Comprehensive Study Guide to the Human Nervous System

A comprehensive vocabulary review of human nervous system anatomy, physiology, cellular structures, pathways, and clinical conditions based on the lecture material.

Neurology

The medical study of how the nervous system works.

Interneurons (Connector Neurons)

Nerve cells that sit completely inside the central nervous system (CNS), linking sensory and motor pathways to make processing decisions.

Central Nervous System (CNS)

The division of the nervous system consisting of the brain and spinal cord that analyzes sensory data, starts movements, generates thoughts and feelings, stores memories, and controls muscles and glands.

Peripheral Nervous System (PNS)

The division of the nervous system made up of nerves branching off the brain and spine, along with nerve clusters called ganglia.

Somatic Sensory

The sensory division that senses stimuli you consciously feel, such as touch from your skin or sight from your eyes.

Visceral Sensory

The sensory division that detects stimuli inside your internal organs that you do not consciously notice.

Somatic Motor

The motor subdivision that carries voluntary control instructions to move skeletal muscles on purpose.

Autonomic Motor

The motor subdivision under involuntary control that directs targets running on their own, including heart muscle, smooth organ muscle, and glands.

Sympathetic Division

The fight-or-flight branch of the autonomic motor system used during stress or emergencies.

Parasympathetic Division

The rest-and-digest branch of the autonomic motor system that manages calm, everyday maintenance when you are relaxed.

Ganglion

A cluster of nerve cell bodies located in the peripheral nervous system (PNS).

Nucleus (Nervous System)

A cluster of nerve cell bodies situated inside the central nervous system (CNS).

Nerve

A cord-like cable composed of many nerve fibers running together in the peripheral nervous system (PNS).

Tract

A bundle of nerve fibers running through the central nervous system (CNS).

Ascending Tracts

Fiber bundles in the central nervous system carrying sensory signals up the spinal cord to the brain.

Descending Tracts

Fiber bundles in the central nervous system carrying movement orders down the spinal cord from the brain.

Excitability

The key trait of a neuron to react to a stimulus by producing an electrical signal.

Conductivity

The ability of a nerve cell to transmit an electrical signal along the entire length of the cell.

Secretion

The ability of a neuron to release chemical messengers called neurotransmitters.

Amitotic

A characteristic of mature neurons meaning they do not undergo cell division and cannot replicate themselves.

Cell Body (Soma)

The control center of a neuron, containing the nucleus and standard cell organelles.

Dendrites

Short, branching extensions of a neuron that receive incoming messages and direct them toward the cell body.

Axon

The long tail of a neuron that carries electrical impulses away from the soma toward another nerve, muscle, or gland.

Epineurium

The tough outer connective tissue sleeve enclosing an entire peripheral nerve.

Perineurium

The middle connective tissue sheath wrapping around bundles of nerve fibers called fascicles.

Endoneurium

The delicate inner connective tissue layer wrapping each individual nerve fiber and its insulation.

Astrocytes

Star-shaped glial cells in the CNS that form the blood-brain barrier (BBB), balance body fluids, and guide developing neurons.

Ependymal Cells

Glial cells that line the open fluid-filled ventricles and spaces of the brain to help produce cerebrospinal fluid (CSF).

Microglia

Tiny phagocytic glial cells in the CNS that engulf and clear away dead cells and invading pathogens.

Oligodendrocytes

Glial cells that produce and wrap myelin insulation around nerve fibers within the central nervous system (CNS).

Satellite Cells

Support cells in the PNS that cushion and nourish nerve cell bodies located in ganglia.

Schwann Cells (Neurolemmocytes)

Support cells that produce and wrap the myelin sheath around nerve fibers in the peripheral nervous system (PNS).

Myelin Sheath

Layers of fat and protein wrapped around a nerve fiber to insulate it and significantly speed up signal transmission.

Nodes of Ranvier (Neurofibril Nodes)

Tiny unmyelinated gaps along an axon between adjacent myelin segments where electrical impulses jump.

Saltatory Conduction

The rapid jumping of nerve impulses from one node of Ranvier to the next along a myelinated axon.

White Matter

Regions of the brain and spinal cord composed primarily of myelinated, insulated nerve fibers.

Gray Matter

Regions of the nervous system consisting mainly of neuronal cell bodies, dendrites, and unmyelinated fibers.

Depolarization

A shift or loss of the resting electrical charge across a neuron membrane when stimulated.

Repolarization

The restoration of the electrical charge across the neuron membrane back to its resting polarized state.

Synapse

The microscopic junction where two neurons meet and communicate without physically touching.

Synaptic Cleft

The microscopic, fluid-filled space between the presynaptic and postsynaptic membranes.

Cauda Equina

A collection of nerve roots extending inferiorly past the lower end of the spinal cord resembling a horse's tail.

Central Canal

The small fluid-filled channel located in the center of the spinal cord that circulates cerebrospinal fluid (CSF).

Dorsal Root Ganglion

A visible swelling on the posterior root of a spinal nerve containing the cell bodies of sensory neurons.

Phrenic Nerve

A critical branch of the cervical plexus that innervates the diaphragm to enable breathing.

Sciatic Nerve

The longest nerve in the body, originating from the sacral plexus and traveling down the leg.

Sciatica

Pain radiating down the buttock and leg caused by compression or damage to the sciatic nerve.

Reflex

A rapid, predictable, and automatic motor response to a sudden change in the environment designed for protection.

Dual Innervation

The arrangement where most internal organs receive nerve fibers from both sympathetic and parasympathetic divisions.

Gyri

The raised folds or ridges on the surface of the cerebral cortex.

Sulci

The shallow grooves or dips separating adjacent gyri on the brain surface.

Longitudinal Fissure

The deep midline groove that separates the cerebrum into right and left cerebral hemispheres.

Corpus Callosum

The thick band of white matter fibers linking and allowing communication between the two cerebral hemispheres.

Precentral Gyrus

The strip located on the frontal lobe that acts as the primary motor control area for voluntary muscle movement.

Broca's Area

The motor speech area in the frontal lobe, typically on the left side, that coordinates muscles for vocalization.

Postcentral Gyrus

The primary somatosensory cortex located on the parietal lobe that receives and interprets body touch sensations.

Wernicke's Area

The brain region dedicated to processing, interpreting, and comprehending spoken and written words.

Basal Nuclei (Basal Ganglia)

Subcortical gray matter clusters that smooth out automatic muscle movements and assist short-term memory.

Thalamus

The sensory relay station of the diencephalon that filters and routes all incoming sensory data (except smell) to the cerebral cortex.

Hypothalamus

The master regulator of homeostasis in the brain that controls the ANS, pituitary gland, body temperature, hunger, thirst, and sleep-wake cycles.

Substantia Nigra

A dark-pigmented midbrain structure that controls subconscious muscle actions and degenerates in Parkinson's disease.

Decussation of the Pyramids

The crossing over of motor tracts in the medulla oblongata, causing the left hemisphere to control the right side of the body.

Cerebellum

The region located below the posterior cerebrum that coordinates smooth muscle activity, posture, and muscle memory.

Ataxia

A condition characterized by unsteady gait, slurred speech, or lack of muscle coordination resulting from cerebellar damage.

Limbic System

A functional ring of forebrain structures known as the emotional brain, regulating pain, pleasure, feelings, and memory.

Reticular Formation

A network of neurons in the brainstem responsible for maintaining wakefulness, alertness, and resting muscle tone.

Pia Mater

The delicate, innermost layer of the meninges clinging directly to the surface of the brain and spinal cord.

Arachnoid Mater

The middle web-like meninx situated between the dura mater and pia mater.

Dura Mater

The tough, fibrous outermost protective membrane of the meninges.

Subarachnoid Space

The CSF-filled space beneath the arachnoid mater where lumbar punctures are performed.

Meningitis

Inflammation or infection of the protective meningeal membranes caused by bacterial or viral pathogens.

Cerebrospinal Fluid (CSF)

The clear liquid providing buoyancy, shock absorption, and chemical homeostasis for the central nervous system.

Choroid Plexus

Networks of capillaries covered by ependymal cells within the brain ventricles that synthesize cerebrospinal fluid.

Hydrocephalus

A condition characterized by an excessive accumulation of cerebrospinal fluid in the ventricles, exerting pressure on brain tissue.

Blood-Brain Barrier (BBB)

A tight protective barrier formed by capillary endothelial cells and astrocytes that restricts harmful bloodborne substances from reaching brain tissue.

Vagus Nerve (CN X)

The tenth cranial nerve, which serves as the primary parasympathetic conduit to the thoracic and abdominal organs.

Concussion

A mild traumatic brain injury resulting in temporary altered mental function, dizziness, confusion, or amnesia.

Contusion (Brain)

A physical bruise of brain tissue accompanied by localized bleeding and rupture of capillaries.

Contrecoup Injury

Brain contusion occurring on the side opposite the site of impact due to the brain rebounding within the skull.

Paraplegia

Paralysis involving the lower half of the body and legs resulting from spinal cord trauma in the thoracic region.

Quadriplegia

Paralysis affecting all four limbs resulting from spinal cord trauma occurring in the cervical area.

Spina Bifida

A congenital disorder where the caudal aspect of the embryonic neural tube fails to close completely during development.

Transient Ischemic Attack (TIA)

A brief episode of neurological dysfunction caused by a temporary disruption of cerebral blood flow, serving as an early stroke warning.

Multiple Sclerosis (MS)

An autoimmune disorder characterized by immune-mediated destruction of oligodendrocytes and CNS myelin sheaths.