test 1 ch 2 Flashcards
(37 cards)
synapse
gap between neurons where a specialized type of communication occurs
charles s. sherrington
deduced properties of the synapse from experiments on reflexes
reflexes are slower than conduction along axon; delay at synapses
synapse is able to summate different stimuli
synapses are connected so excitation of one leads to decreased excitation or inhibition of others
either depolarization or hyperpolarization of postsynaptic neuron
graded potential
EPSP
excitatory postsynaptic potential that occurs when Na+ ions enter postsynaptic neuron
magnitude decreases as it moves along membrane
repeated stimulation of one presynaptic neuron occurring within brief period of time
temporal summation
presynaptic neuron
the neuron that delivers synaptic potential
neuron that receives message
postsynaptic neuron
several synaptic inputs originating from separate locations exerting cummulative effect on postsynaptic neuron
spatial summation
temporary hyperpolarization of postsynaptic cell
inhibitory postsynaptic potential (IPSP)
K+ leaves cell or Cl- enters cell after stimulated
ability to produce action potentials without synaptic input
spontaneous firing rate
Otto Loewi
fluid from stimulated frog heart cused new heart to react as is stimulated
exocytosis
action potential -> presynaptic terminal -> voltage dependent calcium channels open -> calcium influx -> neurotransmitter release into synaptic cleft
Dale’s Principle
a neuron can release only one neurotransmitter
modified (Dale’s Principle) concept
neuron releases same combination of neurotransmitters at all branches of its axon
ionotropic effect of neurotransmitters
neurotransmitter attaches to receptor causing immediate opening of ion gate
glutamate opens sodium (Na) gates- excitatory
GABA open chloride gates- inhibitory
metabotropic effects
neurotransmitter + receptor -> alters configuration of the receptor protein -> react with a G protein -> activation of second messengers
slower and longer lasting than ionotropic effects
include behaviors as taste, smell, and pain
G protein
coupled to GTP (guanosine triphosphate)(energy storing molecule)
second messengers
chemicals that carry a message to different areas within postsynaptic cell
neuromodulators
differeent neurotransmitters utilized by metabotropic effects
release reuires repeated stimulation
released peptides trigger other neurons to release same neuropeptide
diffuse widely and affect many neurons via metabotropic receptors
electrical synapses
few special purpose synapses
faster than chemical ransmissions
depolarization occurs in both cells, resulting in two nerons action as if they were one
gap junction
direct contact of membrane of one neuron with membrae of another
inactivation of neurotransmitters
broken down by enzymes
acetylcholine can be broken into acetate and choline by acetylcholinesterase
myasthenia gravis
disorder of motor function because of deficit of Ach transmission, treated by AchE blocker
reuptake of neurotransmitters
taken by transporters located on presynaptic neurons
serotonin and catecholamines are converted into inactive chemicals by enzymes