Nervous System Study Guide

A comprehensive set of vocabulary flashcards covering the structural and functional divisions of the nervous system, neuron anatomy, neuroglia, physiology of action potentials, cranial nerves, spinal cord anatomy, and reflex classifications.

Central Nervous System (CNS)

Comprised of the brain and spinal cord.

Peripheral Nervous System (PNS)

Comprised of the nerves that originate from the brain (cranial nerves) and spinal cord (spinal nerves).

Sensory (Afferent)

Functional division that carries signals from receptors to the CNS.

Motor (Efferent)

Functional division that carries signals from the CNS to effectors (muscles/organs).

Autonomic Nervous System (ANS)

System that controls involuntary activities such as heart rate, breathing, and digestion.

Sympathetic Division

A division of the ANS often associated with "fight or flight" responses.

Parasympathetic Division

A division of the ANS often associated with "rest and digest" or homeostatic maintenance.

Vagus nerve (CN X)

A primary component of the autonomic system that monitors organs and regulates breathing/heart rate.

Multipolar Neurons

The most common neurons, possessing one axon and many dendrites.

Soma (Cell Body)

Acts as the biosynthetic center of a neuron.

Dendrites

Short, branched processes that receive incoming information and convey it toward the soma.

Axon

The long process that conducts impulses away from the cell body toward other neurons or effectors.

Interneurons

Also known as Association Neurons, these are found within the CNS to process sensory information and determine motor response.

Oligodendrocytes

Glial cells responsible for myelination within the Central Nervous System (CNS).

Schwann Cells

Glial cells responsible for myelination within the Peripheral Nervous System (PNS).

Resting Membrane Potential (RMP)

The electrical charge of a neuron’s plasma membrane when it is not actively sending a signal.

Astrocytes

CNS glial cells that provide structural and metabolic support.

Ependymal Cells

Cells that line the ventricles and central canal which are involved in cerebrospinal fluid (CSF) production.

Microglia

Cells that act as immune cells within the CNS.

Depolarization

A step in an action potential where the membrane becomes less negative as sodium ($Na^+$) enters the cell.

Repolarization

A step in an action potential where the membrane returns toward its resting state as potassium ($K^+$) leaves the cell.

Hyperpolarization

A step in AP where the membrane briefly becomes more negative than the RMP before stabilizing.

Synaptic Cleft

The fluid-filled gap between the pre-synaptic neuron and the post-synaptic cell.

Chemical Synapses

Synapses that use neurotransmitters (chemical messengers) to transmit signals across the cleft.

Electrical Synapses

Synapses involving direct physical contact via gap junctions, allowing ions to flow directly between cells.

The All-or-None Law

The principle that an action potential either happens completely if the stimulus reaches "threshold" or not at all.

Continuous Conduction

Conduction occurring in unmyelinated axons where the signal travels the entire length of the axon slowly.

Saltatory Conduction

Conduction occurring in myelinated axons where the signal "jumps" from one Node of Ranvier to the next.

CN I Olfactory

Cranial nerve responsible for the sense of smell.

CN II Optic

Cranial nerve for the sense of vision; crosses at the optic chiasma and travels to the occipital lobe.

CN III Oculomotor

Controls eye muscles, lifts eyelids, and changes pupil diameter.

CN IV Trochlear

Cranial nerve that controls the superior oblique eye muscle.

CN V Trigeminal

Nerve with three branches involved in somatic sensation from the face and chewing (mastication).

CN VI Abducens

Controls the lateral rectus muscle and abducts the eye.

CN VII Facial

Controls muscles of facial expression and the sense of taste.

CN VIII Vestibulocochlear

Cranial nerve responsible for hearing and balance (equilibrium).

CN IX Glossopharyngeal

Involved in taste, touch from the tongue, and the pharynx (swallowing/speech).

CN XI Accessory

Controls muscles of the neck and pharynx and aids swallowing.

CN XII Hypoglossal

Controls tongue muscles for speech, taste, and swallowing.

Conus Medullaris

The tapering, inferior end of the spinal cord located at the $L1$ vertebra.

Cauda Equina

Meaning "Horse’s tail," it is a bundle of nerve roots extending inferiorly from the conus medullaris.

Filum Terminale

A thin strand of pia matter that attaches the conus medullaris to the coccyx.

Cervical Enlargement

Spinal cord region containing neurons for the upper limbs.

Lumbar Enlargement

Spinal cord region containing neurons for the lower limbs.

Shingles

A reactivation of a latent chickenpox virus that travels through sensory axons to the skin along a dermatome.

Monosynaptic Reflex

A reflex where the sensory neuron synapses directly with a motor neuron, has no interneuron (sensory to motor), such as the Patellar reflex.

Polysynaptic Reflex

A reflex action that involves one or more interneurons.

Ipsilateral

A response that occurs on the same side as the stimulus.

Contralateral

A response that occurs on the opposite side of the stimulus.

Somatic

nervous system that controls voluntary movements and reflexes. (control skeletal muscles)

Visceral Reflex

control internal organs, glands, and smooth or cardiac muscles (e.g., heart rate regulation, digestion

Limbic System

a complex set of structures in the brain that manages emotions, memories, and arousal.

Sensory Nuclei

clusters of neurons in the central nervous system that process sensory information from the body, such as touch, pain, and temperature.

Motor Nuclei

clusters of neurons in the central nervous system that are responsible for processing and coordinating motor control and movement.