Spinal Reflexes Flashcards Preview

Neuroanatomy I > Spinal Reflexes > Flashcards

Flashcards in Spinal Reflexes Deck (19):
1

Lower Motor Neurons

In Ventral horn
Axons run peripheral to terminate in skeletal muscles

2

Alpha Motor Neurons

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

3

Gamma Motor Neurons

Smaller neurons in Ventral horn
Innervate contractile portion of intrafusal fibers of MUSCLE SPINDLES

4

Reflex reaction

Simple stereotyped response to a particular sensory stimulus

5

Reflexes basics

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

6

Reflex receptors are in....

Skin
Skeletal muscle
Tendons
Joint capsules

7

Afferent (SENSORY) Limb of reflex arc

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

8

Interneuron

May or may not be a component

9

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

10

Effector

skeletal muscle

11

Intrasegmental

Involve or affect only a single spinal cord level

12

Intersegmental

They involve or affect numerous spinal cord level

13

Suprasegmental

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

14

Muscle Stretch Reflex

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

15

Reciprocal Inhibition

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

16

Autogenic Inhibition reflex

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

17

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

18

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

19

Maintenance of muscle tone

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