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Chapter 8

PSY290H1 Chapter Notes - Chapter 8: Patellar Ligament, Neuromuscular Junction, Tendon Reflex

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Junchul Kim

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Chapter 8 Continuation
Comparing the Two Dorsolateral Motor Pathways and the Two Ventromedial Motor
o Both have axon tracts descending into spinal cord and brain stem TO spinal cord
o They differ:
o More diffuse i.e. the axons
innervate interneurons on both sides
of spinal gray matter
o Motor neurons project to
proximal muscles
o Axons here terminate directly
on motor neuron
o Motor neurons project to
distal muscles
o Originate in cerebral cortex
o Voluntary movement, however different functions as shown in monkey studies
Sensorimotor Spinal Circuits
o Muscles
- Motor units are smallest unit of motor activity (comprises of a single
motor neuron and all of the individual skeletal muscle fibers)
- Motor neuron fires, all muscle fibers contract
- A motor unit with fewest muscle fibers (fingers) permits highest degree
of selective motor control
- Skeletal muscles have many muscle fibers bound together and attached
to bone via tendon
- Acetylcholine is released by motor neurons at neuromuscular junctions
and activates the motor end-plate causing fiber to contract
- Muscles only generate force in one direction
- All muscle neurons innervating fibers of a muscle MOTOR POOL
- Fast muscle fibers (contract and relax quickly involved in jumping), and
slow muscle fibers (slower, weaker, sustained contraction b/c
vascularized involved in walking)
- Flexors bend or flex a joint BICEPS AND TRICEPS
- Extensors straightening or extending
- Synergistic muscles whose contraction produces the same movement
- Antagonistic muscles that act in opposition
- Muscle activation of two types: increase in tension (isometric), or pulled
together (dynamic contraction)
- Increase in number of neurons, increase in tension b/c this increases the
firing rates
o Receptor Organs of Tendons and Muscles
- Two kinds of skeletal muscle receptors: golgi tendon organs (in tendons)
connect muscle to bone; and muscle spindles (in muscle tissue)
- Both respond to different aspects of muscle contraction
- Golgi responds to increase in tension, insensitive to change in length,
provides CNS with info about muscle tension, protect against damage by
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