Module 2.1
What causes an EPSP?
the opening of sodium channels
A temporary hyperpolarization is known as an ____.
IPSP
What is the primary difference between temporal summation and spatial summation?
Spatial summation depends on contributions from more than one sensory neuron.
On the basis of what evidence were the properties of synapses first inferred?
behavioral observations
Which process will most likely result in an IPSP?
chloride ions entering the cell
An EPSP is to ____ as an IPSP is to ____.
depolarization; hyperpolarization
Depolarization is to ____ as hyperpolarization is to ____.
excitation; inhibition
Spatial summation refers to ____.
multiple weak stimulations that occur at the same time
Even at rest, most neurons have periodic production of action potentials, known as the ____.
spontaneous firing rate
What do temporal summation and spatial summation have in common?
Both enable a reflex to occur in response to weak stimuli.
A graded depolarization is known as an ____.
EPSP
The primary difference between an EPSP and an action potential is that ____.
EPSPs are subthreshold events that decay over time and space
Which statement is TRUE about the spontaneous firing rates of neurons?
EPSPs increase the frequency.
Why is the speed of conduction through a reflex arc slower than the speed of conduction of an action potential along an axon?
Transmission between neurons at synapses is slower than along axons.
A normal, healthy animal never contracts the flexor muscles and the extensor muscles of the same leg at the same time. Why not?
When the interneuron sends excitatory messages to one, inhibitory messages go to the other.
The circuit from sensory neuron to muscle response is called ____.
a reflex arc
The "spontaneous firing rate" of a neuron refers to ____.
its rate of producing action potentials even when it is not stimulated
Spatial summation refers to ____.
multiple weak stimulations that occur at the same time
Increased permeability to which type of ion would most likely result in an IPSP?
potassium
The "decision" for a neuron to fire is determined by the ____.
ratio of EPSPs to IPSPs
To measure temporal summation in single cells, researchers ____.
record depolarizations of the postsynaptic neuron
What is the proper ordering of a reflex arc?
sensory neuron, interneuron, motor neuron
Specialized junctions between neurons are called ____.
synapses
What determines whether a neuron has an action potential?
the combined effects of EPSPs and IPSPs
Sherrington deduced that transmission at a synapse must be slower than conduction along an axon. This was based on what kind of evidence?
the speed of reflexive responses
Which statement is TRUE of EPSPs?
They decay over time and space.
Inhibitory synapses on a neuron ____.
hyperpolarize the postsynaptic cell
When a vertebrate animal contracts the flexor muscles of a leg, it relaxes the extensor muscles of the same leg. Sherrington considered this evidence for the existence of ____.
inhibitory messages
In a reflex arc, the coordination between contraction of certain muscles and relaxation of others is mediated by ____.
interneurons
Temporal summation most likely occurs with ____.
rapid succession of subthreshold excitation
A certain weak stimulus produces no reflexive response, but a rapid repetition of that stimulus may produce such a response. What is this phenomenon called?
temporal summation
Temporal summation is to ____ as spatial summation is to ____.
time; location
