MAP Ch 8.1-8.5

A neuron has one axon with 10 axon collaterals. Each collateral branch synapses on __________. This is an example of __________ 10 different post-synaptic neurons; divergence the same post-synaptic neuron; divergence 10 different post-synaptic neurons; convergence

10 different post-synaptic neurons; divergence

________ is an amino acid neurotransmitter at excitatory synapses whereas ________ is an amino acid neurotransmitter at inhibitory synapses. Gamma-aminobutyric acid : glutamate Glycine : aspartate Gamma-aminobutyric acid : glycine Glutamate : aspartate Aspartate : glycine

Aspartate : glycine

What type of conduction takes place in unmyelinated axons? Saltatory conduction Electrical conduction Continuous conduction Synaptic transmission

Continuous conduction

Nicotinic cholinergic receptors open channels on the plasma membrane that allow both Na+ and K+ to move across the membrane. This will lead to which type of post-synaptic potential? IPSP EPSP

EPSP

Closing of potassium channels causes a hyperpolarization. True False

False

IPSPs can only summate with IPSPs, and EPSPs can only summate with EPSPs. True False

False

What changes occur to voltage-gated Na+ and K+ channels at the peak of depolarization? Activation gates of voltage-gated Na+‎ channels close, while inactivation gates of voltage-gated K+‎ channels open. Inactivation gates of voltage-gated Na+‎ channels close, while activation gates of voltage-gated K+‎ channels open. Inactivation gates of voltage-gated Na+‎ channels close, while inactivation gates of voltage-gated K+‎ channels open. Activation gates of voltage-gated Na+‎ channels close, while activation gates of voltage-gated K+‎ channels open.

Inactivation gates of voltage-gated Na+‎ channels close, while activation gates of voltage-gated K+‎ channels open

In which type of axon will velocity of action potential conduction be the fastest? Myelinated axons with the largest diameter Myelinated axons with the smallest diameters Unmyelinated axons with the largest diameter Unmyelinated axons of the shortest length

Myelinated axons with the largest diameter

Neuron J has a resting membrane potential of -70mV and a threshold value of -50mV. Neuron K releases neurotransmitter onto Neuron J, which causes a 20mV depolarization at the axon hillock. Neuron L causes a 10mV hyperpolarization at the axon hillock. In which of the following scenarios would an action potential be generated at Neuron J's axon? Neuron K and Neuron L each fire once, simultaneously. Neuron L fires once. Neuron K fires once.

Neuron K fires once.

Why does regeneration of the action potential occur in one direction, rather than in two directions? The inactivation gates of voltage-gated Na+‎ channels close in the node, or segment, that has just fired an action potential. The activation gates of voltage-gated Na+‎ channels close in the node, or segment, that has just depolarized. The activation gates of voltage-gated K+‎ channels open in the node, or segment, that has just depolarized. The inactivation gates of voltage-gated K+‎ channels close in the node, or segment, that has just fired an action potential.

The inactivation gates of voltage-gated Na+‎ channels close in the node, or segment, that has just fired an action potential.

In some cases, neurotransmitter will bind to a receptor and activate a G protein whose function is to activate adenylate cyclase. Adenylate cyclase converts ATP to cAMP, which leaves the plasma membrane to go into the cell and activate a protein kinase A. Protein kinase A phosphorylates K+ channels, causing them to close. Based on this information, which of the following statements is correct? The K+ channel is a voltage-gated channel. The initial receptor was indirectly linked to the K+ channel. This response pathway would lead to an IPSP. Protein kinase A is the second messenger in this pathway.

The initial receptor was indirectly linked to the K+ channel.

What is the function of the myelin sheath? The myelin sheath decreases the resistance of the axonal membrane to the flow of charge. The myelin sheath decreases the speed of action potential conduction from the initial segment to the axon terminals .The myelin sheath increases the speed of action potential conduction from the initial segment to the axon terminals. The myelin sheath increases the insulation along the entire length of the axon

The myelin sheath increases the speed of action potential conduction from the initial segment to the axon terminals.

Metabotropic receptor-induced gating of ion channels requires more time to occur because of which of the following? Their gating is linked to a G protein. Ion channels linked to metabotropic receptors must move to the membrane before gating. Intracellular calcium must increase before those channels will open. The channels are slower to open. Metabolic byproducts are required to open those channels.

Their gating is linked to a G protein.

How does temporal summation create an action potential? Generator potentials are at the same tempo on adjacent neurons. The temporal lobe in the brain stimulates EPSPs to trigger an action potential. Potentials are generated on several dendrites at the same time to trigger threshold and the production of an action potential. Two or more postsynaptic potentials are generated in rapid succession at the same synapse before they can dissipate, thereby exceeding threshold. It is frequency modulated and of the same amplitude for intensity.

Two or more postsynaptic potentials are generated in rapid succession at the same synapse before they can dissipate, thereby exceeding threshold

How does increased frequency of action potentials result in increased release of neurotransmitter? With increased firing frequency, the voltage-gated calcium channels at the axon terminal remain open longer, allowing more calcium to enter the cell. With faster firing frequency, subsequent action potentials are larger than previous potentials, which allows more Ca++ channels to be opened at the axon terminal. With increased firing frequency, the axon terminal is depolarized for longer, allowing more Na+ to rush into the cell. Action potentials weaken the secretory vesicles and the plasma membrane at the axon terminal. With faster firing frequency, more neurotransmitter is released because the plasma membrane is made significantly weaker.

With increased firing frequency, the voltage-gated calcium channels at the axon terminal remain open longer, allowing more calcium to enter the cell.

Which of the following correctly completes the sentence? The period of time after an action potential when another action potential cannot be generated is the __________. absolute refractory period repolarization period relative refractory period hyperpolarization period

absolute refractory period

Which of the following neurotransmitters is the most common neurotransmitter in the peripheral nervous system? substance P acetylcholine glycine norepinephrine aspartate

acetylcholine

Which enzyme catalyzes the synthesis of cAMP? monoamine oxidase choline acetyl transferase adenylate cyclase acetylcholinesterase catechol-O-methyltransferase

adenylate cyclase

Voltage-gated calcium channels in the axon terminal open in response to which of the following? summation of graded potentials at the axon hillock arrival of an action potential at the axon terminal neurotransmitter binding to receptor initiation of an action potential in the axon hillock paracrines released from the post-synaptic cell

arrival of an action potential at the axon terminal

The synaptic delay is caused by the time required for which step of neurotransmitter release? the synthesis of neurotransmitter packaging of neurotransmitter into synaptic vesicles calcium entry to trigger exocytosis an action potential to move from axon hillock to axon terminal the neurotransmitter to diffuse across the synaptic cleft

calcium entry to trigger exocytosis

Presynaptic modulation of neurotransmitter release involves modifying ________ at the axon terminal. the vesicles selected for release membrane potential potassium channels calcium influx sodium channels

calcium influx

Opening of __________ channels leads to an __________ chloride; IPSP sodium; IPSP calcium; IPSP potassium; EPSP

chloride; IPSP

What happens to the resting membrane potential of -70 mV when channels for a cation with an equilibrium potential of -30 mV open? repolarization returns to -70 mV membrane stabilization depolarization hyperpolarization

depolarization

What happens to the resting membrane potential of -70 mV when potassium channels close? hyperpolarization membrane stabilization returns to -70 mV depolarization repolarization

depolarization

What happens to the resting membrane potential of -70 mV when sodium channels open? returns to -70 mV depolarization hyperpolarization repolarization membrane stabilization

depolarization

An action potential is self-regenerating because __________. repolarizing currents established by the efflux of Na+‎ flow down the axon and trigger an action potential at the next segment depolarizing currents established by the influx of K+‎ flow down the axon and trigger an action potential at the next segment repolarizing currents established by the efflux of K+‎ flow down the axon and trigger an action potential at the next segment depolarizing currents established by the influx of Na+‎ flow down the axon and trigger an action potential at the next segment

depolarizing currents established by the influx of Na+‎ flow down the axon and trigger an action potential at the next segment

Neurotransmitter release occurs by what mechanism? secondary active transport exocytosis primary active transport diffusion endocytosis

exocytosis

The influx of calcium into the axon terminal of a chemical synapse is responsible for which of the following? diffusion of the neurotransmitter across the membrane and into the cleft initiation of an action potential fusion of vesicles to the membrane and of exocytosis neurotransmitter termination of an action potential movement of calcium through gap junctions

fusion of vesicles to the membrane and of exocytosis neurotransmitter

For cells that communicate by electrical synapses, the message travels between cells via gap junctions. the diffusion of neurotransmitters. ions moving across the synaptic cleft. active transport across the synaptic cleft. passive transport across the synaptic cleft.

gap junctions.

Nitric oxide is a(n) ________ that functions as a neurotransmitter. catecholamine amino acid biogenic amine gas neuroactive peptide

gas

Which of the following neurotransmitters can bind to N-methyl-D-aspartate receptors (NMDA)? GABA epinephrine acetylcholine glutamate

glutamate

What happens to the resting membrane potential of -70 mV when channels for an anion with an equilibrium potential of -80 mV open? hyperpolarization returns to -70 mV depolarization membrane stabilization repolarization

hyperpolarization

The opening of sodium channels causes a rapid ________ of sodium that ________ the neuron's membrane. efflux : depolarizes influx : hyperpolarizes efflux : hyperpolarizes influx : depolarizes influx : repolarizes

influx : depolarizes

The opening of a chloride channel acts to ________ the development of an action potential at the axon hillock. facilitate further inhibit stimulate enhance

inhibit

What type of receptor is both metabotropic and cholinergic? adrenergic muscarinic serotonergic dopaminergic nicotinic

muscarinic

What type of receptor is both ionotropic and cholinergic? muscarinic dopaminergic serotonergic adrenergic nicotinic

nicotinic

The all-or-none principle, associated with the action potential, states that all of the action potentials will be generated from the axon hillock. once membrane potential reaches threshold, an action potential will be generated and that action potential will always be the same magnitude. the positive feedback loop for the sodium channel is terminated by the inactivation gate. there is a positive feedback loop for sodium channels that results in a rapid membrane depolarization. following an action potential, the membrane will be repolarized by the opening of a potassium channel.

once membrane potential reaches threshold, an action potential will be generated and that action potential will always be the same magnitude.

The binding of a neurotransmitter to its receptor at an inhibitory synapse can lead to the ________ of ________ channels. opening : sodium opening : chloride closure : chloride closure : potassium opening : calcium

opening : chloride

Which of the following is a hypothalamic neuropeptide that regulates the sleep-wake cycle? melatonin oxytocin orexin vasopressin substance P

orexin

The fact that a cell has an electrical potential difference across its membrane makes that cell hyperpolarized. repolarized. polar. polarized. depolarized.

polarized.

The repolarization phase of action potentials in neurons is due primarily to increased activity of the Na+/K+ pump. sodium flow out of the cell. sodium flow into the cell. potassium flow into the cell. potassium flow out of the cell.

potassium flow out of the cell.

Which of the following would increase the likelihood of an action potential being generated in a postsynaptic cell? opening of chloride channels on a postsynaptic cell that actively transports chloride ions out of the cell presynaptic excitation at an excitatory synapse presynaptic inhibition at an excitatory synapse opening of potassium channels on the postsynaptic cell opening of chloride channels on a postsynaptic cell with no active transport of chloride ions

presynaptic excitation at an excitatory synapse

When a neuron synapses on the axon terminal of another neuron, causing decreased neurotransmitter release from the post-synaptic neuron, it is an example of __________. presynaptic facilitation presynaptic inhibition post-synaptic inhibition summation

presynaptic inhibition

Neurotransmitters can be reused through the process of ________, where neurotransmitters are transported back across the presynaptic membrane. reuptake resynthesis recycling regeneration receptor binding

reuptake

The action of any chemical messenger ultimately depends not on the nature of the messenger, but rather on the affinity of the receptor. signal transduction mechanism activated. nerve cell stimulated. half-life of the messenger. organ system activated.

signal transduction mechanism activated.

When a weak stimulus is applied in rapid succession, it will often reach threshold due to excitatory summation inhibitory summation spatial summation. voltage potential. temporal summation.

temporal summation.

What limits the maximum number of action potentials on an axon? the absolute refractory period whether the axon is myelinated or not the concentration of sodium within the cytoplasm of the cell the relative refractory period the diameter of the axon

the absolute refractory period

Which of the following is NOT a mechanism whereby neurotransmitters are rapidly removed from the synaptic cleft? degradation by enzymes binding to the receptor transport back up the axon to be immediately repackaged diffusion out of the cleft active reuptake across the presynaptic membrane

transport back up the axon to be immediately repackaged

The job of the axon hillock is to determine whether there are enough depolarizing potentials to reach threshold. What type of membrane channels do you think you would find at the axon hillock? slow-response Na+ channels voltage-gated Ca++ channels voltage-gated Na+ channels fast-response Na+ channels

voltage-gated Na+ channels