1. Muscular nAch 2. Neuronal nAch

Open cation channel: 1. Depolarization leading to muscle contraction 2. Depolarization: excitation → signaling via action potentials

Channel-Linked Receptors Flashcards by Kelsey Madden

Nicotinic Ach receptor consists of?

5 subunits:
2 alpha
1 beta
1 gamma
1 sigma

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Each nicotinic Ach receptor subunit consists of?

4-pass transmembrane protein

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Channel-linked receptors are open dependent on?

Ligand-binding

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Channel-linked receptors are closed dependent on?

Time

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Channel-linked receptors are synonymous to?

Receptor-gated ion channel

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Binding of agonist has what effect on channel?

Opens

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Difference between receptor-gated and voltage-gated ion channels?

Receptor-gated channels open due to agonist binding

Voltage-gated ion channels open based on change in membrane potential (voltage)

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Channel-linked receptors mainly occur in what type of cells?

Excitable cells → muscle or nerve

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Speed of signaling via receptor-gated ion channels

Fast (milliseconds)

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Target tissue of Ach

Skeletal muscle

2. Neurons

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Ach receptor

Muscular nAch

2. Neuronal nAch

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Ach response

Open cation channel:

Depolarization leading to muscle contraction
Depolarization: excitation → signaling via action potentials

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Glutamate and aspartate target tissue

Neurons

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Glutamate and aspartate receptor

NMDA

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Glutamate and aspartate response

Open cation channel: depolarization → excitation → signaling via action portentials

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GABA target tissue

Neurons

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GABA receptor

GABA(A)

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GABA response

Open chloride channel → hyperpolarization → inhibition of signaling

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Glycine target tissue

Neurons

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Glycine receptor

Glycine

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Glycine response

Open chloride channel → hyperpolarization → inhibition of signaling

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When membrane potential reaches threshold, signaling activates what 2 channels?

Voltage-gated Ca2+ channel

2. Voltage-gated Na+ channel

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Voltage-gated Ca2+ channel causes?

Contraction
OR
Release of vesicles containing another signaling molecule

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Voltage-gated Na+ channel causes?

Contraction
OR
Propagation of info as action potentials

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Z = ?

Valence of ion

E(K) = ?

-90 mV

Nernst equation

E = -(60/z)*log(conc. inside / conc. outside)

Z of K+

Z = +1

Z of Na+

Z = +1

E(Na) = ?

+60 mV

Z of Cl-

Z = -1

E(Cl) = ?

-90 mV

Extracellular Ca2+ concentration

High → important Ca2+ source

Ca2+ concentration in cytosol under resting conditions

Low → can rise 10-100x during stimulation

Most important Ca2+ stores

ER (and SR)

Additional Ca2+ store

Mitochondria

How does Ca2+ influx from the extracellular comparment?

1. Voltage-gated Ca2+ channels 2. Receptor-gated Ca2+ channels 3. Receptor-activated Ca2+ channel

Receptor-activated Ca2+ channel is activated by?

Receptor-mediated phosphorylation

Ca2+ influx from intracellular Ca2+ stores via which receptors?

1. IP3 channel | 2. Ryanodine receptor

IP3 channel aka?

IP3 gated Ca2+ channel

Ryanodine receptor aka?

Ryanodine gated Ca2+ channel

How does IP3 channel work?

IP3 binds to receptor → opens channel → Ca2+ released from store

How does ryanodine channel work?

Ca2+ binds to receptor → opens channel → releases Ca2+ from store

2 mechanisms to decrease cytosolic Ca2+

1. Pumped out of cell | 2. Pumped into intracellular Ca2+ stores

2 ways Ca2+ pumped out of cell?

1. Ca2+-ATPase in plasma membrane | 2. Na+/Ca2+ exchanger

Ca2+-ATPase powered by?

ATP

Na+/Ca2+ exchanger powered by?

Na+/K+ ATPase

2 ways Ca2+ pumped into intracellular stores?

1. Ca2+-ATPase in ER or SR | 2. Ca2+/H+ exchanged in inner mitochondrial membrane

Ca2+/H+ exchanger powered by?

H+ gradient

Small depolarization is conducted from?

Neighboring cell via gap junctions

Depolarization from neighboring cell activates?

Fast voltage-gated Na+ channels

Opening of Na+ channels causes?

Large depolarization

Large depolarization caused by opening of Na+ channel activates?

Voltage-gated Ca2+ channel

Voltage-gated Ca2+ channels do what?

1. Maintain depolarization during plateau phase of action potential 2. Allow small Ca2+ inflow (ECM → cytosol)

Ca2+ entering cell activates?

Ryanodine-receptor

Activation of ryanodine-receptor causes?

Large amount of Ca2+ to be released from SR into cytosol

What is responsible for the bulk of cytosolic Ca2+ increase?

Ryanodine-receptor

What mediates contraction?

Increase in cytosolic Ca2+

Large depolarization activates what channels with a delay?

K+

Delayed K+ channels do what?

Mediate repolarization of action potential

How is Ca2+ removed from the cytosol into the SR?

Ca2+ ATPase

How is Ca2+ removed from the cytosol into the extracellular compartment?

Na+/Ca2+ exchanger powered by Na+/K+ ATPase

Depolarization

More positive from -70 mV

Hyperpolarization

More negative from -70 mV