Translational Physiology: NMJ, LEMS, MG, and AI in Clinical Reasoning (Video Notes)

Vocabulary flashcards covering NMJ biology, LEMS/MG features, diagnostic tests, autonomic involvement, and AI-assisted clinical reasoning from the video notes.

Neuromuscular junction (NMJ)

The synapse between a motor neuron and a muscle fiber where nerve signals trigger muscle contraction via acetylcholine release and postsynaptic receptor activation.

Presynaptic proteins

Proteins in the nerve terminal that regulate neurotransmitter release (e.g., voltage-gated calcium channels).

Postsynaptic proteins

Proteins on the muscle endplate that respond to acetylcholine (e.g., nicotinic ACh receptors).

Action potential at NMJ

Nerve impulse leading to Ca2+ influx, ACh release, and activation of muscle ACh receptors to produce contraction.

Synaptic depression

Decrease in neurotransmitter release with repeated stimuli due to vesicle depletion.

Synaptic facilitation

Transient increase in neurotransmitter release due to residual presynaptic calcium, enhancing transmission.

Lambert-Eaton Myasthenic Syndrome (LEMS)

Autoimmune presynaptic disorder with antibodies against P/Q-type VGCCs, causing reduced ACh release; proximal weakness with autonomic symptoms; reflexes may improve with effort; often paraneoplastic with SCLC.

Myasthenia gravis (MG)

Autoimmune disorder with antibodies against postsynaptic acetylcholine receptors, causing fatigable weakness often starting with ocular or bulbar symptoms.

P/Q-type voltage-gated calcium channels (VGCC)

Presynaptic Ca2+ channels whose dysfunction reduces acetylcholine release in LEMS.

+VGCC antibodies

Autoantibodies against P/Q-type VGCCs; strongly associated with LEMS and can indicate underlying malignancy.

Autonomic dysfunction

Autonomic nervous system signs such as dry mouth, constipation, orthostatic changes seen in LEMS.

Proximal muscle weakness

Weakness of proximal muscles (hips, shoulders), a hallmark feature of LEMS.

Reflex facilitation

reflex that temporarily strengthen after brief contraction, characteristic of LEMS.

CMAP (compound muscle action potential)

Electrical response of a muscle to a nerve stimulus; in LEMS, it increases markedly after brief exercise or high-frequency stimulation.

Post-exercise facilitation

Increase in CMAP amplitude after short exercise, signaling NMJ facilitation as seen in LEMS.

Repetitive Nerve Stimulation (RNS)

EMG/NCS test; in LEMS shows incremental (increased) CMAP responses with high-frequency stimulation.

EMG (electromyography)

Recording of muscle electrical activity to evaluate NMJ and neuromuscular disorders; can reveal facilitation patterns in NMJ diseases.

NCS (nerve-conduction studies)

Tests that measure nerve conduction velocity and CMAP amplitudes; used with EMG in NMJ disorder evaluation.

Orthostatic hypotension

Drop in blood pressure on standing; dizziness; a sign of autonomic involvement.

Thymoma

Thymic tumor; commonly discussed in MG workups; imaging may be used to screen for thymic pathology.

Small cell lung carcinoma (SCLC)

Malignancy often associated with paraneoplastic LEMS; chest imaging is used to screen for it.

Anti-ACh receptor antibodies

Autoantibodies against acetylcholine receptors, characteristic of MG.

Tensilon test (edrophonium)

Historically used to diagnose MG; now considered outdated and not routinely recommended.

Automation bias

Overreliance on AI outputs without critical evaluation, risking outdated tests or premature conclusions.

DEFT–AI framework

A structured approach to guide reflection in learner–AI interactions and improve clinical reasoning.

DEFT-AI Pause technique

A Diagnosis & Discussion pause to critique AI outputs and ensure alignment with clinical reasoning.

AI in clinical reasoning

Using artificial intelligence to aid diagnosis and decision-making, which requires critical appraisal and supervision.

Electrodiagnostic testing significance for NMJ

EMG and NCS provide physiologic evidence of NMJ status and help distinguish NMJ disorders from myopathies or neuropathies.