chapter 2 Flashcards
central nervous system
the brain and spinal cord
peripheral nervous system
the part of the nervous system outside of the brain and spinal cord, including the nerves attached to the brain and spinal cord
nerves
bundles of individual neurons contained within a protective membrane that relay sensory to the CNS from the body and relay motor information from the CNS to the rest of the body.
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 central nervous system that controls the contraction of a muscle or the secretion of a gland
interneuron
a neuron located entirely within the central nervous system
soma
the cell body of a neuron which contains the nucleus
dendrite
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
axon
the long, thin, cylindrical structure that conveys information from the soma of a neuron to its terminal buttons
axoplasmic transport
an active process by which substances are propelled along microtubules that run the length of the axon
anterograde
in a direction along an axon from the cell body toward the terminal buttons
retrograde
in a direction along an axon from the terminal buttons toward the cell body
myelin sheath
a sheath that surrounds axons and insulates them, preventing messages from spreading between adjacent axons
terminal buttons
the bud at the end of a branch of an axon; forms synapses with another neuron; sends information 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
cytoskeleton
formed of microtubules and other protein fibers, linked to each other and forming a cohesive mass that gives a cell its shape
microtubule
a long strand of bundles of protein filaments arranged around a hollow core; part of the cytoskeleton and involved in transporting substances from place to place within the cell (tracks for the axoplasmic transport)
cytoplasm
the viscous, semiliquid substance contained in the interior of a cell
nucleus
a structure in the central region of a cell, containing the chromosomes
chromosome
a strand of dna, with associated proteins, found in the nucleus; carries genetic information
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
enzyme
a molecule that controls a chemical reaction, combining two substances or breaking a substance into two parts
mitochondria
organelles that are responsible for extracting energy from nutrients
adenosine triphosphate (ATP)
a molecule of prime importance to cellular energy metabolism; its breakdown liberates energy
gila
the supporting cells of the central nervous system
astrocyte
a gila cell that provides support for neurons of the central nervous system, provides nutrients and other 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
oligodendrocytes
a type of gilial cell in the central nervous system that forms myelin sheath
node of ranvier
a naked portion of a myelinated axon between adjacent oligodendroglia or schwann cells
microgila
the smallest of glial cells; they act as phagocytes and protect the brain from invading microorganisms
schwann cells
a cell in the peripheral nervous system 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; poison’s can be detected there and can initiate vomiting
membrane potential
the electrical charge across a cell membrane; the difference in electrical potential inside and outside the cell
resting potential
the membrane potential of a neuron when it is not being altered by excitatory or inhibitory postsynaptic potentials; approximately -70mV in many neurons
hyperpolarization
an increase in the membrane potential of a cell, relative to the normal resting potential (its more negative than its outside)
depolarization
reduction toward zero of the membrane potential of a cell from its normal resting potential ( its more positive than its outside)
threshold of excitation
the value of the membrane potential that must be reached to produce an action potential
action potential
the brief electrical impulse that provides the basis for conduction of information along an axon
diffusion
movement of molecules from regions of high concentration to regions of low concentration
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 transporters
a protein found in the membrane of all cells that extrudes sodium ions from and transports potassium ions into the cell. Pump three sodium ions out for every two potassium ions in.
ion channel
a specialized 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 information being transmitted in an axon are represented by variations in the rate at which that axon fires
saltatory conduction
conduction of action potentials by myelinated axons. the action potential appears to jump from one node of ranvier to the next
postsynaptic potential
brief depolarizations or hyperpolarization that increase or decrease the rate of action potentials in the axon of the postsynaptic neuron
binding site
the location on a receptor protein to which a ligand binds
ligand
a chemical that binds with the binding site of a receptor
dendritic spine
a small bud on the surface of a dendrite, with which a terminal button of another neuron forms a synapse
presynaptic membrane
the membrane of a terminal button that lies adjacent to the postsynaptic membrane and through which the neurotransmitter is released
postsynaptic membrane
the cell membrane opposite the terminal button in a synapse; the membrane of the cell that receives the message
synaptic vesicle
a small, hollow, beadlike structure found in terminal buttons; contains molecules of a neurotransmitter
postsynaptic receptor
a receptor molecule in the postsynaptic membrane of a synapse that contains a binding site for a neurotransmitter
neurotransmitter-dependent ion channel
an ion channel that opens when a molecule of a neurotransmitter binds with a postsynaptic receptor
ionotropic receptor
a receptor that contains a binding site for a neurotransmitter and an ion channel that opens when a molecule of the neurotransmitter attaches to the binding site
metabotropic receptor
a receptor that contains a binding site for a neurotransmitter; activates an enzyme that begins a series of events that opens an ion channel elsewhere in the membrane of the cell when a molecule of the neurotransmitter attaches to the binding site
G protein
a protein coupled to a metabotropic receptor; conveys messages to other molecules when a ligand binds with and activates the receptor
second messenger
a chemical produced when a G protein activates an enzyme; carries a signal that results in the opening of the ion channel or causes other events to occur in the cell
excitatory postsynaptic potential
an excitatory depolarization of the postsynaptic membrane of a synapse caused by the liberation of a neurotransmitter by the terminal button
inhibitory postsynaptic potential
an inhibitory hyperpolarization of the postsynaptic membrane of a synapse caused by the liberation of a neurotransmitter by the terminal button
reuptake
the reentry of a neurotransmitter released from a terminal button back through its membrane. this process terminates the postsynaptic potential
enzymatic deactivation
the destruction of a neurotransmitter by an enzyme after its release
acetylcholinesterase
the enzyme that destroys acetylcholine soon after it is released from the terminal buttons. this action terminates the postsynaptic potential
acetylcholine
a neurotransmitter found in the brain, spinal cord, and parts of the peripheral nervous system; responsible for muscular contraction
neural integration
the process by which inhibitory and excitatory postsynaptic potentials summate and control the rate of firing of a neuron
autoreceptor
a receptor molecule located on a neuron that responds to the neurotransmitter released by that neuron
presynaptic inhibition
the action of a presynaptic terminal button in an axoaxonic synapses; reduces the amount of neurotransmitter released by the postsynaptic terminal button
presynaptic facilitation
the action of a presynaptic terminal button in an axoaxonic synapse; increases the amount of neurotransmitter released by the postsynaptic terminal button
neuromodulator
a naturally secreted substance that acts like a neurotransmitter except that it is not restricted to the synaptic cleft but diffuses through the extracellular fluid
peptide
a chain of amino acids joined together by peptide bonds. most neuromodulators and some hormones consist of peptide molecules
hormone
a chemical substance that is released by an endocrine gland that has effects on target cells in other organs
endocrine gland
a gland that releases chemical messengers into the extracellular fluid around capillaries and hence into the bloodstrem
target cell
the type of cell that is directly affected by a hormone or other chemical signal
