Neuro Diseases

Question 1

Tetrodotoxin (TTX)

Answer 1

Na+ channel inhibitor

Blocks AP = paralysis

Pufferfish

Question 2

Botulinum/Botox

Answer 2

Prevents ACh release at NMJ

Flaccid paralysis= muscle weakness, hypotonia, paralysis

Found in improperly canned foods

Question 3

Tetanus

Answer 3

Blocks inhibitory interneurons release of NTs glycine and GABA

Strong and painful muscle spasms

Produced by bacteria found in soil

Question 4

Curare

Answer 4

Competitive ACh antagonist at NMJs

Inability to contract muscle=paralysis
Respiratory paralysis at high doses, muscle relaxant at low

South American plants

Question 5

Bungarotoxin

Answer 5

Blocks cholinergic receptors at NMJ

Used in research

Snake venom

Question 6

Hyperkalemic periodic paralysis

Answer 6

Mutation in voltage-gated Na+ channels, meaning they can’t inactive rapidly —constant small stream of Na+ coming in, causing depolarized motoneurons that cannot repolarize quickly to fire another AP.

S+S= myotonia (difficultly relaxing muscle once contracted) and paralysis
High K+ levls in blood
Triggered with cold, exercise, high K foods.

Question 7

Hypokalemic periodic paralysis (HOPP)

Answer 7

Mutation in voltage-gated Ca2+ channels

S+S= episodic weakness without myotonia; low K+
Triggered by stress, emotions, exercise, cold

Question 8

Thomsen’s and Becker’s Diseases

Answer 8

Mutation in voltage-gated Cl- channels resulting in hyperexcitability of skeletal muscle fibers

S+S= myotonia, muscle rigidity, hypertrophy

Question 9

Episodic Ataxia

Answer 9

Mutations in voltage gated K+ channels causing muscles to be reactivated repetitively bc less outward K+ available for repolarization
S+S= ataxia, myokymia (rippling of muscles)
Triggered by stress, startle, exertion

Question 10

B12 deficiency

Answer 10

Demyelination affecting the CNS and PNS bc B12 required for formation and maintenance of myelin

S+S= pale or jaundiced skin, weakness and fatigue, pins and needles , motor disorder

Question 11

Myasthenia gravis

Answer 11

Autoimmune disease where antibodies are made against ACh receptors, destroying them. Reduced number of ACh R, decreased in junctional folds, widening of synaptic space

• drooping eyelids, altered speaking, dysphagia, diplopia
• amplitude of CMAP decreases rapidly over repeated stimulations and jitter from desynchronus contraction
• cold test—cold temp will inhibit acetylcholinesterase, improving function
• Teensilon test—inhibits acetylcholinesterase, improving function
• Tx: acetylcholinesterase inhibitors, plasmapheresis to remove ABs

Question 12

Lambert-Eaton

Answer 12

Autoimmune disorder where ABs are made against Ca2+ channels on presynaptic motoneuron. Fewer synaptic vesicles released.

S+S= muscle weakness and pain, difficulty walking, hyporeflexia
- increasing CMAP amplitude upon repeated stimulation

Question 13

Neuromyotonia (Isaac’s syndrome)

Answer 13

Antibodies target voltage-gated K+ channels on motor nerves resulting in hyperexcitability

S+S= rapid and abnormal bursts of nerve impulses/muscle contractions
Muscle cramps, stiffness, walking difficulties, fasiculations, fatigue, Speech and breathing difficulties maybe.

Look for doublet or triplet EMG, and ABs in bloodwork

Tx: immunosuppressive or anti-seizure meds

Question 14

Strychnine

Answer 14

Glycine receptor antagonist, leading to loss of inhibitory power of inhibitory interneurons = strong painful contractions