Chapter 4: Neural Conduction and Synaptic
4.1 Resting Membrane Potentials
Membrane Potential: The difference in electrical charge between the inside and outside of a cell
Microelectrodes: Extremely fine recording electrodes, which are used for intracellular recording
Resting Potential: The steady membrane potential of a neuron at rest, usually about -70 mV
Ions: Positively or negatively charged particles
Ion Channels: Pores in neural membranes through which specific ions pass.
Sodium(out)-potassium(in) pumps: Active transport pumps that pump NA+ out of neurons and K+ ions
Transporters: Mechanisms in the membrane of a cell that actively transports ions or molecules across
4.2 Generation and Conduction of Postsynaptic Potentials
Depolarize: To decrease the resting membrane potential
Hyperpolarize: to increase the resting membrane potential
Excitatory Postsynaptic potentials (EPSPs): Postsynaptic depolarizations, increase the likelihood that
the neuron will fire
Inhibitory postsynaptic potentials (IPSPs): Postsynaptic hyperpolarizations, decrease the likelihood that
the neuron will fire
Graded Responses: (Both EPSPs and IPSPs are graded responses) the amplitudes of EPSPs and IPSPs are
proportional to the signals that elicit them.
4.3 Integration of Post synaptic Potentials and Generation of Action Potentials:
Axon Hillock: The conical structure at the junction between the axon and cell body
Threshold of excitation: The level of depolarization necessary to generate an action potential, generally
Action Potential (AP): A massive, but momentary-lasting about 1 millisecond- reversal of the membrane
potential from -70 to +50mV. Follows the All or-non principal All-or-none responses: Either fire completely or do not fire at all.
Integration: Neurons integrate incoming signals in two ways: over space and over time.
Spatial summation: The integration of signals that occur on different sites of the neuron’s membrane.
Temporal Summation: The integration of neural signals that occur at different times at the same
4.4 Conduction of Action Potentials
Voltage-activated Ion Channels: Ion channels that open and close in response to changes in the level of
Absolute refractory period: A brief period (typically 1 to 2 milliseconds) after the initiation of an action
potential in the same neuron
Relative refractory period: A period after the absolute refractor period during which a higher-than-
normal amount of stimulation is necessary to make a neuron fire.
Antidromic Conduction: Axonal conduction opposite to the normal direction; conduction from axon
terminals back towards the cell body.
Orthodromic conduction: Axonal conduction in the normal direction-from the cell body toward the
Nodes of Ranvier: The gaps between adjacent myelin segments on an axon
Saltatory conduction: Conduction of an action potential from one node of Ranvier to the next along a
4.5 Synaptic Transmission: Chemical Transmissions of signals among Neurons
Dendritic Spines: The tiny nodules of various shapes that are located the surfaces of many dendrites and
the sites of the most excitatory synapses in the mature mammalian brain
Directed synapses: Synapses at which the site of neurotransmitter release and the site of
neurotransmitter reception are in close proximal distance
Nondirected synapses: Synapses at which the sites of neurotransmitter release and neurotransmitter
reception are not close together
Neuropeptide transmitters: Peptides that function as neurotransmitters, of which about 100 have been
identified; also called neuropeptides
Synaptic Vesicles: Small spherical membranes that store neurotransmitter molecules and release them
into the synaptic cleft. Golgi complex: Structures in the cell bodies and terminal buttons of neurons that package
neurotransmitters and other molecules in vesicles
Coexistence: The presence of more than one neurotransmitter in the same neuron
Exocytosis: The process of releasing a neurotransmitter
Receptors: Cells that are specialized to receive chemical, mechanical, or radiant signals from the
environment; also proteins that contain binding sites for particular neurotransmitters
Ligand: A molecule that binds to another molecule; neurotransmitters are ligands of their receptors
Receptor subtypes: The different types of receptors to which a particular neurotransmitter can bind
Ionoitropic receptors: Receptors that are associated with ligand-activated channel proteins
Metabolic Receptors: Receptors that are associated with signal proteins and G proteins
G Proteins: Proteins t