Motor Flashcards
what type of organisation does the sensorimotor system have
hierarchically organised
give an example of a voluntary movement
run or walk
which is the highest level of the sensorimotor cortex
association cortex
where does the lower motor neuron project to
project to muscle
what is the motor control system made up of
upper and lower neurons = integrated system
where does the upper motor neuron project to
project to lower neurons
how does info flow in the sensorimotor system
info flow down in the hierarchy
decend control
how does the feedback system flow in the sensorimotor system
ascending system up to highest level of association cortex
give an example of an involuntary movement
blinking
what is at the lowest level of the sensorimotor system
motor neurons
state 3 types of muscle
cardiac
smooth
skeletal
what is the biggest muscle in the body
gluteaus maximus
what is the smallest muscle in the body
stapedius - inner ear
what is the strongest muscle in the body
masseter - jaw
how is muscle movement achieved
antagonist arrangement - combined coordinated action of contract and relax
what percentage of body weight do muscles compose
40%
what is the role of overlapping filaments in muscles fibres
form mechanism which allows contracting and relaxing
which chemicals allow transfer at myosin cross bridge cycle
calcium ions
magnesium
atp
what processes occur at the myosin cross bridge cycle
the overlapping filaments of the long axis of muscles fibres contract and stretch
chemical exchange
what is a motor unit
single alpha motor neuron and all muscle fibres it would activate
how do you generate greater movement resolution
use of fewer muscle fibres
what does the motor pool contain
contain alpha and gamma neurons
what is the shape of the motor pool
rod shaped
ventral horn of spinal cord
what is the function of alpha neurons
innervate EXTRAFUSAL MUSCLE fibres of SKELETAL MUSCLE
What is the function of gamma neurons
innervate INTRAFUSAL muscle of muscle spindles
what is the cell body in the ventral horn activated by
sensory info from muscle and brain
what 2 pieces of info must the CNS know to control muscles contracting and relaxing
- tension of muscle
2. muscle length
where is the Golgi tendon located
tendon
what is the function of the Golgi tendon
processes sensory information about tension of muscle
eg. how much force needed for muscle
what does the Golgi tendon do in response to extreme tension
Golgi tendon inhibit muscle fibres to prevent damage
what is the function of muscle spindles
process info on muscle length/stretch
what are extrafusal muscle fibres innervated by
alpha neurons
what are intrafusal muscle fibres innervated by
gamma neurons
what is the aim of muscles spindles to achieve
set optimum length of muscle stretch
what is the role of muscle spindle feedback
info on muscle stretch - form efficient motor system
what is coiled in intrafusal muscles
sensory fibres
what is the role of sensory fibres in intrafusal muscles
keep intrafusal fibres at ideal length to optimise muscle strength
what happens to the action potential when a muscle stretches
action potential rate increases
what happens if only alpha motor neurons generate an action potential
extrafusal muscle contracts
muscle becomes slack - no more AP generated
what happens during coactivation of alpha and motor neurons
extrafusal and intrafusal muscle fibres contract
what is the advantage of acoactivation of alpha and motor neurons
tension maintained in muscle
what type of reflex is a withdrawal reflex
complex reflex
define recipricoal innervation
antagonistic muscle contracts and another muscle would relax
what is the role of the complex reflex system
respond to stretch of muscle fibres
what is the number of muscle fibres dependent on
level of control and stretch of muscle
what is the advantage of slow muscles fibres
they won’t fatigue
state 3characteristics of fast muscle fibres
- can fatigue
- quick
- fewer blood vessels
what is meant by the size principle in the motor system
muscle recruited in size order
why are muscles recruited in size order?
smallest first
fine control of muscles at lower levels
where does the motor cortex project to
lower motor neurons
which 2 brain components feed back to the cortex
basal ganglia and cerebellum
what is the role of the homunculus
contains representations of the complex and overlapping motor commands
state the hierachial processes of the motor system
- association cortex
- primary motor cortex
- brain stem motor nuclei
- spinal motor cortex
why is the ancient brain stem motor control sophisticate
evolutionary changes promote survival
state the 2 types of ventromedial tracts
- ventromedial corticospinal tract
2. ventromedial corticobrain-stem spinal tract
what does the ventromedial corticospinal tract project to
trunk and limb muscles
state 2 characteristics of the ventromedial cortico brain stem spinal tract
- one way organisation
2. bilateral projections
what 5 components make up the basal ganglia
- globus palllidus
- putamen
- caudate nucleus
- thalamus
- substantia nigra
what is the role of the thalamus in the basal ganglia
output information would be relayed back to cortex
which basal ganglia component feeds info to the globus pallidus and substantia nigra
subthalamic nucleus
which 2 basal ganglia components make up the striatum
putamen and caudate
what is the flow of information in the basal ganglia
cerebral cortex - striatum - globus pallidus and substantia nigra - thalamus
what happens if the basal ganglia is removed
unable to select motor commands
what is the selecting problem in the basal ganglia
mutiple commands processed in parallel
all processed through same motor pathway
what is the basal ganglia defined as
central action selector
describe the motor actions of the basal ganglia at rest
- no activity in striatum at rest
- tonically active in globus pallidus
- thalamus in inhibited
- low levels of excitation in motor cortex
what happens when the basal ganglia is excited
striatum is excited
thalamus is disinhibted meaning higher excitation in output to lower motor neurons
what causes the excitement in the striatum
dopamine input from substantia nigra cause transcient inhibition
what is the role of the cerebellum
regulate activity of upper motor neurons
what is cerebral angesis
a brain which does not have a cerebellum
what is dysarthia
disruption of control of speech
how does the cerebellum regulate motor activity
aware of motor commands and project to motor cortex
state some symptoms of a damaged cerebellum
- poor coordination
- loss of voluntary movement
- jerky movements
what are the 3 regions which regulate input and output of the cerebellum
- corticol
- spinal
- vestibular
what is the vestibular region of the cerebellum responsibe for
head movements
what is the spinal input and output of the cerebellum
stimuli on limbs and movement
eg. muscle spindles
name the 2 types of dorsolateral tracts
- dorsolateral corticospinal tract
2. dorsolateral corticorubospinal tract
what is the flow of info through in the dorsolateral corticospinal tract to
tract via medullary pyrmaid to contralateral limb muscles
state characteristics of the dorsolateral corticorubospinal tract
via red nucleus
tract to cranial nerves of facial muscles
what type of projections are both the dorsolateral tracts
contralateral
which tract is an indirect route
ventromedial cortico brain stem spinal tract
