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Unformatted text preview: Reflexes
Reflexes are involuntary
All reflexes have:
peripheral sensory receptors
for vision, temperature, smell, pressure, touch, pain, hearing, movement changes afferent nerve fibers
input to CNS efferent nerve fibers
output from CNS effectors muscles Monosynaptic reflexes (stretch reflex) single synapse Synergist muscle reflex
share the same action as the primary mover (agonist) the Ia branches
p. 94; fig 5.14 Disynaptic (reciprocal) inhibition
Ia can branch and synapse on Ia inhibitory interneurons, which affect antagonist muscles GTOs—nonreciprocal (autogenic) inhibition
Ib afferent —> Ib interneuron (+ or -) —> inhibit the agonist muscle and excite the antagonist muscle Withdrawal reflex (flexor reflex)
removes body from noxious stimuli
nociceptors —> III and IV afferents —> interneuron (+ or -) —> excite flexor muscle and inhibit extensor muscle Flexor Reflex Afferents multiple circuits from multiple sensory input
EX: crossed extension reflex: ipsilateral flexion and contralateral extension Long-Loop Transcortical Reflexes (Responses): Intentional input (cortical) to mediate responses to
- reflexive adjustments made by sudden load disturbances powerful
- integration of peripheral information and the task intention
(depends on the “instructions”)
EX: when you help a person move and they tell you the box is heavy, you prepare your arms but no matter what they will still
drop down and adjust Can reflexes be modified (altered) by other signals within the body?
Things that affect reflexes:
- initial body position
- knowledge of output
- type of afferent stimuli
- biomechanical constraints
- ANS ...
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- Fall '19