Lecture 14-16 - Scrogin - Adrenergics (Receptors)

Question 1

What are the 5 adrenergic receptor sub-types we should know?

Answer 1

Alpha 1 and 2
Beta 1 and 2
Dopamine 1

Question 2

Where are alpha-1 receptors found?

Answer 2

pupillary dilator muscle and most vascular smooth muscle

Question 3

Where are alpha-2 receptors found?

Answer 3

Adrenergic and Cholinergic nerve terminals (pre-synaptic)

Question 4

Where are dopamine-1 receptors found?

Answer 4

Renal and other splanchnic blood vessels

Question 5

Where are beta-1 receptors found?

Answer 5

heart and JG (juxtaglomerular) cells

Question 6

Where are beta-2 receptors found?

Answer 6

Respiratory/Uterine/Vascular smooth muscle

Somatic motor cholinergic nerve terminals (voluntary muscle)

Question 7

What are the actions of dopamine-1 receptors?

Answer 7

relaxation/decreased resistance of renal/splanchnic blood vessels

Question 8

What are the actions of alpha-1 receptors on the pupillary dilator muscle?

Answer 8

Mydriasis (contraction)

Question 9

What are the actions of alpha-1 receptors on vascular smooth muscle?

Answer 9

Vasoconstriction (increased vascular resistance)

Question 10

What are the actions of alpha-2 receptors on adrenergic/cholinergic nerve terminals?

Answer 10

Inhibit NT release

*you can also get some vasoconstriction

Question 11

What are the 2 actions of beta-1 receptors on the heart and where specifically in the heart do they target?

Answer 11

Stimulate HR (chronotropy in SA Node pacemakers)

Increase force (contractility in ventricle myocytes)

Question 12

What are the actions of beta-1 receptors on JG cells?

Answer 12

Stimulate renin release

Question 13

What are the actions of beta-2 receptors on respiratory/uterine/vascular smooth muscle?

Answer 13

Relaxation (bronchodilation, increased blood flow via vasodilation, etc.)

It regulates the degree of airway constriction and peripheral vascular resistance

Question 14

What are the actions of beta-2 receptors on somatic motor nerve terminals (voluntary muscle)?

Answer 14

Stimulates NT release and causes tremor

Question 15

Alpha-1 receptors are coupled to what signaling pathway?

Answer 15

Phospholipase C via G-alpha-q/11 to increase IP3 and DAG

Question 16

What is the mechanism of effect for vasoconstriction mediated by alpha-1 receptors?

Answer 16

Ligand activates G-alpha-q –> activate PLC –> PIP split into IP3 and DAG

IP3 binds IP3 receptor and gives Ca2+ release which binds calmodulin and activates myosin light chain kinase

Question 17

What is the mechanism of effect for inhibited NT release mediated by alpha-2 receptors?

Answer 17

Coupled to G-alpha-i –> inhibits adenylyl cyclase –> dec cAMP –> dec PKA activation –> inhibit Ca2+ release/influx –> dec NE release

Question 18

What is the mechanism of effect for + chronotropy mediated by beta-1 receptors?

Answer 18

Coupled to G-alpha-s –> activates adenylyl cyclase –> inc cAMP –> PKA activation –> phosphorylate Ca2+ channels –> inc inward Ca2+ current and get faster nodal cell depolarization to firing threshold (faster process and lower threshold)

Question 19

What is the mechanism of effect for + intotropy mediated by beta-1 receptors?

Answer 19

Inc cAMP –> PKA activation –> inc phosphorylation of LTCC –> larger trigger for Ca2+ release from SR

*Trigger Ca2+ also enters SR which increases SR storage and gives larger Ca2+ efflux in the next round

Question 20

What is the mechanism of effect for smooth muscle relaxation mediated by beta-2 receptors?

Answer 20

cAMP activates PKA which phosphorylates and inactivates MLCK which reduces its affinity for Ca2+-calmodulin and gives decreased phosphorylation of MLC

Get less smooth muscle conraction

Question 21

What is the mechanism of effect for peripheral vasoconstriction mediated by alpha-2 receptors?

Answer 21

Inhibition of PKA leads to activation of MLCK and vascular smooth muscle constriction