Flashcards in Spinal Reflexes Deck (19):
Lower Motor Neurons
In Ventral horn
Axons run peripheral to terminate in skeletal muscles
Alpha Motor Neurons
Largest neurons Ventral horn
Innervate Extrafusal fibers
Cause contraction of gross muscle
Gamma Motor Neurons
Smaller neurons in Ventral horn
Innervate contractile portion of intrafusal fibers of MUSCLE SPINDLES
Simple stereotyped response to a particular sensory stimulus
Involuntary, instantaneous & protective.
Does not reach brain.
Reflex receptors are in....
Afferent (SENSORY) Limb of reflex arc
Pseudo unipolar neuron DRG
Central process in spinal cord gray matter
May or may not be a component
Efferent (MOTOR) Limb of reflex arc
Formed by motor neuron whose cell body is usually located in the ventral horn of spinal cord.
Axon synapses in skeletal muscle
Involve or affect only a single spinal cord level
They involve or affect numerous spinal cord level
They are influenced by neurons residing in the cerebral hemisphere or brainstem
Occurs at spinal cord level
Muscle Stretch Reflex
Consists of only 2 neurons
May be elicited by tapping a large tendon....
Protects muscle fibers from overstretching
Receptor = muscle spindle Ia.
Sensory neuron bifurcates
aMN = stimulates extensors
inhibitory interneuron inhibits flexor
Autogenic Inhibition reflex
Receptor = GTO
Stretch when quad contracts
Ib fiber activates inhibits aMN that inn. Quad
Relaxes the agonist muscle to protect tendon
Withdrawal Reflex, Nociceptive Reflex
Receptors Ad & C fibers
Pseudo unipolar neurons DRG. Dorsolateral tract of Lissauer where it branches short ascending & descending fibers.
Pain, affected limb flexors activate & extensors withdrawal
Crossed Extension Withdrawal
Ad & C fibers
Unaffected limb of in Withdrawal flexor.
Commissural interneurons cross midline excite those extensors and inhibit flexor .
So opposite leg takes weight