Spinal Mechanisms to Motor Systems pp

Question 1

Muscle Stretch Phases

Answer 1

Dynamic - period which length is changing

Static - When muscle has stabilized at its new length

Question 2

Muscle Spindle as Sensory Receptor

Answer 2

Parallel to the extrafusal muscle fibers
Adequate stimulus to central portion of intrafusal muscle fiber.
Stretch as whole or as fibers stimulated by gamma innervation

Question 3

Group 1a Fiber

Primary Ending

Answer 3

One per muscle spindle
Usually innervates all the intrafusal fibers
Both nuclear bag and nuclear chains

Question 4

Primary ending physiology

Answer 4

Firing has both dynamic and static component

And contains info on both rate of muscle length change and static length

Question 5

Group II Fiber

Secondary ending

Answer 5

Intrafusal fibers best at sensing current length of muscle

Firing gives static info

Question 6

Muscle spindle functions

Answer 6

Sensory input for stretch reflex
Input to cerebellum for unconscious proprioception
Relay to cerebral cortex for conscious proprioception

Question 7

Tonic Stretch Reflex

Answer 7

Exaggerated in rigidity seen in Parkinsons.

Patients w/ spasticity, strength depends on speed muscle is stretched

Question 8

Reciprocal Ihibition

Answer 8

1a fiber fires to alpha motor neuron on extensor and interneuron inhibitor fires to flexor.
Allows joint to move one way

Question 9

Co Contraction

Answer 9

Both prime movers agonist & antagonist contract simultaneously
To stiffen joint and stabilize

Question 10

Gain of stretch reflex

Answer 10

Depends on level of activity of gamma motor neurons
And inhibition excitation of alpha motor neurons
Modified by inhibition
which is decreased in patients w/ spasticity

Question 11

Muscle Tone

Answer 11

Resting tone - slight tension can be felt in a relaxed muscle
Measured by testing the tonic stretch reflex

Question 12

Muscle Tone Due to

Answer 12

Passive Viscoelastic properties of muscles & joints
Many subjects cant relax
Stretch reflexes

Question 13

Spasticity

Answer 13

Hypertonia, component of the upper motor neuron syndrome, sometimes used as whole (NOT)

Question 14

Motor disorder spasticity

Answer 14

Velocity dependent increase in tonic stretch reflex.
Exaggerated Tendon jerks
Due to hyper excitability
More prominent in antigravity muscles

Question 15

Spasticity signs

Answer 15

Babinski sigh
Show clonus
Spastic limb clasp knife response

Question 16

Golgi Tendon Organ

Answer 16

Found btw muscle & tendon in series w/ the muscle

Measures muscle tension

Question 17

GTO Sensory Output

Answer 17

Spinal Cord for Refle
Cerebellum for unconscious proprioception
Cerebral cortex for conscious proprioception

Question 18

Ib Reflex

Answer 18

GTO stimulated by increasing the tension on muscle.

Negative feedback of muscle tension inhibits agonist & excites antagonist

Question 19

Flexion Crossed Extension Reflex

Answer 19

Stimulated leg flexes to w/draw.

Opposite leg extends to support

Question 20

Flexor Withdrawl Reflex

Answer 20

Leg stimulated withdrawl
Extensors inhibit
Flexors excite

Question 21

Renshaw Cell

Answer 21

Recurrent collateral branch of aMN,

recurrent inhibition

Question 22

Positive feedback

Answer 22

Inhibiting an inhibitory neuron is disinhibition

Question 23

Monosynaptic stretch reflex

Answer 23

Fastest reflex, bot 1a and aMN are large conduction axons. and only one synaptic delay