Neuromuscular Physiology, Excitable Tissues and Autonomic Neurotransmission — WACS Viva & Clinical Scenarios (Physiology and Applied Physiology)

Exam-style neuromuscular physiology, excitable tissues and autonomic neurotransmission viva scenarios with examiner probes and model answers for ANAESTHESIA…

Scenarios covered

• SCENARIO 1: State the Nernst equation and the Goldman-Hodgkin-Katz (GHK) voltage equation. Explain the biophysical basis of the resting membrane potential in a mammalian skeletal muscle cell, detailing the relative ionic permeabilities and the role of the sodium-potassium ATPase pump.
• SCENARIO 2: Draw a fully labelled diagram of the Neuromuscular Junction (NMJ). Describe the sequence of events from the arrival of an action potential at the presynaptic motor nerve terminal to the generation of an action potential in the muscle sarcolemma, detailing acetylcholine synthesis, vesicular release mechanisms (SNARE complex), receptor activation, and signal termination.
• SCENARIO 3: Compare and contrast the molecular structure, subunit composition, physiological properties, and anatomical distribution of the adult junctional nicotinic acetylcholine receptor with the fetal/extrajunctional nicotinic acetylcholine receptor. Detail the clinical implications of extrajunctional receptor proliferation for the anaesthetist.
• SCENARIO 4: Describe the excitation-contraction coupling mechanism in skeletal muscle. Detail the roles of the T-tubule system, dihydropyridine receptors (DHPR), ryanodine receptors (RyR1), calcium release, the troponin-tropomyosin complex, the cross-bridge cycle, and sarcoplasmic reticulum calcium re-uptake (SERCA1a). Outline the pathophysiology of Malignant Hyperthermia.
• SCENARIO 5: Outline the Erlanger-Gasser classification of nerve fibres. Provide a table comparing fibre types (A-alpha, A-beta, A-gamma, A-delta, B, C) with respect to diameter, presence of myelin, conduction velocity, anatomical location, and primary physiological function. Explain the physiological order of nerve fibre blockade during regional anaesthesia.