4 - Zill - Muscle Sensory Control

Question 1

Muscle Spindles

Answer 1

Signal muscle length, movement, velocity

Have both sensory and motor innervation (gamma motor neurons)

Sensory sensitive to muscle stretch or

CHANGES IN LENGTH

Question 2

Golgi Tendon Organs

Answer 2

Signal force

Located in muscle tendon or connective tissue attachments

Sensitive to tension in tendon

Question 3

Dorsal Columns

Answer 3

Contain axon branches of sensory neurons that carry fine/discriminative touch, conscious proprioception, and vibration

Question 4

Lateral and Anterior Columns of White Matter

Answer 4

Contains spinothalamic tracts of neurons that receive sensory inputs about crude touch, pain, and temperature

Question 5

stroke

Answer 5

Cerebrovascular accident, interupt or block blood flow to brain (either block or rupture vessel)

Question 6

Kinesthesia

Answer 6

Conscious sense of body position, depends upon signals from muscle receptors

Signals transmitted in pathways that reach brain (thalamus and cortex)

Question 7

What do signals from muscle sensory receptors contribute to?

Answer 7

Conscious sense of body position

Question 8

What does the stretch (“Deep Tendon”) of muscle spindles evoke?

How do these occur?

Answer 8

Stretch Reflex in CNS, producing contraction of muscle

Automatically–do NOT require conscious awareness

Question 9

Guillain Barre Syndrome

Answer 9

Loss of axons in peripheral nerves–demyelination of large fibers, lose proprioception

Question 10

Receptors:

Exteroception

Proprioception

Answer 10

Exteroception - detection of outside world (touch, temperature, etc)

Proprioception - detection of position and movement of body intself

Question 11

Sense Organs:

Proprioceptors

Answer 11

Proprioceptors - sense organs that detect position and movement of body itself

Ex: Muscle spindles and golgi tendon organs

Question 12

What causes skeletal muscles to contract?

Answer 12

Alpha motor neurons (lower motor neurons) fire action potentials

Question 13

What occurs to muscle upon contraction?

Answer 13

Muscle length shortens, generates force

Question 14

How does the nervous system calculate limb position?

Answer 14

Know length, calculate limb position, angles, and velocity. Can calculate rate of limb movement.

Question 15

What detects movement and position?

Force?

Answer 15

Muscle spindles = movement/position

Tendon organs = force

Question 16

What occurs to muscle spindles and golgi tendon organs during isometric contractions?

Answer 16

No movement = no change in muscle spindles

Increase force detected by golgi tendon organs

Question 17

Muscle Tonus

How do you test tonus?

How do you test strength?

Answer 17

Muscle tension at rest, due to activities (background firing) in alpha motor neurons at rest

Slow stretch of relaxed muscle

Resist stretch in isometric fashion–no increase in muscle spindles, but tendon organs sense force

Question 18

Clinical presentation of changes in tonus?

Answer 18

Tonus increased in Upper Motor Neuron Disorders

Question 19

How are muscle spindles oriented to regular muscle cells?

What defines density?

Where is it highest?

Answer 19

Parallel

Density - number of spindles/number of regular muscle cells.

Highest in muscles used for fine control–hands, eyes

Question 20

What occurs when muscle are stretched?

Answer 20

Muscle spindles are stretched due to parallel orientation

Question 21

How are spindle muscle cells innervated?

Answer 21

Sensory neurons (cell bodies in dorsal root ganglia)

and

Motor neurons (cell bodies in ventral horn)

Question 22

Intrafusal Cell

Answer 22

Sindle muscle cells

Question 23

Polar Regions

Answer 23

Home of contraction filaments (can contract)

location of motor innervation

Question 24

Equatorial Region

Answer 24

Nuclei here

Location of sensory nerve endings

Question 25

How do types of intrafusal muscle cells differ?

Answer 25

**Fast** contracting **one** spindle/fiber, **gamma dynamic motor neuron** **Slow** contracting **multiple** spindles/fiber , **gamma static motor neuron**

Question 26

Gamma Motor Neurons Does one possess voluntary control of these?

Answer 26

Innervate only spindle muscle cells (not regular muscle cells) Firing causes spindle muscle to contract but does **not generate much force at the muscle tendon (that occurs through Alpha motor neurons/reflexes)** **- -** **_No_ voluntary control of Gamma Motor Neurons**

Question 27

How does contraction of regular muscle cells occur?

Answer 27

Alpha Motor Neurons and Reflexes

Question 28

Sensory Innervation: Ia II

Answer 28

Ia = 1 per spindle, innervates **all muscle cells** II = 1-5 per spindle, **innervates ONLY slow contracting muscle cells**

Question 29

What type of motor neurons innervate **fast contracting** muscle cells? What type of sensory neurons do these receive?

Answer 29

Gamma Dynamic Motor Neurons ## Footnote **_Only_ Ia Sensory Neurons**

Question 30

What type of motor neurons innervate slow contracting muscle cells? What type of sensory neurons do these receive?

Answer 30

Gamma Static Ia, II

Question 31

What does a Tendon Tap activate?

Answer 31

Activate **all** muscle spindles (like a stretch), does **NOT** activate Golgi Tendon Organs Activates all spindle sensory neurons (Ia / II)

Question 32

What does group Ia and II encode?

Answer 32

Ia - Velocity of Stretch (**how fast is stretch**) II - Magnitude of change of length (**how long is muscle**)

Question 33

Sensing which (group II or Ia) will allow rapid change to body position?

Answer 33

Group Ia, length and **velocity**

Question 34

What sets spingle length to match muscle length? How are sensory signals still set?

Answer 34

Gamma Motor Neurons The muscle spindles are **reset** so they can still signal stretch

Question 35

What occurs to Gamma Dynamic motor neuron activity? What is the result of this?

Answer 35

It is increased in anticipation of pertubations ## Footnote **Selectively enhances 1a sensory neurons (not enhance group II) and increases discharge at start of perturbation (dynamic phase)**

Question 36

Why must patients relax before neurological tests?

Answer 36

Ia can be enhanced by Gamma Dynamic Motor Neurons subconsciously (nervous) in anticipation of perturbations

Question 37

Golgi Tendon Organs end point What type of neuron are these?

Answer 37

Large (Type 1b) sensory neurons end in muscle tendon or connective tissue attachment (myotendinous junction)

Question 38

How would you get a maximum discharge in a Golgi Tendon Organ?

Answer 38

**Isometric Contraction** No discharge from muscle spindles