The Basics of Movement Flashcards
what two components are intertwined?
cognition and action
what are motor deficits often directly linked to?
cognitive problems
how many muscles does it take to make one step?
around 200
what is the strongest muscle in the human body?
Massester (Jaw)
what appendage occupies the least amount of area in our motor cortex?
Arm
^ more fine motor control needed, larger area needed in the motor cortex
What is the latin name for one of the muscles in your big toe?
Flexor hallucis longus
what is dystonia?
a movement disorder that is affected by the toning of the muscles (stiffness where the muscles are overcompensating)
what is pallidotomy?
a treatment for dystonia resulting in electric probes in the brain (baso-nuclei), allowing for better movement
what is the role of the motor cortex?
planning, initiating and directing voluntary movements
- range of reflexes coming out of the motor cortex, not only their coordination within this cortex, but it’s supplemented by the basal ganglia which helps starting and stopping movement and the cerebellum which helps you engage with smooth movement
what is the role of the brainstem centres?
basic movements and postural control
what is the role of the basal ganglia?
gating proper initiation of movement i.e. stopping and starting
what is the role of the cerebellum?
sensory motor cordination
what does the local circuit neurone do?
reflex coordination; help organise / shepard the lower motor neurones in order to enact a movement
* no need to involve higher brain regions in this case
what is also included in the brain system?
peripheral nervous system - signals coming in and out of your body / brain
what is the difference between the upper and lower neurone systems
upper motor neurones require a bit more fine-grained movements and can be supplemented by regions around them (i.e. basal ganglia and cerebellum)
+ other areas of delegation: brain stem centres which you require for basic movements (involuntary control)
whereas lower motor neurones generate movement more in terms of a reflex
what is meant by a ‘hierarchy’ system?
system kicks in as much and when it needs to
what about deficits in the lower and upper motor neurones?
specific deficits can happen
* lower motor neurones can get disrupted in your spinal column and brainstem
* while upper motor neurones (in your cortex) when disrupted will cause troubles with the lower motor neurones getting information out of the spinal column to the peripheral nervous system to the skeletal muscles
what happens if the upper motor neurone is disrupted?
no signal will be found outside the brain at all
the basics of movement
- simple reflex
- posture / postural changes
- locomotion
- sensory orientation
- species specific action patterns
- acquired skills
simple reflex
- stretch reflex, knee jerk
- mediated at the level of the spinal cord
posture and postural change
standing, balancing
locomotion
walking, running
* often doesn’t necessarily involve areas of the cortex -> central pattern generators in your spinal cord and brain stem that allow you to perform the movements without thinking about them
sensory orientation
head turning, eye fixation
species specific action patterns
Ingestion, courtship, escape/defence, grooming, gestures
acquired skills
dressing, painting, driving, sports, guitar hero, texting etc
how can you exert a degree of control over the same type of movement like breathing?
- can breathe in and out voluntary
- but this type of control is delighted and called rhythmic movement (timing and spatial organisation where it’s done automatically)
- then we have reflexive: if we’re underwater -> you will eventually breath in because of your reflexes
- different levels of control over the same muscle group dependent on how we need them and context/situation
PNS and Leprosy
- caused by a bacterium infection (which attacks nerve endings and the bodies ability to feel pain/detect heat)
- peripheral nerves thicken in leprosy, disrupting afferent (sensory inputs coming into local circuit neurones) and efferent (lower motor neurones sending information to skeletal muscles) signals
- thermal sensation is usually the first to go, followed by pain and touch
- inability to feel pain can result in severe limb damage over time
CNS -> PNS -> Muscles
all voluntary and reflex movements are brought about making striated muscles contract
There are three types of muscles, what are they?
cardiac, skeletal and smooth muscle
cardiac muscle
striated but relies on involuntary/rhythmic movements
smooth muscle
around blood vessel, glands, guts and bronchioles
skeletal muscles
- anchors somewhere onto bone and performs voluntary movements
-> at least one end (the origin) is connected to a bone through a tendon
Why are we interested in skeletal muscles?
- they are important for voluntary movements
muscle fibres
- striated because of regular bands composed of proteins: actin (thin filament) and myosin (thick filament)
- sarcomere: basic unit of striated muscle tissue (functional unit of contraction -> contraction makes it shorter)
how do actin and myosin work?
- Actin and Myosin overlap slightly.
- Myosin has a long fibrous tail and a globulus head which brings to actin and allows it to pull itself along [lots of them do this at once]
- Electrochemical reaction, pulls actin over myosin which releases calcium binding to actin and causing it to change configuration (provides an anchor site for the myosin to pull itself along, pulling it along)
myosin
has a long fibrous tail and globules head
how many sarcomeres does the bicep contain?
100,000
Lower Motor Neurone -> Muscles
- Sacromere is organised into fibres/bundles; each fibres innervated by a single motor neurone
- each lower motor neurone controls lots of muscle fibres, but each muscle fibre is controlled by only one motor neurone -> this is a motor unit
- each muscle fibre receives input from a single motor neurone, each motor neurone innervates multiple muscle fibres (another level of organisation and goes from top to bottom
- A motor neuron send signals through efferent connections.
- Voluntary muscle contraction is initiated by nerve impulse via the PNS.
- A single motor neurone will control several muscle fibres.
- A motor unit is the motor neuron and all the fibres it controls.
how does a motor neurone send signals?
through efferent connections
voluntary muscle are initated by what?
nerve impulses via the PNS
how many muscle fibres does a single motor neurone control?
several
what is a motor unit
motor neuron and all the fibres it controls
spinal columns (another level of organisation within this)
- proximal to distal (core of body develops first and tiger tier arms and legs)
- reflected in structure of spinal column
*Signals come out from cortex, and journeys through the brain to spinal cord where it crosses over to other side of the body (desiccation/crossing the midline) [probably to do with sensory intergration] - why those with strokes in the brain will often be paralyzed down one side of the body
how do signals get sent from the cortex?
signals come out from cortex, and journeys through the brain to spinal cord where it crosses over to other side of the body (desiccation/crossing the midline) [probably to do with sensory intergration] - why those with strokes in the brain will often be paralyzed down one side of the body
white matter
writing/sending signals
grey matter
processing
what why is acetylcholine important for nerve communication and movement generation?
when nerves talk to each other it has to be done by chemical transmission and acetylcholine is very important to that. Electrical activity in the motor neurone through these action potentials, will travel down the axon and cause chemical acetylcholine to be released in muscles.
^ acetylcholine produces an action potential which allows calcium to be released in muscles which changes the actin to generate movements
if you block acetylcholine, what happens?
muscle fibres cannot be activated because actions potential is not activated?
curare toxin
Acetylcholine receptor blocked in muscle tissue:
1. Made from various plants.
2. (Reversibly) inhibits muscles within 25 mins.
3. Inability of the muscle to respond to motor nerve stimulus.
4. No contraction of the muscle fibre.
Myasethenia Gravis
- abnormality in acetylcholine receptors (aren’t enough sites).
- people with this condition are very weak as they can only activate a few of their striated muscle fibers -> trouble smiling.
how do motor neurones help us move muscles?
Voluntary signals (beginning with signals in your cortex) are deprived from your upper motor neurones. Cortical spinal fibers activate motor neurons to the muscles (lower motor neurones).
How do we make a sustained movement?
- a single action potential travelling down to a lower motor neurone leads to a single muscle twitch
- a train of action potentials spaced apart in time give rise to a sequence of twitches.
- if they arrive within 10-100 milliseconds of each other (depends on type of striated muscle) the muscle contractions add up and give rise to large and prolonged contractions.
- these are called tetanic contractions
what is motor recruitment?
refers to the activation of additional motor neurone to accomplish an increase in contractile strength in your muscles
* i.e. differences in motor neurones between picking up a light and heavy thing
what is a motor unit?
consists of one motor neuerone and all the fibres that stimulate it
all motor neurones innovating a muscle are called?
a motor neurone pool
how are all motor neurones in a motor neurone pool put together?
clustered together in the spinal cord
what happens when a neurone is activated?
all muscle fibres controlled by the motor neurone are stimulated and contract
the difference in the activation of neurones
- activation of one neurone will lead to a very weak but very distributed muscle contraction
BUT activation of more motor neurones -> more muscle fibres activated -> stronger muscle contraction
motor unit recruitment
measure of how many motor neurone are expected in a particular muscle -> therefore a measure of how many muscle fibres of that muscle are activated
* high recruitment -> stronger the muscle contraction will be
what does motor unit recruitment conclude for us?
why movements are graded based on wants and needs in our environment
motor neurone problems
- Lower motor neurones can be damaged in motor neurone disease, in a trauma where a peripheral nerve is cut, in polio or by alcohol.
- Lower acetylcholine levels, more muscle wastage
- Such damage leads to lower motor neurone syndrome.
symptoms of motor neurone problems include..
- paralysis (flaccid)
- muscle wasting
- no reflexes
- fasciculation (spontaneous contraction of muscles - signals from nerves cause them to depolarise and fire)
- hip tonio - decreased muscle tone (no signal from nervous system means no background acetylcholine which is necessary to maintain your muscle tone - use it, or lose it policy [rapid wastage])
what does amyotrophic lateral sclerosis affect?
upper and lower motor neurones
what are motor programs?
an abstract representation of movement(s) that centrally organizes and controls the many degrees of freedom involved in performing an action (Schmidt, Lee and Donald, 2005).
* can be considered commands for ‘pre-planned’ (pre-stored) sequences of movement.
* can be used without feedback from the moving limb or extremity.
* equivalence: are independent of muscle groups (and we can transfer our ability to do this to different muscles).
Supplementary motor cortex (SMA): Actions in the Brain
- AKA the ‘supplementary motor area’.
- Well learned actions that do not place strong demands on monitoring the environment
- Like writing your name
Primary motor cortex (PMC): Actions in the Brain
- Responsible for the execution of all voluntary movements of the body.
- Is the ‘doing’ area.
Posterior Parietal Cortex (PPC): Actions in the Brain
- Is a ‘planning’ area.
- Also involved in spatial reasoning and attention.
Premotor cortex (PMA): Actions in the Brain
- Links action with visual objects.
- Selects sequences of appropriate movements for the appropriate complex i.e. reaching and grabbing an apple intentionally.
- Modulates primary motor cortex.
- An ‘intention’ area (allowing you to do things).
Somatotropic organisational the motor areas
larger motor areas (disproportionate), require finer motor control i.e lips, jaw, mouse, hand, tongue
* input via sensory cortex -> receiving information from the body
* output via motor cortex -> controlling the body
you can get a Jacksonian seizure?
sensation migrates up your body and follows the route of this topographical map of your body representation. (shows parts of your body exists and are represented in your brain)
cortical ‘map’ - evidence for somotasensory
- fMRI and PET (higher resolution representation and shows an overlap between different regions when you get participants to move parts of their body, you can see representations of the topographical map) scans are good
- You can see the blood oxygen levels in the brain when an area is stimulated
- Also just because you’re missing a limb, doesn’t mean the area in the motor cortex disappears (phantom limb syndrome happens)
Experimental Example: with monkeys who love juice (perform certain actions for juice)
Rasta plots: measure of electrical activity in certain part of the brain
Train monkeys on visual cues = shift
* Put into conditions (either visual cue or prior training condition) where there was a visual cue and indicate a sequence of panels (indicating the lit up panel or sequence they had learned previously)
* visual cues does not rely on pre-learned repertoire of movements whereas prior training condition do
Both conditions, primary motor cortex firing (good cause monkeys moving) whereas in visual cue, we got activity from premotor cortex and very little activity in supplementary motor area.
* in prior training condition, we see less activity in the premotor area and a spike of activity in the supplementary motor area (evidence of dissociation - difference levels of functionality in a monkey)
* also if you continue training monkeys on visual cues, you see a shift in retrieval dependency basically over to supplementary motor area giving a sufficient amount of training
what is apraxia?
an inability to carry out movements in response to commands
how is apraxia caused?
- Damage to the posterior parietal cortex.
- Difficulty in motor planning to perform tasks or movements when asked.
- This is despite understanding the command and being motivated.
what is motor apraxia?
deficits in ability to plan or complete motor actions that rely on semantic memory so unable to imagine/act out a movement such as pretending to answer the phone but when the phone rings, they can actively answer the phone (which they couldn’t do voluntarily earlier)
what is ideational apraxia?
an inability to conceptualise task with an impaired ability to complete a multistep process
In apraxia, there are no symptoms of…
- No paralysis.
- No loss of comprehension.
- No loss of motivation.
Anticipatory Firing
- Premotor areas -> more abstract planning (can see electrical activity build up and discharge when a movement takes place).
- Interpreted by the primary motor cortex as which motor program to run.
- ‘Winding up’ movements = a hierarchy.
- Our brains will help prepare us to make movements in the environment
- These brain areas will help coordinate primary motor cortex in order to engage movement, which can also be measured at a neurological level
Free Will or Determinism -> at what point is neurological activity in your brain detectable when making a decision?
- Readiness potential: where you expect build up of electrical activity when you’ve made a decision to do something
- Action potential: made decision, complete control over when and how they can do this
- Will is 3rd variable: appear that there sensation of choice kicks in about 200 milsec because moving their body part but neurological activity detectable at 550 milisec before it happened which is 350milsec before we are consciously awar
what does the CNS branch out to?
PNS to control muscles and movement
what does the motor cortex initate?
movements via the brainstem and spinal cord
how is the motor cortex organised?
somatrophically organised for generating movements
what is the organisation of our motor areas like?
hierarchical
upper motor neurone
modulate reflex strength
lower motor neurones
involved in maintaining structural integrity of a muscle
with respect to lower motor neurones
damage leads to fibrillation
an upper motor neurone
degenerates in stroke affecting the motor cortex
primaru motor cortex
contains the motor homunculus
chorea is not a symptom of what
uppermotor neurone syndrome
what are symptoms of upper motor neurone syndrome
paralysis, hyperflexia and spasticity
the representation of the body that runs across primary motor cortex
was suggested by the ‘Jacksonian march’ of seizure activity across the body surface
