Nerve MUSCLE PHYSIOLOGY

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Presentation transcript:

Nerve MUSCLE PHYSIOLOGY

Molecular Mechanism Of Muscle Contraction Sliding filament mechanism Walk along theory Ratchet theory

Walk Along Theory

Interaction B/W Actin & Myosin

Walk Along (Ratchet) Theory

Relaxed & Contracted

NEUROMUSCULAR JUNCTION

Motor Unit Single Motor Neuron & all Muscle Fibers it innervates constitute a single Motor Unit. α- motor N

NeuroMuscular Junction

Release of Acetylcholine

Ligand Gated Channel (Acetylcholine) Closed Open

Safety factor for transmission at the Neuromuscular junction. Fatigue of Neuromuscular Junction

Myasthenia Gravis 1 in every 20,000 persons. Antibodies against acetylcholine receptors. Autoimmune disease. Muscle paralysis ---- inability of neuromuscular junction to transmit enough signals . Neostigmine ---- anticholinesterase drug.

Sarcoplasmic Reticulum T-Tubule & Longitudinal Tubule

Sarcoplasmic Reticulum T-Tubule & Longitudinal Tubule

Sarcoplasmic Reticulum(T-tubule) DHP & Ryanidin Receptor (Hypothetical Model)

A.P entering the Sarcoplasmic Reticulum causing release of Ca++ ions

Excitation-Contraction coupling “The process by which the depolarization of the muscle fiber initiates contraction”

Sequence of Events in contraction of Muscle Stimulation of Motor Neuron. Release of neurotransmitter (Acetylcholine) at Motor End-plate. Binding of Ach to Nicotinic Receptors. Increased Na+ conductance through Ach Channels Generation of end-plate potential Generation of Action Potential in Muscle Fiber

Sequence of Events in Contraction Inward spread of depolarization along T-Tubule- Sensing by DHP receptors & opening of Rayanidine receptors in terminal cisterns. Release of Ca++ from terminal cistern of Sarcoplasmic Reticulum and diffusion to myofilaments Binding of Ca++ to Troponin-C, uncovering Myosin binding on Actin filaments Formation of Cross linkages between Actin & Myosin leading to sliding of thin on thick filaments, producing movement of Z-lines toward the centre

Steps involved in Relaxation of Muscle ATP attaches to Myosin head Ca++ Pumped Back in Sarcoplasmic Reticulum. (Ca++ Mg++ ATPase Pump always On ) Release of Ca++ from Troponin Cessation of Interaction between Actin & Myosin filaments