Motor Systems Flashcards
What is the function of the BASAL GANGLIA in the motor system?
enforcement of desired movement
AND
suppression of undesired movements
What is the function of the CORTEX in the motor system?
planning, initiation of voluntary movement
AND
integration of inputs
What is the function of the CEREBELLUM in the motor system?
timing/precision of fine movement
adjusting ongoing movements
motor learning
What is the function of the BRAINSTEM in the motor system?
control of balance/posture
coordination of head, neck, eye movement
What is the function of the SPINAL CORD in the motor system?
reflexes, rhythmic movements, motor outflow
What is the function of the MUSCLES in the motor system?
movement of body
sensory organs
What is a motor unit?
A single neuron and all of the muscle fibers it innervates
SMALLEST division of the motor system can control individually
Describe Slow-Twich (Type I) muscle fibers
- dark fibers (due to myoglobin)
- aerobic metabolism
- more myoglobin and MT
- contract slower
- less force
- RESIST fatigue
Describe Fast-Twitch (Type II) muscle fibers
-Pale fibers
-anaerobic metabolism
more glycolytic enzymes
-contract fast
-more force
-FATIGUE fast
Describe Fast Fatigue-Resistant muscle fibers
intermediate b/t fast and slow fibers
What determines muscle type? (Fast-twitch, slow-twitch, etc)
Never innervation. NOT muscle fiber
Describe Muscle Fiber Recruitment
small motor neurons–> slow-fatigue
then medium motor neurons–> fast fatigue-resistant
then large motor neurons–> fast fatigue
Identify the 3 parts of the spindle
intrafusal fibers, afferent sensory neuron, and gamma motor neuron
Describe the afferents of the Dynamic Bag fibers and Static bag, and nuclear chain fibers
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
What do Golgi Tendon organs measure? Which afferent fibers go to Golgi tendons?
Measure tension. Type Ib afferent fibers.
Describe the topographical organization the spinal cord
Medial–> Axial muscles
Lateral–> Distal muscles
Ventral–> Extensors
Dorsal–> Flexors
What is the difference between medial and lateral interneurons?
Medial–> Bilateral projections. travel farther.
Lateral–> travel up and down a few segments, confined to one side
What are the different interneurons and their functions?
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
Describe the stretch reflex
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
Describe Felxion Withdrawal Reflex
PAIN REFLEX
Flexion of same limb away from pain stimulus AND “Crossed-Extensor Reflex”–> extension of contralateral limb to maintain posture
Upper vs. Lower Motor Neuron Disease (weakness, atrophy, reflexes, spasticity, Babinski)
UMN: weakness, NO atrophy, INCREASED reflexes, spasticity, and Babinski (+)
LMN: weakness, atrophy, DECREASED reflexes, NO spasticity, NO Babinski (-)
Neurogenic vs Myopathic Disease (atrophy, fasciculations, loss of reflexes, creatine kinase, muscle biopsy, EMG)
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
What is ALS?
Amyotrophy= muscle atrophy
Lateral Sclerosis= sclerosis (scarring) of lateral corticospinal tracts in spinal cord
Describe the difference between Central and Peripheral Dysarthria
Central: “Spastic Dysarthria” speed is low, articulation is fairly clear
Peripheral: “Nasal Dysarthria” speed is normal, articulation is bad. Palatal weakness–> nasal quality
Other Symptoms of ALS
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
Treatment for ALS (Multidisciplinary)
Respiratory care, weight maintenance, fall prevention, communication therapy, Pseudobulbar effects, pain, depression, spasticity, cramps, cognitive impairment
What cells lie in Layer 5 of Primary Motor Cortex?
Betz cells of the corticospinal tract
Naming of spinal nerves and vertebrae
C1-C7 share same # as vertebral segment BELOW it
C8 exits BELOW C7
Rest of nerves share same # as vertebral segment ABOVE it
What is the difference between Cauda Equina Syndrome and Conus Medullaris Syndrome?
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
Describe the Deep Tendon Reflexes (cord segment and muscle)
Ankle jerk: S1, Gastrocnemius Knee jerk: L2-L4, Quadriceps Biceps: C5-C6, Biceps Forearm: C5-C6, Brachioradialis Triceps: C7-C8, Triceps
What are the White Communicating Rami and Gray communicating Rami?
White: Myelinated Pre-ganglionic sympathetic fibers
Gray: Unmyelinated Post-ganglionic sympathetic fibers
What is the Ventral Corticospinal tract?
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)
Where does the Hypothalamospinal Tract project to? Lesion?
Interomediolateral cell column
Lesion: Horner syndrome
What is the difference between fasciculations and fibrillations?
Fasciculations: spontaneous depolarizations of group of muscle fibers by 1 motor neuron
Fibrillations: small spontaneous depolarizations of single denervated muscle fiber
What is Brown- Sequard Syndrome?
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
Describe the events at the NMJ
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
Describe Myesthenia Gravis. How do you diagnose?
Autoimmune disease against NAChRs. Diagnosis via Tensilon Test (Edrophonium administration rapidly improves symptoms). This test is Negative in Lambert-Eaton.
Describe Lambert-Eaton.
Autoimmune against presynaptic VG-Ca channels at NMJ.
Clinically, what is difference between Myasthenia Gravis and Lambert-Eaton?
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.
What is the epineurium, perineurium, and endoneurium?
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.
