Lect 24 - Motor Control Flashcards
What is the Prefrontal cortex?
Neurons involved in decisions to move; planning the desired movement outcome
What is the Premotor cortex?
Neurons involved in organising
movement sequences to achieve
the outcome
What is the Primary motor cortex?
Upper motor neuron cell bodies. Involved in directing voluntary movement.
What is the function of Basal nuclei?
Neurons involved in modifying
movement by influencing posture, automatic
movements, regulation of muscle tone and
elimination of unwanted movement.
What is the function of the Cerebellum?
Neurons involved in modifying
movement by learning, storing and executing
motor programs, monitoring sensory input and
organizing timing of muscle contractions.
What is Latency
The time delay between a
stimulus (e.g. touch or tendon tap) and a
response (e.g. voluntary or reflex
movement)
What is a Interneuron?
Any ‘connector’ neuron that
isn’t a sensory or motor neuron.
What is the function of the Prefrontal Cortex?
Decision to move, Signals sent to premotor cortex
What is the function of the Premotor Cortex?
Select movement sequences, Signals sent to primary motor cortex, basal nuclei and cerebellum
What is the function of the Primary Motor Cortex?
Initiate movements, Signals sent down corticospinal
pathway
What is the function of Basal nuclei and cerebellum?
Modify movements, Signals sent back and forth to each other as well as to frontal cortex
and down descending pathways
Where do upper motor neurons in the corticospinal pathway originate?
In the primary motor cortex.
What happens when upper motor neurons in the primary motor cortex fire action potentials?
The action potentials propagate along axons extending down the spinal cord.
What is the next step after the action potentials propagate down the spinal cord?
They activate lower motor neurons in the spinal cord.
What occurs when lower motor neurons in the spinal cord fire action potentials?
The action potentials propagate along axons within peripheral nerves.
What is the final target of the action potentials in the corticospinal pathway?
Skeletal muscle.
What type of movement can small motor units produce?
More precise movements (e.g., of hand, lips, tongue).
What type of movement can large motor units produce?
More forceful movements (e.g., of limbs).
What are reflex movements?
Rapid, reproducible, automatic motor responses to external stimuli.
What type of neural circuit do reflex movements employ?
A simple neural circuit involving neurons within peripheral nerves and the spinal cord.
What is the primary purpose of reflex movements?
They are protective and prevent injury.
Do reflex movements require involvement of neurons in the brain?
No
What is the typical latency for reflex movements?
approximately 40 milliseconds
What characterizes voluntary movements?
Varying speed, duration, and complexity.
What type of processing is typically involved in voluntary movements?
Complex patterns of sensory and motor processing.
What is the purpose of voluntary movements?
They enable us to interact with the environment.
How are voluntary movements initiated?
Voluntarily by neurons in the brain.
What is the typical latency for voluntary movements?
Variable latency, typically over 100 milliseconds.
What is the typical latency for a reflex response to a tendon tap?
Approximately 30-40 milliseconds.
How would you describe the consistency of the reflex response to a tendon tap?
Very consistent and reproducible.
What is the primary purpose of the stretch reflex?
To protect the muscle from tearing.
What is the neural path for the stretch reflex response to a tendon tap?
From stretched muscle spindles to the spinal cord and back to the stretched muscle.
Can the stretch reflex response time be changed with training?
No
What initiates the stretch reflex response?
A tendon tap causes a sudden, fast stretch of the quadriceps muscle.
What gets stretched within the muscle when a tendon tap occurs?
Muscle spindles, which are proprioceptors/stretch receptors within the muscle.
What happens in the muscle spindles when they are stretched?
Mechanically-gated Na+ channels open in the membrane of the dendritic endings of the sensory neuron of the muscle spindle.
What is the result of Na+ entry into the sensory neuron?
Na+ entry causes depolarization that leads to an action potential.
Where does the action potential propagate after it is generated in the sensory neuron?
The action potential propagates along the sensory axon to the spinal cord.
What happens when the action potential reaches the sensory axon terminal in the spinal cord?
Synaptic transmission from the sensory axon terminal causes depolarization in the motor neuron cell body.
What occurs after depolarization in the motor neuron cell body?
An action potential fires and propagates along the motor axon to the neuromuscular junction (NMJ) of the quadriceps.
What is the final result of the action potential reaching the NMJ of the quadriceps?
The quadriceps muscle is stimulated to contract, causing the foot to kick out.
What type of stimulus triggers the withdrawal reflex?
Painful stimuli.
What receptors are activated in response to painful stimuli?
Nociceptors.
What happens after nociceptors are activated?
The sensory neuron depolarizes, and an action potential fires and propagates to the spinal cord.
What is the role of sensory neurons in the withdrawal reflex?
Sensory neurons stimulate interneurons in the spinal cord.
What is the effect of interneuron stimulation in the withdrawal reflex?
It leads to the excitation of motor neurons that stimulate flexor muscles.
What happens to motor neurons that stimulate extensor muscles during the withdrawal reflex?
They are inhibited.
What is the overall result of the withdrawal reflex?
It enables the withdrawal of the affected limb.
