Neuro Early

animal model

a scientist's use of animals to examine the process they wish to understand in humans.

cell theory

all tissues are composed of microscopic units called cells.

natural selection

the theory in which a population evolves and changes over time and the population with the more advantageous characteristics has a greater fitness or rate of survival.

neuron doctrine

the concept that the neuron is the elementary functional unit of the brain and that neurons communicate with each other by contact, not continuity.

Nissl stain

a class of basic dyes that stain the somata of neurons. Distinguishes neurons and glia from one another.

phrenology

correlating the structure of the head with personality traits.

ventricles

hollow spaces in the brain where there is fluid.

cytosol

the watery fluid inside the cell; a salty, potassium-rich solution.

neurofilament

a type of intermediate filament found in neurons, 10nm in diameter; an important component of the neuronal cytoskeleton.

adenosine triphosphate (ATP)

the molecule that is the cell's energy source.

ribosome

a cellular organelle that assembles new proteins from amino acids according to the instructions carried by mRNA.

axon hillock

a swelling of the axon where it joins the soma.

translation

the process of synthesizing a protein molecule according to genetic instructions carried by a mRNA molecule.

retrograde transport

axoplasmic transport from an axon terminal to the soma.

astrocyte

a glial cell in the brain that supports neurons and regulates the extracellular ionic and chemical environment.

stellate cell

a neuron characterized by a radial, star-like distribution of dendrites.

oligodendroglial cell

a glial cell that provides myelin in the central nervous system.

anion

a negatively charged ion.

diffusion

the temperature-dependent movement of molecules from regions of high concentration to regions of low concentration, resulting in a more even distribution.

concentration gradient

a difference in concentration from one region to another.

phospholipid bilayer

the arrangement of phospholipid molecules that forms the basic structure of the cell membrane. The core of the bilayer is lipid, creating a barrier to water and to water-soluble ions and molecules.

membrane potential

the voltage across a cell membrane.

equilibrium potential

the electrical potential difference that exactly balances an ionic concentration gradient.

calcium pump

an ion pump that removes cytosolic Ca2+.

depolarization

a change in membrane potential, taking it from the value at rest (e.g. -65 mV) to a less negative value (e.g. 0 mV).

overshoot

the part of an action potential when the membrane potential is more positive than 0 mV.

threshold

a level of depolarization sufficient to trigger an action potential.

absolute refractory period

the period of time, measured from the onset of an action potential, during which another action potential cannot be triggered.

patch clamp

a method that enables an investigator to hold constant the membrane potential of a patch of membrane while current through a small number of membrane channels is measured.

saltatory production

propagation of an action potential down a myelinated axon.

voltage-gated potassium channel

a membrane protein forming a pore that is permeable to K+ ions and gated by depolarization of the membrane.

spike initiation zone

a region of the neuronal membrane where action potentials are normally initiated, characterized by a high density of voltage-gated sodium channels.

channelopathy

a human genetic disease caused by alterations in the structure and function of ion channels.

tetrodotoxin

a toxin that blocks Na+ permeation through voltage-gated sodium channels, thereby blocking action potentials.

action potential conduction

the process of using voltage to conduct an action potential in a cell.

active zone

a presynaptic membrane differentiation that is the site of neurotransmitter release.

secretory granule

a spherical membrane-enclosed vesicle about 100 nm in diameter containing peptides intended for secretion by exocytosis.

exocytosis

the process whereby material is released from an intracellular vesicle into the extracellular space by fusion of the vesicle membrane with the cell membrane.

autoreceptor

a receptor in the membrane of a presynaptic axon terminal that is sensitive to the neurotransmitter released by that terminal.

receptor agonist

a drug that binds to a receptor and activates it.

second messenger

a short-lived chemical signal in the cytosol that can trigger a biochemical response.

synaptic integration

the process by which EPSP and/or IPSP combine within one postsynaptic neuron, sometimes triggering one or more action potentials.

spatial summation

the combining of excitatory postsynaptic potentials generated at more than one synapse on the same cell.

temporal summation

the combining of excitatory postsynaptic potentials generated in rapid succession at the same synapse.

internal resistance

the resistance to electrical current flows longitudinally down a cable or neurite.

membrane resistance

the resistance to electrical current flow across a membrane.

shunting inhibition

a form of synaptic inhibition in which the main effect is to reduce membrane resistance, thereby shunting depolarizing current generated at excitatory synapses.

modulation

a term used to describe the actions of neurotransmitters that do not directly evoke postsynaptic potentials but modify the cellular response to EPSPs and IPSPs generated by other synapses.