PSYA01H3 Chapter Notes -Peripheral Nervous System, Myelin, Neuroplasticity
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PSY – Chap 4 Terms
Central nervous system: the brain and the spinal cord
Spinal cord: a long, thin collection of nerve cells attached to the back of the brain and running
the length of the spinal column
Nerve: a bundle of fibers that transmits information between the central nervous system and the
body’s sense organs, muscles and glands
Peripheral nervous system: the cranial and spinal nerves, that part of the nervous system
peripheral to the brain and spinal cord
Cranial nerve: a bundle of nerve fibers attached to the base of the brain; conveys sensory info
from the face and head and carries messages to muscles and glands
Spinal nerve: a bundle of nerve fibers attached to the spinal cord; conveys sensory info from the
body and carries messages to muscles and glands
Brain stem: the “stem” of the brain, including the medulla, pons, and midbrain
Cerebral hemisphere: (left and right) the largest part of the brain, covered by the cerebral
cortex and containing parts of the brain that evolved most recently
Cerebellum: a pair of hemispheres resembling the cerebral hemispheres but much smaller and
lying beneath and in back of them, controls posture and movements, especially rapid ones
Vertebra: one of the bones that encase the spinal cord and constitute the vertebral column
Meninges: the three-layered set of membranes that enclose the brain and spinal cord
Cerebrospinal fluid (CSF): the liquid in which the brain and spinal cord float, provides a
Blood-brain barrier: a barrier between the blood and the brain produced by the cells in the
walls of the brain’s capillaries, prevents some substances from passing from the blood into the
Cerebral cortex: the outer layer of the cerebral hemispheres of the brain, approximately 3mm
Grey matter: the portions of the central nervous system that are abundant in cell bodies of
neurons rather than axons.
White matter: the portions of the central nervous system that are abundant in axons rather than
cell bodies of neurons. The colour is from the presence of the axons’ myelin sheaths.
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Neuron: a nerve cell: consists of a cell body with dendrites and an axon whose branches end in
terminal buttons that synapse with muscle fibers, gland cell of other neurons.
Glial cell: a cell of the central nervous system that provides support for neurons and supplies
them with some essential chemicals.
Dendrite: a tree-like part of the neuron on which other neurons form synapses.
Dendritic spine: (post-synaptic) a small bud-like protuberance on the surface of a neuron’s
Soma: a cell body, the largest part of a neuron.
Axon: a long, thin part of a neuron attached to the soma, divides into a few or many branches,
ending in terminal buttons.
Terminal button: (pre-synaptic) the rounded swelling at the end of the axon of a neuron,
releases transmitter substance.
Neurotransmitter: a chemical released by the terminal buttons that causes the postsynaptic
neuron to be excited of inhibited.
Myelin sheath: the insulating material that encases most large axons.
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.
Ion: a positively or negatively charged particle, produced when many substances dissolve in
Ion channel: a special protein molecule located in the membrane of a cell, controls the entry or
exit of particular ions.
Ion transporter: a special protein molecule located in the membrane of a cell, actively
transports ions into or out of a cell.
All-or-none law: the principle that once an action potential is triggered in an axon, it is
propagated, without getting smaller, to the end of the axon.
Sensory neuron: a neuron that detects changes in the external or internal environment and sends
info about these changes to the central nervous system.
Motor neuron: a neuron whose terminal buttons form synapses with muscle fibers. When an
action potential travels down its axon, the associated muscle fibers will twitch.
Synapse: the junction between the terminal button of one neuron and the membrane of a muscle
fiber, a gland, or another neuron.
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