xBrain sends signals to muscles (causing behaviour) and glands (producing adjustments in
internal physiological processes)
Spinal nerves: A bundle of nerve fibres attached to the spinal cord; conveys sensory info
from the body and carries the message to the muscles and glands. Serves all the body
below the neck
Cranial nerve: A bundle of nerve fibres attached to the base of the brain; convey sensory
info from the face and head and carried messages to muscles and glands.
Neuron: A nerve cell; consists of a cell body with dendrites and an axon whose branches end
in terminal buttons that synapse with muscle fibres, gland cells, or other neurons.
Glial cell: A cell of the central nervous system that gives support for neurons and supplies
them with some essential chemicals.
Soma: A cell body; the largest part of the neuron. Contains mechanisms that control
metabolism and maintenance of cell. Receives messages from other neurons.
Dendrites: A treelike part of a neuron in which other neurons form synapses. Transmit info
Axon: A long, thin part of the neuron attached to the soma; divides into a few or many
branches, ending in terminal buttons. Carries message away from soma. These messages
called action potentials, consist of brief changes in the electrical charge of the axon.
Dendrite spine: A small bud-like protuberance on the surface of a neuron's dendrite.
Appear on neurons of the brain.
Terminal button: The rounded swelling at the end of the axon; releases transmitter
substance. Connect to dendrites, dendrite spine, soma and the axon of another neuron.
Transmitter substance: A chemical released by the terminal buttons that causes the
postsynaptic neuron to be excited or inhibited. Aka Neurotransmitters
Myelin sheath: The insulating material that encases most large axons. Increases speed of
action potential and prevents the scrambling of messages.
xMyelin: part protein, part fat--produced by special cells, the glial cells, that individually wrap
themselves around segments of the axon.
xMultiple sclerosis: immune system attacks its own body. Hard and damages tissue of brain
and spinal cord. Attacks protein of myelin sheath. Suffer from sensory/motor impairments.
xMembrane of axon is electrically charged. When resting- charged at -70millivolts with
respect to the outside
Action potential: A brief electrochemical event that is carried by an axon from the soma of
the neuron to its terminal buttons; causes the release of a transmitter substance.
xElectrical charge of an axon occurs because of unequal distribution of + and - charged
particles from inside the axon and in the fluid surrounding it
Ions: A positively or negatively charged particle; produced when many substances dissolve
Ion channel: A special protein molecule located in the membrane of a cell; controls the
entry or exit of particular ions.
Ion transporters: A special protein molecule located in the membrane of a cell; actively
transports ions into or out of the cell using the energy resources of the cell.
xOutside of membrane is positively charged and vice-versa
xWhen an axon is resting, its ion channels are closed-ions cannot move in or out
xOpening of channels permits positively charged sodium ions to enter (reverses membrane
potential at that place). This reversal causes nearby channels to open, which produces
xAs soon as the charge reverses, the ion channels close and another set of channels open for