Receptors

Question 1

α₁ receptor pathway

Answer 1

NE&raquo_space; Epi | Gq | ↑ IP₃, DAG → ↑ Ca²⁺ | PKC, Ca²⁺-dependent kinases | Vasoconstriction, mydriasis, ↑ sphincter tone

Question 2

α₂ receptor pathway

Answer 2

NE&raquo_space; Epi | Gi | ↓ cAMP | ↓ PKA | ↓ NE release (negative feedback), ↓ insulin

Question 3

β₁ receptor pathway

Answer 3

NE = Epi | Gs | ↑ cAMP | ↑ PKA | ↑ HR, ↑ contractility, ↑ renin secretion

Question 4

β₂ receptor pathway

Answer 4

Epi&raquo_space; NE | Gs | ↑ cAMP → ↓ MLCK | ↑ PKA | Bronchodilation, vasodilation, ↓ uterine tone, ↑ insulin/glucose

Question 5

M₁ receptor pathway

Answer 5

ACh | Gq | ↑ IP₃, DAG → ↑ Ca²⁺ | PKC, Ca²⁺-dependent kinases | CNS excitation, ↑ gastric acid secretion

Question 6

M₂ receptor pathway

Answer 6

ACh | Gi | ↓ cAMP, ↑ K⁺ efflux | ↓ PKA | ↓ HR, ↓ atrial contractility (SA node hyperpolarization)

Question 7

M₃ receptor pathway

Answer 7

ACh | Gq | ↑ IP₃, DAG → ↑ Ca²⁺ | PKC, Ca²⁺-dependent kinases | Smooth muscle contraction, ↑ secretion, miosis

Question 8

Nicotinic receptor mechanism

Answer 8

ACh | Ion channel (Na⁺/K⁺/Ca²⁺) | Fast depolarization | Skeletal muscle contraction, ganglionic transmission

Question 9

Receptor mnemonic song

Answer 9

🎶 Gq to IP₃ and Ca, Gi to fall cAMP,
Gs gets cAMP to rise, with PKA so high!
α1, M1, M3 – go Gq and squeeze!
α2 and M2 – chill with Gi breeze.
β1 and β2 – Gs will excite you! 🎶

Question 10

PKA-activating receptors

Answer 10

β₁, β₂ (via Gs → ↑ cAMP → ↑ PKA) → heart stimulation, relaxation, metabolic effects

Question 11

PKC-activating receptors

Answer 11

α₁, M₁, M₃ (via Gq → ↑ DAG & Ca²⁺) → contraction, secretion

Question 12

Receptors that ↓ PKA

Answer 12

α₂, M₂ (via Gi → ↓ cAMP → ↓ PKA) → ↓ HR, ↓ NE, ↓ insulin

Question 13

M₃ receptor in lungs

Answer 13

ACh → M₃ → Gq → ↑ Ca²⁺ → MLCK activation → Bronchoconstriction, mucus secretion

Question 14

β₂ receptor in lungs

Answer 14

NE/Epi → β₂ → Gs → ↑ cAMP = increased PKA → ↓ MLCK → Bronchodilation