Chapter 12 (7)
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What is a stretch reflex?
Provides automatic regulation of skeletal muscle length.
What are the steps of the patellar reflex?
- Arrival of stimulus and activation of receptor.
- Activation of sensory neurons.
- Information processing in cns.
- Activation of motor neuron.
- Response of peripheral receptor.
Describe Muscle spindles.
- Are sensory receptors of stretch reflex
- Consist of a bundle of specialized muscle fibers (intrafusal muscle fibers)
- Are surrounded by larger skeletal muscle fibers responsible for muscle tone and contraction of entire
- Sensory neuron surrounds muscle spindle and is always sending impulses to CNS through dorsal root
- Are innervated by gamma motor neurons that alter tension in spindle and control sensitivity of
What are postural reflexes?
Coordinated activities of opposing muscles to keep body’s weight over feet.
Describe polysynaptic reflexes.
- Responsible for automatic actions involved in complex movements.
- May involve sensory and motor responses on the same side of body or opposite sides:
- -Same side: ipsilateral reflexes
- -Examples: stretch reflex, withdrawal reflex
- -Opposite sides: contralateral reflexes
- -Example: crossed extensor reflex
Describe withdrawl reflexes.
- Move affected body parts away from stimulus
- Strongest are triggered by painful stimuli but other stimuli can initiate
- Show tremendous versatility because sensory neurons activate many pools of interneurons
- Example: flexor reflex, crossed extensor reflexes
- Activate motor neurons in anterior gray horn to contract flexor muscles
- Activated inhibitory interneurons keep extensors relaxed
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