Chapter 1: Nerve Cells and Nerve Impulses on Study it

Microglia

cell that removes waste material and other microorganisms from the nervous system

Oligodendrocytes

glia cell in the brain or spinal cord that builds myelin sheaths

Schwann cells

glia cell in the periphery of the body that builds myelin sheaths

Astrocyte

star shaped glia that synchronizes the activity of the axons

neuron

cell that receives information and transmits it to other cells

Nucleus

structure that contains chromosomes

endoplasmic reticulum

network of thin tubes that transport newly synthesized proteins to other locations

ribosome

site for protein synthesis

motor neuron

cell that receives excitation from other neurons and conducts impulses to a muscle

sensory neuron

cell that is highly sensitive to a specific type of stimulation

dendritic spine

short outgrowth that increases the surface area available for synapses

axon

thin fiber of constant diameter

myelin sheath

insulating material that covers vertebrate axon

node of Ranvier

interruptions in the myelin sheath of vertebrate axons

presynaptic terminal

point where an axon releases chemicals

afferent axon

structure that brings information into a structure

efferent axon

structure that carries information away from a structure

intrinsic neuron

cell whose axons and dendrites are all confined within a given structure

glia

type of cell in the nervous system that does not conduct impulses over long distances

radial glia

cell that guides neuron migration and axon and dendrite growth during embryological development

active transport

protein-mediated process that expends energy to enable a molecule to cross a membrane

thiamine

B1 vitamin, necessary to use glucose

electrical gradient

difference in electrical charges between the inside and outside of the cell

selective permeability

ability of some chemicals to pass more freely than others through a membrane

concentration gradient

difference in distribution of ions across the neuron's membrane

action potential

all-or-none message sent by axon

threshold of excitation

minimum amount of membrane depolarization necessary to trigger an action potential

local anesthetic

drug that attaches to the sodium channels of the membrane, stopping action potentials

propagation of the action potential

transmission of an action potential down an axon

refractory period

time when the cell resists the production of further action potentials

absolute refractory period

time when the membrane is unable to produce an action potential

relative refractory period

time that requires a stronger stimulus to initiate an action potential