nsc 20-21

What are "movements" in motor control?

Simple reflexes with brief muscle activation, like a hiccup or finger twitch.

What are "acts" or "action patterns"?

Complex, sequential movements like writing your name or playing guitar.

What is a motor plan (or motor program)?

A set of muscle commands prepared before the action occurs.

What is the primary reason the brain exists, according to the slide?

To move and guide movement.

What does open-loop control optimize?

Speed.

Does open-loop control use external feedback?

No.

What are ballistic movements?

Rapid actions that are completed regardless of sensory feedback.

What does closed-loop control optimize?

Accuracy.

What type of movement is used in closed-loop control?

Ramp movements (smooth, slower, guided by feedback).

What do skeletal muscles do?

Power movement.

What does the spinal cord control?

Skeletal muscles.

What role does the brainstem play in motor control?

Integrates motor commands.

What does the primary motor cortex do?

Initiates commands for action.

What does the nonprimary motor cortex do?

Initiates cortical processing.

What role do the cerebellum and basal ganglia play?

They tweak and fine-tune motor systems.

What are antagonist muscles?

Muscles that perform opposite actions, like biceps and triceps.

What is a tremor?

A rhythmic alternation of antagonist muscle contractions.

Why are poorly regulated tremors a problem?

They can be debilitating and interfere with movement.

What do motoneurons do?

Carry action potentials from the spinal cord to the muscles.

Where do motoneurons connect with muscle fibers?

At the neuromuscular junction.

What is released at the neuromuscular junction?

Acetylcholine (ACh).

What is a motor unit?

One motor neuron and all the muscle fibers it innervates.

What does a low innervation ratio mean?

Few muscle fibers per neuron — allows fine, precise movements.

What is proprioception?

Awareness of body position and movement.

What do muscle spindles detect?

Stretch in the muscle.

What do Golgi tendon organs detect?

Muscle contraction.

What do muscle spindles detect?

Stretch in the muscle.

What type of muscle fibers are inside muscle spindles?

Intrafusal fibers.

Which neuron adjusts spindle sensitivity?

Gamma motor neuron.

What is the muscle spindle stretch reflex?

A reflex where a stretched muscle contracts to maintain preset length.

What does alpha-γ coactivation ensure?

That both extrafusal and intrafusal fibers adjust together for movement accuracy.

Why is the antagonist muscle inhibited in the stretch reflex?

To allow the agonist to contract unopposed.

What causes spasticity?

Loss of cortical inhibition over spinal reflexes.

What are examples of spasticity symptoms?

Clonus and hyperreflexia.

What structure detects muscle contraction more than stretch?

Golgi tendon organ.

What happens when the cortex stops inhibiting reflexes?

Reflexes become exaggerated (spinal disinhibition).

What does the pyramidal system control?

Voluntary movement of the body and limbs.

What does the extrapyramidal system do?

Coordinates and refines movement.

What brain structures are part of the extrapyramidal system?

Basal ganglia, cerebellum, thalamus.

Where do upper motor neurons start and end?

Start in primary motor cortex, end in anterior horn of spinal cord.

What happens to the upper motor neuron at the medulla?

It crosses over to the opposite side.

Where do lower motor neurons go?

From spinal cord to muscle.

What is the motor homunculus?

A map showing how much brain space is used to control each body part.

What does the primary motor cortex (M1) do?

Sends movement commands to the body.

What does the supplementary motor area (SMA) do?

Plans learned sequences of movements.

What does the premotor cortex do?

Fires before performing a movement.

What does the cerebellum control?

Coordination, balance, and timing.

What does the basal ganglia help with?

Starting and stopping movement.

What is the role of Purkinje cells in the cerebellum?

They send only inhibitory signals to control and fine-tune movement.

How does the cerebellum guide movement?

By slowing or stopping signals to make movement smooth and accurate.

Which structures are involved early in movement?

Primary motor cortex and basal ganglia.

Which structures help during or after movement?

Supplementary motor area and cerebellum.

What does the extrapyramidal system do before voluntary movement?

Predicts and prepares posture adjustments to keep balance.

Which muscle may activate before the arms during a lift?

Gastrocnemius (a leg muscle).

What are central pattern generators (CPGs)?

Spinal cord circuits that produce rhythmic movements like walking.

Where are CPGs located?

In the spinal cord.

What is an example of CPG-controlled behavior?

Walking or trotting in a horse.

What does the retina do in a visual-motor task?

It captures the image and sends it to the brain.

Which brain region decides "Should I move?"

Prefrontal cortex.

What brain region loads the motor plan?

Premotor cortex.

Which area sends the final movement command?

Primary motor cortex (M1).

What structure gives feedback and adjusts movement?

Cerebellum.

What is ataxia?

A disorder causing clumsy, uncoordinated movements.

Which system controls strength?

Pyramidal system.

Which system controls tone/posture?

Extrapyramidal system.

Are strength and tone independent?

No, they work together to produce smooth, stable movement.

What does pyramidal system damage cause?

Weakness in voluntary movement.

What does extrapyramidal system damage affect?

Movement control, coordination, and posture.

What can cause someone to miss a target when reaching?

Dysfunction in the cerebellum or basal ganglia.

What is a myopathy?

A primary disorder of the muscle itself.

What is muscular dystrophy?

A genetic disease that causes muscles to weaken and break down over time.

What protein is involved in muscular dystrophy?

Dystrophin.

Where is the dystrophin gene located?

On the X chromosome.

Who is more affected by muscular dystrophy?

Males, because they have only one X chromosome.

What kind of disorder is Myasthenia Gravis?

Autoimmune disorder.

What happens in Myasthenia Gravis?

Antibodies block acetylcholine receptors, leading to weakness.

What virus destroys spinal motor neurons?

Poliovirus.

What does ALS do to the nervous system?

Kills motor neurons, causing muscle atrophy.

What are fasciculations?

Muscle twitches seen early in ALS.

What happens in a spinal cord injury?

Reflexes, strength, and sensation are lost below the injury level.

What is apraxia?

A disorder where a person can't plan or sequence movements, even though muscles are fine.

What are ramped acts?

Slow, feedback-controlled new movements.

What are ballistic acts?

Fast, automatic, well-learned movements.

What causes Parkinson’s symptoms?

Loss of dopamine-producing cells in the substantia nigra.

What are the key signs of Parkinson’s disease?

Tremor, bradykinesia, shuffling gait, and postural instability.

What drug helps treat Parkinson’s?

L-dopa (a precursor to dopamine).

What causes Huntington’s disease?

Too many CAG repeats in the HTT gene.

Which brain areas are affected in Huntington’s?

Caudate nucleus, putamen, and cerebral cortex.

What is chorea?

Involuntary, rapid, dancing-like movements.

What is ataxia?

Lack of muscle coordination due to cerebellum damage.

What are causes of ataxia?

Cerebellar tumors, alcohol use, or inherited degeneration.

What is dystonia?

Abnormal, sustained postures caused by basal ganglia issues.

What brain region is associated with dystonia?

Basal ganglia.

What brain regions are affected in Tourette syndrome?

Basal ganglia and cortex.

Who is more likely to have Tourette syndrome?

Boys more than girls.

Where do tics usually occur?

Face and shoulders.

What is coprolalia?

Involuntary swearing, rare in children with Tourette's.

What causes hemiparetic gait?

Stroke or motor cortex damage.

What does “paresis” mean?

Weakness in voluntary movement.

Describe hemiparetic gait.

One leg is stiff; the opposite arm is flexed and held tight.