Ligand gated ionotropic and metabotropic receptors 2 (1)

What is the mechanism of ionotropic receptors?

They bind neurotransmitters, causing conformational changes that open ion channels, allowing ions to flow according to concentration gradients.

What happens when Na⁺ ions enter a neuron via ionotropic receptors?

It depolarizes the membrane, increasing the likelihood of an action potential.

How do inhibitory ionotropic receptors work?

They permit the flow of Cl⁻ ions into the neuron, leading to hyperpolarization and decreasing the likelihood of an action potential.

What is an example of an ionotropic receptor?

The AMPA receptor for glutamate, which allows Na⁺ flow and causes rapid excitation.

What defines metabotropic receptors?

They do not contain ion channels themselves and exert effects through G-protein activation and second messenger systems.

Explain the activation process of metabotropic receptors.

The neurotransmitter binds, activating a G-protein, which then triggers effector proteins and second messengers, leading to various cellular changes.

What is an example of a metabotropic receptor and its function?

The dopamine receptor can lead to diverse effects via second messenger pathways influencing behavior and mood.

How do ionotropic and metabotropic receptors differ in speed of response?

Ionotropic receptors exhibit fast responses (milliseconds), while metabotropic receptors reflect slower responses (seconds to minutes).

What is the role of voltage-gated Na⁺ channels in synaptic transmission?

They open in response to depolarization, allowing Na⁺ to flow into the cell and further depolarizing the membrane.

How do neurotransmitter vesicles release their contents?

An action potential triggers Ca²⁺ channels to open, allowing Ca²⁺ to flow in, leading to vesicle fusion and neurotransmitter release.

What occurs at the neuromuscular junction?

Acetylcholine binds to nicotinic receptors, causing depolarization, which triggers muscle contraction.

What is the role of acetylcholinesterase in neurotransmission?

It degrades acetylcholine to terminate the signal and prevent prolonged stimulation of the postsynaptic cell.

How do glycine receptors function?

They are chloride channels that allow Cl⁻ to enter, hyperpolarizing the neuron and inhibiting action potential firing.

Explain the concept of phasic GABAA receptors.

They are activated by high concentrations of GABA at synapses, leading to rapid inhibitory responses.

What is the difference between phasic and tonic GABAA receptors?

Phasic receptors respond to brief, high concentrations of GABA, while tonic receptors detect lower, sustained levels of GABA.

What triggers the NMDA receptor to open?

NMDA receptors require both glutamate binding and postsynaptic depolarization to remove the Mg²⁺ block and allow ion flow.

What is long-term potentiation (LTP)?

LTP is a process that strengthens synapses based on recent patterns of activity, crucial for learning and memory.

What role do endocannabinoids play in neuronal excitability?

They act as circuit dampeners, reducing neurotransmitter release and neuronal excitability during hyperactivity.

What activates the adenylyl cyclase pathway in G-protein signaling?

A transmitter binding to a G-protein-coupled receptor (GPCR) activates a G-protein which then stimulates adenylyl cyclase.

What is the primary outcome of the PLC pathway in G-protein signaling?

It produces inositol triphosphate (IP3) and diacylglycerol (DAG), leading to increased intracellular Ca²⁺ levels.

How does Ca²⁺ function in signaling?

Calcium ions act as secondary messengers, triggering a variety of intracellular processes and biochemical cascades.

What are the two main types of metabotropic receptors?

Receptor tyrosine kinases and G-protein-coupled receptors (GPCRs).

What is the significance of the GPCR structure?

They are composed of seven transmembrane regions and are crucial for binding neurotransmitters, triggering intracellular signaling.

What is the primary inhibitory neurotransmitter in the CNS?

GABA (gamma-aminobutyric acid).

What is the reversal potential (Erev) for glycine receptors?

Approximately -70 mV, which indicates the membrane potential at which there is no net ion flow.

How do agonists affect nicotinic receptors?

Agonists like acetylcholine activate the receptor, leading to depolarization and potential action potential firing.

What effect do antagonists have on nicotinic receptors?

Antagonists block the receptors, preventing neurotransmitter binding and inhibiting muscle contraction.

How do synaptic receptors contribute to rapid signaling?

They enable fast transmission of signals by allowing ions to flow immediately in response to neurotransmitter binding.

What is required for NMDA receptor activation beyond glutamate binding?

Postsynaptic depolarization is also required to relieve the Mg²⁺ block.

What are Cys-loop receptors?

A family of ionotropic receptors that include nicotinic receptors, GABAA receptors, and glycine receptors.

Describe the function of glutamate receptors in the CNS.

They mediate fast excitatory transmission essential for learning, memory, and neuronal communication.

What is the role of transporters for GABA?

They remove GABA from the extracellular space, regulating both phasic and tonic inhibitory signaling.

What causes the release of neurotransmitters at the presynaptic terminal?

The influx of Ca²⁺ ions through voltage-gated channels when an action potential arrives.

Explain how second messengers affect cellular response.

They activate or inhibit various signaling pathways, leading to changes in cell function, gene expression, and other responses.

What is the importance of receptor subunit composition?

Different combinations of receptor subunits give rise to receptors with unique properties and functional responses.

How do GPCRs influence cell signaling pathways?

They catalyze the activation of G-proteins, which then trigger various intracellular signaling mechanisms.

What happens when a neurotransmitter binds to a GABAA receptor?

The receptor opens, allowing chloride ions to flow into the neuron, resulting in hyperpolarization.

Contrast synaptic and extrasynaptic GABAA receptors.

Synaptic receptors respond quickly to GABA release, while extrasynaptic receptors maintain a tonic level of inhibition.

What kind of channels are AMPA receptors?

They are ligand-gated ion channels that facilitate fast excitatory neurotransmission.

What does the NMDA receptor's Mg²⁺ block signify?

It means that NMDA requires depolarization to function, making it a coincidence detector.

How does the extracellular environment influence glycine receptor activity?

Chloride ion influx through these receptors causes hyperpolarization, regulating neuronal excitability.

What is an example of a fast response in the nervous system?

The action of ionotropic receptors that rapidly alter neuronal membrane potential following neurotransmitter binding.

What are the outcomes of G-protein signaling?

Activation of downstream effectors, production of secondary messengers, and initiation of biochemical cascades.

How does the CB1 receptor affect neurotransmitter release?

Activation of CB1 inhibits calcium channels, reducing neurotransmitter release from the presynaptic neuron.

What role does Ca²⁺ play in long-term potentiation?

The influx of Ca²⁺ during NMDA receptor activation triggers intracellular changes that strengthen synapses.

What is the role of gephyrin in glycine receptor function?

Gephyrin is necessary for clustering glycine receptors at inhibitory synapses.

What happens when excessive amounts of GABA are released in the brain?

Phasic receptors may be overwhelmed, leading to tonic inhibition that stabilizes neuronal activity.

How does Strychnine affect glycine receptors?

Strychnine blocks glycine receptors, leading to muscle spasms due to reduced inhibitory signaling.

What features characterize G protein-coupled receptors?

They consist of seven transmembrane domains and interact with G-proteins to relay signals inside the cell.

How do ionotropic receptors impact reflex actions?

They provide rapid synaptic transmission necessary for quick reflex responses.

What is an example of a competitive antagonist at nicotinic receptors?

Curare, which blocks the receptor and prevents muscle contraction.

How do NMDA receptors contribute to learning?

They facilitate calcium-dependent signaling that leads to synaptic strengthening, essential for memory formation.

What type of receptors are involved in mood regulation?

Metabotropic receptors, which influence long-term changes in neuronal activity.

What is the primary mechanism of action for drugs targeting GPCRs?

They modulate receptor activity, influencing various physiological responses and are often used in pharmacotherapy.

Explain the difference in signaling between ionotropic and metabotropic receptors.

Ionotropic receptors facilitate immediate ion flow, while metabotropic receptors activate longer, signaling cascades involving second messengers.

Describe the functional implications of synaptic versus extrasynaptic receptors.

Synaptic receptors mediate fast signaling, whereas extrasynaptic receptors offer sustained inhibition and stabilization of neuronal activity.

What determines the specificity of G-protein signaling?

The specific G-protein activated is determined by the GPCR it couples with, leading to different physiological outcomes.

How does the ion flow differ between excitatory and inhibitory neurotransmission?

Excitatory neurotransmission involves Na⁺ inflow, while inhibitory neurotransmission involves Cl⁻ inflow.

What are the main products of phospholipase C (PLC) activity when activated by a GPCR?

Diacylglycerol (DAG) and inositol triphosphate (IP3), both of which act as second messengers.

What is the significance of ligand-gated ion channels in synaptic transmission?

They enable rapid signaling and are essential for the immediate effects of neurotransmitter release.

How do receptor subunits influence responses to neurotransmitters?

The specific arrangement and type of subunits determine the sensitivity and behavior of the receptors in response to neurotransmitters.

What is the consequence of prolonged exposure to neurotransmitters at synapses?

It can lead to receptor desensitization, reducing the efficacy of neurotransmission over time.

What physiological responses can cAMP influence?

cAMP can activate protein kinases, leading to various cellular responses including metabolism, gene expression, and cell division.

What effect does sustained depolarization have on NMDA receptors?

Sustained depolarization removes the Mg²⁺ block, allowing for calcium entry and activation of intracellular signaling pathways.

What is the effect of GABAA receptor activation in the CNS?

It typically results in rapid inhibition, helping to regulate neuronal excitability and prevent excessive firing.

How do metabotropic receptors differ in their effects compared to ionotropic receptors?

Metabotropic receptors lead to slower and longer-lasting effects through signaling cascades, while ionotropic receptors result in immediate changes.

What type of signaling do potassium channels primarily mediate?

They primarily mediate inhibitory signaling by allowing K⁺ efflux, which hyperpolarizes the neuron.

What neurotransmitter is primarily involved in excitatory transmission in the CNS?

Glutamate.

What characteristic of the NMDA receptor is critical for synaptic plasticity?

Its activity as a coincidence detector, requiring both ligand binding and depolarization for activation.

What role do GABA transporters play at synapses?

They help clear GABA from the synaptic cleft, regulating inhibitory signaling.

What is the significance of having multiple subtypes of GABAA receptors?

Different subtypes allow for modulated responses to varying GABA levels, contributing to diverse inhibitory effects in the brain.

What do glutamate receptors mediate in neural communication?

They mediate fast excitatory signaling necessary for synaptic plasticity and communication between neurons.

Which receptor type is primarily responsible for rapid muscle contractions?

Nicotinic acetylcholine receptors located at the neuromuscular junction.

How does endocannabinoid signaling mitigate neuronal excitability?

By activating presynaptic CB1 receptors, which inhibit calcium influx and reduce neurotransmitter release.

What is the clinical significance of targeting GABAA receptors?

They are targets for anxiolytics and sedatives, affecting inhibitory neurotransmission and mood regulation.

What role do second messengers like cAMP and IP3 play in cellular signaling?

They propagate and amplify the signaling cascades initiated by receptor activation, influencing several cellular processes.

How does excessive activation of NMDA receptors contribute to pathology?

It can lead to excitotoxicity, contributing to neurodegenerative disorders by causing neuronal damage.

What neurotransmitter is primarily associated with the autonomic nervous system functions?

Acetylcholine.

How do potassium ion channels influence neuronal activity?

They regulate membrane excitability by facilitating K⁺ efflux, contributing to repolarization after action potentials.

What happens to synaptic signaling in the presence of antagonists like curare?

Antagonists block receptor activation, preventing neurotransmitter-mediated responses, such as muscle contraction.