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A neurotransmitter is a signaling molecule secreted by a neuron to affect another cell across a synapse.
Answer: True
The fundamental definition of a neurotransmitter is a signaling molecule released by a neuron to influence another cell across a synaptic junction.
Neurotransmitters exclusively target other neurons, never glands or muscle cells.
Answer: False
Neurotransmitters can target other neurons, as well as glands and muscle cells, enabling a wide range of physiological responses.
The specific effect a neurotransmitter has on a target cell is primarily determined by the type of receptor it binds to, rather than the neurotransmitter itself.
Answer: True
The identity of the receptor to which a neurotransmitter binds is the primary determinant of the resulting effect on the target cell, allowing for diverse responses from a single neurotransmitter.
Neurotransmitters can only have either an excitatory or an inhibitory effect on a target cell.
Answer: False
Neurotransmitters can exert excitatory, inhibitory, or modulatory effects on target cells, depending on the specific receptors they bind to.
A receiving neuron will generate an action potential if its overall inhibitory influences outweigh its excitatory influences.
Answer: False
A receiving neuron generates an action potential if its overall excitatory influences outweigh the inhibitory influences, reaching the firing threshold.
Volume transmission involves neurotransmitters diffusing through the extracellular space to reach distant receptors, affecting large brain volumes.
Answer: True
Volume transmission describes the diffusion of neurotransmitters through the extracellular space to reach receptors beyond the immediate synapse, influencing broader brain regions.
What is the fundamental definition of a neurotransmitter?
Answer: A signaling molecule secreted by a neuron to affect another cell across a synapse.
Which of the following cell types can be a target for a neurotransmitter's signal?
Answer: Neurons, glands, or muscle cells.
What primarily determines the specific effect a neurotransmitter has on a target cell?
Answer: The specific receptor it binds to.
Which of the following is NOT one of the three types of effects neurotransmitters can have on a target cell?
Answer: Destructive.
A receiving neuron will generate its own action potential under which of the following conditions?
Answer: If the overall excitatory influences outweigh the inhibitory influences.
What is 'volume transmission' in the context of neurotransmitter systems?
Answer: Neurotransmitters diffusing through extracellular space to reach distant receptors.
Many neurotransmitters are synthesized from complex, rare precursors that require numerous biosynthetic steps.
Answer: False
Many neurotransmitters are synthesized from simple and plentiful precursors, such as amino acids, often requiring only a few biosynthetic steps.
Over 100 unique neurotransmitters have been identified in humans, though the exact total is unknown.
Answer: True
The exact number of unique neurotransmitters in humans is not fully known, but more than 100 have been identified, indicating the vast complexity of neural communication.
The primary classes of neurotransmitters include amino acids, monoamines, and peptides, but do not include purine neurotransmitters.
Answer: False
The primary classes of neurotransmitters include amino acids, monoamines, and peptides, and also encompass purine neurotransmitters, as well as metabolic products like nitric oxide and carbon monoxide.
Serotonin, a monoamine, is synthesized from the amino acid tryptophan through a process of altering a single amino acid.
Answer: True
Monoamines like serotonin are synthesized by modifying a single amino acid, with tryptophan serving as the precursor for serotonin.
Neuropeptides are small-molecule neurotransmitters that primarily elicit direct, rapid excitatory effects.
Answer: False
Neuropeptides are larger protein transmitters that typically exert modulatory effects, rather than direct, rapid excitatory actions, distinguishing them from classical small-molecule neurotransmitters.
The purine neurotransmitters listed in the table are dopamine and norepinephrine.
Answer: False
Dopamine and norepinephrine are classified as monoamine neurotransmitters, while ATP and GTP are listed as purine neurotransmitters.
Neurotransmitters are generally stored in synaptic vesicles at the axon terminal, awaiting an electrical signal for release.
Answer: True
Synaptic vesicles at the axon terminal serve as the primary storage sites for neurotransmitters, which are released in response to an electrical signal.
All known neurotransmitters are stored in synaptic vesicles before their release.
Answer: False
Not all neurotransmitters are stored in vesicles; metabolic gases like carbon monoxide and nitric oxide are synthesized and released immediately without prior storage.
Co-localization describes the phenomenon where a neuron releases only one type of neurotransmitter from its synaptic terminal.
Answer: False
Co-localization refers to a neuron releasing *more than one* type of neurotransmitter from its synaptic terminal, often involving neuropeptides.
From what common type of precursor are many neurotransmitters synthesized?
Answer: Amino acids.
Approximately how many unique neurotransmitters have been identified in humans, according to the source?
Answer: More than 100.
Which of the following is NOT listed as a common example of a neurotransmitter in the source?
Answer: Insulin.
Which of the following is identified as a primary class of neurotransmitters in the text?
Answer: Monoamines.
The amino acid tryptophan serves as the precursor for which monoamine neurotransmitter?
Answer: Serotonin.
How do neuropeptides primarily differ from classical small-molecule neurotransmitters in their function?
Answer: They are larger protein transmitters that often elicit a modulatory effect.
According to the provided table, which group of neurotransmitters is categorized as monoamines?
Answer: Serotonin, Epinephrine, and Dopamine.
Which of the following are listed as purine neurotransmitters in the provided table?
Answer: ATP and GTP.
Where are neurotransmitters generally stored within a neuron prior to their release?
Answer: In synaptic vesicles.
Which of the following neurotransmitters are exceptions to the rule of being stored in vesicles before release?
Answer: Carbon monoxide and Nitric oxide.
In the context of neurotransmission, what does 'co-localization' specifically refer to?
Answer: A neuron releasing more than one transmitter from its synaptic terminal.
Neurotransmitters are released directly into the target cell's cytoplasm before binding to receptors.
Answer: False
Neurotransmitters are released into the synaptic cleft and then bind to specific receptors located on the target cell's membrane, not directly into its cytoplasm.
Neurotransmitter release from the presynaptic terminal occurs exclusively via exocytosis in response to an action potential.
Answer: False
While exocytosis in response to an action potential is the typical mechanism, a low-level baseline release of neurotransmitters also occurs independently of electrical stimulation.
The elimination of neurotransmitters from the synaptic cleft is essential to prevent continuous activation of receptors and ensure precise signaling.
Answer: True
Precise and transient signaling requires the rapid removal of neurotransmitters from the synaptic cleft to prevent prolonged receptor activation.
The three main mechanisms for neurotransmitter removal from the synaptic cleft are reuptake, enzymatic degradation, and direct absorption by the postsynaptic neuron.
Answer: False
The three main mechanisms for neurotransmitter removal are diffusion out of the cleft and absorption by glial cells, enzymatic degradation, and reuptake into the presynaptic neuron. Direct absorption by the postsynaptic neuron is not listed as a primary mechanism.
Astrocytes contribute to synaptic communication by absorbing excess neurotransmitters and can also release gliotransmitters.
Answer: True
Astrocytes play a vital role in synaptic function by clearing excess neurotransmitters and by releasing gliotransmitters that modulate synaptic transmission.
Type I (excitatory) synapses typically have flattened synaptic vesicles and are found on the cell body.
Answer: False
Type I (excitatory) synapses typically have round synaptic vesicles and are found on dendrite shafts or spines, whereas Type II (inhibitory) synapses often have flattened vesicles and are on the cell body.
After being released into the synaptic cleft, where do neurotransmitters interact with specific receptors?
Answer: On specific neurotransmitter receptors located on the target cell's membrane.
What is the typical mechanism for neurotransmitter release from the presynaptic terminal in response to an action potential?
Answer: Exocytosis.
What is the immediate action of neurotransmitters after they diffuse across the synaptic cleft?
Answer: They bind to specific receptors on the postsynaptic neuron.
The elimination of neurotransmitters from the synaptic cleft is critical for what reason?
Answer: To avoid continuous activation of receptors and ensure precise signaling.
What enzyme is responsible for the elimination of acetylcholine from the synaptic cleft?
Answer: Acetylcholinesterase.
Which of the following is NOT listed as a main mechanism for removing neurotransmitters from the synaptic cleft?
Answer: Active transport into the postsynaptic neuron's nucleus.
How do astrocytes primarily contribute to the removal of neurotransmitters from the synaptic cleft?
Answer: By absorbing excess neurotransmitters that diffuse out of the cleft.
Which structural characteristic is typical of a Type I (excitatory) synapse?
Answer: Denser pre- and postsynaptic membranes.
Glutamate is primarily an inhibitory neurotransmitter, and its excessive release can lead to excitotoxicity.
Answer: False
Glutamate is the primary *excitatory* neurotransmitter in the brain, and its excessive release can indeed lead to excitotoxicity.
GABA is the primary excitatory neurotransmitter in the brain, and many sedative drugs enhance its effects.
Answer: False
GABA is the primary *inhibitory* neurotransmitter in the brain, and many sedative drugs enhance its inhibitory effects.
The majority of serotonin in the body is produced by central nervous system neurons, with a smaller amount produced in the intestine.
Answer: False
Approximately 90% of the body's serotonin is produced in the intestine, with the remainder synthesized by central nervous system neurons.
Norepinephrine primarily stimulates the release of epinephrine from the adrenal glands in the peripheral nervous system.
Answer: True
In the peripheral nervous system, norepinephrine's primary role is to stimulate the release of epinephrine from the adrenal glands, contributing to the fight-or-flight response.
Epinephrine causes vasodilation and decreases heart rate, contributing to the 'rest and digest' response.
Answer: False
Epinephrine causes vasoconstriction and increases heart rate, playing a central role in the 'fight-or-flight' response, not the 'rest and digest' response.
Trace amines directly inhibit neurotransmission in monoamine pathways by blocking TAAR1 receptors.
Answer: False
Trace amines modulate neurotransmission in monoamine pathways by signaling through TAAR1 receptors, rather than directly inhibiting by blocking them.
What is the primary role of glutamate in the brain, and what can result from its excessive release?
Answer: Primary excitatory neurotransmitter; leads to excitotoxicity.
What is the main function of GABA in the brain?
Answer: It is used at the majority of fast inhibitory synapses.
Which of the following is NOT a primary function of dopamine in the brain?
Answer: Regulation of body temperature.
Approximately 90% of the body's serotonin is produced in which location?
Answer: In the intestine.
In the peripheral nervous system, what is the primary role of norepinephrine?
Answer: To stimulate the release of epinephrine from the adrenal glands.
Which of the following is a key physiological effect of epinephrine, as described in the source?
Answer: Bronchodilation effects that relax airways.
How do trace amines modulate neurotransmission in monoamine pathways?
Answer: By signaling through trace amine-associated receptor 1 (TAAR1).
Cocaine enhances dopamine reuptake, leading to a shorter duration of dopamine's effect in the synaptic cleft.
Answer: False
Cocaine blocks dopamine reuptake, thereby prolonging dopamine's presence and effect in the synaptic cleft, rather than shortening it.
A receptor antagonist binds to a receptor and activates it, mimicking the action of an endogenous substance.
Answer: False
A receptor antagonist binds to a receptor and blocks its activation, thereby reducing the physiological activity of an endogenous substance, rather than mimicking it.
An agonist is a chemical that binds to a receptor and initiates the same reaction as the endogenous substance, effectively mimicking its action.
Answer: True
An agonist is defined as a chemical that binds to a receptor and elicits a physiological response similar to that of the endogenous ligand, effectively mimicking its action.
Fluoxetine (Prozac) works by blocking the reuptake of serotonin, thereby increasing its concentration and duration in the synaptic cleft.
Answer: True
Fluoxetine, a selective serotonin reuptake inhibitor (SSRI), enhances serotonin's effects by preventing its reabsorption into the presynaptic neuron, increasing its synaptic availability.
Strychnine acts as a glycine agonist, enhancing its inhibitory effects.
Answer: False
Strychnine acts as a glycine *antagonist*, blocking glycine's inhibitory effects, which can lead to severe muscle spasms.
Caffeine increases wakefulness by acting as an agonist at adenosine receptors, promoting their normal inhibitory effects.
Answer: False
Caffeine increases wakefulness by acting as an *antagonist* at adenosine receptors, thereby blocking adenosine's normal inhibitory effects.
Opiates like morphine relieve pain by acting as antagonists at mu-opioid receptors.
Answer: False
Opiates like morphine relieve pain by acting as *agonists* at mu-opioid receptors, mimicking the effects of endogenous opioid peptides.
Cocaine impacts dopamine neurotransmission by performing which action?
Answer: Blocking dopamine reuptake, prolonging its effect.
In pharmacology, a receptor antagonist is defined as a chemical that does what?
Answer: Reduces physiological activity by blocking a receptor without activating it.
What is the definition of a receptor agonist?
Answer: A chemical that binds to a receptor and initiates the same reaction as the endogenous substance.
How does Fluoxetine (Prozac) primarily affect serotonin neurotransmission?
Answer: It blocks the reuptake of serotonin by the presynaptic cell.
What is the effect of Strychnine on the glycine neurotransmitter system?
Answer: It blocks the action of glycine as an antagonist.
How does caffeine exert its stimulant effects on wakefulness?
Answer: By acting as an antagonist at adenosine receptors.
What is the mechanism of action for opiates like morphine in pain relief?
Answer: They act as agonists at mu-opioid receptors.
Low levels of dopamine are linked to Parkinson's disease, while high levels are associated with schizophrenia.
Answer: True
Dysfunctions in dopamine levels are implicated in several disorders: low levels in Parkinson's disease and high levels or dysregulation in schizophrenia.
Problems with dopamine production in the substantia nigra are associated with Parkinson's disease.
Answer: True
Parkinson's disease is characterized by problems in dopamine production, particularly in the substantia nigra, leading to motor control deficits.
The theory that depression is solely caused by lower-than-normal serotonin levels has been consistently supported by research.
Answer: False
The theory that depression is solely caused by lower-than-normal serotonin levels has not been consistently supported by subsequent research, indicating a more complex etiology.
Excessive glutamate has been associated with neurological diseases such as Parkinson's disease, multiple sclerosis, and Alzheimer's disease.
Answer: True
Excessive glutamate can lead to excitotoxicity and has been linked to the pathology of several neurological diseases, including Parkinson's disease, multiple sclerosis, and Alzheimer's disease.
Scientifically established normal levels for different neurotransmitters in the brain are readily measurable and well-defined.
Answer: False
There are no scientifically established 'normal' levels or balances for neurotransmitters in the brain, and their real-time measurement is practically impossible.
Chronic physical or emotional stress and genetics can both contribute to changes in neurotransmitter systems.
Answer: True
Both chronic stress and genetic factors are known to influence and contribute to alterations within neurotransmitter systems.
Neurotransmitter switching is a process where neurons permanently lose the ability to release certain neurotransmitters.
Answer: False
Neurotransmitter switching is a phenomenon where neurons *change* the type of neurotransmitters they release, not a permanent loss of ability.
Problems with dopamine production, particularly in the substantia nigra, are associated with which neurological disorder?
Answer: Parkinson's disease.
According to the source, what is the current understanding regarding the theory that depression is solely due to lower-than-normal serotonin levels?
Answer: This theory was not consistently supported by subsequent research.
Excessive glutamate has been associated with which of the following neurological diseases?
Answer: Multiple sclerosis.
What is the scientific consensus regarding established normal levels or balances for different neurotransmitters in the brain?
Answer: There are no scientifically established normal levels or balances, and measurement is practically impossible.
Which of the following factors can contribute to changes in neurotransmitter systems?
Answer: Chronic physical or emotional stress and genetics.
What is neurotransmitter switching?
Answer: A phenomenon where neurons change the type of neurotransmitters they release.
Before the early 20th century, scientists widely believed that most synaptic communication was chemical.
Answer: False
Prior to the early 20th century, the prevailing scientific belief was that most synaptic communication was electrical, not chemical.
Otto Loewi confirmed chemical neurotransmission and discovered acetylcholine in 1921.
Answer: True
Otto Loewi's seminal experiment in 1921 provided definitive proof of chemical neurotransmission and led to the discovery of acetylcholine.
One criterion for identifying a neurotransmitter is that its direct application to target cells must produce a different response than its natural release.
Answer: False
A key criterion for identifying a neurotransmitter is that its direct application to target cells should produce the *same* response as its natural release.
Modern understanding limits neurotransmitters to only chemicals that directly affect membrane voltage, excluding those that change synapse structure.
Answer: False
Modern understanding has expanded the definition of neurotransmitters to include chemicals that can alter synapse structure or send retrograde messages, even if they have minimal direct impact on membrane voltage.
Who is credited with confirming chemical neurotransmission and discovering acetylcholine (ACh) in 1921?
Answer: Otto Loewi.
Ramón y Cajal's discovery of a 20 to 40 nm gap between neurons, now known as the synaptic cleft, suggested what about neuronal communication?
Answer: That communication occurred via chemical messengers traversing this space.
According to the source, which of the following is a typical criterion for identifying a chemical as a neurotransmitter?
Answer: Its direct application to target cells should produce the same response as its natural release.