Motor System Flashcards
Two main muscle systems in the body
- axial or proximal
2. distal
axial or proximal muscles mediate
posture and balance movements
distal muscles mediate
limb movements and fine movements of digits, throat and tongue
motor neurons innervating PROXIMAL muscles are located
MEDIALLY in the ventral horn
motor neurons innervating DISTAL muscles are located
LATERALLY in the ventral horn
Medial brainstem pathway is what %?
75%
medial - vestibulospinal tracts originate in
the vestibular nuclei
medial - vestibulospinal tracts carry information for
reflex
medial - vestibulospinal tracts control
balance and posture
medial - reticulospinal tracts originate in
the reticular formation of the pons and medulla
medial - reticulospinal tracts descend
ipsilaterally
medial - reticulospinal tracts synapses in
the spinal cord on interneurons and motor neurons
medial - reticulospinal tracts they maintain
posture
medial - reticulospinal tracts they are controlled by
the motor cortex
medial - tectospinal tracts originate in the
superior colliculus of the midbrain
medial - tectospinal tracts descends
ipsilaterally and contralaterally
medial - tectospinal tracts goes down only to the
cervical level
medial - tectospinal tracts coordinates
head and eye movement
medial - tectospinal tracts is controlled by the
motor cortex
lateral brainstem pathway is what %?
25%
lateral - rubrospinal tract originates in the
magnocellular portion of the red nucleus in the midbrain
lateral - rubrospinal tract is controlled by the
motor cortex
aminergic pathways are involved with
reticular formation and are important for sleep
muscle sensory receptors and stretch reflexes -
LOWEST LEVEL of motor hierarchy
reflex definition
involuntary, relatively stereotyped motor response to a specific sensory stimulus
location of a stimulus determines
what muscle is activated
strength of stimulus determines
amplitude of motor response; response is graded
spinal reflexes
reflex is where a stimulus arises from receptors in muscles, joints or skin and where the neural circuitry is responsible for the motor response and contained entirely in the spinal cord
spinal reflexes are used by
higher brain centers to generate more complex behaviors and used in clinical diagnosis
muscle sensory receptors
sensory receptors that detect features of skeletal muscle and their afferent input is used in spinal reflex circuits
muscle spindel senses muscle
length and rate of change
it’s embeded in the muscle
two types: group Ia and group II
golgi tendon organ senses muscle
tension during contraction
located at junction between muscle fibers and tendon
connected in a series with the muscle
sensory axons are group Ib
where do axons of gamma motor neurons enter the spinal cord?
in the center of the spinal cord
where to axons of gamma motor neurons terminate at?
the top and bottom polar regions of intrafusal fibers
where do gamma motor neurons live?
ventral horn of spinal cord
activation of gamma motor neurons innervating the spindle causes contraction of
both polar ends of intrafusal fibers
control of posture
intermediate level of motor hierarchy
posture is the overall
position of the body and limbs relative to one another and their orientation in space
3 main functions of postural adjustments
- support the head and body against gravity
- maintaining the body’s center of mass over the base of support
- stabilize the supporting parts of the body while other parts move
anticipatory (feedforward)
these predict or anticipate disturbance to posture and make adjustments BEFORE motor acts - can be refined with experience like balance on a bike
postural set
the preparatory state where a specific postural response is selected in advance of the stimulus so that it is then execute automatically
compensatory (feedback)
automatic adjustments produced in a reflex-like fashion when there is an actual loss of balance to the body
these responses are flexible
postural adjustments are generated by
pre-existing organized motor patterns that are triggered by sensory experiences; can be enhanced or reduced by the highest level fo motor hierarchy
voluntary movement
highest level of motor hierarchy
voluntary movement entails 5 major phases: 1. goal elicitation
involves prefrontal cortex
Ex: i want to walk across the room
voluntary movement entails 5 major phases: 2. target identification
occurs in the posterior parietal cortex, involves both visual and somatosensory cortex
what is it you want to act on?
voluntary movement entails 5 major phases: 3. planning
occurs in secondary motor cortex, specifically the premotor cortex and supplementary motor cortex
this is not conscious planning - that occurs in the basal ganglia this is more like programming
voluntary movement entails 5 major phases: 4. execution
mediated by the primary motor cortex
it sends out the commands
voluntary movement entails 5 major phases: 5. feedback monitoring
occurs in the cerebellum
monitors commands coming out of cortex
cerebellum is divided into 4 functional parts: 1. vestibulocerebellum
makes connections with the vestibular systme to control the medial motor systema nd vestibular reflexes
flocculondoular lobe
cerebellum is divided into 4 functional parts: 2. spinocerebellum
controls axial and proximal muscles of the medial motor system - how the cerebellum is monitoring the entire body
vermis
cerebellum is divided into 4 functional parts: 3. spinocerebellum - intermediate hemisphere
controls distal motor neurons of lateral motor system
cerebellum is divided into 4 functional parts: 4. cerebrocerebellum
monitors the activity of the motor cerebral cortex and plays a role in initiation planning and timing of movements
cerebellar cortex consits of 2 triads
- located in granular layer
2. located in molecular layer
basal ganglia consists of 4 functial circuits: 1. motor circuit
motor planning and control (frontal lobe)
basal ganglia consists of 4 functional circuits: 2. oculomotor circuit
control of saccade eye movements, eye movement used when looking at objects
basal ganglia consists of 4 functial circuits: 3. dorsolateral prefrontal cortex cirucit
modulation of prefrontal executive cognitive functions
basal ganglia consists of 4 functial circuits: 4. lateral orbiofrontal circuit
behavioral set, context, emotions and motivation
the basal ganglia is like a what on the cerebral cortex??
a break!
Direct Pathway of the basal ganglia
excites the cortex
indirect pathway of the basal ganglia
inhibits the cortex
