Sensory Neuron
A neuron that detects changes in the external or internal environment and sends information about these changes to the CNS.
Motor Neuron
A neuron located within the CNS that controls the contraction of a muscle or the secretion of a gland.
Interneuron
A neuron located entirely within the CNS.
Local Interneurons
Form circuits with nearby neurons and analyze small pieces of information
Relay Interneurons
Connect circuits of local interneurons in one region of the brain with those in other regions.
Central nervous System (CNS)
Consists of the parts that are encased by the bones of the skull and spinal column (Brain and Spinal Cord)
Peripheral Nervous System (PNS)
Is found outside these bones and consists of the nerves and most of the sensory organs.
OR
The part of nervous system outside the brain and spinal cord, including the nerves attached to the brain and spinal cord.
The four structures of a Neuron
Cell body or soma, dendrites, axon, and terminal buttons.
Soma or Cell Body.
Contains the nucleus and much of the machinery that provides for the life processes of the cell. Its shape varies considerably in different kinds of neurons.
OR.
The cell body of a neuron, which contains the nucleus.
Dendrites or Dendron (Greek word for tree)
A branched, treelike structure attached to the soma of a neuron; receives information from the terminal buttons of other neurons.
Synapse
A junction between the terminal button of an axon and the membrane of another neuron. Communication goes in one direction: from their terminal button to the membrane of the other cell.
Axon
The long, thin cylindrical structure that conveys information from the soma of a neuron to its terminal buttons. (often covered by a myelin sheath)
The basic message it carries is called an action potential
Action Potential
A brief electrical/chemical event that starts at the end of the axon next to the cell body and travels toward the terminal buttons. it is like a brief pulse in a given axon it is always the same size and duration. When it reaches the point where the axon branches it splits but does not diminish in size. Each branch receives it at full strength.
Multipolar Neuron
A neuron with one axon and many dendrites attached to its soma.
Bipolar Neuron
A neuron with one axon and one dendrite attached to its soma. Their dendrites detect events occurring in the environment and communicate information about events in CNS.
Unipolar Neuron
A neuron with one axon attached to its soma; the axon divides, one branch receiving sensory information and the other sending the information into the CNS. Detect touch temperature changes and other sensory events that affect the skin.
Nerves
Are bundles of many thousands of indivdual fibers, all wrapped in a tough protective membrane.
Nerve Fibers
Transmit messages through the nerve from a sense organ to the brain or from the brain to a muscle or gland.
Terminal Button
The bud at the end of a branch of an axon; forms synapses with another neuron; sends information to that neuron.
OR.
When an action potential traveling down the axon reaches them they secrete a chemical called a neurotransmitter.
Neurotransmitter
A chemical that is released by a terminal button; has an excitatory or inhibitory effect on another neuron.
Membrane
A structure consisting principally of lipid (fatlike) molecules that defines the outer boundaries of a cell and also constitutes many of the cell organelles.
Cytoplasm
The viscous, semiliquid substance contained in the interior of a cell.
OR.
A jellylike substance that contains small specialized structures, just as the body contains specialized organs.
Mitochondria
An organelle that is responsible for extracting energy to other nutrients.
OR.
breaks down nutrients such as glucose and provides the cell with energy to perform its functions. It produces Adenosine Triphospate (ATP) which can be used throughout the cell as an energy source
Adenosine Triphosphate (ATP)
A molecule of prime importance to cellular energy metabolism; its breakdown liberates energy.
Nucleus
A structure in the central region of a cell, containing the chromosomes.
Chromosomes
A strand of DNA, with associated proteins found in the nucleus; carries genetic information.
AND
They contain the recipe for making proteins
Deoxyribonulceic Acid (DNA)
A long complex macromolecule consisting of two interconnected helical strands along with associated proteins, strands of DNA constitute the chromosomes.
Genes
Chromosomes that contain the recipes for individual proteins.
Cytoskeleton
Gives the neuron its shape. It is made of various kinds of protein strands linked to each other and forming a cohesive mass.
Enzymes
The cell's marriage brokers or divorce judges. They cause particular molecules to join together or split apart. They determine what gets made from the raw materials contained int eh cell, an they determine which molecules remain intact.
Axoplasmic Transport
is an active process that propels substances from one end of the axon to the other.
Microtubles
Bundles of thirteen filaments arranged around a hollow core. Serve as railroad tracks guiding the progress of the substances being transported.
Anterograde Axoplasmic Transport (Antero- means toward the front)
Movement from the soma to the terminal button.
It is really fast up to 500 mm a day
Energy is provided by the ATP energy is provided by the mitochondria
Retrograde Axoplasmic Transport (Retro-means toward the back)
carries substances from the terminal buttons back to the soma. About half as fast as the other. Energy is provided by ATP from the mitochondria
Glia
Glues the CNS together, but they do much more than that. They surround the neuron and hold them in place controlling their supply of nutrients and some of the chemicals they need to exchange messages with other neurons; they insulate neurons from one another so that neurons from one another so that neural messages do not get scrambled and they even act as housekeepers destroying and removing the carcasses of neurons that are killed by disease or injury.
Glia Cells
Three types: astrocytes, oligodendrocytes and microglia.
Astrocyte "Star Cell"
Provide physical support to neurons and clean up debris within the brain. They produce some chemicals that neurons need to fulfill their functions. They help to control the chemical composition of the fluid surrounding the neurons by actively taking up or releasing substances whose concentrations must be kept within critical levels. They are involved in providing nourishment to neurons.
Phagocytosis
The process by which ells engulf and digest other cells or debris caused by cellular degeneration.
Oligodendrocytes
Main purpose is to proved support to axons and to produce myelin sheath.
Myelin Sheath
A sheath that surrounds axons and insulates them preventing messages from spreading between adjacent axons.
Node of Ranvier
A naked portion of a myelinated axon, between adjacent oligodendroglia or Schwann cells.
Microglia
The smallest of glial cells; act as phagocytes and protect the brain from invading microorganisms.
Schwann Cell
A cell in the peripheral nervous system (PNS) that is wrapped around a myelinated axon, providing one segment of myelin sheath.
Blood-brain Barrier
A semipermeable barrier between the blood and the brain produced by the cells in the walls of the brain's capillaries.
Paul Ehrlich
Discovered that if a blue dye is injected into an animal's bloodstream all tissues except the brain and spinal cod will be tinted blue.
Area Postrema
A region of the medulla where the blood-brain produced by the cells in the walls of the brain's capillaries. (controls vomiting)
Lesion
A wound or injury
Ex. When a researcher destroys part of a brain it is referred to as a brain lesion.
Experimental Ablation
The removal or destruction of a portion of the brain of a laboratory animal; presumably the functions that can no longer be performed are the ones the region previously controlled. In most cases it does not involve the removal of brain tissue; instead the researcher destroys some tissue and leaves it in place.
Magnetoencephalography
A procedure that detects groups of synchronously activated neurons by means of the magnetic field induced by their electrical activity; uses an array of superconducting quantum interference devices (SQUIDs)
Excitotoxic Lesion
A brain lesion produced by intracerebral injection of an excitatory amino acid (kainic acid) It is also more selective)
Sham Lesion
A "Placebo" procedure that duplicates all the steps of producing a brain lesion except for the one that actually causes the brain damage.
Histology
Fixation and sectioning, staining and electron microscopy. (Histo-refers to body tissue)
Anterograde Labeling Method
A histological method that labels the axons and terminal buttons of neurons whose cell bodies are located in a particular region.
Retrograde Labeling Method
A histological method that labels cell bodies that give rise to the terminal buttons that form synapses with cells in a particular region.
Electroencephalogram (EEG)
An electrical brain potential recorded by placing electrodes on the scalp.
Functional MRI (FmRI)
A modification of the MRI that permits the measurement of regional metabolism in the brain.
Transcranial Magnetic Stimulation (TMS)
Stimulation of the cerebral cortex by means of magnetic fields produced by passing pulses of electricity through a coil of wire placed next to the skill; interferes with the functions of the brain region that is stimulated.
Radio Frequency Neuron
Alternating current of a very high frequency. The passage of the current through the brain tissue produces heat that kills cells in the region surrounding the tip of the electrode.
Functional Imaging
A computerized method of detection metabolic or chemical changes in particular regions of the brain.