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How is the primary motor cortex functionally organized?

It has a somatotopic organization like the somatosensory cortex, with each body part represented proportionally to its motor output demand.

What is the origin and function of the lateral motor pathway?

Originates from the motor cortex and red nucleus, crossing at the medulla and pons; it controls voluntary movement.

What is the origin and function of the ventral medial pathway?

Originate from the vestibular nucleus, reticular nuclei, and superior colliculus; it controls posture, balance, and locomotion unconsciously.

How can you retrograde trace a neural pathway trans-synaptically?

By using a genetically modified rabies virus tagged with GFP that can cross synapses in 1-4 days.

What are the ascending pathways from skeletal muscle to cortex?

The dorsal column (touch) and anterolateral (pain/temp) pathways through spinal cord, medulla, pons, midbrain, thalamus, and cortex.

What is the limitation of the motor homunculus?

Fine-scale topography doesn't persist; neural activity spreads across broader cortical areas than the map suggests.

What are the functions of motor cortex areas 4 and 6?

Area 4 (M1): Direct control of voluntary movement. Area 6 (PMA and SMA): Planning movement and using mirror neurons for social/emotional processing.

How is movement direction encoded in the motor cortex?

Through population vectors from hundreds of neurons, not single neurons.

How are neural prosthetics controlled?

Via electrodes implanted in the motor cortex that decode population vectors and control robotic limbs based on intention.

What are the main functions of the cerebellum?

Fine control of movement and motor learning.

What are the major cerebellar input pathways?

Mossy fibers (from pons/spinal cord) and climbing fibers (from inferior olive in medulla).

What are the key processing and output cells in the cerebellum?

Granule cells -> Purkinje cells -> Deep cerebellar nuclei -> Brainstem/thalamus -> Cortex.

What are the four main components of the basal ganglia?

Striatum (caudate + putamen), globus pallidus (internal + external), subthalamic nucleus, substantia nigra (SNc and SNr).

What is the function of the basal ganglia?

Regulates global motor control and initiates movement through cortical and brainstem interactions.

What is the difference between the direct and indirect basal ganglia pathways?

Direct (D1): Inhibits GPi/SNr -> less inhibition -> promotes movement. Indirect (D2): Inhibits GPe -> disinhibits STN -> excites GPi/SNr -> more inhibition -> suppresses movement.

What is the net effect of activating the D1 vs D2 pathways?

D1 activation: Increased movement. D2 activation: Decreased movement.

What are the key differences between the parasympathetic and sympathetic nervous systems?

Parasympathetic: Rest and digest; long preganglionic, short postganglionic; uses acetylcholine. Sympathetic: Fight or flight; short preganglionic, long postganglionic; uses acetylcholine and norepinephrine.

What are the autonomic effects on the heart?

Parasympathetic: Slows heartbeat. Sympathetic: Accelerates heartbeat.

What are the effects on blood vessels?

Parasympathetic: Dilates vessels. Sympathetic: Constricts vessels.

Effects on gastrointestinal tract?

Parasympathetic: Stimulates digestion. Sympathetic: Inhibits digestion.

Effects on the lungs?

Parasympathetic: Constricts bronchi, dilates pulmonary vessels. Sympathetic: Dilates bronchi, constricts pulmonary vessels.

Effects on adrenal medulla?

Parasympathetic: Decreases activity. Sympathetic: Increases adrenaline release.

Effects on external genitalia?

Parasympathetic: Relaxation and dilation. Sympathetic: Constriction.

Effects on cardiac muscle?

Parasympathetic: Slows heart via SA/AV node. Sympathetic: Increases heart rate and strength.