chapter 12-12.7
The equilibrium potential for potassium ion occurs at approximately
-90 mV
The function of the astrocytes in the CNS includes which of the following?
-adjusting the composition of the interstitial fluid -guiding neuron development -maintaining the blood-brain barrier -repairing damaged neural tissue (All of the answers are correct.)
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. -quantity of neurotransmitters released. (All of the answers are correct.)
The axoplasm of the axon contains which of the following?
-neurotubules -mitochondria -vesicles -neurofibrils (All of the answers are correct.)
The efferent division of the peripheral nervous system innervates ________ cells.
-skeletal muscle -smooth muscle -heart muscle -glandular (All of the answers are correct.)
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 -through chemically gated channels as in neuromuscular transmission (All of the answers are correct.)
Any stimulus that opens a ________ ion channel will produce a graded potential.
-voltage-gated -chemically gated -sodium -mechanically gated (All of the answers are correct.)
At the normal resting potential of a typical neuron, its sodium-potassium exchange pump transports
3 intracellular sodium ions for 2 extracellular potassium ions.
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
________ neurons are small and have no anatomical features that distinguish dendrites from axons.
Anaxonic
________ neurons are short, with a cell body between dendrite and axon, and occur in special sense organs.
Bipolar
Type ________ fibers have the largest diameter axons.
C
________ open or close in response to binding specific molecules
Chemically gated channels
Which of the following is not true regarding the establishment of a neuron's resting potential?
Electrical forces push sodium ions into the cell.
________ line the brain ventricles and spinal canal.
Ependymal cells
________ are the most numerous type of neuron in the CNS.
Interneurons
Which of the following is true about threshold for an action potential?
It is more positive than the resting potential.
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
________ neurons are the most common structural class in the CNS.
Multipolar
________ account for roughly half of the volume of the nervous system.
Neuroglia
Clusters of RER and free ribosomes in neurons are called
Nissl bodies
The neurilemma of axons in the peripheral nervous system is formed by
Schwann cells
________ neurons form the afferent division of the PNS.
Sensory
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.
Cholinergic synapses release the neurotransmitter
acetylcholine
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.
Neurons that are rare, small, and lack features that distinguish dendrites from axons are called
anaxonic.
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 axon is connected to the soma at the
axon hillock
Neurons that have one axon and one dendrite, with the soma in between, are called
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
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
Which type of synapse is most common in the nervous system?
chemical
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
Functions of astrocytes include all of the following except
conducting action potentials.
Integral membrane proteins that connect electrical synapses are called
connexons
A threshold stimulus is the
depolarization necessary to cause an action potential.
Opening of sodium channels in the axon membrane causes
depolarization.
What triggers the release of acetylcholine from a synaptic terminal?
diffusion of calcium ions into the synaptic terminal
Which of the following is not a function of the nervous system?
direct long-term functions, such as growth
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
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
If the permeability of a resting axon to sodium ion increases,
inward movement of sodium will increase and the membrane will depolarize.
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
The sodium-potassium ion exchange pump
moves sodium and potassium opposite to the direction of their electrochemical gradients.
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
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.
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
The myelin sheath that covers many CNS axons is formed by
oligodendrocytes
The cytoplasm that surrounds the nucleus of a neuron is called the
perikaryon
During repolarization of a neuron
potassium ions move out of the cell.
Which of the following is not a recognized structural classification for neurons?
pseudopolar
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
Which of the following activities or sensations is/are not monitored by interoceptors?
sight
When cholinergic receptors are stimulated,
sodium ions enter the postsynaptic neuron.
The ________ nervous system controls the skeletal muscles.
somatic
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
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
the intracellular concentration of potassium ions will increase.
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
Sensory information from skeletal muscles travels over ________ fibers.
type A
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
Neurons in which dendritic and axonal processes are continuous and the soma lies off to one side are called
unipolar.
Sensory neurons of the PNS are
unipolar.
Neurotransmitters ready for release are stored in synaptic
vesicles.
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
Most CNS neurons lack centrioles. This observation explains
why CNS neurons cannot divide to regenerate damaged tissue.
