Chapter4 Flashcards
Membrane potential
Difference in electrical charge between the inside and the outside of the cell.
Microelectrodes
Extremely fine recording electrodes, which are used for intracellular recordings.
Resting potential
Resting state of a neuron, about -70mV. Neuron is said to be polarized.
Ions
Positively or negatively charged particles.
Ion channels
Specialized pores in the neural membranes that ions pass through. Each one is specialized for the passage of a specific particle.
Sodium-potassium pumps
Active transport mechanisms that pump Na+ ions out of neurons and K+ ions into the neurons.
Transporters
Mechanisms in the membrane of a cell that actively transport opens or molecules across the membrane.
Depolarize
Decreasing the resting membrane potential of the neuron…..membranes becomes more positive
Hyperpolarize
Increasing the resting membrane potential of the neuron.
Excitatory postsynaptic potentials (EPSPs)
Graded postsynaptic depolarizations, increase the likelihood of generating an action potential.
Inhibitory postsynaptic potentials (IPSPs)
Graded postsynaptic hyperpolarizations, decreases the likelihood of generating an action potential.
Graded responses
Amplitudes are proportional to the intensity of the signals that elicit them. Weak signals elicit small postsynaptic potentials, strong signals elicit large postsynaptic potentials.
Neurotransmitters
Chemicals released from neurons at terminal buttons and interact with specialized receptor molecules on the next neuron- first messengers.
Axon hillock
The conical structure at the junction between the cell body and the axon.
Axon initial segment
Where action potentials are generated, adjacent to the axon hillock.
Threshold of excitation
The level of depolarization necessary to elicit an action potential, usually about -65mV.
Action potential
Massive, momentary reversal of the membrane potential from about -70mV to +50mV.
All-or-none responses
Responses that are not graded, they either occur to their full extent or do not occur at all.
Integration
Adding or combining a number of individual signals into one overall signal.
Spatial summation
The integration of signals that occur at different sites on the neuron’s membrane.
Temporal summation
Postsynaptic potentials produced in rapid succession at the same synapse sum to form a greater signal.
Voltage-activated ion channels
Ion channels that open or close in response to the changes in the level of the membrane potential.
Absolute refractory period
Brief period of about 1 to 2 milliseconds after the initiation of an action potential during which it is impossible to elicit a second one.
Relative refractory period
Period during which it is possible to fire the neuron again but only by applying higher-than-normal levels of stimulation.
Antidromic conduction
If electrical stimulation of sufficient intensity is applied to the terminal end of an axon, and action potential will be generated and will travel along the axon back to the cell body.
Orthodromic conduction
Axonal conduction in the natural direction -cell body to terminal ends.
Nodes of ranvier
Gaps between adjacent myelin segments.
Saltatory conduction
Transmission of action potentials in myelinated axons.
Dendritic spines
Nodes of various shapes that are located on the surface of many dendrites. Where most axodendritic synapses terminate.
Directed synapses
Synapse at which the site of neurotransmitter release and the sire of neurotransmitter reception are in close proximity.
Nondirected synapses
Synapses at which the site of release is at some distance from the site of reception.
Neuropeptides
Short amino acid chains comprising between 3 and 36 amino acids. Large neurotransmitters.
Synaptic vesicles
Small spherical membranes that store neurotransmitter molecules and releases them into the synaptic clef.
Golgi complex
Packages neurotransmitteres into synaptic vesicles.
Coexistence
Many neurons contain two neurotransmitters. Involves one small-molecule neurotransmitter and a neuropeptide.
Exocytosis
Process of neurotransmitter release.
Receptors
Where neurotransmitters bind in the postsynaptic membrane.
Ligand
Any molecule that binds to another. Ex: neurotransmitter ___ of its receptor.
Receptor subtypes
The different types of receptors to which a particular neurotransmitter can bind.
Ionotropic receptors
Associated with ligandactivated ion channels.
Metabotropic receptors
Associated with signal proteins and G proteins.
G proteins
Guanosine-triphosphate-sensitive proteins. Proteins that are located inside neurons and are attached to metabotropic receptors in the cell membrane.
Second messenger
A chemical synthesized in a neuron in response to the binding of a neurotransmitter to a metabotropic receptor in it’s cell membrane.
Autoreceptors
Metabotropic receptors that have two unconventional characteristics: bind to their neuron’s own neurotransmitter molecules and they are located in the presynaptic rather than the post synaptic membrane.
Reuptake
More common of the two deactivating mechanisms. Draw neurotransmitters back into the presynaptic buttons by transporter mechanisms.
Enzymatic degradation
A deactivating mechanisms where there is a breakdown of the chemical by enzymes.
Enzymes
Proteins that stimulate or inhibit biochemical reactions without being affected by them.
Acetylcholinesterase
An enzyme used to breakdown acetylcholine in enzymatic degradation.
Gap junctions
Narrow spaces between adjacent cells that are bridged by fine, tubular, cytoplasms-filled proteins called, connexins. They transmit signals more rapidly than chemical synapses.
Axodendritic synapses
Synapses of axon terminal buttons on dendrites.
Axosomatic synapses
Synapses of axon terminal buttons on somas
Dendrodendritic synapses
Often capable of transmission in either direction.
Axoaxonic synapses
Mediate presynaptic facilitation and inhibition.
Amino acid neurotransmitters
A class of small-molecule neurotransmitters, which includes the amino acids glutamate and GABA…. usually found in fast acting synapses
Glutamate
The brain’s most prevalent excitatory neurotransmitter, whose excessive release cause much of the brain damage resulting from cerebra ischemia.
Aspartate
An amino acid neurotransmitter that is a constituent of many the proteins that we eat.
Glycine
An amino acid neurotransmitter that is a constituent of the proteins that we eat.
Gamma-aminobutyric acid (GABA)
An amino acid neurotransmitter that is synthesized by a simple modification of the structure of glutamate and is the most prevalent inhibitory neurotransmitter.
Monoamine neurotransmitters
Slightly larger than amino acid neurotransmitters with more diffuse effects.
Dopamine
One of the three catecholamine neurotransmitters; dopaminergic neurons are damages in Parkinson’s disease.
Epinephrine
One of the three catecholamine neurotransmitters.
Norepinephrine
One of the three catecholamine neurotransmitters.
Serotonin
An indolamine neurotransmitter; the only member of this class of monamine neurotransmitters found in the mammalian nervous system.
Catecholamines
The three monoamine neurotransmitters that are synthesizes from the amino acid tyrosine: dopamine, epinephrine, and norepinephrine.
Indolamines
The class of monoamine neurotransmitters that are synthesized from tryptophan; serotonin is the only member of this class found in mammalian nervous system.
Acetylcholine
A small-molecule neurotransmitter that is at neuromuscular junctions, synapses in the autonomic nervous system, and at synapses at several parts of the central nervous system.
Soluble-gas neurotransmitters
Produced in neural cytoplasm and immediately diffuse through the cell membrane into the extracellular fluid and into nearby cells. Exists for only a few seconds and are soluble in lipids.
Nitric oxide
A soluble-gas neurotransmitter.
Carbon monoxide
A soluble-gas neurotransmitter.
Endocannabinoids
A class of unconventional neurotransmitters that are similar to THC. They are produced immediately before they are released. They are synthesized in fatty compounds in the cell membrane, are released from dendrites and cell body, and have most the effects on the presynaptic neurons, inhibiting subsequent synaptic transmission.
Anandamide
Most widely studied endocannabinoids.
Neuropeptide transmitters
Large molecule neurotransmitters. Consists of 5 groups: pituitary peptides, hypothalamic peptides, brain-gut peptides, opioid peptides, and miscellaneous peptides.
Pituitary peptides
Contains neuropeptides that were first identified as hormones released by the pituitary.
Hypothalamic peptides
Contains neuropeptides that were first identified as hormones released by the hypothalamus.
Brain-gut peptides
Contains neuropeptides that were first discovered int he gut.
Opioid peptides
Contains neuropeptides that are similar in structure to the active ingredient in opium.
Miscellaneous peptides
Catch-all category of neuropeptides that contain all of the neuropeptides that do not fit into one of the other four categories.
Agonists
Drugs that facilitate the effects of a particular neurotransmitter.
Antagonists
Drugs that inhibit the effects of a particular neurotransmitter.
Receptor blockers
Antagonistic drug that binds to receptors without activating them, blocking the access of the usual neurotransmitter.
Atropine
Receptor blocker that exerts it’s antagonistic effect by binding to muscarinic receptors. Pupil dilating effect.
Botox
Botulinium toxin. A neurotoxin released by a bacterium often found in spoiled food. It is a nicotinic antagonist that blocks the release of acetylcholine at neuromuscular junctions.
Periaqueductal gray (PAG)
The gray matter around the cerebral aqueduct, which contains opiate receptors and activates a descending analgesia circuit. Connects the third and fourth ventricles.
Endogenous
Naturally occurring in the body.
Enkephalins
The first class of endogenous opioids to be discovered.
Endorphins
A class of endogenous opioids.
