autonomic NS Flashcards

1
Q

What is the big picture of GPCRs?

A

first messenger activates GPCR with activates effector which activates second messenger which causes cellular response

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2
Q

What is the G protein made of?

A

3 subunits… alpha, beta, gama

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3
Q

What does a G protein do? How does it do this?

A

It either stimulates or inhibits an effector (enzyme or ion channel)

A Gs protein:
alpha subunit detaches from GPCR, GDP–> GTP

once first messenger disassociates, alpha subunit releases GTP and goes back to beta and gamma (now GDP again)

A Gi protein:
the alpha subunit of a Gi protein will turn off an effector

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4
Q

what is an effector/ its function? what are examples of them?

A

its function is to activate a 2nd messenger
it can either be an enzyme (like adenylate cyclase and phospholipase C) or an ion channel (we haven’t learned these)

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5
Q

what is the role of second messenger systems?

A

allows for system amplification
a single molecule initiates a process that activates a large number of physiologic changes

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6
Q

what are 5 second messengers we should know?

A

cyclic adenosine monophosphate (cAMP)
cyclic guanosine monophosphate (cGMP)
Inositol triphosphate (IP3)
Diacyglycerol (DAG)
Calcium Ion

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7
Q

What is the type of signal transduction of receptor a1? Its effector? its second messenger? does it increase or decrease second messenger?

A

Gq. increase phospholipase C. increases IP3 DAG and Ca

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8
Q

What is the type of signal transduction of receptor a2? Its effector? its second messenger? does it increase or decrease second messenger?

A

Gi. decreases adenylate cyclase. decreases camp

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9
Q

What is the type of signal transduction of receptor b1? Its effector? its second messenger? does it increase or decrease second messenger?

A

Gs. increases adenylate cyclase, increase camp.

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10
Q

What is the type of signal transduction of receptor b2? Its effector? its second messenger? does it increase or decrease second messenger?

A

Gs. increases adenylate cyclase, increase camp.

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11
Q

What is the type of signal transduction of receptor M1, M3, M5? Its effector? its second messenger? does it increase or decrease second messenger?

A

Gq. increases PLC. Increases IP3, DAG, Ca

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12
Q

What is the type of signal transduction of receptor M2, M4? Its effector? its second messenger? does it increase or decrease second messenger?

A

Gi. decreases adenylate cylcase. decreases camp

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13
Q

What is the Gq pathway?

A
  1. agonist binds
  2. alpha unit displaces GDP turns into GTP
  3. activates phospholipase C (cell membrane)
  4. PLC cleaves phosphatidylinostitol 4,5- biphosphate (PIP3) into inosital triphosphate (IP3) and diacyclgerol (DAG, which stays in membrane)
  5. IP3 mobilizes Ca stores in ER
  6. Ca activates MLC kinase, activates myosin which causes smooth muscle contratcion
  7. Ca also sensitizes Ca channels, allowing more in, as well as promotes activates of PKC
  8. DAG activates protein kinase C (PKC) –> activates phosphorylation cascade –> inhibits MLC phosphatase
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14
Q

What is the Gi pathway?

A

Inhibits adenylate cyclase to turn ATP into cAMP

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15
Q

What is the Gs pathway?

A

overall effect is increasing cAMP. but cAMP has different effects depending where it is…

cardiac (B1):
1.agonist binds.
2. activates adenylate cyclase.
3. cyclates ATP to cAMP
4. activates protein kinase A
5. PKA opens up Ca channel on cardiac myocyte as well as on SR

smooth muscle of lungs (B2)
1. same 1/2/3 steps
2. cAMP inhibits MLC kinase (no phosphorylation happening, thus no contraction)

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16
Q

What is the physiologic response of the B1 receptor in myocardium and conduction system?

A

Increased contractility, increased HR, increased conduction speed

17
Q

What is the physiologic response of the M2 receptor in myocardium and conduction system?

A

decreased contractility, decreased HR, decreased CV

18
Q

Which receptors are in the arterial smooth muscle VASCULATURE? What is the physiologic response?

A

a1> a2. vasoconstriction

a1= Gq
a2= Gi

19
Q

Which receptors are in the venous smooth muscle VASCULATURE? What is the physiologic response?

A

a2 > a1. vasoconstriction

a2= Gi
a1=Gq

20
Q

Which receptors are in the myocardium smooth muscle VASCULATURE? What is the physiologic response?

A

B2. vasodilation

b2= Gs

21
Q

What receptors are in the skeletal muscle smooth muscle VASCULATURE? what is the physiologic response?

A

B2.Vasodilation

B2= Gs

22
Q

What receptors are in the renal bed smooth muscle VASCULATURE? what is the physiologic response?

A

DA. vasodilation

Gi

23
Q

What receptors are in the mesenteric muscle smooth muscle VASCULATURE? what is the physiologic response?

A

DA. vasodilaton

Gi

24
Q

What receptors are in the bronchial tree? what is the physiologic response?

A

B2. bronchodilation
M3. Bronchoconstriction

25
Q

what receptors are in renal tubules? what is the physiologic response?

A

a2. diuresis (ADH inhibition)

26
Q

what does B1 stimulation in kidneys cause?

A

increased renin release

27
Q

where is the location of a2 receptors ? role in each place?

A

presynaptic - Gi. decreases release of NE
postsynaptic- smooth muscle and several organs. Gi

28
Q

why does dexmetodomine transiently increase BP?

A

rapid admin causes a2 receptors on postsynaptic smooth muscle vasculature in arterial and venous circulation to constrict. CNS effect lags behind (ultimately this will kick in to increase SNS tone, and bring down BP)