Chapter 4: Neural Conduction & Synaptic Transmission Flashcards
“Reptilian stare is sometimes used to describe the widely opened, unblinking eyes and motionless face of
Parkinson’s disease
Dopamine is not an effective treatment for Parkinson’s disease because
Dopamine does not readily penetrate the blood-brain barrier
Parkinson’s disease is treated with
L-DOPA
A membrane potential is the difference in electrical charge between
The inside and outside of a cell
The tips of intracellular recording electrodes are
A) About the size of a neuron
B) Too small to be seen with the naked eye
C) Less than one thousandth of a millimeter in diameter
Both B and C
At rest,
A) a neuron has a membrane potential of about -70 mV
B) the electrical charge outside the neuron is 70 mV less than inside the neuron
C) a neuron is polarized
Both A and C
In its resting state, a neuron is said to be
Polarized
Salts in solution separate into positively and negatively charged
Ions
Outside the membranes of resting neurons, there are many more
Na+ ions
Na+ ions are encouraged to move into neurons by
Electrostatic pressure
Which of the following is a passive force that acts to encourage Na+ ions to enter resting neurons?
A) random motion, which tends to move ions down their concentration gradients
B) electrostatic pressure, which forces ions down their electrostatic gradients
C) sodium-potassium pumps, which distribute Na+ and K+ ions equally
Both A and B
Ions pass through the neural membrane via specialized pores called
Ion channels
Na+ ions are continuously forced into neurons by
A) their high internal concentration
B) their high external concentration
C) the negative resting potential
Both B and C
Sodium-potassium pumps maintain the resting membrane potential by transporting
A) Na+ ions into neurons
B) K+ ions into neurons
C) Na+ ions out of neurons
Both B and C
According to the theory of Hodgkin and Huxley,
K+ ions continuously leak out of a resting neuron
Contributing to the unequal distribution of ions on either side of a resting neural membrane,
Are sodium-potassium pumps
Sodium-potassium pumps are
Transporters
EPSPs are
A) graded responses
B) postsynaptic responses
C) transmitted decrementally
D) depolarization
All of the above
A change in the resting potential of a postsynaptic dendrite from -70 mV to -72 mV is called
An IPSP
Hyperpolarization is to depolarization as
Inhibitory is to excitatory
IPSP is to EPSP as
Hyperpolarization is to depolarization
The transmission of postsynaptic potentials is
A) active
B) decremental
C) extremely rapid
Both B and C
How far do most postsynaptic potentials travel before they die out?
No more than a couple of millimeters
Which of the following are membrane potentials?
A) EPSPs
B) IPSPs
C) APs
All of the above
Action potentials originate at the
Axon initial segment, adjacent to the axon hillock
A neuron normally fires when
The degree of depolarization on the axon adjacent to the hillock exceeds the threshold of excitation
APs are said to be all-or-none: this means that all APs
In a particular neuron are the same
Another word for “integration” is
“Summation”
There are three kinds of spatial summation and
Two kinds of temporal summation
Action potentials are produced by the
Opening of voltage-activated sodium channels
During an action potential, the change in membrane potential associated with the influx of sodium ions triggers the
Opening of potassium channels
The end of the rising phrase of an action potential occurs when the
Sodium channels close
After a neuron fires, the resting potential is re-established by the
Random movement of ions
The brief period of time immediately after the initiation of an action potential when it is absolutely impossible to initiate another one in the same neuron is called the
Absolute refractory period
The wave of absolute refractoriness that follows an action potential
Keeps the action potential from spreading actively back along an axon towards the cell body
Neurons do not normally fire more than 1,000 times per second because
The absolute refractory period is typically about 1 millisecond
Conduction of action potentials along an axon is
Nondecremental
Active conduction is to passive conduction as
APs are to EPSPs
The conduction of an action potential along any axon is mediated by the action of
Voltage-activated ion channels
Conduction of APs from the axon into the cell body and dendrites of a multipolar neuron is
Antidromic
Action potentials can be conducted
A) actively
B) passively
C) orthodromically
D) antidromically
All of the above
Conduction of action potentials in myelinated axons
Is faster than in unmyelinated axons
In large myelinated human motor neurons, impulses travel at about
60 meters per second
With respect to the maximum speed of axonal conduction in motor neurons, cats are to humans as
100 is to 60 meters per second
Neurons without axons do not
Generate action potentials
In neurons without axons, conduction occurs entirely in the form of
Passive, decrementally conducted potentials
Axodendritic synapses
Always terminate on dendrites
Prevalent in the cytoplasm of most terminal buttons are
A) nuclei
B) mitochondria
C) synaptic vesicles
Both B and C
Nondirected synapses
A) involve the release of neurotransmitter molecules diffusely into the extracellular fluid
B) include string-of-beads synapses
C) involve the movement of neurotransmitter molecules across gap junctions
Both A and B
Both presynaptic facilitation and inhibition are mediated by
Axoaxonic synapses
Neurotransmitter are often stored in
Synaptic vesicles
Neurotransmitter molecules are often packaged in vesicles by
Golgi complexes
Neuropeptides are synthesized in the cell body on
Ribosomes
Peptide neurotransmitters (i.e., neuropeptides) are synthesized in the cell body and
Transported in vesicles along microtubules to the buttons
Vesicles travel from the cell body to the buttons
A) on action potentials
B) along microtubules
C) at a rate of 40 centimetres per second
D) at a rate of 40 centimetres per day
Both B and D
Neuropeptides are transported in vesicles from the cell body to the buttons at a speed of about
40 centimetres per day
Many buttons contain two sizes of vesicles; the larger ones typically contain
Neuropeptides
Many neurons contain and release two neurotransmitters. This situation is called
Coexistence
The process of neurotransmitter release is referred to as
Exocytosis
The release of neurotransmitter molecules from buttons is often triggered by
An influx of calcium ions
Once released, neurotransmitter molecules typically produce signals in postsynaptic neurons by
Binding to postsynaptic receptors
A ligand of acetylcholine is a substance that
Binds to acetylcholine
Ionotropic receptors are linked to
Ligand-activated ion channels
Metabotropic receptors are linked to
Signal proteins and G proteins
When a small-molecule neurotransmitter molecules binds to an ionotropic receptor, the
Associated ion channel opens or closes
In comparison to ionotropic receptors, metabotropic receptors
A) are more prevalent
B) produce longer lasting effects
C) produce effects that are more diffuse
D) produce effects that take longer to develop
All of the above
In comparison to ionotropic receptors, metabotropic receptors generally produce
Longer lasting effects
In comparison to metabotropic receptors, ionotropic receptors produce effects that
A) are less diffuse
B) develop more rapidly
C) are more enduring
Both A and B
Second messengers can
A) be synthesized in response to activation of metabotropic receptors
B) influence metabolic activities of the cell
C) induce IPSPs or EPSPs
D) bind to DNA to influence protein synthesis
All of the above
Second messengers are formed in the
Postsynaptic neuron
Autoreceptors are commonly found in
Presynaptic membranes
Autoreceptors of a neuron are sensitive to the neuron’s own
Neurotransmitter
Which of the following are thought to play a role in reducing excessive neurotransmitter release?
A) dendritic receptors B) autoreceptors C) dendritic spines D) postsynaptic receptors E) somatic receptors
Autoreceptors
Which of the following is currently thought to be a valid general principle of synaptic transmission?
A) each neuron releases only one neurotransmitter
B) each neurotransmitter acts on only one receptor subtype
C) all receptors are in postsynaptic membranes
D) all neurotransmitters are released into the synaptic cleft
None of the above
After release, most neurotransmitters are deactivated by
Reuptake
After release, neurotransmitters are deactivated in the synapse by
A) reuptake
B) enzymatic degradation
C) G proteins
Both A or B
There is only one neurotransmitter that is known to be deactivated in the synaptic cleft by enzymatic degradation; this neurotransmitter is
Acetylcholine
The one enzyme whose function is to deactivate a specific neurotransmitter once it has been released into the synapse is
Acetylcholinesterase
Neurons recycle
A) neurotransmitter molecules that have been drawn back into the terminal buttons after being released
B) the breakdown products of neurotransmitter molecules that have been degraded in the synapse by enzymes
C) vesicles that have been integrated into the button membrane during exocytosis
All of the above
Glial cells have been shown to
A) release chemical transmitters
B) contain receptors for neurotransmitters
C) conduct signals
D) influence synaptic transmission
All of the above
Recent technological developments have led to the discovery of _________ throughout the mammalian brain; they seem to link the activities of inhibitory interneurons of the same type
Gap junctions
Which of the following are considered to be small-molecule neurotransmitters?
A) neuropeptide transmitters
B) monoamine neurotransmitters
C) amino acid neurotransmitters
Both B and C
Which is considered to be the most prevalent inhibitory neurotransmitter in the mammalian CNS?
GABA
Which is considered to be the most prevalent excitatory neurotransmitter in the mammalian CNS?
Glutamate
Glycine, aspartate, and glutamate are
A) amino acid neurotransmitters
B) small-molecule neurotransmitters
C) transmitters at fast-acting, directed synapses
D) building blocks of proteins
All of the above
Monoamines are divided into two groups:
Catecholamines and indolamines
Which neurotransmitters are often released from string-of-beads axons?
Monoamines
Which of the following is not a monoamine?
A) acetylcholine B) dopamine C) epinephrine D) serotonin E) norepinephrine
Acetylcholine
Which of the following are synthesized from tyrosine?
A) monoamines
B) indolamines
C) catecholamines
D) amino acids
Catecholamines
In the presence of the appropriate enzyme, dopamine is converted to
Norepinephrine
Which of the following is not found in neurons that release norepinephrine?
A) dopamine B) L-DOPA C) norepinephrine D) epinephrine E) tyrosine
Epinephrine
Which of the following is synthesized directly from tyrosine?
A) dopamine B) epinephrine C) L-DOPA D) serotonin E) GABA
L-DOPA
The abbreviation 5-HT stands for
A) serotonin
B) dopamine
C) acetylcholine
Both A and B
Serotonin is synthesized from
Tryptophan
Adrenergic neurons release
Epinephrine
Acetylcholine is created by the addition of an acetyl group to
A choline molecule
Acetylcholine is
A) a large-molecule neurotransmitter
B) synthesized by adding an acetyl group to a choline molecule
C) an indolamine
Synthesized by adding an acetyl group to a choline molecule
Nitric oxide
A) is a soluble gas neurotransmitter
B) is considered to be an unconventional neurotransmitter
C) participates in retrograde synaptic transmission
All of the above
Soluble-gas neurotransmitters
A) are synthesized in the neural cytoplasm
B) once synthesized, immediately diffuse through the cell membrane into the extracellular fluid and into nearby cells
C) diffuse into target cells through their cell membranes
D) once in other cells, stimulate the synthesis of a second messenger and are immediately broken down
All of the above
Which of the following is an endocannabinoid neurotransmitter?
A) nitric oxide B) aspartate C) anandamide D) THC E) indolamine
Anandamide
About how many neuropeptides are currently classified by most experts as neurotransmitters?
Just over 100
Peptide neurotransmitters are
A) synthesized in the cell body
B) amino acid chains
C) large-molecule neurotransmitters
All of the above
Drugs that facilitate the activity of synapses of a particular neurotransmitter are said to be _________ of that neurotransmitter
Agonists
With respect to neurotransmitters, which of the following is a correct sequence?
A) synthesis, storage, exocytosis, reuptake
B) reuptake, synthesis, deactivation, exocytosis
C) deactivation, postsynaptic binding, synthesis, storage
D) storage, deactivation, synthesis, exocytosis
E) exocytosis, postsynaptic binding, synthesis, reuptake
Synthesis, storage, exocytosis, reuptake
This drug is a muscarinic acetylcholine antagonist; it is an extract of the belladonna plant; and it has pupil-dilating effects
Atropine
Drugs that block the reuptake of a neurotransmitter from the synapse are usually
Agonists of that neurotransmitter
Drugs that bind to a neurotransmitter’s autoreceptors without activating them are usually
Agonists
Drugs that bind to a neurotransmitter’s receptors on the postsynaptic membrane without activating them are
A) receptor blockers
B) agonists of the neurotransmitter
C) antagonists of the neurotransmitter
Both A and C
Drugs that degrade vesicles and cause the neurotransmitter molecules to leak into the cytoplasm, where they are destroyed by enzymes, are
Antagonists of the neurotransmitter
Which drug was extracted from the belladonna plant and used by the ancient Greeks for cosmetic purposes?
Atropine
Atropine is
A muscarinic antagonist
The receptors of the neuromuscular junction are
A) cholinergic
B) nicotine
C) muscarinic
Both A and B
Which of the following is a cholinergic antagonist?
Curare
By binding to nicotine cholinergic receptors, this drug produces paralysis and death
Curare
Which of the following is a nicotinic antagonist?
A) botox
B) curare
C) atropine
Both A and B
Botox is
A) a deadly poison
B) used to reduce tremors
C) a nicotinic antagonist
All of the above
Opiates play a role in
A) analgesia
B) pleasure
C) retrograde transport
Both A and B
Some of the morphine-like substances that occur naturally in the brain are
Endorphins
Endorphins are
Neuropeptides
Cocaine and amphetamines are
Dopamine agonists
Cocaine and amphetamines in high doses can produce a temporary disorder that is similar to
Schizophrenia
Many effective antischizophrenic drugs
Are D2 blockers
Which of the following is not an amino acid neurotransmitter?
A) aspartate B) glutamate C) glycine D) indolamine E) GABA
Indolamine
