Chapter 6
The ______ is like the cerebrum in that it consists of paired hemispheres with an outer layer of cortical cells and several deeper cell clusters. It does not initiate motor movements, but is an important center for coordinating movements and for coordinating posture and balance.
cerebellum
A collection of neuron cell bodies within the central nervous system is properly referred to as a _____.
nucleus
Place the following structures in the order they would be penetrated by a surgeon accessing the brain to remove a tumor. Start with the first structure at the top of the list.
1. skin 2. skull bone 3. Dura Mater 4. Arachnoid mater 5. Subarachnoid space 6. Pia mater
Arrange these events in the order that most logically explains how a cell goes from having no membrane potential to having a steady negative resting membrane potential. Start with the earliest step at the top.
1. the Na+/K+ ATPase pump moves Na+ out of the cell and K+ into the cell, setting up concentration gradients across the membrane 2. due to a permeability difference, there is a greater net movement of K+ out of the cell than of Na+ into the cell 3. the membrane potential becomes negative, approaching the K+ equilibrium potential 4. Equal leaks of Na+ and K+ are offset by the continued activity go the na+/K+ ATPase pump
What gaseous neurotransmitter is produced from L-arginine by nitric oxide synthetase?
NO
Exposure to which of the following factors can negatively impact fetal brain development?
Radiation Zika virus Alcohol
Unmyelinated regions of axon in between regions covered by myelin are known as the nodes of
Ranvier
Action potentials tend to travel in only one direction along an axon for which two reasons?
Refractoriness of the region of membrane where an action potential has just occurred prevents a propagating action potential from reversing direction They begin propagating at one end of an axon, and not in the middle
Which of the following is true about graded potentials?
The flow of charge decreases with distance.
Consider an experimental set-up with two fluid-filled chambers that are separated by a plasma membrane with open K+ channels but no other ion permeability. If you were to add 100 mM of NaCl into side 1 and 100 mM of KCl into side 2, what would you expect to happen?
The membrane will develop a membrane potential that is positive on side 1 compared to side 2.
Which is TRUE regarding the effect of the Na+/K+-ATPase pump on the membrane potential of excitable cells?
The pump has a minor electrogenic effect that directly contributes to the negative value of the resting membrane potential.
Where in the brain is white matter located?
Deep to the cortex and surrounding the subcortical nuclei.
Which of the following are classified as neuropeptide neurotransmitters/neuromodulators?
Dynorphin Beta-endorphin Enkephalin
Which of the following may be attributed to the effects of endogenous opioids?
Exercise euphoria Eating and drinking behavior Pain relief
Which term is used to describe areas of the central nervous system with a high proportion of cell bodies and dendrites?
Gray matter
Which best describes a neuromodulator?
A compound that indirectly alters the effectiveness of a synapse by altering release of, or responsiveness to, a neurotransmitter.
Nicotine is a plant alkaloid compound that binds to one of the subtypes of the neurotransmitter receptors that normally binds to
ACh
Which of the following are purines that are co-released from neurons and act as neuromodulators?
ATP Adenosine
are purines that are sometimes co-released with one or more neurotransmitters at synapses, and act mainly as neuromodulators.
ATP and adenosine
The main neurotransmitter released onto skeletal muscle cells by motor neurons is called
Acetylcholine
Which of these explains why an action potential is able to propagate along the full length of an axon?
Action potentials are regenerated in each patch of membrane by depolarizing local currents arriving from previously-depolarized patches of membrane.
Removal of neurotransmitters from synapses occurs by which of the following mechanisms?
Active transport back into the presynaptic terminal Active transport into nearby cells, such as glial cells Enzymatic transformation into inactive substances Diffusion away from the synapse
Which of the following are receptors for the neurotransmitter glutamate?
Alpha-amino-3 hydroxy-5 methyl-4 isoxazolepropionic acid (AMPA) N-methyl-D-aspartate (NMDA)
Which accurately describes the "axon hillock" of a neuron?
Another name for it is "initial segment"; it is the region nearest the cell body where action potentials are initiated.
Which of the following are layers of the meningeal membrane?
Arachnoid mater Pia mater Dura mater
Which of the following structures are part of the central nervous system?
Brain, spinal cord
_______ are a subclass of monoamines derived from tyrosine that include dopamine, norepinephrine and epinephrine.
Catecholamines
Match the descriptions of the spinal nerves with their locations.
Cervical Nerves that innervate the neck, shoulders, arms and hands. Thoracic Nerves that innervate the chest and upper abdomen. Lumbar Nerves that innervate the lower abdomen, hips and legs. Sacral Nerves that innervate the genitals and lower digestive tract. Coccygeal Nerves that innervate the skin over the region of the tailbone.
Which is generally true regarding how postsynaptic potentials initiate action potentials at synapses between neurons?
Individual EPSPs are small, so initiating an action potential requires the summation of multiple excitatory inputs within a short time period.
Which of the options are correctly identified as lipid neurotransmitters?
Leukotrienes Thromboxanes Prostaglandins Endocannabinoids
Which of the following statements about nitric oxide (NO) are true?
Mediates penile erection Causes an increase in the concentration of cyclic GMP in target cells Acts as a neurotransmitter
Some babies of women infected with the Zika virus during pregnancy are born with severely underdeveloped brains. This condition is known as
Microcephaly
After the initiation of an action potential in a given region of a neuronal membrane, there is a period of time during which a second action potential cannot be stimulated no matter how strong the stimulus. This is called the
absolute refractory period
Large, rapid, all-or-none depolarizations of neuron membrane polarity are called
action potentials
Prior to activation of a chemical synapse, many vesicles are docked on the presynaptic membrane at release regions known as
active zones
Synaptic vesicles ready to be released at chemical synapses are at locations known as ________.
active zones
Because the voltage-gated K+ channels of an axon close relatively slowly, immediately after the action potential there is a period of time where the membrane is transiently hyperpolarized towards the K+equilibrium potential; this portion of the action potential is called the ______.
afterhyperpolarization
When voltage-gated K+ channels are slow to close, the membrane potential is between the normal resting potential and the K+ equilibrium potential. This phase of the action potential is known as the __________ phase.
afterhyperpolarization
Drugs that bind to and activate receptor proteins are called
agonists
An action potential is either generated because a stimulus is suprathreshold, or is not generated because the stimulus is subthreshold. This property of action potentials is referred to as the ______-________-_______ property.
all-or-none
Drugs that bind to and reduce the activity of receptor proteins are called
antagonists
Receptor potentials ______.
are graded potentials in afferent neurons
Neurotransmitters do not stay bound to receptors indefinitely; instead, they ______.
are transported back into the presynaptic cell via reuptake are broken down into component parts by enzymes diffuse away from the synapse
A long neuronal cellular projection that conducts impulses called action potentials from the cell body to nerve terminals is called a(n)
axon
The long process that carries information away from a neuron's cell body is called a(n)
axon
The nerve fiber extending from a neuron that carries outgoing signals to its target cells is also called a(n)
axon
The exchange of substances between blood and the extracellular fluid in the CNS is different from the exchange between blood and the extracellular fluid of other tissues; it is more restrictive in the CNS due to the ______.
blood-brain barrier
The ______ receptors are the targets of tetrahydrocannabinol (THC).
cannabinoid
Dendrites and axons extend from the region of a neuron called the soma, or , which contains the nucleus
cell body
What is the part of the neuron that contains the nucleus and is responsible for the production of most of the cell's macromolecules?
cell body
Which part of a neuron contains the nucleus and ribosomes?
cell body
The ______ provides both a structural and functional connection between the cerebral hemispheres.
corpus callosum
The left and right cerebral hemispheres are physically connected, internally, by a fiber tract called the
corpus callosum
The part of the neuron that carries information toward the cell body is the ______.
dendrite
Thin branching processes that extend from a neuronal cell body and receive information from other neurons are called
dendrites
Sensory fibers of a spinal nerve are found in the (dorsal or ventral?) root, and motor fibers are found in the (dorsal or ventral?) root.
dorsal, ventral
Synapses that consist of gap junctions which allow the local currents from action potentials in one neuron to flow directly across the junction to another neuron are called
electrical synapses
True or false: A fundamental physical principle is that charges of the same type (such as 2 positive charges) attract each other, while charges of opposite types (positive and negative) repel each other.
false
The non-neuronal cells of the nervous system that provide physical and metabolic support to neurons are collectively called
glial cells
Chemical synapses ______.
have a synaptic cleft between pre- and postsynaptic cells may contain more than one transmitter at a time use neurotransmitters released by the presynaptic cell to transmit signals to the postsynaptic cell
The portion of the diencephalon responsible for homeostatic regulation of the internal environment and for behaviors having to do with preservation of the individual (such as eating, drinking, and so on), is called the ______.
hypothalamus
The region of the brain below the thalamus, which is also the master command center for nervous and endocrine system coordination, is called the
hypothalamus
Receptors found in postsynaptic densities of synapses that both bind to neurotransmitters and act as ion channels are known as ______.
ionotropic receptors
The resting membrane potential of body cells ______.
is negative, with values varying from -5 to -100 mV
A membrane ion channel operated by the binding of a specific molecule to the channel protein is said to be
ligand-gated
Neurotransmitter receptors that act indirectly on separate ion channels through a G protein and/or a second messenger are referred to as ______.
metabotropic receptors
Some axons in both the PNS and CNS are surrounded by a(n) ______ sheath which increases the speed at which the axons can conduct impulses.
myelin
A substance released by cells that alters the effectiveness of a synapse indirectly by acting at non-synaptic locations, for example by altering the presynaptic cell's release of neurotransmitter or the postsynaptic cell's response to the neurotransmitter, is called a(n)
neuromodulators
The specialized cells of the nervous system that conduct electrical signals are called
neurons
Chemical messengers released by neurons that enable communication with other cells are called ______.
neurotransmitters
Within the CNS, an aggregation of neuron cell bodies is called a(n)
nucleus
The nerves that connect the brain and spinal cord with the body's muscles, glands, and sense organs make up the ______ nervous system.
peripheral
The nerves that connect the brain and spinal cord with the body's muscles, glands, and sense organs make up the general anatomic division known as the ________ nervous system.
peripheral
Fibers from the cerebellum connect directly or indirectly with the ______, ______, and the ______.
pons and spinal cord. reticular formation. primary motor cortex.
The gating of Na+ channels during the depolarization of an action potential is an example of __________ feedback, while the gating of K+ channels during the repolarization of an action potential is an example of __________ feedback.
positive, negative
The efferent autonomic neurons that synapse onto effector cells such as smooth and cardiac muscle are referred to as _________ neurons.
postganglionic
When a receptor responds normally when first exposed to a neurotransmitter but then eventually fails to respond despite the continued presence of the neurotransmitter, this is known as
receptor desensitization
Acetylcholine (ACh) is ______.
released by neurons within the brain a neurotransmitter released onto skeletal muscle cells by motor neurons
Ions with charges of the same type ______ each other, while ions with opposite charges ______ each other.
repel; attract
The term used to describe the type of action potential propagation that regenerates itself at nodes in a myelinated axon is _____ conduction.
saltatory
The ions that enter a neuron and cause the depolarization phase of a typical action potential are ____________ ions.
sodium
Knoblike outgrowths of dendrites that increase the surface area of the dendrites are called dendritic
spines
Describing an action potential as "all-or-none" means that ______.
stimuli are either suprathreshold (action potential occurs) or subthreshold (no action potential); action potentials are not graded
A stimulus that causes a graded depolarization that is too small to generate an action potential is called a(n) ________ stimulus.
subthreshold
The autonomic nervous system has two main efferent subdivisions. The__________ nervous system exits the CNS from the thoracic and lumbar regions of the spinal cord, and the ________ nervous system exits the CNS from the brainstem and sacral region of the spinal cord.
sympathetic, parasympathetic
A synapse could be excitatory or inhibitory depending on ______.
the type of postsynaptic ion channel influenced by the signal transduction mechanism
A stimulus that is just strong enough to trigger the voltage-gated channels of the initial segment of an axon to open and begin the action potential is called a(n) ________ stimulus.
threshold
True or false: Graded potentials can either depolarize or hyperpolarize the membrane potential.
true
True or false: Many EPSPs occurring in a short period of time are generally required to initiate an action potential in a postsynaptic neuron.
true
An ion channel that opens in response to a change in the membrane potential of the cell is called a __________ channel.
voltage gated
During the relative refractory period of an axon ______.
voltage-gated Na+ channels change from the inactivated state to the closed state
In an experiment with an artificial cell, the equilibrium potentials for ions X+, Y- and Z+ are +50 mV, -50 mV, and +5 mV, respectively. If the cell is equally permeable to ions X+ and Y-, but 10 times more permeable to ion Z+ than to ion Y-, which statement is most likely true?
All three ions have higher concentrations outside the cell than inside, and the resting membrane potential is positive.
Two fluid-filled experimental chambers are separated by a plasma membrane that has open Cl- channels but no other ion permeability. Into side 1 you put 200 mM NaCl and into side 2 you put 100 mM KCl. Which of the following will occur?
Cl- will flow from side 1 to side 2 and the membrane will develop a membrane potential that is positive on side 1 and negative on side 2.
At inhibitory chemical synapses, the potential change in the postsynaptic neuron is generally a hyperpolarizing graded potential, referred to by the abbreviation
IPSP
The predominant ions in the extracellular fluid are ______, and the predominant ions in the intracellular fluid are ______.
Na+ and Cl-; K+ and phosphate compounds
When a neuronal membrane is depolarized by a stimulus, which voltage-gated channels typically open the fastest?
Na+ channels
What is the name of the regions in between patches of myelin where the axon membrane is not covered?
Nodes of Ranvier
Which of the following are catecholamines?
Norepinephrine Dopamine
What term describes the situation in which a receptor at first responds to a neurotransmitter, but over time becomes non-responsive despite the continued presence of the neurotransmitter signal?
Receptor desensitization
Which is a true statement regarding the voltage-gated Na+ and K+ channels that mediate neuronal action potentials?
The Na+ channels have inactivation gates, but the K+ channels do not.
During action potential propagation, when an action potential is occurring in one patch of membrane what induces the neighboring patch of membrane to depolarize to threshold?
The flow of local positive current from the depolarized patch to the neighboring patch of membrane.
Which two are TRUE regarding dendritic spines?
They are a site of reception of signals from other neurons. They increase the surface area of a dendrite.
An IPSP is ______.
a graded potential in a postsynaptic cell that decreases the likelihood that the cell will reach the threshold for an action potential
Neurons that convey information from the tissues and organs of the body toward the CNS are classified as
afferent
The glial cells of the nervous system ______.
are non-neuronal cells that provide physical and metabolic support to neurons
The portion of an axon closest to the cell body is where action potentials generally begin, and this region is called the
axon hillock
Spinal nerves exiting between vertebrae of the spinal column contain ______.
axons of both afferent and efferent neurons
Access of therapeutic drugs to the central nervous system is restricted compared to that of other tissues because of the presence of the ______.
blood-brain barrier
Starting from the top of the spinal column, there are 8 pairs of spinal nerves in the ________ region, 12 pairs of spinal nerves in the ________ region, 5 pairs of spinal nerves in the ________ region, and 5 pairs of spinal nerves in the ________ region.
cervical, thoracic, lumbar, sacral
A synapse that transmits information via the release of neurotransmitters into the synaptic cleft between cells is termed a(n)
chemical
A synapse that transmits information via the release of neurotransmitters into the synaptic cleft between cells is termed a(n) ________ synapse.
chemical
Many axons split into multiple branches, with each branch ending in multiple axon terminals. A main branch off of an axon is called an axon
collateral
What are the branches of an axon called?
collaterals
The contributions of Na+, K+ and Cl- to the overall membrane potential are mainly a function of their ______.
concentration gradients and relative permeabilities
Electrical synapses ______.
conduct an action potential directly between cells via connecting gap junctions transmit signals faster than chemical synapses
The function of interneurons is to ______.
connect neurons within the CNS
Which term refers to the thin branching processes of neurons that provide receptive sites for incoming signals?
dendrites
A subthreshold stimulus to a neuron ______.
does not generate an action potential depolarizes the local membrane potential briefly before it returns to the resting potential
Threshold stimuli ______.
elevate the membrane potential sufficiently to generate an action potential
The ability of cells with voltage-gated ion channels to produce electrical signals is called ______.
excitability
The capability of a cell to produce electrical signals through the action of a voltage-gated ion channels is called
excitability
At an ______, the membrane potential of a postsynaptic neuron is brought closer to threshold (depolarized).
excitatory synapse
True or false: Whether a synapse is excitatory or inhibitory is determined by what neurotransmitter is released from the presynaptic cell.
false
True or false: If an action potential was started in the middle of an axon it could only propagate in one direction—away from the cell body.
false (It would propagate in both directions away from the middle; action potentials generally move "one-way" because they generally start at one end of the axon)
The most common excitatory amino acid neurotransmitter in the central nervous system is
glutamate
A(n) ___________ potential is decremental; that is the flow of the charge decreases as the distance from the site of origin increases. This is unlike what happens in a(n) ________ potential, where the signal is regenerated in each section of the axon membrane.
graded (or local) , action
An action potential ______.
is conducted without decrement occurs very rapidly is an all-or-none event
The absolute refractory period of a neuronal membrane ______.
is dependent upon the length of time it takes Na+ channels to recover from inactivation
The myelin sheath that covers some axons ______.
is formed by Schwann cells in the peripheral nervous system (PNS) is formed by oligodendrocytes in the central nervous system (CNS)
What type of channels in the postsynaptic membrane open when neurotransmitters bind to them?
ligand-gated channels
The subtype of acetylcholine receptor found at neuromuscular junctions and which are stimulated by plant alkaloids found in tobacco products are ____ actylcholine receptors.
nicotinic
Axons of neurons in the ______ can regrow and restore function as long as the cell body is intact.
peripheral nervous system
The permeability of a resting plasma membrane is greater for ______ than it is for ______; therefore, a net negative membrane potential develops.
potassium; sodium
If neurotransmitter release from neuron A increases the amount of Ca2+ that enters neuron B during an action potential, ______ of the synapse between neuron B and C will occur.
presynaptic facilitation
When neurotransmitters such as GABA or ACh are released from neuron A and bind to receptors embedded in the membrane of the axon terminal of neuron B, causing a decrease in the amount of an excitatory neurotransmitter released by neuron B, it is called ______.
presynaptic inhibition
In afferent neurons, the initial depolarization to threshold that initiates action potentials is achieved by a graded potential called a(n) _______ potential.
receptor
All cells under resting conditions have a voltage difference between the inside and outside of their plasma membranes, which is referred to as the ______.
resting membrane potential
All inactive cells in the body maintain a voltage difference across their membrane, called the _______ _______ ________ , in which the inside of the cell is negatively charged in comparison to the outside of the cell.
resting membrane potential
The ______ runs throughout the core of the brainstem and consists of loosely arranged nuclei intermingled with bundles of axons. Its axons release biogenic amines that are critical in regulating sleep and wakefulness.
reticular formation
the ______ ________ runs throughout the core of the brainstem and consists of loosely arranged nuclei intermingled with bundles of axons. It receives and integrates information from all regions of the CNS and is involved in motor functions, respiratory control, and the mechanisms that regulate sleep and wakefulness.
reticular formation
The enlarged portion of the neuron that contains the nucleus is called the cell body or
soma
A stimulus that causes a graded depolarization that is too small to generate an action potential is called a(n) stimulus.
subthreshold
True or false: Action potentials in neurons are very brief events, and may repeat at high frequencies-up to several hundred per second.
true
True or false: Most cells have resting membrane potentials that are negative on the inside compared to the outside.
true
True or false: Axon regrowth following an injury in the peripheral nervous system proceeds at a rate of only about 1 mm per day, so in some cases it could take over a year for complete function to return.
true (Reason: Due to the extremely slow regrowth of peripheral axons, after damaging a sensory neuron connected to a finger, it could take up to 2 years for sensation to return.)
True or false: In most cells, the Na+/K+-ATPase pump makes a small electrogenic contribution to creating the negative resting membrane potential.
true (Reason: Moving 3 Na+ out of the cell in exchange for moving 2 K+ into the cell has a small direct effect to make the inside of the membrane more negative in resting cells.)
Ion channels that are closed when the cell is at its resting potential but open when the cell's membrane potential changes are categorized as __________ - ________ ion channels.
voltage-gated
Which 3 of the following are true about action potential conduction in myelinated axons?
Propagation occurs without a decrease in action potential size. It is faster than in unmyelinated axons. It is called called saltatory conduction.
Which ion species are in higher concentration in the cytosol of neurons than in the extracellular fluid?
Phosphate ions K+
Which are TRUE about the anatomy of efferent autonomic pathways of the autonomic nervous system?
Postganglionic neurons originating in ganglia in the PNS synapse onto smooth muscle, cardiac and gland cells. Preganglionic neurons originating in the CNS synapse onto postganglionic neurons in a ganglion in the PNS.
What are the two major subdivisions of the efferent autonomic nervous system?
Sympathetic Parasympathetic
Which four of the following are TRUE during the relative refractory period?
Some voltage-gated Na+ channels are closed while some are still inactivated. Voltage-gated Na+ channels are resetting from the inactivated to the closed position. Voltage-gated K+ channels are resetting to the closed position. K+ is continuing to flow out of the cell.
Neurons that carry information from the CNS toward the tissues and organs of the body are known as ________ neurons.
efferent
The repolarization phase of a neuronal action potential is produced primarily by the ______.
efflux of K+
Synapses that consist of gap junctions which allow the local currents from action potentials in one neuron to flow directly across the junction to another neuron are called ________ synapses.
electrical
The membrane potential of a postsynaptic neuron is either driven farther from threshold (hyperpolarized) or stabilized at its resting potential at an ______.
inhibitory space
Neurons entirely within the CNS that form links between other neurons and comprise 99% of all neurons are called
interneurons
