chapter 39 ~ neurons Flashcards
Cells in the nervous system that send and receive electrical signals are called….
Neurons
Which component of a neural signaling pathway sorts and interprets messages?
Integration
Which sequence of the neural signaling pathway is correctly arranged from the earliest to the latest event as it occurs in the nervous system?
Reception, transmission, integration, transmission, response
Which cells serve as electrical insulators in the central nervous system?
Oligodendrocytes
Which type of neuron directly stimulates a muscle or gland?
Efferent neurons only
A frog sees a fly and immediately sticks his tongue out to catch it. Which type of cell transmitted the visual signal from his eye to his brain?
Afferent neuron
A trapeze artist loses her grip and falls off the trapeze, causing her heart rate to increase in response to the rear of falling (despite the net below to prevent injury). Which type of neurons is directly responsible for this increase in heart rate?
Efferent neuron
In humans, and some primates, the most abundant neurons are the…
Interneurons
Which part of the neuron conducts the electrical signals away from the cell body of a neuron?
Axon
Which gilal cell(s) is/are only found in the peripheral nervous system?
Schwann cells
In the context of the nervous system, what does the term “nucleus” mean?
A cluster of neurons in the CNS with a related function
Where is a ganglion found?
Peripheral nervous system
Which cells assist and nourish neurons that transmit electrical signals?
Glial cells
Which category of organic macromolecule allows myelinated sheaths to act as electrical insulators?
Lipids
Otto Loewi demonstrated that neurons transmit signals across synapse by _______.
Chemical signals
Which process is responsible for the release of neurotransmitters from the presynaptic neurons into the synapse?
Exocytosis
Electrical synapses are most common in the….
Retina
If a drug inhibits the uptake of an excitatory neurotransmitter after it has been released into the synaptic cleft, what is the most likely result?
An increased number of EPSPs
If a drug binds irreversibly to a postsynaptic receptor to prevent the binding of an excitatory neurotransmitter, what is the most likely result?
A decreased number of EPSPs
If a drug binds to a receptor, which normally triggers the opening of a Na+ channel, causing it to open in the absence of neurotransmitter release, what is the most likely result?
An increased number of EPSPs
In an effort to determine the mechanism of neuronal signaling, Otto Loewi isolated_____.
Frog brains
For a neuron at rest, there is a higher concentration of ______ outside the cell than inside.
Na+
When measuring membrane potential, the tip of a microelectrode is inserted into a(n) _______.
Axon
What is the typical resting potential of an isolated neuron?
-70 mv
The nernst equation is used to calculate the _______.
Equilibrium potential
Calculate the ENa for a neuron that has an extracellular concentration of Na + of 78 mM and an intracellular concentration of Na+ of 6 mM
68.0 mv
An abrupt and transient change in membrane potential is called a(n)
Action potential
When a neuron membrane potential becomes less negative, it is said to be_______.
Depolarized
The minimum level of depolarization required to initiate an action potential in an excitable cell is called the ____ potential.
Threshold
When a neuron membrane potential goes below its resting value it becomes______.
Hyperpolarized
The refractory period of a neuronal plasma membrane is important because it _______.
Ensures that an impulse will travel in a one-way direction.
During an action potential, the membrane potential can reach as high as______.
+30 mv
When threshold potential is reached______.
The activation gates of Na+ channels open
As the action potential peaks….
The inactivation gates of Na+ channels close
If the K + channels of an excitable plasma membrane were blocked by the action of a drug, which process(es) would be disrupted?
Repolarization and hyper polarization
Depolarization of the neuronal plasma membrane occurs due to…
The diffusion of Na+ into the cell
At which point in this action potential diagram are Na+ inactivation gates opening?
D
Answer the question using the accompanying figure. At which point in this action potential diagram are many Na+ activation gates open and K + activation gates closed?
A
Answer the question using the accompanying figure. At which point in this action potential diagram does the onset of Na+ channel inactivation stop the inward flow of Na+?
B
Answer the question using the accompanying figure. At which point in this action potential diagram does the K+ channel close to stabilize the membrane potential?
E
An action potential is propagated down an unmyelinated neuronal plasma membrane because it stimulates voltage-gated ____ channels adjacent to it. (Choose the most accurate answer)
Na+
Action potentials are propagated in a one-way direction down a neuronal plasma membrane because _____.
The adjacent channels upstream from the action potential are in a refractory period.
The magnitude of an action potential _____ as it is propagated down an excitable membrane due to the ____ principle.
Remains constant, all or nothing principle
The intensity of an electrical impulse is reflected in the _____ of action potentials
Frequency
The duration of an action potential is approximately five _____.
Milliseconds
Action potential propagation is the fastest in….
A myelinated axon with a large diameter
The spaces between adjacent Schwann cells are called ________.
Nodes of ranvier
Jean-Luc Eiselé and his coworkers used_____ receptors in their research on neurotransmitter receptor function.
Artificial
The neurotransmitter receptor research of Jean-Luc Eiselé and his coworkers showed that…
The parts of a receptor binding a neurotransmitter and conducting ions function independently
Place the events in chemical synapse transmission in the correct order.
Action potential reaches axon terminal of presynaptic neuron
Ca2+ enters axon terminal
Neurotransmitter released by exocytosis
Neurotransmitter binds to postsynaptic receptor
Ligand-gated ion channels open in postsynaptic membrane
4,1,5,3,2
What removes Ca 2+ from the inside of an axon terminal of a chemical synapse after an electrical impulse has passed?
Active transport pumps
When an action potential reaches the axon terminal, the ___ channels are activated to trigger synaptic vesicle release.
Voltage-gated Ca2+ channels
What will be the effect of a drug that prevents the release of intracellular calcium?
Decreased neurotransmitter release
The binding of a neurotransmitter to ligand-gated K + channels will cause ____ in the postsynaptic membrane.
Hyperpolarization
The binding of a neurotransmitter to ligand-gated Cl- channels will cause ___ in the postsynaptic membrane.
Hyperpolarization
The binding of a neurotransmitter to ligand-gated Na+ channels will cause _____ in the postsynaptic membrane.
Depolarization only
In vertebrates, the neurotransmitter acetylcholine ____
Can act as a direct neurotransmitter between neurons and muscle cells
Neuropeptide neurotransmitters…
Can act as pain reducers and initiate euphoria
When a fish clenches to grasp a pencil, which neurotransmitter is most likely involved?
Acetylcholine
Which neurotransmitter is most likely to be inhibitory?
GABA
After burning your hand on a hot burner, which neurotransmitter will most likely be released from the pain receptors?
Substance P
To which class of neurotransmitters does glutamate belong?
Amino acids
To which class of neurotransmitters does substance p belong?
Neuropeptides
To which class of neurotransmitters does dopamine belong?
Monoamines
A graded, subthreshold change in the postsynaptic membrane potential that moves it toward threshold is called a(n)
EPSP
At which neuronal structure does summation occur?
Axon hillock
Which neuronal structure has the greatest density of voltage-gated Na + channels, resulting in the lowest threshold potential along a neuron?
Axon hillock
Assume a neuron receives EPSPs and IPSPs from several adjacent neurons. How might that neurons threshold potential be reached, causing it to produce its own action potential?
If EPSPs outnumber IPSPs
Approximately how many neurons comprise the human brain?
86,000,000,000
Despite recent advances, ____ is/are needed to revolutionize the field of neuroscience and allow for better understanding of neural networking
Computational simulations
Axon terminal of presynaptic cell
A
Plasma membrane of postsynaptic cell
E
Receptors
D
Synaptic cleft
C
Synaptic vesicles
B
An IPSP, for example
C, hyperpolarization
An EPSP, for example
A, depolarization
Occurs in a postsynaptic membrane when ligand-gated Cl- channels open.
C , hyperpolarization
Occurs due to the diffusion of Na+
A, depolarization
Causes a neuron membrane potential to become more negative, allowing it to approach its resting potential
B, repolarization
Occurs in a postsynaptic membrane when ligand-gated Na+ channels open
A, depolarization
The phase of an action potential when the membrane potential becomes more positive
A, depolarization
Begins when Na+ channel inactivation gates close and K+ activation gates open
B, repolarization
Describes the change in resting membrane potential that causes it to approach threshold potential
A, depolarization
Occurs when a membrane potential becomes more negative than its resting membrane potential
C, hyperpolarization
Explain how the resting membrane potential and resting ion distributions are established in a neuron
A resting membrane potential of -70 mV is established due to the unequal distribution of ions across the neuron plasma membrane. Na+/K+ pumps accumulate Na+ outside the plasma membrane and K+ inside the plasma membrane, while the presence of negatively charged anions inside the cell give the inside of the plasma membrane an overall negative charge relative to the outside.
Explain how neuron action potential propagation rate can be increased
Neuron action potential propagation can be increased in two ways
1. By increasing axonal diameter
2. Myelinating the axon.
Increased axonal diameter reduces electrical resistance to current flow. Myelination causes an electrical current to “jump” from one node of ranvier to the next by saltatory conduction, which is more rapid than conduction in an unmyelinated neuron
A toxin interferes with the opening Na+ channels in the postsynaptic membrane so they open more slowly when bound to a neurotransmitter, what effect would there be on action potential formation in the postsynaptic membrane?
This would cause a postsynaptic membrane action potential to form more slowly (if at all), as well as slow action potential propagation speed.
Valium is a drug that causes voltage-gated Cl- channels to open. What effects would this cause in a postsynaptic membrane?
Valium would cause hyperpolarization in the postsynaptic membrane. Thus, it would take more frequent, or a greater number, of EPSPs to generate an action potential in a postsynaptic membrane
In terms of changes in membrane potential, compare and contrast action potentials and graded potentials
Action potentials are all or none phenomena that form when a membrane potential of an excitable cell reaches threshold potential. Graded potentials are additive sub-threshold changes in the membrane potential of an excitable cell. The net effect of graded potentials may cause a membrane potential to move closer to, or further away from, threshold potential
Afferent neurons carry electric impulse directly to muscles and glands.
False- efferent neurons
Oligodendrocytes are responsible for myelinating central nervous system axons
True
Neurotransmitters are stored in vesicles located within axon terminals
True
If the equilibrium potential is close to the resting membrane potential, the net ionic movement across the membrane fill be very small
True
Depolarization occurs due to the diffusion of K+ across a neuron plasma membrane
False Na+
Saltatory conduction is the slowest form of action potential propagation
False- fastest
Neurotransmitters that bind to G-protein coupled receptors act more rapidly than those ionotropic receptors
False- less
Whether a neurotransmitter is inhibitory or excitatory depends on the type of receptor it binds to on the postsynaptic neuron
True
The additive effect of one neuron sending many EPSPs to another neuron over a brief period of time is called spatial summation
False- temporal summation
EPSPs can form due to the diffusion of Na+ across a neuron plasma membrane
True
