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Q: How is the primary motor cortex functionally organized?
A: It has a somatotopic organization like the somatosensory cortex. Each body part is represented
proportionally to its motor output demand, explaining the large representation of the hands.
Q: What are the origin and function of the lateral motor pathway?
A: Originates from the motor cortex and red nucleus; crosses midline at medulla (cortex origin) and
pons (red nucleus). It controls voluntary movement.
Q: What is the function and origin of the ventral medial pathway?
A: Originates from the vestibular nucleus, reticular nuclei, and superior colliculus; controls posture,
balance, and locomotion. It operates unconsciously.
Q: How can you retrograde trace a neural pathway trans-synaptically from muscle to
brainstem?
A: By using a genetically modified, less toxic rabies virus tagged with GFP that can cross synapses
in 1-4 days.
Q: What are the ascending pathways from skeletal muscle to cortex?
A: The dorsal column (touch) and anterolateral (pain/temp) pathways through spinal cord, medulla,
pons, midbrain, thalamus, and cortex.
Q: What is the limitation of the motor homunculus?
A: Fine-scale topography doesn't persist-neural activity spreads across broader cortical areas than
the map suggests.
Q: What are the functions of motor cortex areas 4 and 6?
A: Area 4 (M1): Direct control of voluntary movement.
Area 6 (PMA and SMA): Planning movement and using mirror neurons for social/emotional
processing.
Q: How is movement direction encoded in the motor cortex?
A: Through population vectors from hundreds of neurons, not single neurons.
Q: How are neural prosthetics controlled?
A: Via electrodes implanted in the motor cortex that decode population vectors and control robotic
limbs based on intention.
Q: What are the main functions of the cerebellum?
A: Fine control of movement and motor learning.
Q: What are the major cerebellar input pathways?
A: Mossy fibers (from pons/spinal cord) and climbing fibers (from inferior olive in medulla).
Q: What are the key processing and output cells in the cerebellum?
A: Granule cells -> Purkinje cells -> Deep cerebellar nuclei -> Brainstem/thalamus -> Cortex.
Q: What are the four main components of the basal ganglia?
A: Striatum (caudate + putamen), globus pallidus (internal + external), subthalamic nucleus,
substantia nigra (SNc and SNr).
Q: What is the function of the basal ganglia?
A: Regulates global motor control and initiates movement through cortical and brainstem
interactions.
Q: What is the difference between the direct and indirect basal ganglia pathways?
A: Direct (D1): Inhibits GPi/SNr -> less inhibition -> promotes movement.
Indirect (D2): Inhibits GPe -> disinhibits STN -> excites GPi/SNr -> more inhibition -> suppresses
movement.
Q: What is the net effect of activating the D1 vs D2 pathways?
A: D1 activation: Increased movement (mouse moves continuously).
D2 activation: Decreased movement (mouse appears frozen).
Q: What are the key differences between the parasympathetic and sympathetic nervous
systems?
A: Parasympathetic: Rest and digest; long preganglionic, short postganglionic; uses acetylcholine.
Sympathetic: Fight or flight; short preganglionic, long postganglionic; uses acetylcholine and
norepinephrine.
Q: What are the autonomic effects on the heart?
A: Parasympathetic: Slows heartbeat.
Sympathetic: Accelerates heartbeat.
Q: What are the effects on blood vessels?
A: Parasympathetic: Dilates vessels.
Sympathetic: Constricts vessels.
Q: Effects on gastrointestinal tract?
A: Parasympathetic: Stimulates digestion.
Sympathetic: Inhibits digestion.
Q: Effects on the lungs?
A: Parasympathetic: Constricts bronchi, dilates pulmonary vessels.
Sympathetic: Dilates bronchi, constricts pulmonary vessels.
Q: Effects on adrenal medulla?
A: Parasympathetic: Decreases activity.
Sympathetic: Increases adrenaline release.
Q: Effects on external genitalia?
A: Parasympathetic: Relaxation and dilation.
Sympathetic: Constriction.
Q: Effects on cardiac muscle?
A: Parasympathetic: Slows heart via SA/AV node.
Sympathetic: Increases heart rate and strength.