HAP
Substances that bind to chemically gated channels of neurons are known as ____________________.
neurotransmitters.
The gaps between Schwann cells that are essential for the conduction of the action potential are called:
nodes of Ranvier.
Which of the following is not a function of astrocytes?
provide the defense for the CNS
An action potential ____________________.
refers to a large change in membrane potential from -70mV to +30mV and back to -70mV.
An impulse from one nerve cell is communicated to another nerve cell via the ________.
synapse
The conductive region of the neuron where the action potential occurs is called:
the axon
The specific region on the axon where an action potential is generated is called:
the axon hillock.
The stimulus for opening ion channels in the postsynaptic neuron is caused by:
the binding of neurotransmitters.
Which event happens immediately after a neurotransmitter binds to its postsynaptic membrane receptor?
Chemically gated ion channels open.
What is the correct order of the path of information in a neuron from input to output?
Dendrites, soma, axon
As more and more K+ ions leave a cell, what force will tend to pull K+ ions back into the cell?
Electrical gradient
A chemically gated channel is also known as a voltage gated channel.
False
A common characteristic of an action potential is that it disappears (decays) as it travels the length of the axon.
False
A neurotransmitter is the chemical signal that opens voltage-gated ion channels.
False
A normal synaptic potential is higher in amplitude than an action synaptic potential.
False
All neurotransmitters are enzymatically degraded.
False
An incoming signal to the neuron is known as an action potential.
False
Immediately after generating an action potential, a neuron can generate another one.
False
Ion channels allow for the random movement of all ions across the neuronal cell membrane.
False
The nodes of Ranvier are found on the dendrites of neurons.
False
The rising phase of the action potential ends when the permeability of K+ decreases.
False
Neurons may be classified according to structure and function characteristics. Which of the following is NOT correct?
Fast twitch neurons
Which statement is CORRECT?
Hyperpolarization results in a membrane potential that is more negative than the resting membrane potential. Answers: Hyperpolarization results in a membrane potential that is more negative than the resting membrane potential. Hyperpolarization results when sodium moves into the cell after the cell repolarizes. All answers are correct.
Excitable cells are most permeable to which of the following ions?
K+
What is the major cation inside the cell?
K+
The fastest conduction of an action potential would occur in an axon with which of the following characteristics?
Large diameter and myelinated
Calcium ____________________.
More than one answer is correct.
What is the name of the disease in which the myelin sheaths of central nervous system axons are destroyed?
Multiple sclerosis
The action potential is a transient change in the resting membrane potential from -70 mV to +30 mV, then back to -70 mV. This change is caused by the opening of first _____ then _____ voltage-gated channels.
Na+ then K+
Which of the choices below describes the PNS?
Nerve fibers that conduct nerve impulses to and from the CNS to smooth muscle, cardiac muscle, and glands and sensory organs
Neurons can communicate with, or stimulate, which of the following?
Neurons, muscles, and glands
What support cell forms the myelin sheaths in the central nervous system?
Oligodendrocytes
Which of the following would increase membrane permeability to K+?
Opening of voltage-gated K+channels
What support cell forms the myelin sheaths in the peripheral nervous system?
Schwann cells
Increasing the number of synapses from different neurons would cause which type of summation?
Spatial summation
Which event occurs immediately after extracellular calcium enters the axon terminal region?
Synaptic vesicles fuse with the membrane.
Increasing the number of action potentials on a presynaptic axon in a given period of time would cause what type of summation?
Temporal summation
During a laboratory experiment, an isolated neuron was stimulated. An initial reading found the resting membrane potential to be -70 mV. After a single stimulus, the membrane potential was -55 mV. Which statement about the experiment is CORRECT?
The neuron reached threshold and an action potential was generated.
Match each statement to its correct answers.
chemically gated channels A.Responsible for the resting membrane potential of the neuron. voltage-gated channels C.Responsible for generation and propagation of the outgoing signal, the action potential. Passive (nongated) channels B.Responsible for incoming signals, the synaptic potentials.
When a neuron is at rest, voltage gated channels are ____________________.
closed.
Multiple neurons synapsing on a single neuron is known as
convergence
The part of a neuron that conducts impulses towards the cell body is called a(n) ________.
dendrite
Bipolar neurons are commonly ________.
found in the retina of the eye
Synaptic potentials are also called:
graded potentials
When the neurotransmitter binds to a receptor located on the postsynaptic membrane ____________________.
it binds to chemically gated channels
Potentiation/facilitation of a synaptic potential is caused by:
keeping the postsynaptic membrane potential slightly depolarized.
Ion movement across the postsynaptic membrane as a result of neurotransmitter binding ____________________.
may depolarize or hyperpolarize the postsynaptic neuron.
Neuroglia that control the clear cellular debris and protect against pathogens around neurons are ________.
microglia
The substance released at axon terminals to propagate a nervous impulse is called a(n) ________.
neurotransmitter
Schwann cells are functionally similar to ________.
oligodendrocytes
Repolarization occurs when voltage-gated ____________________.
potassium channels open allowing potassium to leave the cell.
Which of the following is a function of mircroglial cells?
provide the defense for the CNS and clear cellular debris
Which of the following describes the nervous system motor function?
responds to stimuli by gland secretion or muscle contraction
The region of the neuron where most metabolic processes take place:
the soma (cell body).
One of the roles of divergent neural pathways is
to allow for amplification of a neural impulse and quicker reaction times
Chemically gated ion channels ____________________.
All answers are correct.
During the absolute refractory period ____________________.
All answers are correct.
Channel selectivity depends on ____________________.
All statements are correct.
Which statement is CORRECT?
Depolarization refers to the process where the neuronal membrane becomes more positive. Answers: Local electrical signals travel long distances down the axon. Depolarization refers to the process where the neuronal membrane becomes more positive.
Do EPSPs (excitatory postsynaptic potentials) hyperpolarize or depolarize the membrane?
Depolarize
A myelinated axon will conduct an action potential faster than an unmyelinated axon.
True
The job of a neuron is to select a single output (action potential) from competing inputs (synaptic potentials).
True
Neuroglia that control the chemical environment around neurons are ________.
astrocytes
A cell that received ten EPSPs and two IPSPs to the axon hillock would most likely ____________________.
generate an action potential.
After an action potential, the membrane becomes more negative than -70 mV. This period is called:
hyperpolarization.
A neuron without channels will NOT be able transport ions.
True
During an action potential, voltage-gated sodium channels open rapidly, then inactivate, and finally reset to the closed state.
True
EPSPs always results in the depolarization of the postsynaptic cell.
True
EPSPs decay as they travel away from the synapse.
True
Efferent nerve fibers may be described as nerve fibers that transmit impulses away from the CNS.
True
If bacteria invaded the CNS tissue, microglia would migrate to the area to engulf and destroy them.
True
Ion channels can be voltage gated or chemically gated.
True
It takes many EPSPs to depolarize a neuron to threshold.
True
Large-diameter nerve fibers conduct impulses much faster than small-diameter fibers.
True
Myelination of the nerve fibers in the central nervous system is the job of the oligodendrocyte.
True
Reflexes are rapid, automatic responses to stimuli.
True
Synapses located a great distance from the axon hillock will be less likely to trigger an action potential.
True
Synaptic transmission ends when the neurotransmitter leaves it receptor and is removed from the synaptic cleft.
True
Synaptic transmission occurs when the neurotransmitter from the presynaptic cell diffuses across the synaptic cleft and binds to its receptors located on the postsynaptic membrane.
True
The presynaptic neuron releases the neurotransmitter into the synaptic cleft.
True
Threshold refers to the voltage that opens the voltage-gated channels located in the axon hillock region of the neuron.
True
Voltage-gated potassium channels open when the action potential reaches its peak.
True
When and only when a neuron reaches threshold, a positive feedback loop for opening sodium channels is established.
True
Which statement is INCORRECT?
Voltage across the cell membrane cannot be measured. Answers: Some gated channels have gates that are controlled by voltage. Voltage across the cell membrane cannot be measured.
At the end of the depolarization phase, what voltage-gated channels open to help restore the resting membrane potential?
Voltage-gated K+ channels
Which of the following describes the nervous system integrative function?
analyzes sensory information, stores information, makes decisions
The part of a neuron that conducts impulses away from its cell body is called a(n) ________.
axon
If an axon branches, these branches of the neuron are called:
axon collaterals.
The term central nervous system refers to the ________.
brain and spinal cord
The presence of ion channels within the neuron cell membrane ____________________.
allow for the movement of ions across the membrane and are responsible for the excitable properties of neurons.
Which statement is CORRECT?
Action potentials begin in the axon hillock region of the neuron. Answers: Each depolarization that reaches the axon hillock will generate an action potential. When the stimulus reaches the axon hillock and depolarizes the membrane to about +60 mV, an action potential will occur.
After the action potential is generated at the axon hillock ____________________.
All answers are correct.
Rapid firing of presynaptic action potentials will result in ____________________.
All answers are correct.
Summation of excitatory postsynaptic potentials ____________________.
All answers are correct.
Which type of ion channels is generally found on the axon hillock, all along unmyelinated axons, and at the nodes of Ranvier of myelinated axons?
All answers are correct.
A neurotransmitter ____________________.
All statements are correct.
When an action potential reaches the end terminal region of a presynaptic neuron ____________________.
All statements are correct.
When threshold is reached ____________________.
All statements are correct.
Which statement is CORRECT?
All statements are correct. Answers: Large protein molecules that span the lipid bilayer are known as integral proteins. All statements are correct. Some protein channels contain watery pores through which ions flow.
Match the following neuroglial cells with the correct description
Astrocytes 2.Produce myelin for neurons of the central nervous system (CNS) Oligodendrocytes 1.Provide framework and maintain a stable environment for neurons Microglial cells 3.Clear cellular debris and protect the CNS and PNS from infection Schwann cells 4.Produce myelin for neurons of the peripheral nervous system (PNS)
Which potentials decay as they move along the neuronal membrane?
Both EPSPs and IPSPs
Signals from other neurons are received on what parts of the neuron?
Both dendrites and the soma
What is the process called when all the EPSPs and IPSPs are added together to determine whether there will be an action potential?
Cellular integration
Inhibitory synapses have the maximum effect if they are located on what part of the neuron?
The cell body, near the axon hillock
Which statement is CORRECT?
The mechanism by which neurotransmitters are returned to the terminal is specific to each neurotransmitter.
If depolarization reaches -55 mV, an action potential will be generated. What is this -55 mV trigger point called?
Threshold
When the electrical and chemical gradients for K+ are equal, what will happen to the net movement of K+?
There will be no net movement of K+ across the membrane.
All of the following are characteristics of ion channels EXCEPT:
They are always nongated.
Which of the following is not a special characteristic of neurons?
They are mitotic.
What happens to synaptic potentials as they travel away from the synapse?
They weaken.
