PSYC 211 Chapter Notes - Chapter 8: Ventral Anterior Nucleus, Subthalamic Nucleus, Putamen
13 Feb 2013
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Most are attached to bones at each end. Movement types: flexion: contraction of a flexor muscle. The drawing in of a limb: extension: contraction of extensor muscles. Antigravity muscles: muscles contract, limbs flex. Anatomy: skeletal muscles are composed of 2 types of muscle fibers. Extrafusal muscle fibers: served by axons of the alpha motor neurons. Intrafusal muscle fibers: sensory organs that are served by 2 axons (1 sensory, 1 motor) Central region (capsule) contains sensory endings sensitive to stretch. Gamma motor neuron causes intrafusal muscle fiber to contract (very little force) to modify the sensitivity to stretch: 1 myelinated axon of alpha motor neuron serves many. Extrafusal muscle fibres (from 1 per 10 to 1 per 100s: motor unit: 1 alpha motor neuron + its axon + associated extrafusal muscle fibres. A bundle of myofibrils (with overlapping strands of actin and myosin) (overlap zone is called a striation)
