Fns Lecture 11: Spinal Reflexes I

Front 1

Define: An involuntary stereotyped response to a sensory input.

Back 1

Reflex

Front 2

List the two types of sensory receptors which provide continuous sensory feedback of information from each muscle to the spinal cord.

Back 2

Muscle spindles
Golgi Tendon Organs

Front 3

Define: A stretch receptro that conssits of 8-12 specialized muscle fibers of two types with a connective tissue capsule surrounding the middle thrid of the fibers.

Back 3

Muscle spindle

Front 4

What types of information does a muscle spindle provide?

Back 4

Either the length of the muscle or rate of change of its lenght (velocity of contraction)

Front 5

What provides the sensory signal for the myotatic (stretch) reflex?

Back 5

The muscle spindle

Front 6

Where is muscle spindle density gretest?

Back 6

Muscles that carry out precision movements (hand muscles for example).

Front 7

Where is the greatest number of muscle spindles?

Back 7

Large muscles.

Front 8

True/False: Intrafusal fibers show cross striations throughout their length.

Back 8

False. Intrafusal fibers show cross striation only at their ends.

Front 9

Wat are the two types of intrafusal fibers?

Back 9

Nuclear Bag fibers
Nuclear Chain Fibers

Front 10

Define: Nuclei are collected in expanded central position; contractiel elements are at poles
1-3 ____ fibers/muscle spindle
are sensitive to change in muscle length and the rate of that change (static & dynamic sensitivity).

Back 10

Nuclear Bag fibers

Front 11

Define:
Nuclei are arranged in a single file chain mainly in central non-contractile portion of intrafusal fibers
Twice as many/spindle compared to nuclear ___ fibers. Are senstivite only to change in muscle length (static sensitivity).

Back 11

Nuclear Chain fibers (___ is bag)

Front 12

What are the two types of sensory innervation for muscle spindles?

Back 12

Large myelinated Group Ia fibers
Smaller Group II

Front 13

What is the single type of motor innervation?

Back 13

Gamma motor neurons in LAM IX.

Front 14

Type Ia or II? During Static phase (stretched lenght is constant mains firign rate

Back 14

Group II fibers

Front 15

Type Ia or II? During Dynamic phase (lenght of spindle increasing) increase AP frequency quickly'
peak firing rate is proportional to velocity
signals change of length 7 velocity of the change.

Back 15

Group Ia

Front 16

Type Ia or II? During Dynamic phase (length of spindle increasing)
Increase frequency of AP more slowly
Signal change in length but not velocity

Back 16

Group II Fibers

Front 17

Type Ia or II? During Dynamic phase (lenght of spindle increasing) increase AP frequency quickly'
peak firing rate is proportional to velocity
signals change of length 7 velocity of the change.

Back 17

Group Ia

Front 18

Type Ia or II? Release of stretch (contraction) momentarily silenced, then resume firing based on the new muscle length.

Back 18

Type Ia

Front 19

Type Ia or II? During Release of stretch (contraction) there is decrease firing rate momentarily but are not silenced.

Back 19

Type II

Front 20

Define:
Located at the junctions between muscles and tendons
Provides information about tendon tension or the rate of change of tension (velocity of tension).

Back 20

Golgi Tendon Organ

Front 21

Define: A monosynaptic reflex that involves two neurons (one afferent and one efferent) and a single intervening synapse. Initiated by muscle stretch.

Back 21

Myotatic reflex

Front 22

Where do the Group Ia endings go to for the myotatic reflex?

Back 22

Ia fibers course in the dorsal root to the spinal cord ventral horn and synapse directly on alpha motor neurons in lamina IX of the anterior (ventral) horn.

Front 23

Give another name for the deep tendon reflex.

Back 23

Myotatic reflex

Front 24

What makes the myotatic reflex reliable?

Back 24

It is mediated by a monsynaptic connection between fast conducting fibers.

Front 25

Describe the reciprocal inhibition of antagonist in the myotatic reflex.

Back 25

The same Ia afferent fiber from the agonist muscle sends a collateral to make an excitatory synapse with an inhibitory interneuron. This connection allos for inhibition of the alpha motor neuron of the ipsilateral antagonist muscle.

Front 26

What are small multipolar motor neurons which exit the spinal cord in the ventral root and course in spinal nerves to innervate the polar, contractile region of intrafusal fibers?

Back 26

Gamma Efferent motor neurons

Front 27

Describe alpha-gamma co-activation and its purpose.

Back 27

Alpha and gamma neurons are activated in paaralledl in many voluntary, purposeful movements. Ensures that the muscle spindle maintains its sensitivity to stretch as the muscle contracts

Front 28

What is another term for the levle of gamma motor neuron activity?

Back 28

Gamma bias or gain.

Front 29

What are two ways to adjust gamma bias/gain?

Back 29

UMN pathways
Local reflex activity

Front 30

What is one thing which determines muscle tone?

Back 30

Excitability of the motor neurons

Front 31

Define: A decrease in the resting muscle tone and a decreased resistance to passive limb manipulations

Back 31

Hypotonia

Front 32

What can be caused to damage to alpha motor neurons or Ia sensory fibers in dorsal root or spinal nerve or certain supraspinal center?

Back 32

Hypotonia

Front 33

Define: An increase in the resting muscle tone manifested by an increased resistance to passive stretch of a limb.

Back 33

Hypertonia

Front 34

Define: A series of alternating contractions and relaxations of flexores and extensors produce by passive stretch of alimb or part of limb(ankel)
is seen in corticospinal damage.

Back 34

Clonus

Front 35

What is associated with slasp-knife phenomenon in which increased resistance to stretch melts or decreasees with continuous stretch.

Back 35

Spasticity

Front 36

What is a velocity-dependent increase in muscle tone (hypertonia) and exaggeration of myotatic reflexes )hyperreflexia).

Back 36

Spasticity