Module 7: Motor Control & Motor Learning Flashcards
What is the definition of motor control?
The ability to regulate or direct the mechanisms essential to movement
What is the difference between hierarchical control and parallel control?
Hierarchical view: the cortical areas have higher level of control than other areas of the brain over voluntary movement (top down control)
Parallel view: different areas of the nervous system control movement and they occur in parallel (voluntary and involuntary movements occurring at the same time)
What structures form the central nervous system?
The brain and the spinal cord
What structures form the peripheral nervous system?
The peripheral nerves that branch off the CNS
What are the 3 main cortical areas responsible for movement?
Cerebral Cortex, Basal Ganglia, Cerebellum
What are the primary functions of the primary motor cortex?
Receive information from other motor areas
Direct pathway to the spinal cord (corticospinal tract) from the brain
Control voluntary movement of the contralateral side
Where is the primary motor cortex located?
Part of the frontal lobe, a narrow strip just in front of the central sulcus
What are the primary functions of the supplemental and premotor areas?
Planning of movements
Close communication with primary motor cortex
Receive information from other brain areas to initiate and plan movement
Where are the supplemental and premotor areas located?
Supplementary Motor Area: Frontal lobe, medial part of the hemisphere, near the apex of the brain, just anterior to the PMC
Premotor Cortex: Lateral surface of the frontal lobe, just anterior to the PMC, lateral to the SMA
What is the motor homunculus?
Visual representation of the body of the PMC in the brain showing which areas of the motor cortex control specific parts of the body. The body parts are proportional to the amount of motor control required, not their actual size. The areas finely controlled (digits) have larger portions of the somatosensory cortex. Areas which are coarsely controlled (trunk) have smaller portions. The map highlights the relationship between different regions of the PMC and the corresponding muscles they control throughout the body.
What does somatotopic organization mean?
The point-for-point correspondence of an area of the body to a specific point on the PMC
What are the primary functions of the associative areas?
Integration of somatosensory and visual information
Provide transition from “perception” to action
Constant feedback to premotor areas
Where are the associative areas located?
Posterior Parietal Cortex (area 5 and 7)
Dorsolateral Prefrontal Associative cortex
What are the five nuclei that form the Basal ganglia?
Putamen
Caudate
Globus pallidus
Subthalamic nucleus
Substantia nigra (neurotransmitter releaser)
What are the main functions of the Basal ganglia?
Constant feedback to motor cortex to control movement
Initiation and regulation of movement via thalamus:
o Direct pathway: facilitate movement
o Indirect pathway: inhibition of movement
Name one disease that has the basal ganglia as the primary affected area.
Parkinson’s Disease
What is the difference between the direct and indirect pathway in the Basal ganglia?
Direct pathway: facilitation of movement.
Indirect pathway: inhibition of unwanted movement.
What is the main function of the cerebellum?
Control of coordinated and fast movements
Maintenance of balance
Compares information of plan and output of movement to make necessary correction
Where is the cerebellum located?
Posterior part of the brain, inferior to the occipital lobe of the cerebellum, superior to the brainstem
Name two symptoms that a person with a cerebellar dysfunction will likely present with.
Balance and stability problems
Ataxia (lack of coordination and control over voluntary movements)
What are the structures that form the Brainstem?
Midbrain
Pons
Medulla oblonga
What are the primary functions of the brainstem?
- Exit for cranial nerves
- Vital involuntary functions for respiration, heart rate, blood pressure
- Integrates signals to maintain posture and balance against gravity
- Works in conjunction with the cerebellum, basal ganglia, and cortical regions to generate and coordinate gross motor movements (reflexive and stereotyped movements; walking, balance)
- Comprises the reticular formation (area that receives and transmits many inputs from and to different brain areas for arousal and consciousness, sensory processing, motor control)
What are the primary functions of the spinal cord?
Final common pathway: last processing level
Relay: Information travels back and forth through the neurons in the spinal cord. PNS > CNS > PNS
Reflex arcs
What is a spinal reflex?
Rapid, involuntary, and predictable responses to specific stimuli that are mediated by the spinal cord without requiring input from the brain. They occur as automatic, involuntary responses to stimuli generated within the nervous system
What will happen to a person’s movement if she/he has a complete injury to the spinal cord?
A complete SCI affects all pathways. No signal gets through which means permanent loss of all abilities below the injury, including paralysis.
Where is the gray matter located in the brain and in the spinal cord?
Brain: the outer surface of the brain (cerebral cortex), surrounds the white matter within the brain
Spinal cord: resembles an H or butterfly at the centre of the spinal cord, surrounded by white matter.
What does the gray matter represent?
Unmyelinated neurons, the integrative area for the spinal reflexes and other automatic motor functions
What does the white matter represent?
Myelinated neurons (myelin sheaths on axons), serves as the communication network, highway in spinal cord
What is an action potential?
A rapid change in membrane potential that allows transmission of nerve signals from one cell to another.
What is membrane potential?
The electrical charge difference between the inside and outside of a cell, with the resting potential occurring when the cell is not depolarized.
Describe in your own words how an action potential propagates in the axon.
- The axon begins at a resting state, it has a more negative charge inside than outside
- The neuron receives a stimulus signal. It triggers a change in the charge at a specific spot on the axon. If this change reaches threshold (via summation or frequency) it will cause an AP.
- Voltage gates in the axon membrane open. Na⁺ enters the axon making the inside of the axon more positively charged than the outside.
- The change in charge is an AP. As Na⁺ enters, they push on neighboring Na⁺ channels to open too. This causes the AP to move down the axon like a wave.
- After a section of the axon peaks by becoming positively charged, another set of gates opens, allowing K⁺ to exit the axon. This returns that part of the axon back to its resting negative charge.
- This process of Na⁺ coming in and K⁺ going out continues along the axon. The AP moves down the axon, reaching the end where it will communicate with the next neuron or muscle.
- If the axon is covered in myelin, the AP can jump between nodes of Ranvier, making the signal travel much faster compared to an unmyelinated axon.
What is a synapse?
A junction that transfers information from one neuron to the next: or to an effector.
Describe in your own words how a synapse occurs
- When an AP reaches the axon terminal, it causes voltage-gated Ca²⁺ channels to open. Ca²⁺ flows into the axon.
- The influx of Ca²⁺ triggers exocytosis vesicles to fuse with the presynaptic membrane, releasing neurotransmitters (ACh) into the synaptic cleft.
- Neurotransmitters travel across the synaptic cleft and bind to receptors on the postsynaptic neuron.
- Binding of neurotransmitters can either excite (depolarize) or inhibit (hyperpolarize) the postsynaptic neuron, influencing if it will generate its own AP.
What ions are responsible for the difference in membrane potential in the axon? Which is more concentrated inside the cell, and which is more concentrated outside the cell?
Ions responsible: K⁺, Na⁺
Concentrated inside: K⁺
Outside: Na⁺
What is the depolarization phase of an action potential?
Na⁺ voltage-gated channels open in response to a threshold stimulus.
Na⁺ rushes into the cell, making the inside of the neuron more positive.
The membrane potential reverses, leading to the peak of the AP.
What is the repolarization phase of an action potential?
After the peak of the AP, voltage-gated Na⁺ channels close shutting out any more Na⁺; voltage-gated K⁺ channels open allowing K⁺ to leave the cell, restoring the negative charge of the cell to its membrane potential.
What is the function of the muscle spindle?
A sensory receptor in muscles that detects changes in muscle length and the rate/speed of the change.
Describe the mechanism by which the muscle spindle protects the muscle from a sudden change in length.
The stretch reflex of the muscle spindle responds to sudden muscle lengthening by causing an immediate, reflexive contraction of said muscle to counteract the stretch. Inhibitory neurons at the interneuron of this arc may be activated to cause relaxation of the antagonist muscle (the muscle opposed to the one being stretched)
Describe the role of the Gamma muscle cells within the muscle spindle.
Gamma motor neurons ensure that the muscle spindle remains sensitive to stretching, even in muscle contraction.
They keep tension in the muscle spindle’s intrafusal fibers allowing it to continue detecting changes in muscle length.
This constant sensitivity helps regulate muscle tone and reflexes, contributing to smooth and coordinated movements
What is the function of the Golgi tendon organ?
A sensory receptor at a muscle/tendon junction that detects changes in muscle tension and the rate/speed of the change.
Describe how the Golgi tendon organ detects change in tension in the muscle.
- When the muscle generates excessive tension (like a heavy contraction or stretch), the GTO activates and sends signals through afferent nerve fibers to the spinal cord
- In response to excessive tension, the GTO triggers a reflex inhibition of the same muscle that is producing the tension. This mechanism causes the muscle to relax and lengthen to prevent damage, like tears or tendon injuries.
- By inhibiting muscle contraction when tension becomes too high, the GTO helps maintain a balance between muscle contraction and relaxation, preventing injury due to overexertion.
Name the 3 systems that are used for balance and posture control.
The vestibular system detects head position and motion,
The visual system provides information about the environment and position within it,
The proprioceptive system provides feedback about body position and movement.
What are central pattern generators?
A cluster of neurons in the spinal cord responsible for the rhythmical, stereotypical pattern of stepping during gait without needing sensory feedback or conscious control.
So I can walk and talk at the same time.
What is neuromuscular junction?
Special type of synapse between the motor neuron axon and the muscle fibre.
What is the name of the neurotransmitter involved in the transmission of action potential from the axon to the muscle fibre?
Acetylcholine
What ion is released in the sarcoplasmic reticulum to cause a muscle contraction?
Ca²⁺
What is the definition of motor learning?
A set process associated with practice of experience leading to relatively permanent changes in skilled behaviour
How does calcium allow the formation of a cross bridge?
When Ca²⁺ binds to troponin, it causes a conformational change in tropomyosin. The change moves tropomyosin away from the binding sites on actin, allowing myosin heads to bind to actin and form cross-bridges
Describe the Closed-loop Theory of Motor Control
Stage 1: Stimulus Identification
1. Stimulus Detection: Recognizing inputs from sensory receptors in the periphery, like visual, auditory, or tactile signals.
I see/smell coffee; note time of day and need the coffee.
2. Stimulus Interpretation: Stimuli are interpreted based on previous experiences or similar situations.
I know that picking up the mug, drinking the coffee means I will have a good day
3. Stimulus Selection: The brain filters and prioritizes the information received based on attentional focus; concentrate on the most relevant stimuli and ignore distractions.
Even with other stimuli [lights, radio, fridge], I am focused on my coffee
Stage 2: Response Selection
1. Based on Previous Experience: The brain evaluates options for response based on learned motor patterns and contextual cues.
2. Selection of Movement Plan: The individual chooses a specific movement plan or strategy that best fits the identified stimulus and context.
If I reach out with right hand to get the cup, I know I will get what I want.
Stage 3: Response Programming
1. Execution of the Task: The response is executed, translating the selected movement plan into physical action.
2. Use of Feedback to Adjust/Adapt: During or after the execution of the motor response, feedback is utilized to adjust or adapt future actions based on the outcomes.
I act on my movement plan, reach for and grab the mug and I use the continuous stimuli to alter my response (big mug, too full, too hot).
Stage 4: Feedforward
Adapting movement based on environment
Not all motor responses require detailed planning and feedback; some movements can be done using a feedforward approach:
Fast automatic motor programs use feedforward mechanisms
I decide, based on movement planning, what my movement pattern is going to be. I am constantly feeding into this continuous loop
Do I need to drop something in my other hand? Move a pen?
Memory is accessed to initiate motor programs
Back to Stage 1.
Describe the Dynamic System Theory of motor control.
Based on the principle that there is an optimal pattern of movement that leads to the best outcome with the least energy cost
* Constant trial-and-error trying to find this optimal pattern of movement
* Skill acquisition: the body will program a movement pattern to occur with the least amount of energy
* One single best way to produce an outcome
What is the definition of a skilled movement?
Accuracy, consistency and efficiency of movement.
Describe the maturation phase of motor learning.
Periods of stability and instability (both consistent and inconsistent)
What does accuracy of a skill mean?
Precise movement for the desired outcome.
What does efficiency of a skill mean?
Minimal effort required.
What does consistency of a skill mean?
The same movement brings similar results in most attempts.
What is the role of practice or repetition on motor learning?
Skill acquisition requires practice and learning. Practice and repetition are foundational to motor learning.
