Muscle Receptors, Spinal Reflexes, And Central Pattern Generation

Question 1

Do muscle spindles provide negative or positive feedback?

Answer 1

Negative feedback

Question 2

What 3 things do muscle spindles contribute to?

Answer 2

Locomotion
Kinesthesia
Muscle tone

Question 3

Group Ia afferent

Answer 3

• Innervate bag and chain
• sensitive to change in length and velocity
• active during phasic or dynamic change of length change

Question 4

Group II afferents

Answer 4

• innervate chain fibers
• NOT velocity specific, NOT active during phasic length
• most sensitive to absolute length —> steady state phase of length change and static property

Question 5

Dynamic gamma motor neurons

Answer 5

Sensitive to velocity of length change

Active during dynamic phase

Question 6

Static gamma motor neuron

Answer 6

• alters spindle sensitivity to length

- active during steady-state phase

Question 7

Rate- Sensitivity

Answer 7

Bi-directional

Will pause in firing during a fast shortening then resumes steady state firing rate

Question 8

What do dynamic motor neurons specifically care about?

Answer 8

Velocity of stretch (only bag)

Question 9

What is the net effect of static motor neurons?

Answer 9

Enhance information on current muscle length (bag and chain)

Question 10

Take home message of the gamma system

Answer 10

Maintains spindle firing rate within an optimal range for signaling length changes, whatever the optimal length of the muscle

Question 11

Muscle contraction & GTOs

Answer 11

Muscle contraction —> collagen fibers shorten —> 1b nerve endings are stretched —> increased firing rate

Question 12

What are GTOs very sensitive to?

Answer 12

Effects of recruitment

Question 13

What is a myotactic (deep tendon) reflex an excitatory connection between?

Answer 13

Group 1a afferent and alpha motor neurons

Question 14

Autogenic excitation myotactic (deep tendon) reflex

Answer 14

Monosynaptic excitatory synapse between spindle 1a afferent and alpha motor neurons of the same muscle, resulting in contraction

Question 15

Synergist activation myotactic (deep tendon) reflex

Answer 15

Group 1a afferents also may have excitatory synapses on motor neurons innervating synergist muscles

Question 16

Reciprocal Inhibition (deep tendon reflex)

Answer 16

Via Interneuron, activation of group 1a afferents results in inhibition of antagonist

Question 17

Tonic vibratory reflex

Answer 17

Primary endings respond to vibrations
Contraction of vibrated muscle
Inhibition of antagonist

Question 18

When is tonic vibratory reflex strongest?

Answer 18

Under isometric conditions

The longer the initial length of the muscle, the stronger the contraction

Question 19

Recurrent inhibitions

Answer 19

Increase in alpha motor neuron activity increases activity of inhibitory renshaw cell
Excited renshaw cell dampens firing rate of alpha motor neuron

Question 20

Inverse myotactic reflex

Answer 20

• Golgi tendon organ
• 1b afferents excite inhibitory Interneuron
• inhibits contracting muscle, excites antagonist m

Question 21

What activates flexion reflexes?

Answer 21

Sensory receptors and afferents

Question 22

Crossed extension reflex

Answer 22

• concurrent with activation of flexor withdrawal reflex in ipsilateral limb
• occurs in contralateral limb
• inhibits flexors and activates extensors to maintain balance

Question 23

Key points of central pattern generator

Answer 23

• CPGs or other spinal circuitry encode a basic sequence of rhythmic locomotor activity
• final locomotory pattern will reflect fine-tuning by peripheral sensory input and descending projections from brain

Question 24

What are abnormal stretch reflexes often associated with?

Answer 24

Abnormal tone

Question 25

What type of reflexes are present immediately post-spinal transection?

Answer 25

Hypoactive