Ch3 pt1-Concept of the Synapse Flashcards
communication BETWEEN neurons is primarily…
chemical
communication WITHIN neurons is primarily….
electrical
specialized gap between neurons
synapse
demonstrated communication between one neuron & the next differs from communication along one axon
Charles Scott Sherrington
also coined term synapse
automatic muscular responses to stimuli
reflexes
circuit from sensory neuron to muscle response
reflex arc
Sherrington observed what when studying reflexes on dogs
a) reflexes are slower than conduction along axon
b) several weak stimuli presented at slightly different times or slightly different locations produce stronger reflex than single stimulus does
c) when one set of muscles becomes excited, a different set becomes relaxed
speed of conduction through reflex arc was never more than ______ m/sec
15
Sherrington validated idea of synapse by
concluding some process was slowing conduction through reflex
repeated stimuli within a brief time have a cumulative effect (stronger than single stimuli)
temporal summation
cell that RECEIVES message
postsynaptic neuron
cell that DELIVERS message
pre-synaptic neuron
graded depolarization; occurs when sodium ions enter the cell (decay over space & time; discovered by Eccles)
excitatory postsynaptic potential (EPSP)
synaptic inputs from various locations combine their effects on a neuron (critical to brain function)
spatial summation
temporal summation & spatial summation ordinarily occur together
just remember that
flexor muscles
contract
extensor muscles
extend
at inhibitory synapse, input from an axon ______ the postsynaptic cell
hyperpolarizes
occurs when the synaptic input selectively opens the channel for potassium ions to leave the cell or for chloride ions to enter the cell
- come from temporary hyperpolarization
- serves as active “break” away from excitation
Inhibitory postsynaptic potential (IPSP)
importance of Sherrington’s work
researchers can show how nervous system is wired & design systems based on this
periodic reproduction of action potentials even without synaptic input
spontaneous firing rate
which 2 individuals were apart of discovering chemical synapses
Elliot then Loewi
chemicals released by one neuron that affect a second neuron
neurotransmitter
what are the types of neurotransmitters
amino acids, neuropeptides, acetylcholine, monoamines, purines, gases
tiny packets that store high concentrations of neurotransmitters
vesicles
where are most neurotransmitters synthesized
presynaptic terminal
a neuron synthesizes chemicals it needs from what
substances in the diet
chemical that breaks down neurotransmitters
MAO (monoamine oxidase)
release of neurotransmitter in bursts from presynaptic terminal into synaptic cleft
exocytosis
______ enters the presynaptic terminal and causes exocytosis
calcium
a neurotransmitter receptor is a ______
protein
_______ occur at one type of receptor. begin quickly & last for a very brief period of time
ionotropic effects
______ initiates a series of metabolic reactions; slower & longer lasting
metabotropic effects
properties that distinguish neuropeptides (neuromodulators) from neurotransmitters
need repeated stimulation; released through dendrites, cell body, or axon sides
chemicals that are secreted by a gland or other cell & conveyed by the blood to other organs; coordinate long lasting changes
hormones
glands that produce hormones
endocrine glands
accumulation of neurotransmitters is broken down by ______ into inactive chemicals that cannot stimulate dopamine receptors
COMT
detect the amount of neurotransmitter released & inhibit further syntheses & release after it reaches a certain level
autoreceptors
special-purpose synapses that operate electrically (ex: breathing rhythmically in both lungs)
electrical synapses
contact between membrane of one neuron with membrane of another
gap junction
