Chapter 2 Flashcards
Central nervous System
brain and spinal cord
Peripheral Nervous System (PNS)
The part of the nervous system outside of the brain and the 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 from the body to the central nervous system and relay motor information from the central nervous system to the body
Axoplasmic Transport
An active process by which substances are propelled along microtubes that run the length of the axon; occurs only within one axon
Anterograde
In a direction along an axon from the cell body toward the terminal button
Retrograde
In a direction along an axon from the terminal button toward the cell body
Membrane
Structure consisting principally of lipid molecules that defines the outer boundaries of a cell, and also constitutes many of the cell organelles
Presynaptic cell
Sending cell
Postsynaptic cell
Receiving cell
Action Potential
Carried by an axon; involves both an electrical and chemical component to messages; electrical and chemical event that starts near the end of the axon, near cell body and travels to the terminal buttons; always same size and duration; when it reaches end of terminal branches, it splits, but does not lesson in size or duration, and each branch receives full strength of action potential
Cytoskeleton
Formed of microtubes and other protein fibers, linked to each other, and forming a cohesive mass that gives the cell its shape
Microtubule
A long strand of bundles of protein filaments arranged around a hollow core; part of the crytoskeleton and involved in transporting substances from place to place within the cell
Cytoplasm
Semi liquid substance contained in the interior of a cell
Chromosome
Strand of DNA, with associated proteins, found in the nucleus; carries genetic information
Deoxyribonucleic Acid (DNA)
A long complex macro-molecule consisting of two interconnected, helix strands; along with associated proteins, strands of DNA constitute the chromosomes
Gene
Functional unit of the chromosomes, which direct 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; breaks down glucose and other nutrients
Adenosine Triphosphate (ATP)
A molecule of prime importance to cellular energy, metabolism; it’s breakdown liberates energy
Glia
The supporting cells of the central nervous system
Astrocyte
A glia 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
Process by which cells engulf and digest other cells or debris caused by cellular degeneration
Oligodendrocyte
A type of glia cell in the CNS that forms myelin sheaths
Microglia
The smallest of the glial cells; they act as phagocytes and protect the brain from invading microorganisms
Schwann Cell
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 semi-permeable barrier between the blood and the brain produced by the cells in the walls of the brains capillaries
Area Postrema
Region in the medulla where the blood-brain barrier is weaker; poisons can be detected there and initiate vomiting
Membrane potential
The electrical charge across a 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; when the inside of an axon becomes more negative than the outside
Depolarization
Reduction (toward zero) of the membrane potential of a cell from its normal resting position; inside of axon is more positive than the outside
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
Ion
A charged molecule
Cation
Positively charged ion
Anion
Negatively charged ion
Electrostatic Pressure
The attractive force between atomic particles charged with opposite signs with repulsive force between atomic particles charge with the same sign
Intracellular Fluid
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
Specialized protein molecule that permits specific ions to enter or leave cells
Voltage Dependent Ion Channel
Ion channel that opens or closes, according to the value of the membrane potential; first, membrane must reach level of excitation, sodium channels in membrane open, Na+ rushes in, propelled by forces of diffusion and electrostatic pressure
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; an action potential either occurs full strength, or it does not occur at all; it does not grow or diminish in size or strength
Rate Law
The principle that variations in the intensity of stimulus or other information, being transmitted in an axon, are represented by variations in the rate at which the axons fire
Salatory Conduction
Conduction of action potential‘s by myelinated axons. The action potential appears to jump from one node of Ranvier to the next; action potential gets re-triggered, or repeated at each node of Ranvier; axons need less energy to maintain sodium balance; speeds up the process
Decremental Conduction
Electrical messages, get smaller as they are passed on the axon, but it is still strong enough to trigger a new action potential at the next node; a decrease in the size of the electrical message
Refractory
When the channel cells become blocked and cannot be opened again
Rate of firing action potential
Represents an axons variable information; a high firing rate causes a strong muscular contraction, and this is caused by strong stimulus
Synaptic Transition
Primary means of communication between neurons; relay messages from one neuron to the other across the synapse
Postsynaptic potential
Alterations in the membrane potential of a postsynaptic neuron, produced by liberation of neurotransmitter at the synapse; brief depolarizations, or hyperpolarizations that increase, or decease the rate of action potential’s in the action of the postsynaptic neuron
Binding Site
Neurotransmitters exert their effects on cells by attaching to a particular region of receptor molecules, called the binding site; the location on receptor protein, to which a ligand binds; neurotransmitter molecules fit into a binding site the way to key fits into a lock
Ligand
A chemical that binds with the binding site of receptors; neurotransmitters are naturally occurring Ligands produced, and released by neurons; can only bind to receptors, cannot enter a neuron through binding site, although they may open ion channels through which ions can enter the cell
Dendritic Spine
A small bump 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
Cell membrane opposite of the terminal button in a synapse; the membrane of a cell that receives the message
Synaptic Vesicles
Small bubble like structure found in the terminal button; contains molecules of neurotransmitter; found in greatest number around the part of the presynaptic membrane that faces the synaptic cleft
Postsynaptic receptor
Receptor molecules in the postsynaptic membrane of a synapse that can find a binding site for a neurotransmitter; sites of special proteins
Neurotransmitter-dependent ion channels
Allow the passage of specific ions in and out of cells; opening, when a molecule of a neurotransmitter binds with the postsynaptic receptor
Iontropic receptor
Direct method, simpler; a neurotransmitter, dependent ion channel equipped with its own binding site; when a molecule of appropriate neurotransmitter attaches to it, the ion channel opens
Metabotropic receptor
Direct method of opening ion channels; requires the cell to spend metabolic energy; a receptor that contains a binding site for 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 metabotropic receptors conveys messages to other molecules, when a ligand binds with and activates the receptor
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 snap caused by the liberation of a neurotransmitter by the terminal buttons
Enzyme deactivation
The destruction of a Neurotransmitter by enzyme after it’s release— for example, the destruction of acetylcholine by acetylcholinesterase
Acetylcholinesterase
Enzyme that destroys acetylcholine soon after it leaves the terminal button; terminates the action potential
Acetylcholine
Neurotransmitter found in the brain, spinal cord, and parts of peripheral nervous system; responsible for muscle contraction
Neural integration
The process by which inhibitory and excitatory postsynaptic potentials summate and control the rate of firing of a neuron
Auto-receptor
A receptor molecule located on a neuron that responds to the neurotransmitter released by that neuron (respond to the neurotransmitter, they themselves released)
Presynaptic inhibition
The action of presynaptic terminal button in an axoaxonic synapse; reduces the amount of neurotransmitter released by the post synaptic terminal button
Axoaxonic Synapse
Do not contribute directly to neural integration; occurs on axon; alters amount of neurotransmitter released by the terminal buttons of the postsynaptic axon; produce presynaptic modulation: presynaptic inhibition or presynaptic facilitation
Presynaptic facilitation
The action of a presynaptic terminal button, in an axoaxonic synpase; increases the amount of neurotransmitter released by the postsynaptic button
Neuromodulator
A naturally secreted substance that acts like a neural transmitter, except that it is not restricted to the synaptic cleft, but is used through extracellular fluid; travels further, and dispersed, more widely than a neurotransmitter
Peptide
A chain of amino acids joined by peptide bonds; most neuromodulators and some hormones made of peptide bonds
Hormone
Chemical substance that is released by the endocrine gland that has effects on target cells, and in other organs
Endocrine Gland
A gland that releases chemical messengers into the extracellular fluid around capillaries, and hence into the bloodstream
Target Cell
The type of cell that is directly affected by hormone or other chemical signal
