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Questions and Answers
What is the primary effect of GABA on ion channels?
What is the primary effect of GABA on ion channels?
What results from GABA channels staying open for too long?
What results from GABA channels staying open for too long?
Which of the following substances is associated with increased inhibition in the central nervous system?
Which of the following substances is associated with increased inhibition in the central nervous system?
What is the main role of glycine receptors in the nervous system?
What is the main role of glycine receptors in the nervous system?
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Which neurotransmitter is likely to cause seizures when present in excessive amounts?
Which neurotransmitter is likely to cause seizures when present in excessive amounts?
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What potential effect can anesthetics have on GABA receptors?
What potential effect can anesthetics have on GABA receptors?
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How does an increase in Cl- entering a neuron affect its activity?
How does an increase in Cl- entering a neuron affect its activity?
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What condition can result from excessive activation of GABAergic pathways?
What condition can result from excessive activation of GABAergic pathways?
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Which property makes the NMDA receptor unique among glutamate receptors?
Which property makes the NMDA receptor unique among glutamate receptors?
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What effect does the activation of AMPA receptors have on NMDA receptors?
What effect does the activation of AMPA receptors have on NMDA receptors?
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What is the primary function of GABA in the brain?
What is the primary function of GABA in the brain?
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Which of the following GABA receptors is classified as ionotropic?
Which of the following GABA receptors is classified as ionotropic?
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What ion is primarily associated with the inhibitory effect of GABAA receptor activation?
What ion is primarily associated with the inhibitory effect of GABAA receptor activation?
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Activation of which type of glutamate receptor is considered important for learning and memory?
Activation of which type of glutamate receptor is considered important for learning and memory?
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What happens to the Mg2+ block during depolarization of the cell?
What happens to the Mg2+ block during depolarization of the cell?
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Which of the following ions primarily flows into the cell upon NMDA receptor activation?
Which of the following ions primarily flows into the cell upon NMDA receptor activation?
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What effect would a toxin that blocks voltage-gated Na+ channels have on action potentials?
What effect would a toxin that blocks voltage-gated Na+ channels have on action potentials?
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Which ions enter the terminal to trigger neurotransmitter release during an action potential?
Which ions enter the terminal to trigger neurotransmitter release during an action potential?
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What are the proteins called that facilitate the fusion of neurotransmitter vesicles with the membrane?
What are the proteins called that facilitate the fusion of neurotransmitter vesicles with the membrane?
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In the process of exocytosis, what role does synaptotagmin play?
In the process of exocytosis, what role does synaptotagmin play?
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What is the immediate consequence of an action potential reaching the axon terminal?
What is the immediate consequence of an action potential reaching the axon terminal?
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What occurs during the exocytosis of neurotransmitters?
What occurs during the exocytosis of neurotransmitters?
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Which of the following toxins prevents voltage-gated Na+ channels from closing?
Which of the following toxins prevents voltage-gated Na+ channels from closing?
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What happens to synaptic vesicles during neurotransmitter release?
What happens to synaptic vesicles during neurotransmitter release?
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Which of the following can be a result of a toxin affecting neurotransmitter release at muscles?
Which of the following can be a result of a toxin affecting neurotransmitter release at muscles?
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What is the term used to describe the physical pulling of vesicles closer to the axon terminal for fusion?
What is the term used to describe the physical pulling of vesicles closer to the axon terminal for fusion?
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Which factor determines whether a post-synaptic potential (PSP) is excitatory or inhibitory?
Which factor determines whether a post-synaptic potential (PSP) is excitatory or inhibitory?
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What is the result of cations entering the cell during an excitatory post-synaptic potential (EPSP)?
What is the result of cations entering the cell during an excitatory post-synaptic potential (EPSP)?
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What role do enzymes play in neurotransmitter action?
What role do enzymes play in neurotransmitter action?
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What occurs during spatial summation?
What occurs during spatial summation?
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What must happen for an action potential to be triggered at the axon hillock?
What must happen for an action potential to be triggered at the axon hillock?
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In temporal summation, what happens to potentials that arrive at the axon hillock?
In temporal summation, what happens to potentials that arrive at the axon hillock?
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What is a characteristic of both EPSPs and IPSPs?
What is a characteristic of both EPSPs and IPSPs?
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Which input at the axon hillock can trigger an action potential?
Which input at the axon hillock can trigger an action potential?
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What is the effect of an anion entering the cell?
What is the effect of an anion entering the cell?
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True or False: Temporal summation is more important than spatial summation in action potential generation.
True or False: Temporal summation is more important than spatial summation in action potential generation.
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Which neurotransmitter primarily affects arousal and sleep/wake cycles?
Which neurotransmitter primarily affects arousal and sleep/wake cycles?
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Which neurotransmitter's dysfunction is most directly associated with Parkinson's disease?
Which neurotransmitter's dysfunction is most directly associated with Parkinson's disease?
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Which receptor types does norepinephrine bind to?
Which receptor types does norepinephrine bind to?
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What is the primary role of serotonin in the brain?
What is the primary role of serotonin in the brain?
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Which neurotransmitter is linked to anxiety and depression treatment?
Which neurotransmitter is linked to anxiety and depression treatment?
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Where does acetylcholine primarily act in the peripheral nervous system?
Where does acetylcholine primarily act in the peripheral nervous system?
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Which neurotransmitter is responsible for reward and reinforcement pathways in the brain?
Which neurotransmitter is responsible for reward and reinforcement pathways in the brain?
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What mechanism do drugs for PTSD target regarding norepinephrine?
What mechanism do drugs for PTSD target regarding norepinephrine?
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Excess norepinephrine relative to serotonin can lead to which condition?
Excess norepinephrine relative to serotonin can lead to which condition?
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Which neurotransmitter is primarily implicated in Alzheimer's disease?
Which neurotransmitter is primarily implicated in Alzheimer's disease?
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Dopamine is released from which area of the brain to influence motor control?
Dopamine is released from which area of the brain to influence motor control?
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How many types of receptors does serotonin act on?
How many types of receptors does serotonin act on?
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The sympathetic nervous system primarily utilizes which neurotransmitter in its response?
The sympathetic nervous system primarily utilizes which neurotransmitter in its response?
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Acetylcholine receptors in the central nervous system are classified as which types?
Acetylcholine receptors in the central nervous system are classified as which types?
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Study Notes
Action Potentials and Toxins
- Blocking voltage-gated Na+ channels prevents action potentials from being generated, as seen with toxins like tetrodotoxin and saxitoxin.
- Batrachotoxin keeps sodium channels open, disrupting normal neural function.
- Agitoxin and beta-bungarotoxin inhibit voltage-gated K+ channels, impacting repolarization.
Neurotransmitter Release at Synapses
- Action potentials at the pre-synaptic terminal open voltage-gated Ca²⁺ channels.
- Ca²⁺ influx triggers synaptic vesicles to fuse with the membrane, leading to neurotransmitter release via exocytosis.
- SNARE proteins (v-SNARES and t-SNARES) facilitate vesicle docking and fusion at the presynaptic membrane.
Exocytosis Steps
- Ca²⁺ binds to synaptotagmin, a sensor that causes vesicles to move closer to the membrane, promoting fusion and neurotransmitter release.
Post-Synaptic Potentials (PSPs)
- The type of neurotransmitter released determines whether a PSP is excitatory or inhibitory.
- Excitatory PSPs (EPSPs) decrease membrane negativity, while inhibitory PSPs (IPSPs) increase negativity.
EPSP and IPSP Processing
- Cation influx results in depolarization (EPSP); anion influx or cation efflux leads to hyperpolarization (IPSP).
- Individual EPSPs and IPSPs are small; summation of these signals occurs in the dendrites.
Summation Types
- Spatial summation combines signals from multiple neurons at various cell parts.
- Temporal summation aggregates signals arriving at the axon hillock in quick succession.
- Successful integration of both types can trigger an action potential if the threshold is met.
Integrative Action Potential Generation
- Action potentials arise from the summation of excitatory and inhibitory inputs, with a threshold of -55 mV to -40 mV being critical.
- Excessive IPSPs can suppress excitability, preventing unregulated firing, as seen in seizure conditions.
Receptors and Neurotransmitter Action
- Ionotropic receptors allow ions to flow through when bound by neurotransmitters; NMDA receptors require both ligand binding and depolarization for activation.
- AMPA receptors' activation can lead to NMDA receptor opening, enhancing EPSP generation, crucial for cognitive functions like learning.
GABA and Glycine
- GABA serves as the main inhibitory neurotransmitter, acting on GABA receptors (GABAA, GABAC, and GABAB).
- GABAA receptors allow Cl⁻ influx, leading to IPSPs and have binding sites for sedatives and anesthetics that can prolong their effect.
- Glycine receptors are ionotropic and also mediate inhibitory signals primarily in the spinal cord and brainstem.
Seizures and Comas
- Excessive glutamate can trigger seizures, while excessive GABA can lead to coma.### Neuromodulatory Transmitters
- Neuromodulatory transmitters alter information processing in the CNS primarily through metabotropic actions.
- They can amplify or dampen signals without directly transferring information quickly.
Norepinephrine/Noradrenaline (NE)
- Originates in the locus coeruleus, projecting throughout the brain and body.
- Crucial for arousal, sleep/wake regulation, and mood, influencing stress and anxiety.
- Enhances cognitive function, particularly decision-making during stress responses.
- Acts through sympathetic nervous system; central to fight/flight responses.
- Metabotropic receptors include α1, α2, β1, and β2.
- Associated with anxiety, stress, hyperarousal; PTSD treatment can involve NE inhibitors.
Serotonin (5-HT)
- Produced in the dorsal raphe, with projections across various brain regions.
- Regulates sleep/wake cycles, feeding behavior, and mood, primarily through metabotropic receptors (15 types).
- Links to anxiety and depression; SSRIs (like Prozac) are common treatments.
- An imbalance of NE and 5-HT is noted in anxiety disorders, with excessive NE impacting serotonin levels.
Dopamine (DA)
- Different effects based on release locations within the brain.
- Originates in the ventral tegmental area, affecting limbic and cortical areas; key in reward and reinforcement.
- Involved in addiction pathways throughout the cortex.
- Another origin in the substantia nigra, projecting to the striatum, aids in motor control; depletion linked to Parkinson's disease.
- Metabotropic receptors range from D1 to D5.
- Disorders linked to dopamine include schizophrenia, drug addiction, and Parkinson's disease.
Acetylcholine (ACh)
- In the CNS, arises from the basal forebrain; released widely and linked to various projections.
- Involved in learning, memory, and attention; affected in Alzheimer’s disease.
- Utilizes ionotropic nicotinic receptors (also impacted by nicotine) and metabotropic muscarinic receptors.
- In the PNS, plays a role at the neuromuscular junction with ionotropic nicotinic ACh receptors crucial for muscle function.
- Lost cholinergic function is a critical feature in neurodegenerative diseases.
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