8: Control of Action Flashcards
Describe the motor system pathway.
premotor and supplementary motor cortex regions –> cerebellum and basal ganglia —> motor cortex –> brainstem —> spinal cord —> output signals to muscles
Explain how the neuromuscular junction works.
Motor neurons at the neuromuscular junction release acetylcholine (neurotransmitter) onto muscle fibers, causing them to contract
- flexed = biceps contrast
- extend/relax = triceps
-The number and frequency of the action potentials and the number of muscle fibers in a muscle determine the force that the muscle can generate.
Primary motor cortex
- execution of movement
- M1 (Area 4)
- If we need to move a certain body part activation will occur here
secondary motor cortex
-planning and control movement
- Area 6
- includes SMA and PMC
Supplementary Motor Cortex = SMA
- internally guided action
- more voluntary action
- we know what we want to move
Premotor Cortex = PMC
- externally guided action
- action and response to external stimulation
posterior parietal cortex
body position
prefrontal cortex
deciding
Area 8
- eye movements
- visually guided
Posterior cingulate
executive motor control
primary somatosensory cortex = S1
body position
-gives info about where our body is located in space
What parts make up the basal ganglia?
- striatum (INPUT): caudate nucleus, putamen
- globus pallidus (OUTPUT)
- sub thalamic nucleus
- substantia nigra
How is the basal ganglia involved in motor function?
-important in selection and initiation of movement
Describe its theorized role as a gatekeeper.
- through complicated pattern of inhibition and excitation acts as a gatekeeper to initiate action
- Allows us to choose btw competing motion actions
- inhibiting undesired movements and contributing to desired movements
- Important in inhibiting incorrect excitation/inappropriate movement
- lets the winning response get the movement and go through while stopping all the other responses
How is the cerebellum involved in motor function?
- important in multiple motor and cognitive functions
- coordination, precision and accurate timing (smooths movement)
-feedback mechanism= telling if intended action matches the action we doing
What is unusual about the organization of the cerebellum?
- ipsilateral organization
- right side involve with right side of body
- left side involve with left side of body
How does the stretch reflex in the knee work? What is its purpose? Is it under cognitive control? Can we control reflexes cognitively?
- Knee is tapped
- Quad is stretched
- Muscle spindle fires
- Spinal reflex neuron contracts the quad
stretch reflex…What is its purpose? Is it under cognitive control? Can we control reflexes cognitively?
- helps maintain stability of leg following unexpected perturbation
- Helps muscle to contract and stabilize movements
- brain is not involved, but can have top-down override of reflex if needed to
- not under cognitive control
What does central pattern generator mean?
-Neuronal circuits that when activated, can produce rhythmic motor patterns such as walking, breathing, flying, and swimming in the absence of sensory or descending inputs that carry specific timing information
-For repetitive movements , brain doesn’t want to be too involved
○ Ex: walking = control by simple circuits in spinal cord
- Brain gets involved if we encounter an interruption and adjust the movement, otherwise is not involved
- Even w/out input from brain, the central pattern generators will continue the pattern of walking
- A lot of central pattern generators that are controlling movements w/out cognitive control
Describe the symptoms and location of lesions in hemiplegia. Apraxia?
- location: primary motor cortex
- symptoms: contralateral loss of voluntary movement
- Sometimes restricted to a particular region , but sometimes it causes paralysis in an entire side of the body
- Inability to move the muscles on one side
- Premotor planning areas still intact, but signals wont move to the muscles to cause actual action
apraxia location and symptoms
- location: left hemisphere secondary motor cortex
- Loss of “praxis” or skilled action, leading to impaired motor planning
- Normal muscle strength and tone and simple gestures, but impaired ability to link gestures into meaningful actions
-Can’t coordinate actions together that lead to meaningful actions
• Ex: waving
Describe the cause, symptoms for Huntington’s Disease
- cause: one inherited autosomal dominant gene
- symptoms: Progressively more severe involuntary jerking movements (chorea), hyperkinesia (excessive movement), dementia, and finally death
- Progresses to severe excessive movement
brain changes, and treatments for Huntington’s Disease
-Brain changes: Degeneration of the basal ganglia and eventually whole brain; Reduced output from basal ganglia = overexcitation of motor cortex
- Huntington’s causes the basal ganglia to lose the ability to inhibit movement
Treatments: None
Parkinson’s disease …causes and symptoms
- Cause: Genetics, environment, MPTP, aging ,Toxic exposure can lead to it
- Symptoms: Reduction in movement (hypokinesia), muscular rigidity, slowness of movement (bradykinesia), a resting tremor, postural instability, and depression
- When reaching for something tremor stops, tremors only at rest
Parkinson’s disease brain changes and treatment
-Brain changes: Degeneration of the basal ganglia (loss of dopaminergic neurons in substantia nigra); Increased inhibitory output from basal ganglia = Reduced activation of motor cortex; Lewy bodies
- Lose dopamine neurons so the substantia nigra is no longer black
- Increased inhibition so can’t excite the muscles to make the movements
- Treatments: L-DOPA, stem cells, deep brain stimulation of STN
○ L-DOPA = works for a while, has to be increased, and eventually stops working
○ STN= stimulates the areas that have been damage
multiple sclerosis causes and symptoms
-Cause: Genetics, environment (climate)
○ Grew up in Northern climate = more risk
-Symptoms: Various cognitive and motor symptoms including muscle spasms, vision problems, difficulty walking (depending on location of lesions)
Multiple sclerosis brain changes and treatment
-Brain changes: Degeneration of myelin
○ Myelin gets damage through the autoimmune processes in MS
-Treatments: Drugs that inhibit immune system, manage symptoms, slow progression
mirror neurons
- Distributed network of neurons that respond both when we do something and when we see it done
- Neurons that fire both when we do an action and we see that action being done
T or F: activation of mirror neurons is affected by level of expertise
true
