Biological Psychology
1 Nerve Cells and Nerve Impulses
Module 1.1 The Cells of the Nervous System
neurons:
Cells that receive information and transmit it to other cells and the brain.
membrane:
Structure that separates the inside of the cell from the outside environment.
nucleus:
Structure that contains the chromosomes.
mitochondrion:
Structure that performs metabolic activities.
ribosomes:
Sites for cell synthesis of new protein molecules.
endoplasmic reticulum:
Network of thin tubes that transport newly synthesized proteins to other locations.
motor neuron:
Neuron that receives excitation from other neurons and conducts impulses to a muscle.
sensory neuron:
Neuron that is highly sensitive to a specific type of stimulation.
dendrites:
Branching fibers from a neuron that receive information from other neurons.
dendritic spines:
Short outgrowths that increase the surface area available for synapses.
cell body or soma:
Structure containing the nucleus, ribosomes, and mitochondria.
axon:
Thin fiber of constant diameter; the neuron’s information sender.
myelin sheath:
Insulating material that covers vertebrate axon.
nodes of Ranvier:
Interruptions in the myelin sheath of vertebrate axons.
presynaptic terminal (or end bulb or bouton):
Point where an axon releases chemicals.
afferent axon:
Axon that brings information into a structure.
efferent axon:
Neuron that carries information away from a structure.
interneuron or intrinsic neuron:
Neuron whose axons and dendrites are all confined within a given structure.
glia:
Type of cell in the nervous system that, in contrast to neurons, does not conduct impulses over long
distances.
- astrocytes:
Star-shaped glia that synchronize the activity of the axons.
, - microglia:
Cells that remove waste material and other microorganisms from the nervous system.
- oligodendrocytes:
Glia cells that build myelin sheaths.
- Schwann cells:
Glia cells that build myelin sheaths.
- radial glia:
Cells that guide the migration of neurons and the growth of axons and dendrites during
embryological development.
blood-brain barrier:
Mechanism that excludes most chemicals from the brain.
(small, uncharged molecules such as O2, CO2 and H2O and molecules that dissolve in fats cross the
barrier passively; glucose, amino acids, purines, choline, certain vitamins and iron pass it actively).
active transport:
A protein-mediated process that expends energy to enable a molecule to cross a membrane.
glucose:
A simple sugar. (vertebrate neurons depend almost entirely on glucose for nutrition).
thiamine:
A B1 vitamin necessary to use glucose.
Module 1.2 The Nerve Impulse
The Resting Potential of the Neuron
electrical gradient or polarization:
Difference in electrical charges between the inside and outside of the cell.
resting potential:
Condition of a neuron’s membrane when it has not been stimulated or inhibited. (typical level: -70
mV).
selective permeability:
Ability of some chemicals to pass more freely than others through a membrane.
sodium-potassium pump:
Mechanism that actively transports sodium (Na+) ions out of the cell while drawing in two potassium
(K+) ions.
concentration gradient:
Difference in distribution of ions across the neuron’s membrane.
The Action Potential
action potential:
All-or-none messages sent by axon.
hyperpolarization:
Increased polarization across a membrane.
depolarize (depolarization):
To reduce polarization toward zero across a membrane.
threshold of excitation:
Minimum amount of membrane depolarization necessary to trigger an action potential.
all-or-none law:
Principle that the amplitude and velocity of an action potential are independent of the stimulus that
initiated it.
voltage-gated channels:
Membrane channel whose permeability to sodium (or some other ion) depends on the volt difference
across the membrane.
,local anesthetic:
Drugs that attach to the sodium channels of the membrane, stopping action potentials.
Propagation of the Action Potential
propagation of the action potential:
Transmission of an action potential down an axon.
The Myelin Sheath and Saltatory Conduction
myelin:
An insulating material composed of fats and proteins.
myelinated axons:
Axons covered with myelin sheaths.
saltatory conduction:
The jumping of action potentials from node to node.
refractory period:
Time when the cell resists the production of further action potentials.
absolute refractory period:
A time when the membrane is unable to produce an action potential.
relative refractory period:
Time after the absolute refractory period that requires a stronger stimulus to initiate an action
potential.
Local Neurons
local neurons:
Neurons without an axon.
graded potential:
A membrane potential that varies in magnitude in proportion to the intensity of the stimulus.
2 Synapses
Module 2.1 The Concept of the Synapse
Properties of Synapses
synapse:
A specialized gap as a point of communication between two neurons.
reflexes:
Automatic muscular responses to stimuli.
reflex arc:
A circuit from sensory neuron to muscle response.
temporal summation:
A cumulative effect of repeated stimuli within a brief time.
presynaptic neuron:
Neuron that delivers transmission to another neuron.
postsynaptic neuron:
Neuron that receives transmission from another neuron.
excitatory postsynaptic potential (EPSP):
Graded depolarization. (sodium ions flow into the neuron).
spatial summation:
Combination of effects of activity from two or more synapses onto a single neuron.
inhibitory postsynaptic potential (IPSP):
Temporary hyperpolarization of a membrane. (synaptic input selectively opens the gates for
, potassium (+) ions to leave the cell or for chloride (-) ions to enter the cell).
Relationship among EPSP, IPSP, and Action Potentials
spontaneous firing rate:
A periodic production of action potentials even without synaptic input.
Module 2.2 Chemical Events at the Synapse
The Discovery of Chemical Transmission at Synapses
The Sequence of Chemical Events at a Synapse
neurotransmitters:
Chemicals released by neurons that affect other neurons.
nitric oxide (NO):
A gas (neurotransmitter) released by many small local neurons.
catecholamines:
Compounds that contain a catechol and an amine group (e.g. dopamine, norepinephrine,
epinephrine).
vesicles:
Tiny nearly spherical packets filled with neurotransmitter molecules.
MAO (monoamine oxidase):
Enzyme that converts catecholamines and serotonin into synaptically inactive chemicals.
exocytosis:
A release of neurotransmitter from the presynaptic neuron into the synaptic cleft.
ionotropic effects:
Synaptic effects that depend on the rapid opening of some kind of gate in the membrane.
transmitter-gated channel or ligand-gated channel:
Ion channel that opens temporarily when a neurotransmitter binds to it.
metabotropic effects:
A sequence of metabolic reactions that produce slow and long-lasting effects at a synapse.
G protein:
A protein coupled to guanosine triphosphate (GTP), an energy-storing molecule.
second messenger:
A chemical that, when activated by a neurotransmitter, initiates communication to many areas within
the neuron.
neuromodulators:
Chains of amino acids.
hallucinogenic drugs:
Drugs that distort perception. (e.g. LSD binds to one type of serotonin receptor).
nicotine:
A stimulant drug that stimulates certain acetylcholine receptors. (binds to one type of acetylcholine
receptor)
opiate drugs:
Drugs derived from the opium poppy. (bind to endorphin receptors).
acetylcholinesterase:
Enzyme that breaks down acetylcholine into acetate and choline.
reuptake:
Reabsorption of a neurotransmitter by the presynaptic terminal.
transporter:
Special membrane protein where reuptake occurs if the neurotransmitter binds to it.
COMT (catechol-o-methyltransferase):
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