Motor Systems

Question 0

What is the function of the BASAL GANGLIA in the motor system?

Answer 0

enforcement of desired movement
AND
suppression of undesired movements

Question 1

What is the function of the CORTEX in the motor system?

Answer 1

planning, initiation of voluntary movement
AND
integration of inputs

Question 2

What is the function of the CEREBELLUM in the motor system?

Answer 2

timing/precision of fine movement
adjusting ongoing movements
motor learning

Question 3

What is the function of the BRAINSTEM in the motor system?

Answer 3

control of balance/posture

coordination of head, neck, eye movement

Question 4

What is the function of the SPINAL CORD in the motor system?

Answer 4

reflexes, rhythmic movements, motor outflow

Question 5

What is the function of the MUSCLES in the motor system?

Answer 5

movement of body

sensory organs

Question 6

What is a motor unit?

Answer 6

A single neuron and all of the muscle fibers it innervates

SMALLEST division of the motor system can control individually

Question 7

Describe Slow-Twich (Type I) muscle fibers

Answer 7

• dark fibers (due to myoglobin)
• aerobic metabolism
• more myoglobin and MT
• contract slower
• less force
• RESIST fatigue

Question 8

Describe Fast-Twitch (Type II) muscle fibers

Answer 8

-Pale fibers
-anaerobic metabolism
more glycolytic enzymes
-contract fast
-more force
-FATIGUE fast

Question 9

Describe Fast Fatigue-Resistant muscle fibers

Answer 9

intermediate b/t fast and slow fibers

Question 10

What determines muscle type? (Fast-twitch, slow-twitch, etc)

Answer 10

Never innervation. NOT muscle fiber

Question 11

Describe Muscle Fiber Recruitment

Answer 11

small motor neurons–> slow-fatigue
then medium motor neurons–> fast fatigue-resistant
then large motor neurons–> fast fatigue

Question 12

Identify the 3 parts of the spindle

Answer 12

intrafusal fibers, afferent sensory neuron, and gamma motor neuron

Question 13

Describe the afferents of the Dynamic Bag fibers and Static bag, and nuclear chain fibers

Answer 13

Dynamic Bag fibers–> Type 1a afferent, phasic response only to CHANGE to length
Static bag fibers and nuclear chain fibers—> Type 1a AND Type II afferents, no phasic response, gradual response

Question 14

What do Golgi Tendon organs measure? Which afferent fibers go to Golgi tendons?

Answer 14

Measure tension. Type Ib afferent fibers.

Question 15

Describe the topographical organization the spinal cord

Answer 15

Medial–> Axial muscles
Lateral–> Distal muscles
Ventral–> Extensors
Dorsal–> Flexors

Question 16

What is the difference between medial and lateral interneurons?

Answer 16

Medial–> Bilateral projections. travel farther.

Lateral–> travel up and down a few segments, confined to one side

Question 17

What are the different interneurons and their functions?

Answer 17

Renshaw: stabilize motor neuron firing rates
Propriospinal: connect different spinal segments (medial and lateral interneurons)
Group 1a: Muscle Spindle inhibition of antagonist muscle, agonist-antagonist coordination
Group 1b: Golgi-Tendon Organ inhibition of agonist muscle to prevent excessive tension

Question 18

Describe the stretch reflex

Answer 18

Type Ia afferents from Muscle Spindle–> excite motor neuron of same muscle and synergistic muscles. Inhibit antagonist muscle through inhibitory Group Ia interneurons
Type Ib afferents from Golgli Tendon–> Inhibit motor neuron of same muscle through inhibitory Group 1b interneurons

Question 19

Describe Felxion Withdrawal Reflex

Answer 19

PAIN REFLEX
Flexion of same limb away from pain stimulus AND “Crossed-Extensor Reflex”–> extension of contralateral limb to maintain posture

Question 20

Upper vs. Lower Motor Neuron Disease (weakness, atrophy, reflexes, spasticity, Babinski)

Answer 20

UMN: weakness, NO atrophy, INCREASED reflexes, spasticity, and Babinski (+)

LMN: weakness, atrophy, DECREASED reflexes, NO spasticity, NO Babinski (-)

Question 21

Neurogenic vs Myopathic Disease (atrophy, fasciculations, loss of reflexes, creatine kinase, muscle biopsy, EMG)

Answer 21

Neurogenic: atrophy, fasciculations, loss of reflexes, NORMAL creatine kinase, Fiber-type grouping in muscle, FEWER and LARGER potentials on EMG

Myopathic: atrophy, NO fasciculations, loss of reflexes, INCREASED creatine kinase, muscle necrosis/regeneration on biopsy, and SMALLER potentials on EMG

Question 22

What is ALS?

Answer 22

Amyotrophy= muscle atrophy

Lateral Sclerosis= sclerosis (scarring) of lateral corticospinal tracts in spinal cord

Question 23

Describe the difference between Central and Peripheral Dysarthria

Answer 23

Central: “Spastic Dysarthria” speed is low, articulation is fairly clear

Peripheral: “Nasal Dysarthria” speed is normal, articulation is bad. Palatal weakness–> nasal quality

Question 24

Other Symptoms of ALS

Answer 24

weight loss, fatigue, pain (due to immobility) psedobulbar affect (emotional lability) (Upper Motor Neurons) depression (10%) cognitive changes bulbar symptoms--> hypoglossal nerve--> dysarthria, dysphagia, drooling, nasal regurgitation, aspiration

Question 26

Treatment for ALS (Multidisciplinary)

Answer 26

Respiratory care, weight maintenance, fall prevention, communication therapy, Pseudobulbar effects, pain, depression, spasticity, cramps, cognitive impairment

Question 27

What cells lie in Layer 5 of Primary Motor Cortex?

Answer 27

Betz cells of the corticospinal tract

Question 28

Naming of spinal nerves and vertebrae

Answer 28

C1-C7 share same # as vertebral segment BELOW it C8 exits BELOW C7 Rest of nerves share same # as vertebral segment ABOVE it

Question 29

What is the difference between Cauda Equina Syndrome and Conus Medullaris Syndrome?

Answer 29

Cauda Equina Syndrome: Slow progression. Unilateral pain and areflexia, muscle atrophy. NO sexual dysfunction. Conus Medullaris Syndome: Fast onset. Bilateral pain, reflexes present, incontinence. SEXUAL dysfunction

Question 30

Describe the Deep Tendon Reflexes (cord segment and muscle)

Answer 30

``` Ankle jerk: S1, Gastrocnemius Knee jerk: L2-L4, Quadriceps Biceps: C5-C6, Biceps Forearm: C5-C6, Brachioradialis Triceps: C7-C8, Triceps ```

Question 31

What are the White Communicating Rami and Gray communicating Rami?

Answer 31

White: Myelinated Pre-ganglionic sympathetic fibers Gray: Unmyelinated Post-ganglionic sympathetic fibers

Question 32

What is the Ventral Corticospinal tract?

Answer 32

``` 10% of descending corticospinal tracts that do not decussate with lateral corticospinal tract Control posture, gross movement of neck, trunk, and lower limbs. Bilateral innervation (Ventral Commissure) ```

Question 33

Where does the Hypothalamospinal Tract project to? Lesion?

Answer 33

Interomediolateral cell column Lesion: Horner syndrome

Question 34

What is the difference between fasciculations and fibrillations?

Answer 34

Fasciculations: spontaneous depolarizations of group of muscle fibers by 1 motor neuron Fibrillations: small spontaneous depolarizations of single denervated muscle fiber

Question 35

What is Brown- Sequard Syndrome?

Answer 35

Loss of ALL sensation within 2 levels of lesion Loss of IPSILATERAL motor function Loss of CONTRALATERAL pain/temp below lesion Loss of IPSILATERAL proprioception/fine touch on

Question 36

Describe the events at the NMJ

Answer 36

ACh--> NAChR--> influx of Na, K, an Ca through sarcolemma--> Ca-induced Ca release form SR--> Ca binds Troponin C--> removes tropomyosin from Myosin-binding sites on Actin--> myosin can bind actin--> muscle contraction

Question 37

Describe Myesthenia Gravis. How do you diagnose?

Answer 37

Autoimmune disease against NAChRs. Diagnosis via Tensilon Test (Edrophonium administration rapidly improves symptoms). This test is Negative in Lambert-Eaton.

Question 38

Describe Lambert-Eaton.

Answer 38

Autoimmune against presynaptic VG-Ca channels at NMJ.

Question 39

Clinically, what is difference between Myasthenia Gravis and Lambert-Eaton?

Answer 39

MG: associated with Thymoma. Muscles are WEAKER with repetition. Manifests with ptosis, diplopia, muscle weakness at END OF THE DAY. LE: associated with small-cell lung cancer. Muscles are STRONGER with repetition. Manifests with difficulty rising from chair, weakness of large muscles IN THE MORNING. Muscle and ocular muscle involvement not as severe.

Question 40

What is the epineurium, perineurium, and endoneurium?

Answer 40

Epineurium: dense conn. tiss--> covers entire nerve. Perineurium: permeability barrier. Surrounds fascicle of fibers. Must be rejoined in limb attachment. Endoneurium: Surrounds single nerve fiber.