Cell Signaling and Neurotransmission Quiz

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Questions and Answers

Which of the following is a feature of ionotropic receptors?

  • They have slow chemical transmission.
  • They include ligand-gated ion channels. (correct)
  • They primarily function in synaptic plasticity.
  • They are G protein coupled receptors.

What is the correct description of neuromodulators in terms of their transmission speed?

  • Even faster than neurotransmitters
  • Slow, compared to neurotransmitters (correct)
  • Fast, similar to neurotransmitters
  • They have variable speeds

Which second messenger system is associated with calcium signaling?

  • cGMP
  • phosphatidyl inositol (correct)
  • metabotropic receptor
  • cAMP

What is a distinct characteristic of metabotropic receptors?

<p>They require GTP and activate G proteins upon ligand binding. (C)</p> Signup and view all the answers

Which of the following accurately represents endocrine signaling?

<p>Hormonal signaling through the bloodstream (C)</p> Signup and view all the answers

What happens after ligand binding to a metabotropic receptor?

<p>Activation of a G protein (D)</p> Signup and view all the answers

Which statement correctly describes the amplified response in metabotropic receptors?

<p>Phosphorylation of various targets (D)</p> Signup and view all the answers

Which process is directly affected by cyclic AMP signaling?

<p>Phosphorylation of ion channels and enzymes (A)</p> Signup and view all the answers

In the phosphatidyl inositol signaling system, what are the second messengers produced?

<p>Inositol trisphosphate and diacyl glycerol (D)</p> Signup and view all the answers

What is the effect of muscarinic Ach receptor activation on cardiac muscle?

<p>Decreases heart rate (B)</p> Signup and view all the answers

Which ion channel is involved in cardiac muscle response to muscarinic Ach receptor activation?

<p>Potassium channel (B)</p> Signup and view all the answers

What is the nature of the mechanism by which muscarinic Ach receptors operate?

<p>G-protein coupled receptor (C)</p> Signup and view all the answers

Which compound acts as an agonist for nicotinic Ach receptors?

<p>Nicotine (C)</p> Signup and view all the answers

In the context of Ach receptor pharmacology, what is 'vagustuffe' associated with?

<p>Inhibition of cardiac muscle (B)</p> Signup and view all the answers

Which receptor type is associated with direct ion channel gating?

<p>Nicotinic Ach receptor (B)</p> Signup and view all the answers

What is the role of G proteins in muscarinic Ach receptor function?

<p>They directly open ion channels (C)</p> Signup and view all the answers

Which is a characteristic function of ionotropic receptors?

<p>Direct gating of ion channels (A)</p> Signup and view all the answers

What is the primary characteristic of homo-synaptic plasticity during stimulation?

<p>Dependence on nerve terminal calcium levels (A)</p> Signup and view all the answers

What role do NMDA Glu receptors play in synaptic plasticity?

<p>Activate calmodulin via Ca2+ (B)</p> Signup and view all the answers

Which neurotransmitter's release is modulated by enkephalins in the spinal cord?

<p>Substance P (A)</p> Signup and view all the answers

What does post-tetanic potentiation refer to in homo-synaptic plasticity?

<p>Long-term facilitation after stimulation (A)</p> Signup and view all the answers

How does pre-synaptic facilitation of hetero-synaptic plasticity increase synaptic efficacy?

<p>Augmented pre-synaptic action potentials (C)</p> Signup and view all the answers

What mechanism leads to pre-synaptic inhibition in hetero-synaptic plasticity?

<p>Shortened pre-synaptic action potential duration (D)</p> Signup and view all the answers

What is the effect of postsynaptic diffusion in synaptic plasticity?

<p>Increased synaptic efficacy (A)</p> Signup and view all the answers

In homo-synaptic plasticity, what is the 'residual calcium hypothesis' related to?

<p>Increased releasing of neurotransmitters (C)</p> Signup and view all the answers

Flashcards

mAchR

Muscarinic acetylcholine receptor that inhibits cardiac muscle.

Ionotropic receptor

Receptor that directly gates ion channels, allowing for fast neurotransmission.

Metabotropic receptor

Receptor that activates G proteins, leading to slower, indirect effects.

Nicotinic AchR

A type of acetylcholine receptor that is ionotropic and excitatory at neuromuscular junctions.

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Muscarinic AchR

A type of acetylcholine receptor that is metabotropic and inhibitory in cardiac muscle.

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Agonists

Compounds that activate receptors, enhancing their action.

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Antagonists

Compounds that block receptors, reducing their action.

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G protein

Molecular switches that mediate signaling from metabotropic receptors.

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G Protein Coupled Receptors

A class of receptors that are linked to a G protein; pivotal in cellular communication.

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Second Messenger Systems

Intracellular signaling pathways activated by first messengers (like hormones) leading to a response.

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Synaptic Plasticity

The ability of synapses to strengthen or weaken over time, crucial for learning and memory.

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Cyclic AMP signaling system

A signaling pathway where a ligand binding activates adenylate cyclase, producing cAMP that activates protein kinase A for further phosphorylation.

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Phosphatidyl Inositol signaling system

A signaling pathway activated by G proteins that leads to phospholipase C activation, producing second messengers inositol trisphosphate and diacylglycerol for cell signaling.

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Homo-synaptic Facilitation

Increased neurotransmitter release during stimulation due to calcium levels.

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Homo-synaptic Potentiation

Post-tetanic potentiation involving enhanced neurotransmitter release after stimulation.

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Homo-synaptic Depression

Decreased neurotransmitter release following intense stimulation.

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Residual Calcium Hypothesis

Increased calcium levels lead to more neurotransmitter release after repetitive action potentials.

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LTP (Long Term Potentiation)

The long-lasting enhancement of signal transmission between two neurons.

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NMDA Glu Receptor

A receptor that, when activated by calcium, triggers signaling pathways involved in learning.

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Hetero-synaptic Plasticity

Changes in synaptic efficacy involving different pathways, either increasing or decreasing neurotransmitter release.

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Enkephalin

A peptide that modulates pain by inhibiting neurotransmitter release from pain pathways.

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Study Notes

Cell Signaling and Neurotransmission

  • Neuromodulation and neurotransmission involve ionotropic and metabotropic receptors.
  • G protein-coupled receptors (G proteins) are central in pharmacology, affecting skeletal muscle, heart, and the central nervous system (CNS).
  • Neurotransmission is a fast process, while neuromodulation is slower.

Second Messenger Systems

  • Cyclic nucleotides (cAMP and cGMP) and other molecules like phosphatidyl inositol, Ca2+/calmodulin, and protein kinases are components of second messenger systems.

Synaptic Plasticity

  • Homo-synaptic and hetero-synaptic plasticity are key aspects of synaptic function, influencing the efficacy of neuronal communication.

Endocrine Signaling

  • Hormones are released directly into the bloodstream.
  • Neurosecretory cells release hormones locally.
  • Paracrine signaling involves local communication between cells.
  • Autocrine signaling involves a cell signaling to itself.

Ligand-Gated Receptors

  • Ionotropic receptors directly affect membrane potential (Vm) through ion channels.
  • They are gated by ligands, mediating fast chemical transmission.

Metabotropic Receptors

  • Metabotropic receptors are G protein coupled receptors that bind to ligands.
  • The ligand binding activates G proteins.
  • The activated G proteins influence second messenger systems and protein kinases that affect cellular processes.
  • Metabotropic receptors exhibit slower chemical transmission and modulation.

Acetylcholine (ACh) Receptor Pharmacology

  • Ionotropic (nicotinic) receptors bind directly to ion channels.
  • Nicotine is an agonist; curare and bungarotoxin are antagonists.
  • Metabotropic (muscarinic) receptors engage in indirect signaling through G proteins.
  • Muscarine is an agonist; atropine and scopolamine are antagonists.
  • ACh receptors (both types) have roles in the central nervous system (CNS).

Acetylcholine (ACh) Receptor Pharmacology: Heart

  • Metabotropic (muscarinic) ACh receptors, found in cardiac muscle, indirectly regulate heart rate.
  • They do this by slowing down heart rate.
  • Otto Loewi's “vagustuffe” experiment illustrated neurotransmitter communication.

Acetylcholine (ACh) Receptor Pharmacology: Sympathetic Ganglion

  • ACh receptor subtypes (ionotropic nicotinic) and (metabotropic muscarinic) are critical in the autonomic nervous system.
  • Ionotropic receptors induce fast excitation.
  • Metabotropic receptors activate or inhibit slower signaling pathways.

Neurotransmission vs Neuromodulation

  • Ionotropic receptors involve ligand binding to receptors that directly alter membrane potential.
  • Metabotropic receptors involve ligand binding that activates G proteins to modulate cellular processes.

G Protein-Coupled Receptors

  • G protein-coupled receptors (GPCRs) have seven transmembrane domains that bind and mediate signals.
  • Activated G proteins can activate enzymes, alter ion channels, and affect second messengers.

Cyclic AMP Signaling

  • Cyclic AMP (cAMP) is a second messenger in cell signaling.
  • Adenylyl cyclase catalyzes cAMP production.

Phosphatidyl Inositol Signaling

  • This system uses inositol triphosphate (IP3) and diacylglycerol (DAG) as second messengers.
  • Key player in cellular calcium signaling.

Other Biochemical Systems

  • cGMP (cyclic GMP) is involved in photoreception, and Ca2+/calmodulin is a prevalent signaling component.

Synaptic Plasticity (Homo-synaptic)

  • Facilitation, potentiation, and depression refer to the changes in synaptic strength.
  • This refers to changes in synaptic strength at a single synapse.
  • These changes are influenced by calcium levels in the nerve terminal.
  • This relies on changes in calcium levels that alter neurotransmitter release.

Synaptic Plasticity (Hetero-synaptic)

  • Hetero-synaptic plasticity involves an interneuron affecting synaptic transmission.
  • Pre-synaptic facilitation enhances neurotransmitter release.
  • Pre-synaptic inhibition reduces neurotransmitter release.

Enkephalin in Spinal Cord Modulation of Pain

  • Enkephalin is a pain-modulating neuropeptide.
  • It inhibits substance P release, which mediates pain signals.
  • Pain stimuli trigger substance P release, and spinal interneurons release enkephalin to reduce substance P transmission.

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