Autonomic nervous system Flashcards
Sequence of events used to understand each of the GPCR systems?
first messenger to G-protein coupled receptor to effector to second messenger to cellular response
What is the first messenger?
ligand that binds to the GPCR
What can the first messenger be?
This ligand could be something endogenous to the body like a neurotransmitter or hormone or something exogenous to the body like a drug
Where does the G protein reside? Where is the receptor?
The receptor is accessible outside of the cell membrane.
The G-protein itself resides inside of the cell membrane.
What subunits does the G-protein have?
alpha
beta
gamma
What is the function of the G protein?
The G protein either stimulates or inhibits an effector (enzyme or ion channel).
Tell me about G stimulatory proteins?
They turn on an effector and are Gs and Gq proteins
What do G inhibitory proteins do?
They turn off an effector (Gi)
What happens when a ligand binds to the GPCR? (4 steps)
- The ligand- receptor interaction activates the G protein.
- This causes the alpha subunit to dissociate from the beta and gamma subunits.
- The alpha subunit of the Gs or Gq protein will turn on an effector, while the alpha subunit of the Gi protein will turn off an effector.
- When the ligand unbinds from the receptor, the alpha subunit rejoins the beta and gamma subunits, and its interaction with the effector ends.
What is the function of the effector?
To activate the second messenger
You have enzymatic effectors and ion channel effectors, name them?
enzymatic = adenylate cyclase and phospholipase C
Ion channel effectors = GABA-A and M2 receptor at the SA node
What does the second messenger do?
modulates a network of enzymatic activity, including phosphatases and protein kinases. This governs a complex series of intracellular reactions that elicit a specific response within a particular cell type.
Is the response to the 2nd messenger one and done or large in scale?
The 2nd messenger allows for signal amplification.
What is signal amplification (caused by 2nd messenger)
signal amplification is a process that allows a single molecule to initiate a process that activates a large number of physiologic changes - each step progressively increases the magnitude of the response.
The intracellular response to a 2nd messenger is tissue specific… what does this mean?
increased cAMP (or whatever it is stimulating or inhibiting) may cause different effects in different cell types
Five 2nd messengers you should know?
cAMP cGMP IP3 DAG CA+2
cyclic adenosine monophosphate is cAMP
cyclic guanosine monophosphate is cGMP
Inositol triphosphate is IP3
Diacylglycerol is DAG
Calcium ion is Ca+2
Is glutamate a first or second messenger?
first messenger for NMDA receptor
Name the receptors whos signal transduction is inhibitory (3 of them)
Alpha 2
Muscarinic 2 /4
Dopamine 2 (presynaptic)
Alpha 2, M2 and M4, and Dopamine 2 are all inhibitory signal transduction. What is the effector and 2nd messenger details?
decreased adenylate cyclase and decreased cAMP
Name as many receptors as you can?
Alpha 1 and 2 Beta 1 and 2 Nicotinic Muscarinic 1,2,3,4, and 5 Dopamine 1 and 2 Vasopressin 1 and 2 Histamine 1 and 2
Phospholipase C and Adenylate cyclase applies to which step in the GSCP sequence?
a) signal transduction
b) receptors
c) second messengers
d) effectors
d) effectors
Which receptors are Gs and increase adenylate cyclase and cAMP?
B1, B2
D1
V2
H2
Which receptors are Gq and increase phospholipase C which increases IP3, Ca+2, and DAG?
Alpha 1
M 1, 3, 5
V1
H1
SNS receptor for the myocardium and conduction system?
B1
PNS receptor for the myocardium and conduction system?
M2