Receptors And Channels Flashcards

1
Q

Receptor

A

A protein or group of proteins, usually embedded in cell membrane, allows cell to collect info about its surroundings

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2
Q

Ligand

A

A chemical messenger (can be small molecule or peptide) that induces a conformational change in the receptor

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3
Q

Conformational change

A

Change in shape of a receptor that induces some downstream signal transduction

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4
Q

2 main types of receptors

A

Ligand gated ion channels and G protein coupled receptors

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5
Q

2 main types of membrane bound receptors

A

Ligand gated ion channels

G protein coupled receptors

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6
Q

Cells that produce AP

A

Neurons, muscle cells, cardiac cells

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7
Q

Action potential purpose

A

How 3 types of cells communicate w each other

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8
Q

How APs are used to communicate

2 methods

A

APs propagate down axon of a neuron, jump from the end of one neuron to beginning of the next
Ligand gated and voltage gated ion channels

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9
Q

4 steps in Saltatory AP propagation

A
  1. AP occurred in initial segment, Na channel opening and in
  2. Local current makes depolarization brings axolemma at next node to threshold
  3. AP develops at node 2
  4. Local current produces depolarization that brings the 3rd axolemma at node to threshold
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10
Q

RMP

A

Inside of cell overall charge -70

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11
Q

Excitatory

A

Inside of a cells charge approaches 0 mv. Generally by letting + ions into cell

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12
Q

Inhibatory

A

Inside of cells charge becomes more neg, generally by letting neg ions (Cl especially) into cell

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13
Q

Depolarization

A

Excitatory, + ions into cell

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14
Q

Hyperpolarization

A

Inhibatory, - ions into cell

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15
Q

Agonist

A

A ligand that binds to a receptor and activates it

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16
Q

Antagonist

A

A ligand that binds to a receptor that prevents it from activation

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17
Q

Orthosteric antagonist

A

Acts on the main binding site of a receptor

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18
Q

Allosteric antagonist

A

Acts on accessory binding site of a receptor. Therefore agonist unable to go into main binding site.

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19
Q

Pore blocker

A

Physically obstructs the whole channel (ion channels). Nothing can go up or down.

20
Q

Ligand gated ion channels

  • transmission type
  • composed of
A

Fast

Several subunits arranged around a central ion pore. Agonist binding opens pore.

21
Q

Ligand gated ion channels

2 major families

A

Cys loop receptors and ionotropic glutamate receptors

22
Q

Cys loop receptors 3 ex

A

Nicotinic acetylcholine receptor
Glycine receptor
5HT3 receptor

23
Q

Ionotropic glutamate receptors

3 ex

A

AMPA
NMDA
Kainate

24
Q

Cys loop receptors

Named for what

A

Loop formed by disulfide bond between 2 cysteines near the N terminus

25
Q

Cys loop receptors

Composed of what

A

5 subunits arranged around a central pore. 5 subunits: 2 alpha, beta, gamma, delta

26
Q

Excitatory cys loop receptors

A

Nicotinic acetylcholine

Serotonin

27
Q

Inhibatory cys loop receptors

A

Glycine and gaba a

28
Q

Ligand Gating

What allow things in

A

Agonist binding changes the conformation, moving the obstruction and allowing ions to flow through

29
Q

Ligand gating

What blocks things

A

2nd transmembrane domain of the a subunit generally obstructs the ion pore

30
Q

Drugs that work on ligand ion channels: cys loop

A

Nicotinic acetylcholine: nicotine, vareniciline (chantix)

Glutamate: NMDA receptors (ketamine), AMPA receptors (aniracetam- cognition enhancer)

31
Q

Ex of cys loop receptor: nicotinic acetylcholine

  • exists where
  • contain what
A
  • NMJ and in the CNS
  • NMJ NAChR contain alpha, beta, delta, and gamma
  • neuronal only contain alpha and beta
32
Q

Ex of cys loop receptor: nicotinic acetylcholine

  • what kind of conduction, ions passed
  • composed of what
  • what they do in brain in response to smoking
A
  • excitatory- na, k, some ca
  • 5 subunits
  • nAChRs upregulate in response to chronic smoking
33
Q

NAChR activation states

A

Can go interchangeably from closed, open, and desensitized

Longer ligand bound more of a chance of being desensitized

34
Q

Ionotropic glutamate ligand receptors

  • 3 types
  • what they are/pass what
A

AMPA, NMDA, and kainate

-excitatory: pass na and k ions. NMDA can also pass ca ions

35
Q

Ionotropic glutamate ligand receptors

  • composed of what
  • each subunit has what, NMDA in particular
  • all must be what
A
  • 4 subunits. Each one has 4 transmembrane domains. 2nd TM domain forms ion pore
  • binding site- not all are for glutamate.
  • NMDA- 2 binding sites for glutamate, 2 for glycine
  • all 4 binding sites must be occupied for channel to open
36
Q

Long term potentiation

A

The more often a neuron fires, the stronger the synapse gets. Implicated in learning and memory

37
Q

At RMP, NMDA receptors are blocked by what. About this process

A

Mg ions. Mg block is voltage dependent. Depolarization of neuron relieves this block, allows NMDAR to open

38
Q

NMDARs pass what, process of leading to stronger synapse. What these are also known as

A

Ca, activates CAMKII, leads to AMPARs inserted into synapse. More ampars= stronger synapse.
NMDARs= coincidence detectors

39
Q

G protein coupled receptors

  • rate of signaling
  • role w genome
  • target for what
A
  • slower than ligand gated ion channels
  • 3% of our genome dedicated to GPCR coding
  • for more than 1/2 of current pharmaceuticals
40
Q

GPCR classes

A

A- adrenergic receptors, muscarinic acetylcholine receptors
B- Parathyroid hormone receptor
C- metabotropic glutamate receptors, GABAb receptors

41
Q

G protein activation

A

Alpha and beta gamma G proteins nearby. Alpha has GDP bound at rest. When receptor occupied by agonist recruits alpha, GTP replaces GDP. GTP causes alpha to go to target protein. GTP hydrolyzed back to GDP. Energy from this causes something to happen to target

42
Q

Ga subunits
Gas
Gai

A

S- activation of adenylyl cyclase and increase in cAMP

I- inhibition of adenylyl cyclase and decrease in cAMP

43
Q

Ga subunits

Gaq

A

Activation of phospholipase c, phosphoinositol hydrolysis, increase in IP3 and DAG, release of Ca from intracellular stores

44
Q

GPCR desensitization
How it occurs
Independent of what

A
  • if a ligand bound to GPCR for long period B-arrestin binds to receptor, tags it for internalization. Contributes to drug tolerance.
  • GPCR B-arrestin complex can act as protein scaffold in the cell
  • independent of G protein signaling
45
Q

Cholera toxin mechanism

A

Cholera internalized by cell. Disrupts conversion of GTP to GDP. Inc level GTP leads to abn hi cAMP levels. Activates cl ion pumps, release more cl into interstitial lumen. Na, k, and hco3 ions follow, leading to more h20 held in intestine to balance osmolarity