)
1. Fatigue-dec in d/c of postsynaptic neuron 2. pH-alkalosis inc excitability/acidosis depresses excit 3. Hypoxia-cessation 3-7 seconds-> unconscious 4. Drugs - Caffeine (reduces threshold) - Strychnine-inhibits glycine in spinal cord - Anesthetics-inc threshold for excitation-> decreases transmission
26
Drugs stimulating muscle fiber by ACh-like action (3)
1. Methacholine 2. Carbachol 3. Nicotine * These aren't broken down by cholinesterase (last longer)
27
Drugs that stim NMJ by inactivating ACh (3)
1. Neostigmine 2. Physostigmine 3. Diisopropyl fluorophosphate * Results in muscle spasm
28
Drugs that block transmission at NMJ
Curariform drugs: D-tubocurarine | *Prevents AP
29
Skeletal Muscle Contraction (7)
1. AP travels along motor nerve to NMJ 2. Nerve secretes ACh, opens ACh-gated channels 3. Na+ diffuses in, initiates AP 4. AP travels along muscle membrane, T tubules 5. AP depolarizes muscle, causing SR to release Ca++ 6. Ca++ initiates actin and myosin sliding 7. Ca++ pumped back into SR, stopping contraction
30
Walk along/ratchet mechanism (4)
1. Troponin-tropomyosin keeps F-actin inhibited, dec Ca 2. Ca + troponin C-> conformational change 3. Power stroke (tilt), release ADP + Pi 4. New ATP binding detaches myosin head from actin
31
I think it's the motor nerves that have
pre and post ganglionic portions
32
Autonomic Neurotransmitters (2)
1. Acetylcholine | 2. Norepinephrine
33
Cholinergic fibers secrete
acetylcholine
34
Adrenergic fibers secrete
norepinephrine
35
All preganglionic neurons are
cholinergic
36
ACh is excitatory to all
postganglionic neurons
37
Most parasympathetic postganglionic neurons are
cholinergic
38
Most sympathetic postganglionic neurons are
adrenergic
39
Acetylcholine receptors (2)
1. Muscarinic - autonomic | 2. Nicotinic - somatic
40
Muscarinic Acetylcholine receptors
Found on all effector cells stimulated by postganglionic cholinergic neurons of sypathetic or PS systems
41
Nicotinic Acetylcholine receptors (2)
1. Found in autonomic ganglia at synapses between pre- and postganglionic neurons of sympathetic and PS systems 2. Also present at NMJs
42
Adrenergic receptors
``` Alpha 1 - Vasoconstriction -Smooth muscle contraction Alpha 2 -Negative feedback on NE - excitatory?!?! Beta 1 - excitatory in heart Beta 2 - inhibitory to smooth muscle (relaxation) Bronchi ```
43
NE excites mainly
alpha adrenergic receptors
44
Epi excites
Alpha and Beta receptors about equally
45
Motor neurons (3)
1. Alpha 2. Gamma 3. Interneurons
46
Alpha motor neurons (2)
1. Innervates skeletal muscle | 2. One alpha nerve fiber excites 3 to hundreds of muscle fibers (motor unit)
47
Gamma motor neurons (2)
1. Transmit impulses through smaller nerves | 2. Intrafusal muscle fibers to control muscle tone
48
Interneurons (2)
1. Present in spinal cord gray matter | 2. Renshaw cells-lateral inhibition of motor neurons
49
The Lower motor neuron
Efferent neuron of the PNS that connects the CNS with the muscle to be innervated
50
General somatic efferent (GSE) (4)
1. Alpha motor neuron 2. Striated skeletal muscle 3. All spinal nerves 4. CN III, IV, I, VI, VII, IX, X, XI, XII
51
General visceral efferent (GVE)
1. Alpha motor neuron 2. Smooth and cardiac muscle and glands 3. Sympathetics: all spinal and splanchnic nerves 4. Parasympathetics: Sacral spinal nerves 5. CN III, VII, IX, X, XI
52
Wallerian degeneration
Something about nerve damage distal to injury or something....
53
Tetanus is a
spinal cord dz
54
Nerve root dz
Polyradiculoneuritis
55
Nerve disease
Polyneuropathies - axon - myelin
56
Nerve junction diseases (4)
1. Tick paralysis 2. Botulism 3. Myasthenia gravis 4. Snakes
57
Categories of muscle diseases
1. Inflammatory 2. Infectious 3. Neoplastic 4. Snakes
58
F wave evaluates
Nerve root-only motor | *only way to eval nerve root!
59
Orthodromic stimulus
muscle contraction (M wave)
60
Antidromic stimulus
Small, second CMAP called F wave
61
Polyneuropathy DDXs (6)
1. Degenerative 2. Paraneoplastic 3. Endocrine 4. Genetic/heritable 5. Infectious 6. Toxic: Vincristine toxicity
62
Vincristine tox (NAVLE)
1. Microtubule modulator 2. Cumulative toxicity with multiple dosing 3. Not common
63
Sciatic release
1. Exaggerated patellar 2. Can't withdraw * lab polyneuropathy thing
64
Endocrine Neuropathies
1. Paraneoplastic-insulinoma 2. Hypothyroidism-theoretic, not common 3. Diabetic neuropathy-feline
65
Nerve conduction studies affected by
1. Age 2. Limb temperature 3. Limb length
66
Nerve Conduction studies (5)
1. amplitude (strength, proportional to number of axons) 2. velocity of conduction (speed, reflects degree of myelination) 3. M wave 4. Need at least 2-3 points on leg 5. I think this hurts and we anesthetize dogs
67
Cat's don't get megaesophagus because
They have smooth muscle in their esophaguses
68
Categories of myopathies (5)
1. Immune mediated 2. Infectious - Neospora caninum - Hepatozoon americanum 3. Preneoplastic - lymphoma 4. Dermatomyositis 5. Congenital - muscular dystrophies
69
Electromyography
Healthy muscle is electricaly silen
70
Endocrine myopathies (4)
1. Hypothyroidism-dogs 2. Hyperthyroidism-cats 3. Glucocorticoid excess-dogs 4. Electrolyte derangements
71
Myokymia
Looks like worms underskin | -snakebite causes calcium interference on nerve membrane
72
DDX Acute LMN paresis to plegia (6)
1. Polyradiculoneuritis 2. Tick paralysis 3. Coral snake envenomation 4. Mojave rattlesnake in southern cali 5. Botulism 6. Fulminant myasthenia gravis

Neuro junior (14 decks)

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