Vision, Vestibular System, and Motor Control (Video Notes)

Vocabulary flashcards covering key concepts from vision, vestibular, and motor control topics from the video notes.

Corticospinal tract

Major motor pathway from the cortex to the spinal cord that controls voluntary movement; about 90% of fibers cross in the medulla to form the lateral corticospinal tract, while about 10% remain ipsilateral as the anterior corticospinal tract.

Pyramidal tract

Another name for the corticospinal tract.

Lateral corticospinal tract

Crossed fibers that primarily control limb and digit movements.

Anterior corticospinal tract

Uncrossed corticospinal fibers that mainly influence trunk and proximal muscles.

Internal capsule

White matter bundle through which cortex-to-brainstem/spinal tracts (including corticospinal) pass.

Upper motor neurons

Motor neurons in brain or brainstem that project to the spinal cord and synapse on lower motor neurons.

Lower motor neurons

Motor neurons in the ventral horn of the spinal cord that directly innervate skeletal muscles.

Alpha motor neurons

Lower motor neurons that innervate extrafusal muscle fibers to cause contraction.

Gamma motor neurons

Lower motor neurons that innervate intrafusal muscle fibers, regulating spindle sensitivity.

Primary motor cortex (Brodmann area 4)

Initiates voluntary movement and controls force and rate of change of force; major source of corticospinal fibers.

Supplementary motor area (SMA, area 6)

Involved in planning and sequencing of movements and motor learning; contributes to new motor programs.

Premotor cortex

Plans movements and selects a motor program when more than one option exists.

Basal ganglia

Subcortical nuclei that modulate movement, influence initiation and smoothness of movement, via thalamocortical circuits.

Parkinson's disease

Dopamine depletion in the basal ganglia leading to reduced movement, dyskinesia, akinesia, bradykinesia, and resting tremor.

Dyskinesia

Involuntary, irregular movements often seen with basal ganglia dysfunction or its treatment.

Bradykinesia

Slowness of movement; a hallmark of Parkinsonian syndromes.

Akinesia

Impaired ability to initiate movement.

Resting tremor

Tremor that occurs at rest, commonly associated with Parkinson's disease.

Rigidity

Increased muscle tone causing stiffness and resistance to movement.

Cerebellum

Brain structure that coordinates movement, detects errors, and integrates sensory input for timing and accuracy.

Cerebellar ataxia

Lack of coordination, wide-based gait, dysmetria, and often intention tremor; may accompany cerebellar dysfunction.

Nystagmus

Involuntary, rhythmic eye movements often indicating vestibular or cerebellar disturbance.

Intention tremor

Tremor that worsens near a target, typical of cerebellar dysfunction.

Vestibular system

Sense of head position and movement; stabilizes gaze and maintains posture.

Vestibulo-ocular reflex (VOR)

Eye movements that stabilize images on the retina during head movement.

Semicircular canals

Three inner-ear structures that detect angular acceleration and head rotation.

Utricle

Otolith organ that senses linear acceleration and head tilt in the horizontal plane.

Saccule

Otolith organ that senses linear acceleration in the vertical plane.

Endolymph

Fluid within the labyrinth of the inner ear that helps transduce vestibular signals.

Cranial nerve VIII (Vestibulocochlear N.)

Nerve carrying vestibular (and hearing) information from the inner ear to the brainstem.

Cranial nerve III (Oculomotor N.)

Nerve that controls most eye movements and pupil constriction; part of coordinating eye movement with head.

Thalamus

Relay center for sensory information en route to the cortex; also involved in motor pathways' integration.

Primary somatosensory cortex (S1, areas 3,1,2)

Processes tactile and proprioceptive information; crucial for knowing body position in space.

Posterior column (dorsal column) system

Ascending sensory tract carrying crude touch, proprioception, two-point discrimination, and deep touch.

Gracile fasciculus

Medial dorsal column tract carrying proprioceptive and fine touch information from the lower body.

Cuneate fasciculus

Lateral dorsal column tract carrying proprioceptive and fine touch information from the upper body.

Lateral spinothalamic tract

Ascending tract for pain and temperature.

Anterior spinothalamic tract

Ascending tract for crude/light touch.

Visual pathway

Retina → optic nerve → optic chiasm → optic tract → lateral geniculate nucleus → optic radiations → primary visual cortex (areas 17–19).

Retina

Light-sensitive layer at the back of the eye containing rods and cones.

Rods

Photoreceptors in the peripheral retina that detect low light levels (night vision).

Cones

Photoreceptors concentrated in the fovea responsible for color and high-acuity daytime vision.

Fovea

Central retina region with the highest cone density and sharpest vision.

Optic nerve

Cranial nerve II; transmits retinal signals from the eye to the brain.

Optic chiasm

Site where nasal retinal fibers cross to the opposite side (partial decussation).

Optic tract

Fibers after the chiasm carrying visual information to the thalamus.

Lateral geniculate nucleus (LGN)

Thalamic relay for visual information before it reaches the visual cortex.

Primary visual cortex (Area 17, V1)

First cortical processing area for vision in the occipital lobe.

Visual association areas (Areas 18–19)

Higher-order visual processing areas for color, motion, form, and interpretation.

Decussation

Crossing of nerve fibers to the opposite side, such as at the optic chiasm or medullary pyramidal decussation.

Visual field

Area of the environment visible at a given moment; mapped to retina and cortex.

Visual pathway analysis (movement, color, detail)

Describes how the visual system analyzes movement, color, and detail in the cortex.

Static vs. dynamic vestibular function

Dynamic: angular acceleration via semicircular canals; Static: head position via utricle/saccule and linear acceleration.

Cerebral peduncle

Midbrain structure containing motor tracts, including corticospinal fibers en route to the brainstem.

Cranial nerve pathways (general)

Cranial nerves connect brainstem with head and neck muscles; III and VIII are involved in eye movement and balance.

Pain physiology

Field studying how pain signals are generated and processed through the nervous system.

Blood supply to the cortex (MCA/PCA)

Middle cerebral artery supplies frontal, parietal, and temporal lobes; posterior cerebral artery overlaps at the occipital lobe.