Muscle Structure and Function

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Neuromuscular Junction

Arrival of an action potential releases vesicles of acetylcholine from the presynaptic membrane. The ACh molecules diffuse across the synaptic cleft and bind to receptors on the postsynaptic membrane causing depolarisation.

Compare to a synapse. 

Types of muscle

Voluntary muscle

  • Striated
  • Cylindrical cells are multinucleate
  • Found attached to bone (skeletal muscle)
  • Controlled by somatic nervous system
  • Contracts quickly; fatigues quickly

Involuntary muscle

  • Unstriated
  • Spindle-shaped cells each have a single nucleus
  • Found in the walls of tubular structures such as gut, blood vessels, ducts
  • Controlled by autonomic nervous system
  • Contracts slowly; fatigues slowly

Cardiac muscle

  • Semi-striated
  • Cylindrical cells, each with a single nucleus, branch and connect with other cells
  • Found only in the heart
  • Controlled by the autonomic nervous system
  • Contracts spontaneously without fatigue

The fight or flight response

  • Sensory neurones of the somatic nervous system carry impulses from receptors

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