motor Flashcards
what do skeletal muscles do in order to move bones?
- pull at the tendons to move bones
what are the types of muscle?
- striated: skeletal
- smooth muscle (in organs, innervated by autonomic nervous system)
function of flexors:
flexion at the joint
function of extensors:
extends at the joint
function of agonists/synergists:
muscles that contract together
function of antagonists:
the muscles working against agonists
- while agonists contract, antagonists relax to create smoothmovement
function of axial muscles?
move trunk, maintain posture
function of proximal/girdle muscles?
move shoulder, pelvis, elbow, knee; locomotion
function of distal muscles?
move hands, feet, digits; fine motor skills, specialized in humans
fast twitch - force and fatigue?
high force, rapid fatigue
slow twitch - force and fatigue?
low force, slow fatigue
fast vs. low twitch mitochondria and stored energy?
fast
- low mitochondria -> uses anaerobic
- high stored energy
slow
- high mitochondria
- low stored energy
capillary density and blood supply fast vs. slow?
fast
- low
slow
- high
how does the spinal cord send motor neuron axons to the brain?
through the ventral horn
cervical and lumbar segments of the spinal cord represent ?
used for fine motor control
cervical = arms/hands/digits
lumbar = legs
lateral ventral vs. medial ventral horn control?
lateral controls -> lateral muscles(hands)
medial controls -> ventral muscles(torso)
what is a neuromuscular junction?
a synaptic connection between the terminal end of a motor nerve and a muscle
define a muscle fiber/muscle cell?
the basic unit of the muscle
what does a muscle fiber get input from?
one alpha motor nueron
- fast reliable
- uses ACh
where does a muscle fiber synapse?
at the motor end plate
motor unit?
1 alpha motor neuron and all the muscle fibers it innervates
what does a smaller motor unit indicate?
less muscle fibers per alpha motor neuron -> finer control
what is a motor pool?
all the alpha motor neurons that innervate 1 muscle
what are the 2 methods of generating more force?
1) fire more, more fire
2) increase number of active motor neurons
fire more, more fire method?
increase firing rate of active motor neurons
- temporal summation of twitches
- fasciculation:
spontaneous firing of individual MNs
-> spontaneous motor unit contractions -> uncoordinated muscle twitches
increase number method?
size principle
- small motor units recruited before large ones
- smaller motor units have smaller MNs so they are easier to activate
what input do alpha motor neurons receive?
- sensory
- nearby spinal segments
- brain
what is proprioception?
sense of body position and movement so your body knows what your doing and where you are in space
what 2 places receive information from proprioceptive field?
- golgi tendon organs
- muscle spindles
define golgi tendons and their function?
- respond to muscle tension
- allows us to regulate how much force to use for different tasks
where are golgi located and what are they innervated by?
- in series with muscle fibers
- at the junction between muscle and tendon
innervated = 1b axons
golgi tendon mechanism
1) alpha motor neuron activates causing muscles to contract
2) muscle contraction pulls golgi tendon organ and squeezes collagen fibrils
3) 1b axons interwoven with collagen deform and activate
-> mechanosensitive ion channels on 1b open
-> depolarize
4) 1b axon fired more to encode increased tension in muscle
force feedback
GTO innervates inhibitory interneurons
-> reduces alpha motor neuron activity
-> reduces muscle tension if its overloaded
muscle spindle location and innervation?
what are they made of?
location
- in parallel with muscle fibers
- wrapped around these muscle fibers 1a afferent axons
they are made of capsules containing muscle fibers
muscle spindle mechanism?
1) muscle stretches, they also pull the spindles and intrafusal muscle fibers
2)stretch opens mechanosensitive ion channels
3) 1a fibers fire more
what are gama motor neurons, what do they do?
innervate intrafusal fibers and make them contract/re-adjust length until 1a fibers come online again
stretch reflex sequence?
what is its function?
1) tap patellar tendon
2) breifly stretches quadriceps
3) spindle stretch receptors -> 1a axon activation
4) 1a axon synapses onto alpha motor neuron innervating quads
5)alpha motor neuron activates
-> quads contract
maintain muscle at constant lenght
reciprocal inhibition?
as agonists contract, antagonists relax
flexor-crossed extensor reflex/right foot thumbtack sequence?
1) pain stim -> nociceptive adelta axons carry signals to spinal cord
2) alpha delta axons excited excitatory interneurons that synapse on other interneurons
3) excitatory interneurons on right leg flexors and lest leg tensors
4) inhibitory interneurons onto R leg extensors and L leg flexors
right leg=flex
left leg=bend
pathway for motor?
motor cortex (area 6, and 4)
-> basal ganglia and cerebellum
what are the 2 control pathways?
cerebellar and basal ganglia
what controls strategy? what movement is relevant
cortex area 6, basal ganglia, higher order association areas
what controls the tactics? how we do the movement
motor cortex area 4, cerebellum
what controls the execution? doing the movement
brainstem, cerebellum, spinal cord
what are the main pathways?
- lateral pathway
- ventromedial pathway
lateral
- control
- body parts
- tract
- voluntary movement
- distal muscles
- corticospinal tract
ventromedial
- control
- body parts
- posture, gait balance, head position
- axial/proximal muscles
where does the ventromedial pathway originate?
where does it collect information from?
brainstem
collects information from
- superior colliculus, cerebellum, vestibular nucleus
what is the main aspect of the lateral pathway to focus on?
- cortico spinal tract
what is the purpose of the cortico spinal tract?
voluntary movements
- particularly, distal muscles
where does the corticospinal tract decussate?
at the caudal medulla
what happens if you damage above the medulla in lateral pathway?
damage on opposite side
what happens if you damage below or at medulla in lateral pathway?
damage on both sides
area4/M1 motor cortex activity?
movement and movement control
what would lesioning M1 do?
damage movement
what does electrical stimulation of M1 do?
evoke movment
what is the activity of M1 neurons associated with?
execution of the movement
what is area 6 associated with?
SMA and PMA
- strategy and tactic
- motor planning, the intent to move
what is area 4 associated with?
M1
- execution
what is M1 do?
move a specific area of the body
what do SMA and PMA stand for?
sub-motor area
pre-motor area
M1 and S1 in figer example?
finger flexion alone
SMA, PMA and M1 in finger example?
sequence of finger movements
SMA and PMA in finger example?
mentally moveing fingers
what does the middle cerebral artery do?
supplies blood to cortical areas key to sensation and movement
what does a stroke do?
stops blood flow through the middle cerebral artery
what is brocas area important for?
where is it located and what happens in the case of a stroke?
speech, language production
- located near middle cerebral artery
stoke
- slurred/difficult speech
what are 4 things that are signs of damage to motor tracts?
1) paresis - weakness
2) plegia - paralyisis
3) spasticity
- hypertonia, hyperflexia, clonus
4) sign of babinski
- toes should curl in adults
how much space does the cerebellum take up?
10% of brain volume
50% of brains neurons
what is the cerebellum made of?
folia not gyri
what input does the cerebellum recieve?
motor control
what does cerebellum modulate?
what is it the key to?
motor learning
execution of movement
what side of the body does the cerebellum control?
ipsilateral side
what does cerebral damage cause?
effects the ipsilateral side of the body
what is axtasia?
poor coordination of voluntary movements, disruption of timing and spatial accuracy
what are other symptoms of axtasia?
- slow to begin and end movement
- intention tremor
- drunken gait
- melographia - large handwriting
- hypotonia (knee jerks)
- disrupted balance
what is the basal ganglia made of?
- caudate nucleus
- putamen
- globus pallidus
what is the input of the basal ganglia loop?
large areas of cortex
what is the output of the basal ganglia root?
- movement initiation
- filters out irrelevant/inappropriate movements
basal ganglia loop sequence?
1) cortex projects to striatum
2) striatum projects to globus pallidus
3) globus pallidus projects to VLo
4) VLo projects to cortex
what amine is key to the basal ganglia circuit pathway?
dopamine
what happens to this circus with various diseases?
hyper or hypokenises
what are the basal ganglial diseases caused by?
VLo thalamus inhibition/excitation correlated with basal ganglia output
what does increased inhibition by global pallidus do? in basal ganglial pathway?
parkinsons - hypokinesia (not enough movement)
what does decreased inhibition by global pallidus do? in the basal ganglia pathway?
huntingtons disease - hyperkinesia (excess movement)
what are the symptoms of basal ganglial diseases?
dyskinesias - involuntary movements
akinesia - difficulty with movement
rigidity - problems with muscle tone
ballism - excessive, uncontrolled movement
what causes parkinsons, what are some symptoms
death of dopsminergic neurons in substantia nigra
- akinesia - difficulty with inviluntary movement
- brady kinesia - slowless
- masked face
- rigidity
