Motor System - Overview & Cortical Influence Flashcards
Motor activity is generated and controlled through complex interactions of
- Brainstem tracts
- Frontal lobe, particularly primary motor cortex
- Cerebellum
- Basal ganglia
- Thalamus
complex pattern of muscle activation must be
planned and generated
Feedback occurs at all levels, but is primarily processed by
cerebellum
Peripheral motor control begins with?
the innervation of muscle by alpha motor neurons
alpha motor neuron innervates
one or more muscle fibers
size of a motor unit depends on what?
the number of muscle fibers it innervates
1 single motor neuron will innervate what?
1 fiber
Smaller motor neurons with lower thresholds (and lower contraction force) are what?
recruited first
larger motor neurons have what?
higher thresholds & generate more forces
Type I / S is what?
slow oxidative (SO)
- Small force
- slow twitch
- fatigue resistant
- Oxidative
- innervated by small diameter slow conducting axons
Type I / S = slow oxidative (SO)
postural control axons would be innervated by what kind of muscle fiber?
Type I / S = slow oxidative (SO)
Metabolic pathways are oxidative and anaerobic glycolytic would be innervated by what kind of muscle fiber?
Type IIa / FR = fast oxidative glycolytic (FOG)
gastrocnemius would be innervated by what kind of muscle fiber?
Type IIb / FF = fast glycolytic (FG)
- Intermediate force
- relatively fast contractile time
- generates larger tension
- intermediate to slow rate of fatigue
- innervated by large diameter rapidly conducting axons
Type IIa / FR = fast oxidative glycolytic (FOG)
Type IIa / FR is what?
fast oxidative glycolytic (FOG)
- rapidly contracting fibers
- rapidly fatigue
- white muscle
- contain large stores of glycogen
- high contraction force
- recruited later in the contraction pattern to recruit - - large forces
- large fibers supplied by large diameter axons
Type IIb / FF = fast glycolytic (FG)
Type IIb / FF is what?
fast glycolytic (FG)
primary peripheral sensory organs within a muscle to detect the speed and extent of muscle stretch
Muscle spindles or intrafusal muscles
a muscle contracts in direct response to its stretch
myotatic reflex
neuron used to adjust the tension or sensitivity of the muscle spindle as the muscle shortens
Gamma motor neuron
what type of muscle is important in the control of muscle tone (tension) in postural muscles mostly at an unconscious level
Gamma motor neuron
result in abnormal tone is a result in damage to what?
Gamma motor neuron
alpha-gamma coactivation
contraction of extrafusal muscle (on the outside [actually the muscle) which lengthens and contracts) while the intrafusal muscle (inside where the spindles are - length & speed of the stretch during actual contraction) or coactivation of alpha motor neuron and gamma motor neurons for accurate monitoring during motor movement
actual force of tension and contraction
Golgi Tendon Organ
sensory fiber supplies what
Golgi Tendon Organ
inhibit the contraction of the agonist and allowing the contraction of the antagonist
Autogenic inhibition
what receptors plays a role in the control of muscle activity both directly (pain influences) and indirectly through central mechanisms
joint and cutaneous receptors
what receptors plays a large role in muscle activity under certain circumstances
Joint receptors (in motor control)
systems are typically under descending system inhibition and may only be released under certain circumstance
flexor reflex afferents
under central inhibition, allowing the plantar flexion response to predominate under normal conditions of innervation
Babinski Reflex
create patterns of sequential activity when activated
Central pattern generators
two major divisions of motor cortex involved in somatic motor function
- Primary motor cortex
- Supplementary motor cortex (and premotor cortex)
- controlling the face and tongue are near the lateral fissure and those
- controlling the legs are near or over the midline
- Parallel processing: considerable variation in motor deficits with lesions of cerebral cortex and the tracts from these areas along with potential mechanisms for recovery
- activated during random movement
- tracts exert their strongest influence over extensor musculature in the proximal body
Primary motor cortex
- contribute to eye movements (frontal eye fields)
- activated by movements that are planned and rehearsed mentally without actually making a movement
Supplementary motor cortex (and premotor cortex)
- control cranial nerve motor functions include eye movements (CN III, IV,& VI)
- control muscles associated with the head (V, VII, IX, X, XI, XII)
Corticonuclear Tract
what percent of axons don’t cross the midline or terminate bilaterally
10 to 15%
