Chapter 3: Neurophysiology Flashcards
The Generation, Transmission, and Integration of Neural Signals
Neurophysiology
The study of electrical and chemical processes in neurons.
Ions
An atom or molecule that has acquired an electrical charge by gaining or losing one or more electrons.
Anions
A negatively charged ion.
Cations
A positively charged ion.
Potassium or Sodim ions
Cations
Protei or chloride ions
Anions
Intracellular Fluid
Cytoplasm - The watery solution found within cells.
Extracellular
The fluid in the spaces between cells (interstitial fluid) and in the vascular system.
Cell Membrane
The lipid bilayer that ensheathes a cell.
Resting Membrane Potential
A difference in electrical potential across the membrane of a nerve cell during an inactive period.
Negative Polarity
A negative electrical-potential difference relative to a reference electrode.
Diffusion
The spontaneous, passive spread of molecules of one substance among molecules of another substance until a uniform concentration is achieved.
Concentration Gradient
Variation of the concentration of a substance within a region.
Ion Channels
A pore in the cell membrane that permits the passage of certain ions through the membrane when the channel is open.
Potassium Ions (K+)
A potassium atom that carries a positive charge because it has lost one electron.
Selective Permeability
The property of a membrane that allows some substances to pass through, but not others.
Sodium Ions (Na +)
A sodium atom that carries a positive charge because it has lost one electron.
Equilibrium
The state in which the number of ions crossing a membrane in one direction is matched by the number crossing in the opposite direction.
Sodium-Potassium Pump
The energetically expensive mechanism that pushes sodium ions out of a cell, and potassium ions in.
Electrostatic Pressure
The propensity of charged molecules or ions to move toward areas with the opposite charge.
Equilibrium Potential
The voltage across a permeable membrane that exactly counteracts the movement of ions from the side with a high concentration to the side with a low concentration.
Calcium Ions
A calcium atom that carries a double positive charge because it has lost two electrons.
Action Potentials
The propagated electrical message a neuron sends along its axon to the presynaptic axon terminals.
Hyperpolarization
An increase in membrane potential (the interior of a neuron becomes even more negative).
Depolarization
A reduction in membrane potential (the interior of a neuron becomes less negative).
Local Potentials
An electrical potential that is initiated by stimulation at a specific site, which is a graded response that spreads passively across the cell membrane, decreasing in strength with time and distance,
Threshold
The stimulus intensity that is just adequate to trigger an action potential.
All-or-None Property
The fact that the amplitude of the action potential is independent of the magnitude of the stimulus.
Afterpotentials
The positive or negative change in membrane potential that may follow an action potential.
Voltage Gated Na+ Channel
A Na+ selective channel that opens or closes in response to changes in the voltage of the local membrane potential. It mediates the action potential.
Refractory
Referring to transiently inactivated or exhausted axonal membrane
Absolute Refractory Phase
A brief period of complete insensitivity to stimuli.
Relative Refractory Phase
A period of reduced sensitivity during which only strong stimulation produces an action potential.
Axon Hillock
A cone shaped area from which the axon originates out of the cell body (integration zone).
Conduction Velocity
The speed at which an action potential is propagated along the length of an axon (section of peripheral nerve).
Saltatory Conduction
The form of conduction that is characteristic of myelinated axons, in which the action potential jumps from one node of Ranvier to the next.
Nodes of Ranvier
A gap between successive segments of the myelin sheath where the axon membrane is exposed.
Multiple Sclerosis (MS)
A disorder characterized by widespread degeneration of myelin.
Tetrodoxin (TTX)
A toxin from puffer fish ovaries that blocks the voltage gated sodium channel, preventing conduction of action potentials.
Batrachotoxin
A toxin, secreted by poison arrow frogs, that selectively interferes with Na+ channels.
Neurotransmitter
The chemical released from the presynaptic axon terminal that serves as the basis of communication between neurons.
Postsynaptic Potentials
A local potential that is initiated by stimulation at a synapse and spreads passively across the cell membrane, decreasing in strength with time and distance.
Excitatory Postsynaptic Potential (EPSP)
A depolarizing potential in the postsynaptic neuron that is caused by excitatory connections. ESPSs increase the probability that the postsynaptic neuron will fire an action potential.
Synaptic Delay
The brief delay between the arrival of an action potential at the axon terminal and the creation of a postsynaptic potential.
Inhibitory Postsynaptic Potential (IPSP)
A hyper polarizing potential in the postsynaptic neuron that is caused by inhibitory connections. IPSPs decrease the probability that the postsynaptic neuron will fire an action potential.
Chloride Ions (CI-)
A chlorine atom that carries a negative charge because it has gained one electron.
Spatial Summation
The summation at the axon hillock of postsynaptic potentials from across the cell body. If this summation reaches threshold, an action potential is triggered.
Temporal Summaton
The summation of postsynaptic potentials that reach the axon hillock at different times. The closer in time the potentials occur, the more complete the summation.
Exocytosis
The process by which a synaptic vesicle fuses with the presynaptic terminal membrane to release neurotransmitter into the synaptic cleft.
Botulinum Toxin
A toxin that splits SNAREs, disabling neurotransmitter release (botox).
Tetanus Toxin
A toxin that splits SNAREs, disabling neurotransmitter release.
Ligand
A substance that binds to receptor molecules, such as those at the surface of the cell.
Acetylcholine (ACh)
A neurotransmitter produced and released by parasympathetic postganglionic neurons, motor neurons, and neurons in the brain.
Receptor Molecules
A protein that binds and reacts to molecules of a neurotransmitter, hormone, or drug.
Endogenous Ligands
Any substance that is produced within the body and selectively binds to the type of receptor that is under study.
Exogenous Ligands
Any substance that originates outside the body and selectively binds to the type of receptor that is under study.
Bungarotoxin
A neurotoxin from the venom of the banded krait that selectively blocks acetylcholine receptors.
Agonists
A molecule, usually a drug, that binds a receptor molecule and initiates a response like that of another molecule, usually a neurotransmitter.
Antagonists
- A molecule (a drug) that interferes with or prevents the action of a transmitter.
- A muscle that counteracts the effect of another muscle.
Cholinergic
Referring to systems that use acetylcholine as a synaptic transmitter.
Upregulation
A compensatory (making up for a loss) increase in receptor availability at the synapses of a neuron.
Downregulation
A compensatory (making up for a loss) reduction in receptor availability at the synapses of a neuron.
Ionotropic Receptors
A receptor protein that includes an ion channel that is opened when the receptor is bound by a neurotransmitter molecule.
Ligand-Gated Ion Channels
An ion channel that opens or closes in response to the prescence of a particular chemical.
Metabotropic Receptors
A receptor protein that does not contain an ion channel but may (when activated) use a second messenger system to alter the functioning of the postsynaptic cell.
G Proteins
A class of proteins that are next to the intracellular portion of a receptor and that are activated when the receptor binds an appropriate ligand on the extracellular surface.
Second Messenger
A substance in a target cell that amplifies the effects of synaptic or hormonal activity and regulates activity within the target cell.
Degradation
The chemical breakdown of a neurotransmitter into inactive metabolites.
Reuptake
The process by which released synaptic transmitter molecules are taken up for reuse by the presynaptic neuron, thus stopping synaptic activity.
Transporters
A specialized receptor in the presynaptic membrane that recognizes neurotransmitter molecules and returns them to the presynaptic neuron for reuse.
Autoreceptors
A receptor for a synaptic transmitter that is located in the presynaptic membrane, telling the axon terminal how much transmitter has been released.
Axodendritic
Referring to a synapse in which a presynaptic axon terminal synapses onto a dendrite of the post synaptic neuron, either via a dendritic spine or directly onto the dendrite itself.
Axosomatic
Referring to a synapse in which a presynaptic axon terminal synapses onto the cell body of the postsynaptic neuron.
Dendrodendritic
Referring to a synapse in which a synaptic connection forms between the dendrites of two neurons.
Ectopic Transmission
Cell to cell communication based on the release of neurotransmitter in regions outside traditional synapses.
Non Directed Synapses
A type of synapse in which the presynaptic and postsynaptic cells are not in close apposition. The neurotransmitter is released by axonal varicosities and diffuses away to affect wide regions of tissue.
Retrograde Synapse
A synapse in which a signal flows from the postsynaptic neuron to the presynaptic neuron, thus counter to the usual direction of synaptic communication.
Electrical Synapse
The region between neurons where the membranes are so close that changes in potential can flow from one to the other without being translated into a chemical message.
Connexons
An assembly of proteins that forms an open ion channel between two neurons, making an electrical synapse between them.
Neural Chain
A simple neural circuit in which neurons are connected linearly, end to end.
Knee Jerk Reflex
A variant of the stretch reflex in which stretching of the tendon below the knee leads to an upward kick of the leg.
Convergence
The phenomenon of neural connections in which many cells send signals to a single cell.
Divergence
The phenomenon of neural connections in which one cell sends signals to many other cells.
Electroencephalogram (EEG)
A recording of gross electrical activity of the brain recorded from electrodes placed on the scalp.
Epilepsy
A brain disorder marked by major sudden changed in the electrophysiological state of the brain (seizures).
Seizure
An epileptic episode.
Tonic Clonic Seizures
A type of generalized epileptic seizure in which nerve cells fire in high frequency bursts.
Simple Partial Seizures
A seizure that is characterized by a spike and wave EEQ and often involves a loss of awareness and inability to recall events surrounding the seizure.
Complex Partial Seizures
A type of epileptic seizure that doesn’t involve the entire brain and therefore can cause a wide variety of symptoms.
Aura
In epilepsy, the unusual sensations or premonition that may precede the beginning of a seizure.
Kindling
A method of experimentally inducing an epileptic seizure by repeatedly stimulating a brain region.
Event Related Potentials (ERPs)
Averaged EEG recordings measuring brain responses to repeated presentations of a stimulus.
Optogenetics
The introduction of genes into neurons that makes them electrically respond to light.
Channelrhodopsin
An ion channel protein that when stimulated by light, depolarizes neurons.
Halorhodopsin
An ion channel protein that when stimulated by light hyper polarizes neurons.
