Nerve Physiology and Systems

Vocabulary flashcards covering Central and Peripheral Nervous System structures, functional divisions, neuron classifications, neuroglial cells, and myelination conduction mechanisms based on the lecture notes.

Central Nervous System (CNS)

Anatomical subdivision of the nervous system consisting of the brain and spinal cord, protected by surrounding bone.

Peripheral Nervous System (PNS)

Anatomical subdivision of the nervous system comprising $12$ pairs of cranial nerves arising from the brain and $31$ pairs of spinal nerves arising from the spinal cord.

Cranial Nerves

$12$ pairs of nerves in the peripheral nervous system arising directly from the brain.

Spinal Nerves

$31$ pairs of nerves in the peripheral nervous system arising directly from the spinal cord.

Sensory (Afferent) Neurons

Neurons that sense changes in the internal and external environment through sensory receptors and conduct information toward the central nervous system.

Association Neurons (Interneurons)

Neurons located in the central nervous system that analyze sensory information, store aspects of it, and make integrative decisions regarding appropriate behaviors.

Motor (Efferent) Neurons

Neurons that carry signals away from the central nervous system to respond to stimuli by initiating action in effectors such as muscles and glands.

Somatic Nervous System

The sub-division of the peripheral nervous system's motor division that communicates with sense organs and voluntary skeletal muscles.

Autonomic Nervous System

The sub-division of the peripheral nervous system's motor division that communicates with internal organs and glands, regulating smooth muscle, cardiac muscle, and glands.

Sympathetic Division

The branch of the autonomic nervous system responsible for arousing functions.

Parasympathetic Division

The branch of the autonomic nervous system responsible for calming functions.

Neurons

The basic structural and functional units of the nervous system, specialized to respond to physical and chemical stimuli, conduct electrochemical impulses, and release chemical regulators.

Neuroglia (Glial Cells)

Supporting cells that aid the function of neurons and are roughly $5\times$ more abundant than neurons; derived from the Middle Greek word 'glia' meaning glue.

Neuron Cell Body (Soma)

The enlarged portion of a neuron containing the nucleus, serving as the nutritional center where cellular molecules are produced.

Nuclei

Clusters of neuron cell bodies located specifically within the Central Nervous System (CNS).

Ganglia

Clusters of neuron cell bodies located specifically within the Peripheral Nervous System (PNS).

Dendrites

Thin, branching processes extending from the neuron cell body cytoplasm (from Greek 'dendron' meaning tree branch) that serve as receptive areas transmitting electrochemical impulses toward the cell body.

Axon

A process arising from the axon hillock that conducts electrical impulses away from the cell body toward presynaptic terminals, varying in length from $1\text{ mm}$ up to $1\text{ m}$.

Axon Hillock

The expanded region of the neuron cell body from which the axon originates.

Presynaptic Terminals (Terminal Buttons)

Small extensions with enlarged ends at the terminus of axon branches that contain vesicles storing neurotransmitters.

Axoplasm

The cytoplasm contained within the axon of a neuron.

Multipolar Neurons

Structural class of neurons having multiple dendrites and a single axon; the most abundant type in the human body and the major neuron type in the CNS (e.g., Purkinje cells of cerebellum, pyramidal cells).

Bipolar Neurons

Rare structural class of neurons with two processes (one axon and one dendrite), found in special sensory organs such as the olfactory mucosa, eye (retinal cells), and ear.

Unipolar (Pseudounipolar) Neurons

Structural class of neurons with a single process that divides into peripheral and central axon branches; found mainly in dorsal root ganglia of the spinal cord and sensory ganglia of cranial nerves.

Astrocytes

Star-shaped neuroglial cells in the CNS whose processes cover blood vessels, neurons, and pia mater; they maintain the blood-brain barrier, regulate extracellular ion and neurotransmitter levels, and provide metabolic support.

Ependymal Cells

Epithelial neuroglial cells lining the ventricles of the brain and central canal of the spinal cord that are involved in producing cerebrospinal fluid (CSF).

Oligodendrocytes

Neuroglial cells in the Central Nervous System that form myelin sheaths around CNS axons and provide a structural framework.

Microglia

Immune neuroglial cells in the CNS that migrate through tissue to phagocytose foreign materials, dead cells, and pathogens.

Schwann Cells

Neuroglial cells in the Peripheral Nervous System that wrap around peripheral axons to form myelin sheaths and aid in neuron maintenance and regeneration after injury.

Satellite Cells

Neuroglial cells in the PNS that surround neuron cell bodies in ganglia and regulate neurotransmitter levels.

Myelin Sheath

An electrical insulator layer wrapped around axons that accelerates the propagation of action potentials down long axons.

Nodes of Ranvier

Short gaps in the myelin sheath along an axon between adjacent glial cell wrappings.

Neurilemma (Sheath of Schwann)

The continuous living outer layer containing Schwann cell cytoplasm and nucleus surrounding the myelin sheath in PNS axons; absent in CNS axons.

White Matter

Regions of nervous tissue consisting of dense collections of myelinated fibers, appearing white due to a high lipid concentration.

Gray Matter

Regions of nervous tissue composed mostly of neuron cell bodies and dendrites that lack myelin sheaths.

Saltatory Conduction

The fast mode of nerve impulse propagation in myelinated axons, where the impulse jumps from one node of Ranvier to the next, consuming less energy (ATP).

Continuous Conduction

The slower mode of nerve impulse propagation along unmyelinated axons, where the action potential must travel continuously down the entire length of the axon.