chapter 9: motor system Flashcards
Describe role of motor cortex, basal ganglia, cerebellum, and spinal cord in general motor system functioning.
cortex plans and initiates, basal ganglia and cerebellum coordinate movement, spinal cord conducts information to muscles.
In initiating movement, which areas of the cortex perform which functions.
Parietal cortex (Broadmann Areas 5 and 7) send goals, prefrontal cortex (BA 9-11, 45-47) plans, premotor cortex (BA 6) sequences, motor cortex (BA 4) executes actions.
What is the anatomical name/location of the primary motor cortex?
The precentral gyrus.
Both the motor and somatosensory homunculi represent the body (right-side up/upside down).
Upside down; feet in central fissure, head near inferior lateral surface.
What are ethological behaviours?
Behaviours an animal might use in everyday activities.
E.g. defensive posture, reaching movements, climbing and leaping postures
What dimensions are included in ethological movements?
Part of body to be moved, destination to which it is directed, function of movement.
Ethological movements can be elicited from __________ cortex stimulation (visual-__________-motor connections).
parietal
movements evoked form parietal lobe map in manner similar to those caused by frontal.
__________ connections integrate sensory and somatosensory information to evoke ethological movements via __________ cortex stimulation.
visual-parietal-motor, parietal
What is the movement lexicon?
The set of movement patterns used to build behaviours.
Describe compensation/compensatory behaviour (in the context of the motor system).
Compensation: modifications/replacements from existing lexicon to replace impaired movements.
How do stroke studied indicate redundancy in the cortex?
Studies indicate that movement is encoded in multiple places in the cortex.
Damage to primary motor cortex impairs __________ movements, while damage to the premotor cortex impairs __________ movements.
individual, complex
Which cortical areas coordinate/blend more basic (pre-learned) movements, such as walking or climbing movements?
The motor planning areas.
What did corticomotor-neuron activity studies (monkey wrist study) indicate about motor cortex planning and execution?
- Motor cortex involved in planning movement
- Activity increased during movement and increased with recruitment
- Neurons encode direction (direction-dependent firing)
- Movement encoded by population of neurons
What are mirroring movements?
Movements learned and modified based on interaction with others.
Where are mirror neurons found? When are they active?
Ventral premotor area; active both when performing movement and observing others do it.
Which areas of the brain are involved in subcortical motor control?
Basal ganglia, cerebellum, brainstem.
Which parts of the basal ganglia are involved in motor control?
Caudate, putamen, globus pallidus.
Damage to which parts of the basal ganglia results in hyperkinetic movement disorders?
Caudate, putamen.
Which movement disorders display hyperkinetic symptoms?
Huntington’s disease, Tourette’s syndrome.
What are dyskinesias?
A type of hyperkinetic symptom: unwanted writhing and twitching movements
Which movement disorder displays hypokinetic symptoms?
Parkinson’s disease.
What causes hypokinetic movement disorders?
Loss of dopamine input from the substantia nigra.
Movement disorders indicate that the role of the basal ganglia is to __________ __________.
modulate movements
Output from the interior portion of the globus pallidus (GPi) projects to which areas involving movement?
The thalamus and motor cortex.
If predominant input to GPi is inhibitory, thalamus (is/is not) inhibited and movement (does/does not) occur. This is the (direct/indirect) pathway.
thalamus is not inhibited, movement does occur, direct pathway.
if predominant input to GPi is excitatory, thalamus (is/is not) inhibited and movement (does/does not) occur. This is the (direct/indirect) pathway.
thalamus is inhibited, movement does not occur, indirect pathway.
Decreasing activity of the interior portion of globus pallidus (increases/decreases) symptoms of Parkinson’s.
decreases
What aspects of motor control is each area of the cerebellum involved in? (flocculus, midline, lateral areas)
Flocculus: balance; receives input from vestibular system
Midline: controls midline of body
Lateral areas: movement of limbs and hands
How does damage to the cerebellum affect timing of movements?
Affects ability to move in regular rhythm, accurately perceive time, monitor movement accuracy.
How is the cerebellum involved in motor feedback?
Cortex sends copy of motor command to cerebellum, sensory and visual input also sent, cerebellum compares intention with results and generates required correction.
What kind of movement pathways originate in the brainstem (as opposed to the motor cortex)?
Coarse movements of the entire body, such as walking/running behaviours.
What movements are controlled by the corticobulbar tracts?
Facial movements.
What movements are controlled by the corticospinal tracts?
Movements of the limbs, digits, body.
Which layer of the neocortex do the corticobulbar and corticospinal tracts originate in?
Layer V.
Approximately __% of descending motor pathways decussate on ventral surface of brainstem (pyramids).
95
(Lateral/Anterior) corticospinal tract decussates and contralaterally influences movements of limbs and digits.
Lateral
(Lateral/Anterior) corticospinal tract does not decussate and ipsilaterally influences movements of the trunk.
Anterior
Lateral, intermediate, and medial spinal motor neurons control which body areas respectively?
Lateral: fingers and hand
Intermediate: limbs
Medial: trunk
__________ binding to receptors at neuromuscular junction causes muscle contraction.
Acetylcholine
