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Review 7 & 8 Whitehurst

Terms in this set (96)

Fristsch & Hitzig
frontal cortex movement on the contralateral side
Ferrier & Sherrington
motor areas in primates was in the percentile gyrus or area 4-6 of the motor cortex
Campbell
cortical area 4 as the motor cortex and motor area 6 was responsible for skilled voluntary movement
Penfield
electrically stimulated cortex of patients with seizures
-speculated on the areas 4 & 6 and confirmed Campbell's hypotheses
motor activity is controlled by
interactions between cerebral cortex, basal ganglia and the cerebellum
neocortex
higher functions, sensory perception, generation of motor commands, spatial reasons, conscious thought, and language.
function of gray matter
route sensory or motor stimulus to internerons of the CNS for creation of a response to stimulus through chemical synapse activity
primary motor cortex
-precentral gyrus
execution of very specific well defined motor activity of the contralateral side
basal ganglia
group of nuclei found at the forebrain
-support subconscious voluntary motor control and procedural learning
-decision making capability
-receives visual, auditory, vestibular and somatosensory input directly from the spinal cord
-sends outputs to the prefrontal, premotor and supplementary areas involved in higher order processing of movement
the main components of the basal ganglia include:
-stiatum
-globus pallidus
-substantia nigra
-subthalamic nucleus
basal ganglia circuitry beings
in the cerebral cortex
direct pathway results in
the excitation of the motor cortex by the thalamus
striatum receives input from
cerebral cortex includes two sectors
-caudate nucleus
-putamen
striatum projects to
external globus pallidus, pars compact of the substantial nigra and the pars reticulata
motor cortex
glutamate
striatum
GABA
globus pallidus is divided into two distinct parts
GPi and GPe, both contain GABA neurons which are inhibitory
substantia nigra
supports movement (eye)
nigra degeneration results in
parkinson's disease
Pars reticulata inhibits targets
basal ganglia
pars compacta release
dopamine to the striatum
dopamine promotes movements in the
striatum
what is the only portion of the ganglia that actually produces an excitatory neurotransmitter glutamate?
subthalamic nucleus (indirect pathway)
indirect pathway
cortex (stimulates) -> striatum (inhibits) -> GPe (less inhibition of STN) -> STN (stimulates) -> SNr-GPi complex (inhibits) -> thalamus (is stimulating less) -> cortex (is stimulating less) -> muscles
direct pathway
cortex (stimulates) -> striatum (inhibits) -> SNr-GPi complex (less inhibition of thalamus) -> thalamus (stimulates) -> cortex (stimulates) -> muscles
basal ganglia feeds back via the
thalamus to the motor cortex
dopamine is synthesized in the
pars compacta
huntington's disease
inhibitory isn't working correctly, excitatory becomes dominant
-irrational behavior
-increased movement of excitatory
cerebellum contributes to
coordination, precision and accurate timing
damage to the cerebellum
does not cause paralysis but instead produces disorders in fine movement, equilibrium, posture, and motor learning.
cerebellum helps to
shape motor plans and modify plans for future movement and during the actual execution of the movement pattern
Marr-Albus model
parallel fibers and single climbing fibers
-climbing fiber serves as a "teaching signal", which indues a long-lasting change in the strength of synchronously activated parallel fiber inputs (long term potentiation).
where is the cerebellum located?
underneath the cerebral hemispheres
what types of neurons are found in the cerebellum?
-purkinje cells
-granule cells
-mossy fibers
-climbing fibers
-deep nuclei
all outputs of the cerebellum go back to the _____ ____ before going to the cerebral cortex and brainstem.
deep nuclei
vestibulocerebellum
balance and spatial orientation
spinocerebellum
fine tun body movements
cerebrocerebellum
sends output to the thalamus and motor cortex areas. motor and cognitive elements are going on simultaneously.
dominant cell types in the cerebellum:
parking cells and granule cells
dominant axons in the cerebellum:
mossy fibers and climbing fibers and parallel fibers
pathway
mossy fibers -> granule cells -> parallel fibers -> purkinje cells -> deep nuclei
cerebellar cortex 3 layers
bottom: granular cells
middle: purkinje cells
top: dendritic trees of the purkinje cells
where is the IO located?
the medulla
two sources coming into the cell body:
mossy fibers and the information from the IO
lateral pathway
involved in voluntary movement, control of distal musculature and under direct cortical control
ventromedial pathways
originate in the brainstem and terminate along the spinal interneurons
-controlling proximal and axial musculature
-control posture, locomotion
-under the control of the brain stem
-involuntary
corticospinal tract
-release glutamate
-synapse on alpha motor neurons
-85-95% of the axons in the CS cross over in the caudal medulla
cortico spinal tract (lateral)
-project to the cervical and lumbosacral spinal cord
-lateral CT mediates the execution of rapid, skilled, voluntary movement of the distal musculature of the upper and lower limbs.
-especially the hands & feet
corticospinal tract (anterior)
-terminate mainly in the anterior horn gray matter of the cervical and upper thoracic spinal cord levels
-innervate the axial and proximal limb (girdle) muscles
-shoulder and trunk
corticonuclear tract
-cranial nerves
-support facial muscle activity
-reflexive eye movements
lesions in the corticospinal tract
if you lesion the corticospinal track the animal is able to sit and maintain posture but unable to make coordinated movements like to grab food
-recovery can occur after several months
ventromedial pathways
-originate in the brainstem
-terminate among interneurons controlling proximal and axial muscles
-reflexively maintain balance and body posture
medial vestibulospinal tract
-balance and posture
-alpha motor neurons to arms, neck & back muscles
-mediated from the brainstem
lateral vestibulospinal tract
-limb and trunk muscles
-balance & head stability
-purkinje cells
pontine (medial) reticulospinal tract
-receives input from both cortices
-supports reflexive movement, not voluntary
-ipsilateral innervation (same side)
tectospinal tracts
-originates in the superior colliculus
-receives input from the retina
-mediates reflexive movement
ventral root and dorsal root join to form a
spinal nerve
motor neurons that inverted distal and proximal muscles are found mainly in the
cervical and limbar sacral segments
axial are found at
all levels
axial muscles are medial to those innervating
distal muscles
somatosensory or proprioceptive information is
largely unconscious
the sensory information from muscle spindles is transmitted directly to
the cerebellum
touch, vibration, and conscious proprioception sensory information is delivered via
spinocerebellar tracts
dorsal spinocerebellar tract
unconscious
medial lemniscus tract
conscious
dorsal spinocerebellar
-lower limb
-posture maintenance
cuneocerebellar
-ipsilateral neck and upper limb
-movement of head and upper limb
ventral (anterior spinocerebellar)
-lower limb
-posture
rostral spinocerebellar
-ipsilateral head and upper limb
-head and upper limb movement
-terminates at the cerebellum
alpha motor neurons innervate
extrafusal muscle fibers of skeletal muscles and are directly responsible for initiating their contraction
alpha motor neurons are considered part of the
somatic nervous system
a collection of alpha motor neurons that innervates a single muscle is a
motor neuron pool
alpha motor neurons innervating the head and neck are found
in the brainstem
1st source of input:
-dorsal root ganglion cells
-muscle spindles
2nd source:
-upper neurons
-motor cortex & brain stem
-initiating and controlling voluntary movement
3rd source:
-largest input
-spinal cord
-spinal motor programs
motor unit recruitment
progressive non-linear activation of muscle by successive recruitment of larger and larger motor units resulting in gradations of contractile strength.
contracting more or less motor units determines
the strength of the contraction
factors contributing to force production:
-number and type of muscle fibers in the unit
-frequency with which the muscle fibers are stimulated
ALS
disease of nerve cells in the brain and spinal cord that control voluntary muscle movement
-genetic defect 10%
-remaining unknown

-proteins within the nerve fiber axons
-inflammation
-mitochondria
-self destruction/apoptosis
myasthenia gravis
-muscle weakness
-autoimmune disease
-antibodies bind to receptors interfering with the normal actions of ACh at the neuromuscular junctions
-degenerative changes in the structure of the neuromuscular junctions occur
-treatment includes drugs inhibiting acetylcholinesterase and suppression of the immune system
-endocytosis
-calcium
-tyrosine kinase is a target for antibodies
muscular dystrophy
-muscle weakness
-afflicts only boys
-wheelchair age 12
-lack the mRNA encoding the dystrophin protein
-unwanted changes in the contractile apparatus
muscle spindle
spindle is a stretch receptor (own motor supply)
-gamma motoneurons activate the infrafusal muscle fibers, changing the firing rate and the stretch sensitivity of the afferents
gamma and beta motor neurons only innervate
intrafusal muscle fibers
gamma drive causes
contraction and stiffening of the end portions of the intrafusal muscle fibers
-modify sensitivity of spinal to stretch
-static axons innervate the chain fibers and increase firing rate
-dynamic axons innervate bag intrafusal and increase stretch sensitivity
alpha gamma coactivation
gamma motoneurons are activated in parallel with alpha motoneurons to maintain the firing of spindle afferents when extrafusal muscles shorten
myostatic reflex
-feedback system
-Ia fibers detect chang in length
-synapse in the spinal cord initiates a reflex contraction of the muscle fibers that it innervates
golgi tendon organs
-ventral horn
-inhibitory on the same muscle
-reverse of myostatic reflex
-GTO helps form a protective reflex arc and under typical conditions serve to further regulate muscle tension within an optimal range
-precise movements
-GTO release tension rather than make tension
when the muscle is relaxed
muscle spindles are active and GTO is not
central pattern generators
are the spinal networks found in the upper thoracic and lumbar regions that can generate patterns of rhythmic activity for locomotion even in the absence of external feedback or supraspinal control.
central pattern generators are
small localized autonomous neural networks generating rhymicity.
-kinetic and potential energy is transferred back and forth
central pattern generators
gravitational potential energy is smallest
when the center of body mass is lowest
potential energy is greatest when the
center of body mass passes over the supporting foot
the action of walking is mediated by the
spinal cord once you being walking
rhythmicity is based on
1) interactions among neurons (network based rhythmicity)
2) interactions among currents in individual neurons (time dependent)
fixed action patterns
instinctive behavior sequence that is indivisible, runs to completion, produced by neural networks in response to an external sensory stimulus.
-behaviors that appear to be hard-wired.
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