This document contains definitions of terms used in the neural functioning tutorial.

A

Amygdala

A collection of nuclei at the base of the temporal lobe, part of the limbic system. Plays a role in several emotional behaviors such as agression and sexual behavior.

Anterior Cerebral Artery

One of the three primary cerebral arteries. Provides blood supply primarily to the frontal and parietal lobes.

Anterior Commissure

A forebrain commissure that provides communication between structures within the temporal lobes.

Autoreceptor

A receptor molecule located in the presynaptic neuron's axon terminal. It is thought to play a role in providing feedback to the presynaptic neuron and play a role in modulating synaptic activity.

Axon

Part of the neuron that carries the neural impulse away from the soma toward the target of the neuron. This part of the neuron carries action potentials.

Axon Hillock

The portion of the axon where the axon leaves the soma. It is here that spatial and temporal summation occur and the action potential begins.

Axon Terminal

The ending of the axon that connects to the neural target. It contains the neural transmitters to be released.

C

Commissure

any fiber tract that connects between structures on the two sides of the central nervous system.

Concentration

The number of molecules of a substance per unit volume.

Concentration Gradient

The difference in level of concentration between two areas. There is a tendency for molecules to flow, by chance movements, from regions of high concentrations to low concentrations.

Corpus Callosum

The largest commissure. Provides communication across the midline for most forebrain structures.

Current

Electrical energy flowing, that is, the kinetic energy form of electricity.

D

Dendrite

Processes of the neuron that receives information from other neurons. That is these structures have places with receptors and are able to form synapses with incoming neurons.

Dendritic Stalk

The thickening of the dendrite where it forms synapses.

Depolarization Phase of the Action Potential

The initial portion of the action potential where the voltage sweeps from the resting potential past the neutral voltage to where the inside of the axon is now positive relative to the outside of the axon.

Diffusion

Diffusion is the effect that the random movement of molecules have that causes the movement of molecules from a region of high concentration to low concentration. Diffusion will stop (that is the change in the relative levels of concentration) when the concentration of the substance in solution is equal at all points.

E

Electricity

Part of the electromagnetic force carried by the movement of charged particles.

Energy

The capacity to do work. What is meant here is that energy makes things happen or change. Without energy, all things stay in their same state.

H

Hippocampus

A structure in the forebrain, part of the limbic system. Seems to be involved in spatial and memory functions.

I

Inferior Colliculus

The lower pair of two pairs of bumbs on the posterior side of the midbrain. These structures relay auditory information from brainstem auditory nuclei to the Medial Geniculate Nucleus.

Internal Carotid Artery

One of the primary arteries that supplies blood to the brain.

Ion

An electrically charged particle. Ions can be positive (e.g. Na+) or negative (e.g. Cl-). Like charges repel or push each other away, and opposite charges attract or draw each other.

K

Kinetic Energy

Energy being expended in performing work.

L

Lateral Ventricles

The two largest cavities, in the forebrain, where the cerebral spinal fluid is produced.

M

Massa Intermedia

A fiber tract that connects the two thalami.

Myelin

A sheath of fatty tissue that covers most axons on the nervous system. It serves to speed conduction my limiting true action potentials to the gaps in the sheath. Under the myelin the neural impulse moves at the speed of light. The layer is formed by Schwann Cells in the periphereral nervous system and Oligodendrocytes in the central nervous system.

N

Node of Ranvier

The gap in the myelin sheath where the action potential occurs during saltatory conduction.

Nucleus

The structure in the soma of the neuron that contains the chromosomes.

O

Occipital Horn

The most posterior porjections of the Lateral Ventricles.

Optic Chiasm

Part of the pathways that carry the visual information from the retina in the eyes to the lateral geniculat nucleus. In particular at this location, the axons carrying information from the nasal half of each retina cross, that is decussate, which the axons from the temporal retina do not decussate.

Optic Nerve

The portion of the axons that originate in the ganglion cell layer of the retina that travels from the retina to the optic chiasm.

P

Potential Energy

Energy that is available to do work.

Presynaptic Neuron

The neuron which releases the neurotransmitters into the synapse. The axon terminal is part of the presynaptic neuron.

Posterior Cerebral Artery

One of the three primary cerebral arteries. Provides blood supply primarily to the temporal and occipital lobes.

Posterior Communicating Artery

Part of the cerebral circulation, more particulary, part of the Circle of Willis that allows blood from any of the supply arteries in the neck to provide blood to all of the cerebral arteries.

Postsynaptic Neuron

The neuron that which receives the neurotransmitters released by the presynaptic neuron. It is in most synapses a dendrite or soma.

R

Receptor

A molecule in the postsynpatic neuron's membrane to which the neurotransmitters bind, which then directly or indirectly will alter the membrane potential by opening or closing ion channels.

Resting Potential

The voltage that is across the membrane of an axon when that portion of the action is not conducting an action potential but is in a state ready to conduction an action potential.

S

Soma

The part of the neuron where the nucleus is found. Most of the protein production and energy storage is performed at this point in the cell.

Sulcus

A groove on the surface of the brain.

Superior Colliculus

The top pair of the two pair of bump on the posterior surface of the midbrain. Plays a role in vision, perhaps a part of the role vision plays in orienting us to the world, and eye movements.

Sylvian Acqueduct

A connecting path for cerebral spinal fluid between the III and IV ventricles.

Sylvian Fissure

The deep groove or sulcus that marks the boundary between the frontal lobe and temporal lobe.

Synaptic Cleft

The space between the two neurons that form the synapse.

Synaptic Vesicle

A membrane structure in the axon terminal that contains the neurotransmitters until they are released.

T

Third (III) Ventricle

One of the four ventricles in brain that produce cerebrospinal fluid.  This one is located in the lower forebrain and midbrain.  It surrounds the massa intermedia.

V

Ventricle

An open area in the brain where cerebrospinal fluid is produced.  These areas help make the brain more buoyant so it rests lighter in the brain.

Voltage

A difference in electrical charge between two locations. One region is more positive than the other. This situation represents the potential energy for electricity.