CHAPTER 2: Synapses Flashcards
(28 cards)
what is a synapse?
a synapse is a specialized gap between neurons and is the point of communication between them
who are the great pioneers of modern neuroscience?
Cajal and Sherrington
what did sherrington study?
reflexes, which are automatic muscular response to stimuli
what is the circuit from sensory neuron to muscle response called?
a reflex arc
What evidence led Sherrington to conclude that transmission at a synapse is not the same as transmission along an axon?
Sherrington found that the velocity of conduction through a reflex arc was slower than the velocity of an action potential along an axon.
Therefore, some delay must occur at the junction between one neuron and the next.
can you explain what Sherrington referred to as a temporal summation?
Sherrington found that repeated stimuli within a brief time have a cumulative effect and with that phenomenon he referred to it as temporal summation which means summation over time
what type of neuron delivers transmission?
presynaptic neuron
what type of neuron receives information?
postsynaptic neuron
what is a graded depolarization know as?
it is known as an excitatory postsynaptic potential
what does Sherrington mean when he says that synapses have the property of spatial summation?
when he pinched two points it activated separate sensory neurons but their axons converged onto one neuron in the spinal cord. so to say it simply, they combined over space.
What is the difference between temporal summation and spatial summation?
Temporal summation is the combined effect of
quickly repeated stimulation at a single synapse.
Spatial summation is the combined effect of several nearly simultaneous stimulations at several synapses onto one neuron.
can you explain what the inhibitory postsynaptic potential is? and when does it occur?
it is the temporary hyperpolarization of a membrane
it occurs when synaptic input selectively opens the gates for potassium ions to leave the cell or for chloride ions to enter the cell
What was Sherrington’s evidence for inhibition in the nervous
system?
Sherrington found that a reflex that stimulates a flexor muscle prevents contraction of the extensor muscles of the same limb.
He therefore inferred that an interneuron that excited motor neurons connected to the flexor muscle also inhibited the input to the extensor muscle
What ion gates in the membrane open during an EPSP?
What gates open during an IPSP?
During an EPSP, sodium gates open
During an IPSP, potassium or chloride gates open.
Can an inhibitory message flow along an axon?
No, only action potentials propagate along an axon.
Inhibitory messages-IPSPs-decay over time and distance
what is a periodic production of action potentials even without synaptic input called?
it is called a spontaneous firing rate
what is temporal summation?
summation of graded potentials from stimuli at different times
what is spatial summation?
the summation of potentials from different locations
is inhibition more than the absence of excitation?
yes, it is also an active brake that suppresses excitation and is as important as excitation in the functioning of the nervous system
who demonstrated a narrow gap separating one neuron from another?
Ramón y Cajal
who physiologically demonstrated that communication between one neuron and the
next differs from communication along a single axon?
inferred a specialized gap between neurons and introduced the term synapse to describe it
Charles Scott Sherrington
who introduced the term ‘synapse’?
Charles Scott Sherrington
what does IPSP stand for?
inhibitory postsynaptic potential
what is an IPSP?
the temporary hyperpolarization of a membrane
