chapter 12
At the normal resting potential of a typical neuron, its sodium-potassium exchange pump transports
3 intracellular sodium ions for 2 extracellular potassium ions
________ open or close in response to binding specific molecules
Chemically gated channels
________ nerves are nerves that connect to the brain.
Cranial
Which of the following is true about threshold for an action potential?
It is more positive than the resting potential
Sensory information from skeletal muscles travels over ________ fibers
Type A
The ________ division of the peripheral nervous system brings sensory information to the central nervous system.
afferent
________ carry sensory information to the CNS
afferent neurons
The part of the peripheral nervous system that carries sensory information to the CNS is designated
afferent.
The all-or-none principle states that
all stimuli great enough to bring the membrane to threshold will produce identical action potentials
The ________ principle states that the size and speed of the action potential are independent of the stimulus strength.
all-or-none
Neurons that are rare, small, and lack features that distinguish dendrites from axons are called
anaxonic
________ neurons are small and have no anatomical features that distinguish dendrites from axons.
anaxonic
Products from the soma of a neuron are transported to the synaptic terminals by ________ transport.
anterograde
IPSPs (inhibitory postsynaptic potentials)
are local hyperpolarizations
The buildup of depolarization when EPSPs arrive in rapid succession is called ________ summation
temporal
When a second EPSP (excitatory postsynaptic potential) arrives at a single synapse before the effects of the first have disappeared, what occurs?
temporal summation
The site in the neuron where EPSPs and IPSPs are integrated is the
axon hillock.
Which type of synapse is most common in the nervous system?
chemical
A postsynaptic neuron will have an excitatory postsynaptic potential (EPSP) when
chemically regulated sodium channels are open and sodium is diffusing into the cell.
If acetylcholine (ACh) causes inhibition of a postsynaptic neuron, to what type of membrane channel did the ACh bind?
chemically-regulated potassium channel
Branches that may occur along an axon are called
collaterals
The ________ division of the nervous system carries motor commands to muscles and glands.
efferent
In a(n) ________ synapse, current flows directly between cells.
electrical
The sum of the electrical and chemical forces acting on an ion is known as its
electrochemical gradient
The most common neuron of the nervous system is the
interneuron
________ are the most numerous type of neuron in the CNS
interneurons
If the permeability of a resting axon to sodium ion increases
inward movement of sodium will increase and the membrane will depolarize
The sodium-potassium ion exchange pump
moves sodium and potassium opposite to the direction of their electrochemical gradients
When pressure is applied to neural tissue, all of the following effects are possible except
neurons are triggered to divide
The same ________ can have different effects depending on the properties of the ________
neurotransmitter; receptor
Which of the following activities or sensations is/are not monitored by interoceptors?
sight
The tiny gaps between adjacent Schwann cells are called
nodes of Ranvier
Adrenergic synapses release the neurotransmitter
norepinephrine
The myelin sheath that covers many CNS axons is formed by
oligodendrocytes
The efferent division of the peripheral nervous system innervates ________ cells
skeletal muscle, smooth muscle, heart muscle, and glandular
When cholinergic receptors are stimulated,
sodium ions enter the postsynaptic neuron.
The ________ nervous system controls the skeletal muscles
somatic
The buildup of depolarization when EPSPs arrive at several places on the neuron is called ________ summation.
spatial
Summation that results from the cumulative effect of multiple synapses at multiple places on the neuron is designated
spatial summation
If the axon terminal of a motor neuron suddenly became permeable to calcium ion,
the motor end plate will be depolarized
A neuron that receives neurotransmitter from another neuron is called
the postsynaptic neuron
The minimum stimulus required to trigger an action potential is known as the
threshold
Ions can move across the plasma membrane in which of the following ways?
through voltage-gated channels as in the action potential, through passive or leak channels, by ATP-dependent ion pumps like the sodium-potassium exchange pump, and through chemically gated channels as in neuromuscular transmission
Which of the following types of nerve fiber possesses the fastest speed of impulse propagation?
type A
In a(n) ________ neuron, the dendrites and axon are continuous or fused
unipolar
Sensory neurons of the PNS are
unipolar
Neurons in which dendritic and axonal processes are continuous and the soma lies off to one side are called
unipolar.
Neurotransmitters ready for release are stored in synaptic
vesicles
Any stimulus that opens a ________ ion channel will produce a graded potential
voltage-gated, chemically gated, sodium, and mechanically gated
Which of the following does not influence the time necessary for a nerve impulse to be transmitted?
whether or not the impulse begins in the CNS
Regions of the CNS with an abundance of myelinated axons constitute the ________ matter
white
Most CNS neurons lack centrioles. This observation explains
why CNS neurons cannot divide to regenerate damaged tissue
Many medications introduced into the bloodstream cannot directly affect the neurons of the CNS because
the endothelium of CNS capillaries forms a blood-brain barrier
When potassium channels open and the ions diffuse through the membrane,
the inside of the membrane will become more negative
If the sodium-potassium pumps in the plasma membrane fail to function, all of the following occur except If the sodium-potassium pumps in the plasma membrane fail to function, all of the following occur except
the intracellular concentration of potassium ions will increase
The equilibrium potential for potassium ion occurs at approximately
-90mV
The following are the steps involved in transmission at a cholinergic synapse. What is the correct sequence for these events? 1. Chemically-gated sodium channels on the postsynaptic membrane are activated. 2. Calcium ions enter the synaptic terminal. 3. Acetylcholinesterase hydrolyzes acetylcholine. 4. An action potential depolarizes the synaptic terminal at the presynaptic membrane. 5. The pre-synaptic terminal reabsorbs choline. 6. Acetylcholine is released from storage vesicles by exocytosis. 7. Acetylcholine binds to receptors on the postsynaptic membrane. 8. Calcium ions are removed from the cytoplasm of the pre- synaptic terminal.
4, 2, 6, 7, 1, 8, 3, 5
The following are the main steps in the generation of an action potential. 1. Sodium channels are inactivated. 2. Voltage-gated potassium channels open and potassium moves out of the cell, initiating repolarization. 3. Sodium channels regain their normal properties. 4. A graded depolarization brings an area of an excitable membrane to threshold. 5. A temporary hyperpolarization occurs. 6. Sodium channel activation occurs. 7. Sodium ions enter the cell and depolarization occurs.
4, 6, 7, 1, 2, 3, 5
Type ________ fibers have the largest diameter axons
A
The axoplasm of the axon contains which of the following? A) neurotubules B) mitochondria C) vesicles D) neurofibrils E) All of the answers are correct.
All of the answers are correct.
The function of the astrocytes in the CNS includes which of the following? A) adjusting the composition of the interstitial fluid B) guiding neuron development C) maintaining the blood-brain barrier D) repairing damaged neural tissue E) All of the answers are correct.
All of the answers are correct.
________ carry motor information to peripheral effectors.
Efferent neurons
Which of the following is not true regarding the establishment of a neuron's resting potential?
Electrical forces push sodium ions into the cell.
________ monitor the digestive, respiratory, cardiovascular, urinary, and reproductive systems
Internoceptors
How would the absolute refractory period be affected if voltage-regulated sodium channels failed to inactivate?
It would last indefinitely
________ channels open or close in response to physical distortion of the membrane surface
Mechanically gated
Clusters of RER and free ribosomes in neurons are called
Nissl bodies
________ monitor the position of skeletal muscles and joints
Proprioceptors
________ nerves are nerves that connect to the spinal cord
Spinal
Opioids relieve pain by blocking the release of
Substance P
Puffer fish poison blocks voltage-gated sodium channels like a cork. What effect would this neurotoxin have on the function of neurons?
The axon would be unable to generate action potentials
How would a chemical that prevents the opening of voltage-regulated Na+ channels affect the function of a neuron?
The neuron will only be capable of producing graded potentials
Which of the following statements about the action potential is false?
The rapid depolarization phase is caused by the entry of potassium ions
How does blocking retrograde axoplasmic transport in an axon affect the activity of a neuron?
The soma becomes unable to respond to changes in the distal end of the axon
Deteriorating changes in the distal segment of an axon as a result of a break between it and the soma is called ________ degeneration
Wallerian
In which of the following would the rate of impulse conduction be the greatest?
a myelinated fiber of 10-µm diameter
If the axolemma becomes more permeable to potassium ion,
a stronger stimulus will be required to cause an action potential
The period during which an excitable membrane cannot respond to further stimulation is the ________ period.
absolute refractory
Cholinergic synapses release the neurotransmitter
acetylcholine.
The largest and most numerous of the glial cells in the central nervous system are the
astrocytes
The neuroglial cells that participate in maintaining the blood-brain barrier are the
astrocytes.
The ________ nervous system provides involuntary regulation of smooth muscle, cardiac muscle, and glandular activity.
autonomic
The plasma membrane of an axon is called the
axolemma
The axon is connected to the soma at the
axon hillock
At a(n) ________ synapse, a neurotransmitter is released to stimulate the postsynaptic membrane
chemical
Neurons that have one axon and one dendrite, with the soma in between, are called
bipolar
________ neurons are short, with a cell body between dendrite and axon, and occur in special sense organs
bipolar
Raising the potassium ion concentration in the extracellular fluid surrounding a nerve cell will have what effect?
both hyperpolarize it and decrease the magnitude of the potassium equilibrium potential
Presynaptic facilitation by serotonin is caused by
calcium channels in the presynaptic membrane remaining open longer
The ion that triggers the release of acetylcholine into the synaptic cleft is
calcium.
The ________ nervous system is composed of the brain and spinal cord
central
Most neurons lack ________ and so are permanently blocked from undergoing cell division.
centrioles
Which of the following is not a possible drug effect on synaptic function?
change the type of receptor found in the postsynaptic membrane
Functions of astrocytes include all of the following except A) maintaining the blood-brain barrier. B) conducting action potentials. C) guiding neuron development. D) responding to neural tissue damage. E) forming a three-dimensional framework for the CNS
conducting action potentials
Integral membrane proteins that connect electrical synapses are called
connexons
A movement of charges in response to a potential difference is called
current
The sensory loss and muscle weakness associated with multiple sclerosis are a consequence of
demyelination.
A shift of the resting transmembrane potential toward 0 mV is called
depolarization
Opening of sodium channels in the axon membrane causes
depolarization
A threshold stimulus is the
depolarization necessary to cause an action potential
What triggers the release of acetylcholine from a synaptic terminal?
diffusion of calcium ions into the synaptic terminal
1) Which of the following is not a function of the nervous system? A) sense the internal and external environments B) integrate sensory information C) coordinate voluntary and involuntary activities D) direct long-term functions, such as growth E) control peripheral effectors
direct long-term functions, such as growth
Which of the following is a recognized class of opioid neuromodulators?
endorphins, enkephalins, endomorphins, and dynorphins
________ line the brain ventricles and spinal canal.
ependymal cells
________ provide information about the external environment
exteroceptors
EPSPs (excitatory postsynaptic potentials) occur when
extra sodium ions enter a cell.
Damage to ependymal cells would most likely affect the
formation of cerebrospinal fluid
In the peripheral nervous system, Schwann cells participate in the repair of damaged nerves by
forming a cellular cord that directs axonal regrowth
The effect that a neurotransmitter has on the postsynaptic membrane depends on the
frequency of neurotransmitter release, nature of the neurotransmitter, characteristics of the receptors, and quantity of neurotransmitters released.
Neuron cell bodies in the PNS are clustered together in masses called
ganglia
Which of the following is the most important excitatory neurotransmitter in the brain that is important in learning and memory?
glutamate
Regions of the CNS where neuron cell bodies dominate constitute the ________ matter
gray
Active neurons need ATP to support which of the following?
he movement of materials to the soma by axoplasmic transport, the synthesis of neurotransmitter molecules, the movement of materials from the soma by axoplasmic transport, and the recovery from action potentials
Voltage-gated channels are present
in the membrane that covers axons
Voltage-gated sodium channels have both an activation gate and a(n) ________ gate
inactivation
A stimulus that changes a postsynaptic neuron's membrane from resting potential to -85 mV is a(n) ________ stimulus
inhibitory
Ion channels that are always open are called ________ channels
leak
Extensive damage to oligodendrocytes in the CNS could result in
loss of sensation and motor control
Graded potentials
may be either a depolarization or a hyperpolarization
Which of the following is not involved in creating the resting potential of a neuron?
membrane permeability for sodium ions greater than potassium ions
Which of the following is not a function of the neuroglia?
memory
After a stroke, what type of glial cell accumulates within the affected brain region?
microglia
Small, wandering cells that engulf cell debris and pathogens in the CNS are called
microglia
________ neurons are the most common structural class in the CNS
mulipolar
Neurons that have several dendrites and a single axon are called
multipolar
The most abundant class of neuron in the central nervous system is
multipolar.
The presence of ________ dramatically increases the speed at which an action potential moves along an axon
myelin
Each of the following is an example of a synapse between neurons and effector cells except the junction between a neuron and a(n)
nerve cell
_______ account for roughly half of the volume of the nervous system
neuroglia
Compounds that alter the rate of neurotransmitter release by the presynaptic neuron or change the postsynaptic cell's response to neurotransmitters are called
neuromodulators
The basic functional unit of the nervous system is the
neuron
The cytoplasm that surrounds the nucleus of a neuron is called the...
perikaryon
The nervous tissue outside of the central nervous system composes the ________ nervous system.
peripheral
During repolarization of a neuron
potassium ions move out of the cell
The separation of positive and negative charges across the membrane creates a ________ difference, or voltage
potential
Which of the following is not a recognized structural classification for neurons? A) anaxonic B) bipolar C) multipolar D) pseudopolar E) unipolar
pseudopolar
After acetylcholinesterase acts, the synaptic terminal
reabsorbs the choline
The period during which an excitable membrane can respond again, but only if the stimulus is greater than the threshold stimulus, is the ________ period.
relative refractory
A change in the conditions in the synaptic terminal can influence the soma as a result of ________ transport
retrograde
The rabies virus travels to the CNS via
retrograde axoplasmic transport.
Rapid impulse conduction from "node" to "node" is called
saltatory propagation
Glial cells that surround the neurons in ganglia are
satellite cells
Which of the following is a type of glial cell found in the peripheral nervous system?
satellite cells
The neurilemma of axons in the peripheral nervous system is formed by
schwann cells
________ neurons form the afferent division of the PNS.
sensory
The site of intercellular communication between a neuron and another cell is the
synapse.
If the chemically gated sodium channels in the postsynaptic membrane were completely blocked,
synaptic transmission would fail
Axons terminate in a series of fine extensions known as
telodendria