Spinal Reflexes

Question 1

Lower Motor Neurons

Answer 1

In Ventral horn

Axons run peripheral to terminate in skeletal muscles

Question 2

Alpha Motor Neurons

Answer 2

Largest neurons Ventral horn
Innervate Extrafusal fibers
Cause contraction of gross muscle
MOVEMENT

Question 3

Gamma Motor Neurons

Answer 3

Smaller neurons in Ventral horn

Innervate contractile portion of intrafusal fibers of MUSCLE SPINDLES

Question 4

Reflex reaction

Answer 4

Simple stereotyped response to a particular sensory stimulus

Question 5

Reflexes basics

Answer 5

Involuntary, instantaneous & protective.
Does not reach brain.
Receptor
Afferent limb
Interneurons
Efferent limb
Effector (muscle)

Question 6

Reflex receptors are in….

Answer 6

Skin
Skeletal muscle
Tendons
Joint capsules

Question 7

Afferent (SENSORY) Limb of reflex arc

Answer 7

Pseudo unipolar neuron DRG
Peripheral receptor
Central process in spinal cord gray matter

Question 8

Interneuron

Answer 8

May or may not be a component

Question 9

Efferent (MOTOR) Limb of reflex arc

Answer 9

Formed by motor neuron whose cell body is usually located in the ventral horn of spinal cord.
Axon synapses in skeletal muscle

Question 10

Effector

Answer 10

skeletal muscle

Question 11

Intrasegmental

Answer 11

Involve or affect only a single spinal cord level

Question 12

Intersegmental

Answer 12

They involve or affect numerous spinal cord level

Question 13

Suprasegmental

Answer 13

They are influenced by neurons residing in the cerebral hemisphere or brainstem
Occurs at spinal cord level

Question 14

Muscle Stretch Reflex

Answer 14

Consists of only 2 neurons
May be elicited by tapping a large tendon….
Protects muscle fibers from overstretching

Question 15

Reciprocal Inhibition

Answer 15

Receptor = muscle spindle Ia.
Sensory neuron bifurcates
aMN = stimulates extensors
inhibitory interneuron inhibits flexor
Contractor/relaxor

Question 16

Autogenic Inhibition reflex

Answer 16

Receptor = GTO
Stretch when quad contracts
Ib fiber activates inhibits aMN that inn. Quad
Relaxes the agonist muscle to protect tendon

Question 17

Withdrawal Reflex, Nociceptive Reflex

Answer 17

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

Question 18

Crossed Extension Withdrawal

Answer 18

Ad & C fibers
Unaffected limb of in Withdrawal flexor.
Commissural interneurons cross midline excite those extensors and inhibit flexor .
So opposite leg takes weight

Question 19

Maintenance of muscle tone

Answer 19

Gamma loop
gamma motor neurons stimulate polar contractile portions of intrafusal fibers. contract pull away from midline.
Annulospiral endings of Ia sensory are stretched and fire
Activate aMN for Extrafusal fibers.
Slight contraction muscle TONE