Darkthorn’s Blog

- skeletal muscle – highly efficient and adaptable

- energy and metabolism, heater, pump, movement and posture

- muscle fibres grouped into bundles

- somatic motor system – skeletal muscles and the part of the motor system that control them

- lower motor neurons – project from spinal cord

- alpha motor neurons – muscle force generation

- gamma motor neurons – sensory (spindles)

- neuromuscular junction – nerve-muscle interface

- motor unit – a single motor neuron (axon) and all the muscle fibers it innervates

- size is determined by the number of fibers attached to the neuron

- to increase force in a muscle – increase in frequency of motor neurons, recruitment of additional motor units (small first, large last)

Neuromuscular Transmission

1. nerve AP reaches axon terminal

2. axon terminal membrane depolarizes

3. calcium channels open, calcium flows into terminal

4. release of Ach and binding to muscle membrane

5. the permeability of muscle membrane increases, causing depolarization

Mechanism of Contraction

- a single muscle action potential is generated from a single neuron

- travels along muscle membrane then down t-tubules

- causes release of Ca2+ from the sarcoplasmic reticulum

- troponin blocks actin and myosin from reacting together, but calcium removes it (cross bridge attachment)