Intro To Autonomic System Flashcards
Which presynaptic receptor provides feedback inhibition of NE
alpha2 receptors
Inhibition of alpha 2 receptor cause
Increase of NE
Location of alpha 1 receptors
- Blood vessels of skin, viscera, kidney , salivary glands
2. Most sympathetic organs (except heart)
Location of alpha 2 receptors
Platelets Vascular smooth muscles Exocrine gland of pancreas Never terminals Fat cells
Beta 1 receptor location
Heart - + ve chronotrophic and inotrophic
kidney- increase renin production
Which adrenergic receptors are inhibitory(hyperpolarize)
Alpha 2
Beta 2
Which receptor binds only to epinephrine
Beta 2
Action of alpha 2 and G protein
G protein- Gi
- constriction of vasculature
- Inhibit lipolysis
- Inhibit insulin secretion
- Increase platelet aggregation
- Inhibit transmitter release
- Decrease secretions
Action of beta 2receptors G protein
G protein- Gs
- Dilation of bronchiole
- Dilation of blood vessels to lund and heart
- Lipolysis
- Glycogenolysis
- Decrease motility of GIT
- Tremors of skeletal muscles
- Relaxation of urinary bladder
- Increase HR and force
Where are beta 3 receptor found
Fat cells
Location and function of D1 receptors
- Splanchnic vessels-dilates
2. Renal vessels- dilate
D2 receptor location and function
Presynaptic nerve terminals- inhibit adenylyl cyclase
Mechanism of action of alpha 1
- Ligand binds
- Gq protein activated
- Activates PLC
- Hydeolyzes PIP2
- Form DAG and IP3
- IP3 cause increase in intracellular Ca2+
- Ca bind calmodulin cause phosphorylation
Mechanism of alpha 2
- Activation Gi
- Inhibits adenylyl cyclase - dec cAMP
- activate K+ channels or inhibit voltage gates Ca2+ channels
Beta receptor with least affinity
Beta 3 but is resistant to desensitization
G protein of D1
Gs - activates adenylyl cyclase-increase cAMP- vasodilation of renal and splanchnic vessels
Mechanism of D2
Activate Gi protein - inhibit adenylyl cyclase- dec cAMP- open K+ channels and Ca 2+ influx
NE more potent at which receptors
alpha 1 and beta 3
Phenylephrine and methoxamine have greater affinity at
Alpha1 more than alpha 2
Clonidine and methylnorepinephrine greater affinity to which receptor
Alpha 2 greater than alpha 1
Phenylephrine and methoxamine receptor, features, action
- Alpha 1
- Not a cathecol derivative
not activated by COMPT
Longer duration of action - Vasoconstriction
Treat hypotension, nasal congestion and cause local mydriasis
Phenylephrine and methoxamine
Milodrine acts on
Selective alpha 1 receptor
Effects if alpha 1 agonist
- mydriasis (ciliary muscle contact)
- Increased BP (arterioles and veins constrict)
- Piloerection
- Bladder sphincters contacted
Hypertension treatment
Presynaptic Alpha 2 agonist- Clonidine, guanabenz, guanfacine, methyldopa, moxonidine
Feedback inhibition of NE release
Side effects of presynaptic Alpha 1 agonist
- Drug withdrawn too quickly- withdrawal symptoms- rebound hypertension
- Dry mouth in 50%patient
- Sexual dysfunction in males
- Nausea
- Dizziness
- Sleep disturbances
Clonidine acts on and effect
- Brain stem alpha 2 receptors
- Dec symp outflow to CVS
- hypotension
- bradycardia
Clonidine acts on and effect
- Brain stem alpha 2 receptors
- Dec symp outflow to CVS
- hypotension
- bradycardia
Fusion proteins
vSNARES- VAMPs ( synaptobrevin)
tSNARES- SNAPs (syntaxin, SNAP 25)
Enzyme that converts Acetyl CoA +choline-> Ach
Choline acetyltransferase
Where is Acetyl and choline got from
Acetyl CoA synthesised in mitochondria
Choline got from outside the cell transported by- choline transporter (CHT) Na dependent
Drugs that act on CHT
HEMICHOLINIUMS
Ach transported in to vesicle by
VAT (vesicle associated transport) driven by proton efflux
VAT anther is blocked by
Vesamicol
Ach in the vesicle is bound to
Negatively charged vesicular proteoglycan ( VPG)
Ca entering the cells interested with what protein to trigger fusion
Ca binds with VAMPs- synaptotagmin on vesicle never
How is Ach vesicle release blocked
Botulinum toxin cleaves 2aa from one or more SNARE proteins
Converts tyrosine to dopa
And drug that invite this process
Tyrosine hydroxylase
Metyrosin
Catecholamine enter vesicle through
This protein is blocked by
VMAT (vesicle monoamine transporter)
Reserpine
- Dopa is converted to dopamine by
2. Dopamine is converted to NE by
- Dopa decarboxylase
2. Dopamine-β - hydroxylase