Seeley's Essentials of Anatomy & Physiology - Chapter 8: Nervous System

A complete list of vocabulary terms and definitions derived from Chapter 8 lecture slides on the Nervous System.

Central Nervous System (CNS)

The major division of the nervous system consisting of the brain and spinal cord.

Peripheral Nervous System (PNS)

The division of the nervous system consisting of all neurons outside the central nervous system.

Dendrite

A structural process of a neuron that receives stimuli from other neurons or sensory receptors.

Cell Body

The part of a neuron that processes stimuli and contains the cell nucleus.

Axon

A structural process of a neuron that transmits stimuli to a gland, muscle, organ, or another neuron.

Myelin Sheath

A fatty, protective wrapping around axons that serves as an excellent electrical insulator.

Nodes of Ranvier

Gaps in the myelin sheath along an axon where action potentials develop.

Saltatory Conduction

The jumping of action potentials from node to node along a myelinated axon, allowing speeds of $3\text{--}15\text{ meters/sec}$.

Multiple Sclerosis

A disease of the myelin sheath that leads to loss of muscle function.

Multipolar Neuron

A neuron structural type having many dendrites and a single axon, typical of CNS neurons and most motor neurons.

Bipolar Neuron

A neuron structural type having one dendrite and one axon, found in sensory organs like the eye and nasal cavity.

Pseudo-unipolar Neuron

A neuron structural type that appears to have an axon and no dendrites, typical of sensory neurons.

Neuroglia

Supporting cells for neurons that are more numerous than neurons and retain the ability to divide.

Astrocytes

Star-shaped, highly abundant neuroglial cells that form the blood-brain barrier.

Ependymal Cells

Neuroglial cells responsible for producing and circulating cerebrospinal fluid (CSF).

Microglia

Neuroglial cells that help remove bacteria and cell debris from the CNS.

Oligodendrocytes

Neuroglial cells that produce the myelin sheath surrounding axons in the central nervous system.

Schwann Cells

Neuroglial cells that produce the myelin sheath surrounding axons in the peripheral nervous system.

Gray Matter

Nervous tissue composed primarily of a collection of nerve cell bodies and dendrites.

White Matter

Nervous tissue composed primarily of collections of axons and their surrounding myelin sheaths.

Resting Membrane Potential

The electrical equilibrium established across a resting cell membrane where K+ diffusion out equals K+ entry, yielding a net positive charge outside ($Na^+$) and a net negative charge inside.

Sodium-Potassium Pump

An active transport mechanism driven by ATP hydrolysis that pumps $3\text{ }Na^+$ out of the cell in exchange for $2\text{ }K^+$ into the cell.

Depolarization

The phase of an action potential in which voltage-gated $Na^+$ channels open and $Na^+$ diffuses into the cell, shifting the membrane potential from $-70\text{ }mV$ to $+20\text{ }mV$.

Repolarization

The phase of an action potential in which $Na^+$ channels close and $K^+$ channels open, allowing $K^+$ to diffuse out and returning the membrane potential to $-70\text{ }mV$.

Synapse

The junction where an axon attaches to a muscle, gland, organ, or another neuron to transmit signals via neurotransmitters across a synaptic cleft.

Acetylcholine (ACh)

A neurotransmitter released at CNS synapses, ANS synapses, and neuromuscular junctions; its reduction is associated with Alzheimer disease and receptor reduction with Myasthenia gravis.

Dopamine

An excitatory or inhibitory neurotransmitter whose secreting neurons are destroyed in Parkinson disease.

Reflex Arc

The neuronal path traveled during an involuntary reflex response, comprising a sensory receptor, sensory neuron, interneuron, motor neuron, and effector.

Converging Pathway

A neuronal pathway pattern in which two or more input neurons synapse onto a single postsynaptic neuron.

Diverging Pathway

A neuronal pathway pattern in which an axon from a single neuron branches to synapse with multiple postsynaptic neurons.

Ascending Tracts

Spinal cord axon pathways that conduct action potentials upward toward the brain.

Descending Tracts

Spinal cord axon pathways that conduct action potentials downward from upper motor neurons to lower motor neurons.

Phrenic Nerve

A key nerve originating from the cervical plexus ($C1\text{--}4$) that innervates the diaphragm.

Medulla Oblongata

The inferior brainstem structure continuous with the spinal cord that regulates heart rate, blood vessel diameter, breathing, swallowing, vomiting, and contains motor pyramids.

Pons

The brainstem region superior to the medulla that acts as a bridge between cerebrum and cerebellum, helping regulate breathing, chewing, salivation, and swallowing.

Midbrain

The brainstem region superior to the pons that coordinates eye movements, pupil diameter, and head turns toward noise.

Reticular Formation

A scattered brainstem neural network regulating cyclical motor functions, respiration, walking, chewing, and the sleep-wake cycle.

Hypothalamus

Diencephalon structure inferior to the thalamus that connects to the pituitary gland via the infundibulum and regulates homeostasis, body temperature, thirst, hunger, fear, and rage.

Cerebral Cortex

The surface layer of gray matter on the cerebrum responsible for thinking, communicating, remembering, understanding, and initiating voluntary movements.

Gyri

Folds on the cerebral cortex that serve to increase the surface area of the brain.

Sulci

Shallow indentations on the surface of the cerebral cortex separating the gyri.

Corpus Callosum

The primary structural connection between the left and right cerebral hemispheres.

Cerebellum

The posterior brain region known as the 'little brain' that controls balance, muscle tone, and coordination of fine motor movements.

Wernicke Area

The sensory speech area located in the parietal lobe where spoken words are heard and comprehended.

Broca Area

The motor speech area located in the frontal lobe where words are formulated.

Electroencephalogram (EEG)

A recording of the brain's electrical activity obtained using electrodes placed on the scalp.

Alpha Waves

EEG brain waves characteristic of an individual who is awake in a quiet, relaxed state.

Beta Waves

EEG brain waves characteristic of intense mental activity.

Delta Waves

EEG brain waves characteristic of deep sleep.

Meninges

The protective connective tissue wrappings surrounding the brain and spinal cord, consisting of the dura mater, arachnoid mater, and pia mater.

Subarachnoid Space

The fluid-filled space between the arachnoid mater and pia mater containing cerebrospinal fluid (CSF).

Sympathetic Division

The division of the autonomic nervous system activated during stress ('fight or flight') that increases heart rate, blood pressure, and breathing rate.

Parasympathetic Division

The division of the autonomic nervous system functioning as the 'housekeeper' during normal conditions to manage digestion, urination, and pupil control.