Intro to Motor Systems pp

Question 1

Voluntary Movement

Answer 1

Purposeful movement
Goal Directed
Movements learned & improved w/ practice
As skilled they require less or even no conscious participation

Question 2

Classes of Movement

Answer 2

Reflex
Rhythmic
Autonomous

Question 3

Movements dependence on Sensory Information

Answer 3

Nervous system needs to know
Initial length
Velocity of change
External loads
Visual & vestibular info

Question 4

Lower Motor Neuron

Answer 4

Motor neurons of the spinal cord & brain stem & directly innervate skeletal muscle
found in anterior horn leave at ventral root

Question 5

Alpha motor neurons

Answer 5

innervate extrafusal skeletal muscle fibers

Question 6

Gamma Motor Neurons

Answer 6

Innervate intrafusal skeletal muscle fibers, the small muscle fibers w/in the muscle spindle

Question 7

Skeletal - fusimotor neurons

Answer 7

Innervate both extrafusal & intrafusal muscle fibers; aka BETA innervation

Question 8

Sizes

Answer 8

Large motor unit has large aMN

Small motor unit has small aMN

Question 9

Disease can affect size of motor unit like Poliomyelitis

Answer 9

Death of many MN
Surviving MN adopt orphaned muscle fibers
Caused by stress on surviving neurons
Undergo repeated remodeling

Question 10

Graded muscle contraction

Answer 10

Increase muscle force
Recruitment or multiunit summation
Increase firing rate of activated motor units

Question 11

Henneman’s Size Principle

Answer 11

1st recruit small aMN to small motor unit

Gradually recruit larger aMN that develop larger force

Question 12

Muscle cells need nervous innervation

Answer 12

Low level stimulation of muscle fiber influences expression of muscle protein genes
Denervation of muscle cause PROFOUND muscle atrophy

Question 13

Lower Motoneuron Disorder

Answer 13

Muscle atrophy
Decreased muscle tone
Weak or absent reflex
Fasiculations
Fibrillations
Flaccid paralysis

Question 14

Effects of Transection of spinal cord

Answer 14

Permanent effects
Loss of voluntary movements
Loss of true sensation
Initial effect
Spinal Shock, flaccid paralysis, areflexia, loss of autonomic function
Few weeks
Hyperreflexia
Different rates
Spastic paralysis

Question 15

Possible recovery from spinal shock

Answer 15

Blood supply - increases swelling
aMN pool hyperexcitable
Loss of descending inhibitory input
Postsynaptic denervation
Collateral sprouting of the dorsal root afferents

Question 16

Upper motor neuron

Answer 16

In higher motor area

Synapses on lower motor neuron

Question 17

UMN & LMN

Answer 17

Cell bodies of UMN of the reticulospinal tracts are in the pons & medulla below LMN of midbrain

Question 18

Spinal cord lesions

Answer 18

damage LMN at the level of injury but most damage due to ascending & descending fibers

Question 19

UMN syndrome

Answer 19

Spasticity
Overactive DTR
Babinski sign
Spastic paralysis

Question 20

AMYOTHROPHIC LATERAL SCLEROSIS

Answer 20

Disease affects both UMN & LMN so can have both signs