solutions
sodium-potassium pump - Answer-Active transport mechanisms that pump Na+ ions out
of neurons and K+ ions in.
coexistence - Answer-The presence of more than one neurotransmitter in the same
neuron.
Enkalphins - Answer-The first class of endogenous opioids to be discovered.
glycine - Answer-An amino acid neurotransmitter that is a constituent of many of the
proteins that we eat.
nondirected synapses - Answer-Synapses at which the site of neurotransmitter release
and the site of neurotransmitter reception are not close together.
graded responses - Answer-Responses whose magnitude is indicative of the magnitude
of the stimuli that induce them.
inhibitory postsynaptic potential (IPSP) - Answer-Graded post-synaptic
hyperpolarizations, which decrease the likelihood that an action potential will be
generated.
aceytalcholine - Answer-A neurotransmitter that is created by the addition of an acetyl
group to a choline molecule.
Periaqueductal gray (PAG) - Answer-The gray matter around the cerebral aqueduct,
which contains opiate receptors and activates a descending analgesia circuit.
agonists - Answer-Drugs that facilitate the effects of a particular neurotransmitter.
Epinephrine - Answer-One of the three catecholamine neurotransmitters.
Carbon monoxide - Answer-A soluble-gas neurotransmitter.
Monoamine neurotransmitters - Answer-Small-molecule neurotransmitters that are
synthesized from monoamines and comprise two classes: catecholamines and
indolamines.
Amino acid neurotransmitters - Answer-A class of small-molecule neurotransmitters,
which includes the amino acids glutamate and GABA.
, Ionotropic receptors - Answer-Receptors that are associated with ligandactivated ion
channels.
Metabotropic receptors - Answer-Receptors that are associated with signal proteins and
G proteins.
Enzymatic degradation - Answer-The breakdown of chemicals by enzymes—one of the
two mechanisms for deactivating released neurotransmitters.
Anandamide - Answer-The first endogenous endocannabinoid to be discovered and
characterized.
Neuropeptides - Answer-Short amino acid chains comprising between 3 and 36 amino
acids.
Synaptic vesicles - Answer-Small spherical membranes that store neurotransmitter
molecules and release them into the synaptic cleft.
Aspartate - Answer-An amino acid neurotransmitter that is a constituent of many of the
proteins that we eat.
Axon initial segment - Answer-The segment of the axon where action potentials are
generated—located immediately adjacent to the axon hillock.
G proteins - Answer-Proteins that are located inside neurons (and some other cells) and
are attached to metabotropic receptors in the cell membrane.
Ion channels - Answer-Pores in neural membranes through which specific ions pass.
Dendritic spines - Answer-Tiny nodules of various shapes that are located on the
surfaces of many dendrites and are the sites of most excitatory synapses in the mature
mammalian brain.
Antidromic conduction - Answer-Axonal conduction opposite to the normal direction;
conduction from axon terminals back toward the cell body.
Endogenous - Answer-Naturally occurring in the body (e.g., endogenous opioids).
Dopamine - Answer-One of the three catecholamine neurotransmitters; dopaminergic
neurons are damaged in Parkinson's disease.
Hypothalamic peptides - Answer-One of the five classes of neuropeptide transmitters; it
consists of those first identified as hormones released by the hypothalamus.
Relative refractory period - Answer-A period after the absolute refractory period during
which a higher-than-normal amount of stimulation is necessary to make a neuron fire.