Test 2 Receptors

Question 1

α1 receptors

Answer 1

Increased vascular smooth muscle contraction via Ca2+ release.

Positively coupled to phospholipase C via Gq/11α and DAG. (increased IP3/DAG)

IP3 –> Ca2+ release from SR –> intracellular Ca2+ –> CaM –> MLCK activation –> phos of myosyin –> contraction

13-13

Question 2

α2 receptors

Answer 2

pre-synaptic α2 receptor activation decreases neurotransmitter release via inhibition of adenylyl cyclase.

Decreased adenylyl cyclase –> decreased cAMP –> decreased PKA –> decreased phos of N-type Ca2+ channels –> reduced Ca2+ influx during AP –> decreased release of NT

Low PKA –> activation of MLCK –> vascular smooth muscle constriction (PKA phosphorylates MLCK and turns it off)

Question 3

β1 receptors

Answer 3

Cardiac pacemaker cells - positively coupled to adenylyl cyclase via Gαs

increased adenylyl –> increase cAMP –> increased PKA –>

ionotropy: –> increased phosporylation of L-type Ca2+ channels –> greater Ca2+ influx and larger trigger for SR release, and increased SR Ca2+ for next release.
chronotropy: –> increased phos of Ca2+ channels –> increased Ca2+ inward current –> decreased threshold/faster nodal cell depolarization

Question 4

β2 receptors

Answer 4

Regulates airway constriction and peripheral vascular resistance. Smooth muscle relaxation.

Positively coupled to adenylyl cyclase via Gαs.

Increased adenylyl cyclase –> increased cAMP –> increased PKA –> phosphorylation and inhibition/deactivation of MLCK –> reduction in affinitely for CaM –> reduced smooth muscle activity and relaxation.

Question 5

M1

Answer 5

Activates myenteric plexus. Increases IP3, DAG, and Ca2+.

Muscarinic

Question 6

M2

Answer 6

Opens K+ channels –> decreased HR and contraction (lowers CO)

Decreases cAMP, Ca2+ –> inhibits NE release from sympathetic nerve terminals

Muscarinic

Question 7

M3

Answer 7

Increased IP3, DAG, and Ca2+ –> contracts circular ciliary musc (constriction of the pupil), bronchiolar muscle, GI smooth muscle, and bladder detrusor muscle.

Stimulates GI secretions, eccrine sweat glands, tear glands, and salivary glands.

Muscarinic

Question 8

Nn

Answer 8

Neuronal nicotinic receptor. Na+/K+ channel. Binds Ach.

Ligand-gated ion channel - 5 subunits, four types. The two α types bind ligand.

Question 9

Nm

Answer 9

Muscle nicotinic receptor. Na+/K+ channel. Binds Ach.

Ligand-gated ion channel - 5 subunits, four types. The two α types bind ligand.