motor systems Flashcards
What are the components of the motor control hierarchy?
Neocortex (conscious), brainstem, and spinal cord (automatic).
How did Hughlings-Jackson describe the nervous system?
Organized in successive layers, with higher levels controlling lower levels; adapted from evolutionary theory.
What is the role of the prefrontal cortex in movement?
Plans movements and specifies goals.
What is the role of the premotor cortex?
Organizes motor sequences appropriate to context.
What is the role of the primary motor cortex?
Produces specific, skilled movements.
Who first discovered the motor cortex’s role in movement?
Fritsch and Hitzig (1870) — electrical stimulation of a dog’s cortex caused movement.
How did Wilder Penfield contribute to motor cortex research?
Mapped human motor cortex using electrical stimulation during neurosurgery.
What is a homunculus in relation to the motor cortex?
A distorted map of the human body based on the cortical area devoted to each part, with larger areas for hands, lips, and tongue.
What is the pyramidal tract?
A bundle of fibers connecting the cerebral cortex to the spinal cord.
What does the lateral corticospinal tract control?
Moves digits and limbs on the opposite side of the body (crosses over).
What does the ventral corticospinal tract control?
Moves muscles of the trunk on the same side (stays ipsilateral).
Where are motor neurons located?
In the ventral horns of the spinal column.
How are motor neurons organized?
Lateral motor neurons: fingers and hands
Intermediate motor neurons: arms and shoulders
Medial motor neurons: trunk
How do motor neurons cause muscle contraction?
By releasing acetylcholine at the neuromuscular junction
How are limb muscles arranged?
In pairs of extensors (extend limb away from trunk) and flexors (move limb toward trunk).
What is quadriplegia?
paralysis of the arms and legs
what is paraplegia?
paralysis of the legs
What structures make up the basal ganglia?
Striatum (caudate, putamen, accumbens), globus pallidus, substantia nigra, subthalamic nucleus.
What is the “volume hypothesis”?
The internal globus pallidus acts as a “volume dial” adjusting movement force by influencing the thalamus and motor cortex.
What is the direct pathway’s function?
Overall excitatory; promotes movement by reducing GPi activity, increasing thalamic activation.
What is the indirect pathway’s function?
Overall inhibitory; suppresses movement by enhancing GPi activity, reducing thalamic activation.
What is a hyperkinetic symptom?
Excessive involuntary movements (e.g., Huntington’s Chorea).
What is a hypokinetic symptom?
Reduced movement (e.g., Parkinson’s Disease).
What causes Huntington’s Chorea?
Genetic disorder causing degeneration of indirect pathway neurons (loss of movement “braking system”).
