The Nervous System: Central Nervous System

Flashcards covering the central nervous system's involuntary movement through reflexes and voluntary motor control, including pathways, structures, and related disorders.

Reflex

An automatic patterned response to a stimulus.

Reflex Arc

The neural pathway for a reflex.

Components of a Reflex Arc

Sensory receptor, afferent neuron, integration center (CNS), efferent neuron(s), and effector organ.

Cranial Reflexes

Reflexes processed predominantly in the brain.

Spinal Reflexes

Reflexes processed predominantly in the spinal cord.

Somatic Reflexes

Reflexes that involve skeletal muscles.

Autonomic (Visceral) Reflexes

Reflexes that involve smooth muscle, cardiac muscle, or glands.

Innate Reflexes

Inborn, genetically programmed reflexes.

Conditioned Reflexes

Learned reflexes.

Monosynaptic Reflexes

Reflexes with only one synapse between the afferent and efferent neurons.

Polysynaptic (Multisynaptic) Reflexes

Reflexes involving multiple synapses and interneurons.

Muscle Spindle Stretch Reflex

A reflex pathway involving stimulation of muscle extensors and reciprocal inhibition of flexors (ipsilateral, mono- and polysynaptic).

Withdrawal Reflex

A polysynaptic reflex causing the flexion of a limb to remove it from a painful stimulus.

Crossed-Extensor Reflex

A polysynaptic reflex complementing the withdrawal reflex, causing extension in the opposite limb to maintain balance.

Pupillary Light Reflex

A cranial, autonomic, innate, polysynaptic reflex involving cranial nerves II and III that controls iris and pupil size in response to light.

Voluntary Motor Control

The process from developing an idea to move, programming motor commands, activating muscles, and using feedback for smooth and successful movement.

Lower Motor Neuron

Efferent neurons originating in the ventral horn of the spinal cord or cranial nerve nuclei that innervate skeletal muscle.

Neuromuscular Junction

The synapse between a motor neuron and a skeletal muscle fiber, which is always excitatory.

Pyramidal Tract Neurons

Neurons that provide input to motor neurons, primarily involved in fine control of voluntary movement.

Extrapyramidal Tract Neurons

Neurons that provide input to motor neurons, primarily supporting voluntary movement of proximal extremities.

Pyramidal Tracts

Descending motor pathways originating in the primary motor cortex responsible for fine control of voluntary movement, particularly of distal extremities.

Upper Motor Neurons

Motor neurons that originate in the primary motor cortex (for pyramidal tracts) and other brain regions, providing direct or indirect input to lower motor neurons.

Decussation

The crossing of nerve fibers from one side of the CNS to the other, characteristic of pyramidal tracts causing contralateral control.

Lateral Pyramidal Tract

A pyramidal tract involved in voluntary movement of the distal extremities, decussating in the medulla, leading to contralateral control.

Anterior Pyramidal Tract

A pyramidal tract involved in voluntary movement of axial muscles and proximal limbs, decussating in the spinal cord, leading to contralateral control.

Extrapyramidal Tracts

All motor pathways outside the pyramidal tracts, supporting voluntary movement, primarily of the proximal extremities, with indirect input to motor neurons.

Rubrospinal Tracts

An extrapyramidal pathway originating in the red nuclei of the midbrain, primarily involved in voluntary flexion of the upper extremities, mainly contralateral.

Vestibulospinal Tract

A ventromedial extrapyramidal pathway originating in vestibular nuclei, involved in involuntary movement of head, neck, and lumbar muscles for posture and balance (bilateral).

Tectospinal Tract

A ventromedial extrapyramidal pathway originating in the superior colliculi, involved in involuntary movement of head and extraocular muscles for tracking objects (contralateral).

Reticulospinal Tract

A ventromedial extrapyramidal pathway originating in the reticular formation, involved in involuntary stimulation or inhibition of leg extensors for upright posture (mostly ipsilateral).

Cerebellum

A brain region critical for motor coordination, providing feedback control of motor function, fine-tuning movements, contributing to muscle tone, and muscle memory.

Basal Nuclei

A brain region critical for motor coordination, providing feedback control of voluntary movements and automatic learned motions, and selecting purposeful over unwanted movements.

Huntington's Chorea

A degenerative genetic disorder of the basal nuclei causing loss of motor coordination, increased involuntary motions (twitches, jerking), and advanced stages involving dementia.

Parkinson's Disease

A degenerative non-genetic disorder of the basal nuclei caused by lack of dopamine production in the substantia nigra, leading to rigidity, tremors at rest, and difficulty initiating/stopping movements.

Substantia Nigra

A midbrain structure whose degeneration and lack of dopamine production is associated with Parkinson's disease.