Part 2 (Chapter 2): Structure and Function of Cells of the Nervous System Flashcards
Sensory neuron
A neuron that detects changes in the external or internal environment and sends information about these changes to the central nervous system.
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.
Central nervous system (CNS)
The brain and spinal cord.
Peripheral nervous system (PNS)
The part of the nervous system outside the brain and spinal cord, including the nerves attached to the brain and spinal cord.
Soma
The cell body of a neuron, which contains the nucleus.
Dendrite
A branched, tree-like structure attached to the soma of a neuron; receives info from the terminal buttons of other neurons.
Synapse
A junction between the terminal button of an axon and the membrane of another neuron.
Axon
The long, thin, cylindrical structure that conveys info from the soma of a neuron to its terminal buttons.
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.
Unipolar neuron
A neuron with one axon attached to its soma; the axon divides, with one branch receiving sensory info and the other sending info into the CNS.
Terminal button
The bud at the end of a branch of an axon; forms synapses with another neuron; sends info to that neuron.
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 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.
Mitochondria
An organelle that is responsible for extracting energy from nutrients.
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 chromosomes.
Chromosome
A strange of DNA, with associated proteins, found in the nucleus; carries genetic info.
Deoxyribonucleic acid (DNA)
A long, complex macromolecule consisting of two interconnected helical strands; along with associated proteins, strands of DNA constitute the chromosomes.
Gene
The functional unit of the chromosome, which directs synthesis of one or more proteins.
Cytoskeleton
Support structure formed of microtubules and other protein fibres that are linked to each other and form a cohesive mass that gives a cell its shape.
Enzyme
A molecule that controls a chemical reaction, combining two substances or breaking a substance into two parts.
Axoplasmic transport
An active process by which substances are propelled along microtubules the run the length of the axon.
Microtubule
A long strand of bundles of protein filaments arranged around a hollow core; part of the cytoskeleton and involved in transporting substances form place to place within a cell.
Glia
The supporting cells of the CNS.
Astrocyte
A glial cell that provides support for neurons of the CNS, provides nutrients and there substances, and regulates the chemical composition of the extracellular fluid.
Phagocytosis
The process by which cells engulf and digest other cells or debris caused by cellular degeneration.
Oligodendrocyte
A type of glial cell in the CNS that forms myelin sheaths.
Myelin sheath
A sheet 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; they act as phagocytes and protect the brain from invading microorganisms.
Schwann cell
A cell in the PNS that is wrapped around a myelinated axon, providing one segment of its 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.
Area postrema
A region of the medulla where the blood-brain barrier is weak; poisons can be directed there and can initiate vomiting.
Electrode
A conductive medium that can be used to apply electrical stimulation or to record electrical potentials.
Microelectrode
A very fine electrode, genreally used to record activity of individual neurons.
Membrane potential
The electrical charge across a cell membrane; the difference in electrical potential inside and outside the cell.
Oscilloscope
A laboratory instrument that is capable of displaying a graph of voltage as a function of time on the face of a cathode ray tube.
Resting potential
The membrane potential of a neuron when it is not being altered by excitatory or inhibitory postsynaptic potentials; approximately -70 mV in the giant squid axon.
Depolarisation
Reduction (towards zero) of the membrane potential of a cell from its normal resting potential.
Hyperpolarisation
An increase in the membrane potential of a call, relative to the normal resting potential.
Action potential
The brief electrical impulse that provies the basis for conduction of info along the axon.
Threshold of excitation
The value of the membrane potential that must be reached to produce an action potential.
Diffusion
Movement of molecules from regions of high concentration to regions of low concentration.
Electrolyte
An aqueous solution of a material that ionizes - namely, a soluble acid, base or salt.
Ion
A charged molecule. Cations are positively charged, and anions are negatively charged.
Electrostatic pressure
The attractive force between atomic particles charged with opposite signs or the repulsive force between atomic particles charged with the same sign.
Intracellular fluid
The fluid contained within cells.
Extracellular fluid
Body fluids located outside of cells.
Sodium-potassium transporter
A protein found in the membrane of all cells that extrudes sodium ions from and transports potassium ions into the cell.
Ion channel
A specialised protein molecule that permits specific ions to enter or leave cells.
Voltage-dependent ion channel
An ion channel that opens or closes according to the value of the membrane potential.
All-or-none law
The principle that once an action potential is triggered in an axon, it is propagated, without decrement, to the end of the fiber.
Rate law
The principle that variations in the intensity of a stimulus or other info being transmitted in an axon are represented by variations in the rate at which the axon fires.
Saltatory conduction
Conduction of action potentials by myelinated axons. The action potential appears to jump from one node of Ranview to the next.
