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effector cells

the muscle cells or gland cells that actually carry out the body's responses to stimuli.


neural "cables" containing many axons. These bundled axons, which are part of the peripheral nervous system, connect the central nervous system with muscles, glands, and sense organs


cell that carries messages throughout the nervous system

cell body

largest part of a typical neuron; contains the nucleus and much of the cytoplasm


branching extensions of neuron that receives messages from neighboring neurons


a part of a neuron that carries impulses away from the cell body

myelin sheath

a layer of fatty tissue segmentally encasing the fibers of many neurons; enables vastly greater transmission speed of neural impulses as the impulse hops from one node to the next

schwann cells

Supporting cells of the peripheral nervous system responsible for the formation of myelin.


the junction between the axon tip of the sending neuron and the dendrite or cell body of the receiving neuron

sensory neurons

neurons that carry incoming information from the sense receptors to the central nervous system


Central nervous system neurons that internally communicate and intervene between the sensory inputs and motor outputs


a simple, automatic, inborn response to a sensory stimulus, such as the knee-jerk response

motor neurons

neurons that carry outgoing information from the central nervous system to the muscles and glands


cells that support, nurture, and insulate neurons, remove debris when neurons die, enhance the formation and maintenance of neural connections, and modify neuronal functioning

excitable cells

Neurons and muscle fibers. These cells exhibit electrical excitability which is the ability to respond to certain stimuli by producing electrical signals such as action potentials. Action potenitals propagate along a nerve or muscle plasma membrane to cause a response. ( i.e. release of nuerotransmitters, muscle contraction)

resting potential

the potential difference between the two sides of the membrane of a nerve cell when the cell is not conducting an impulse


sodium rushes into neuron through membrane, potassium ruses out; results in a change in charge


part of the brain, works with the cerebellum in coordinating voluntary movement; neural stimulation studied in activation synthesis theory may originate here

action potential

a neural impulse; a brief electrical charge that travels down an axon. the action potential is generated by the movement of positively charged atoms in and out of channels in the axon's membrane

saltatory conduction

Rapid transmission of a nerve impulse along an axon, resulting from the action potential jumping from one node of Ranvier to another, skipping the myelin-sheathed regions of membrane.


chemical messengers that traverse the synaptic gaps between neurons. When released by the sending neuron, neurotransmitters travel across the synapse and bind to receptor sites on the receiving neuron, thereby influencing whether that neuron will generate a neural impulse.

gray matter

Brain and spinal cord tissue that appears gray with the naked eye; consists mainly of neuronal cell bodies (nuclei) and lacks myelinated axons.


the middle division of brain responsible for hearing and sight; location where pain is registered; includes temporal lobe, occipital lobe, and most of the parietal lobe

white matter

whitish nervous tissue of the CNS consisting of neurons and their myelin sheaths

spinal nerves

the 31 pairs of nerves located along the spinal column

cranial nerves

12 pairs of nerves that carry messages to and from the brain

brain stem

the part of the brain continuous with the spinal cord and comprising the medulla oblongata and pons and midbrain and parts of the hypothalamus

medulla oblongata

contains centers that control several visceral functions, including breathing, heart and blood vessel activity, swallowing, vomiting, and digestion.


the "little brain" attached to the rear of the brainstem; its functions include processing sensory input and coordinating movement output and balance


the brain's sensory switchboard, located on top of the brainstem; it directs messages to the sensory receiving areas in the cortex and transmits replies to the cerebellum and medulla


a neural structure lying below the thalamus; directs eating, drinking, body temperature; helps govern the endocrine system via the pituitary gland, and is linked to emotion


area of the brain responsible for all voluntary activities of the body; encompasses both hemispheres.

corpus callosum

the large band of neural fibers connecting the two brain hemispheres and carrying messages between them

short term memory

activated memory that holds a few items briefly, such as the seven digits of a phone number while dialing, before the information is stored or forgotten

nerve net

in cnidarians, a network of nerve cells that lacks a central control; impulses pass in any or all directions to produce a generalized response

long term memory

the relatively permanent and limitless storehouse of the memory system. Includes knowledge, skills, and experiences


the faculty through which the external world is apprehended


becoming aware of something via the senses


whitish fibrous membrane (albuginea) that with the cornea forms the outer covering of the eyeball

choroid coat

" the middle layer of the eye"; it is the interlaced with many blood vessels, which nourish the eyes


mucous membrane that lines the eyelids and outer surface of the eyeball


muscular diaphragm that controls the size of the pupil


the adjustable opening in the center of the eye through which light enters


the light-sensitive inner surface of the eye, containing the receptor rods and cones plus layers of neurons that begin the processing of visual information


the transparent structure behind the pupil that changes shape to help focus images on the retina

aqueous humor

watery liquid secreted at the ciliary body that fills the anterior and posterior chambers of the eye and provides nourishment for the cornea, iris, and lens (humor = fluid)

vitreous humor

jellylike substance found behind the lens in the posterior cavity of the eye that maintains its shape

eustachian tube

A narrow tube between the middle ear and the throat that serves to equalize pressure on both sides of the eardrum

inner ear

the innermost part of the ear, containing the cochlea, semicircular canals, and vestibular sacs


the snail-shaped tube (in the inner ear coiled around the modiolus) where sound vibrations are converted into nerve impulses by the Organ of Corti


Micorsopic, fiber-like structures that occupy most cytoplasm in skeletal muscle cells


the thinnest of the three types of fibers in cytoskeleton; two intertwined stands of actin

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