PNS Receptors Flashcards
M2
Tissue
Response
Mechanism
Tissue - heart and axon terminals (auto receptors)
Response - decreases HR, conduction velocity, and contractility (opposite of beta 1 and 2).
Mechanism - Gi, increased K efflux, decreased Ca influx
M3 Tissues of action
Smooth muscle, secretory glands, and vascular endothelium
M3 action on smooth muscle
Types of smooth muscle
Response
Mechanism
Eye, bronchioles, GI tract, urogenital system
Response - contraction
Mechanism - Gq
M3 action on secretory glands
Response
Mechanism
Response - increased secretion
Mechanism - Gq
M3 action on vascular endothelium
Response
Mechanism
Response - vasodilation
Mechanism - Ca++/CaM activates eNOS → ↑ NO → ↑ cGMP → relaxation
Nm
Tissue
Response
Mechanism
Tissue - NMJ
Response - skeletal muscle contraction
Mechanism - Na/K channel opens –> depolarization
Nn tissues of action
Atuonomic ganglia and adrenal medulla
Nn action on autonomic ganglia
Response
Mechanism
Response - depolarizes postsynaptic neurons
Mechanism - opens Na/K pump –> depolarization
Nn action on adrenal medulla
Response
Mechanism
Response - depolarizes medullary cells –> secretion of catecholamines
Mechanism - opens Na/K pump –> depolarization
Alpha 1 tissues of action
smooth muscle (eye, vascular, urogenital, and hair follicles), and liver
Alpha 1 action on smooth muscle
Types
Response
Mechanism
eye, vascular, urogenital, hair follicles
Response - contracts smooth muscle
Mechanism - Gq
Alpha 1 action on liver
Response
Mechanism
Response - increased glycogenolysis and gluconeogenesis
Mechanism - Gq
Alpha 2 tissues of action
Axon terminals (autoreceptors), pancreatic beta cells, vascular smooth muscle, platelets
Alpha 2 action on axon terminals
Response
Mechanism
Response - decreased NE release
Mechanism - Gi and Gq. ↓ AC → ↓ cAMP; ↑ K+ channel efflux; ↓ L- and N-type Ca++ channel influx; ↑ PLC → ↑ IP3, DAG, Ca++
Alpha 2 action on pancreatic beta cells
Response
Mechanism
Response - decreased insulin release
Mechanism - Gi and Gq. ↓ AC → ↓ cAMP; ↑ K+ channel efflux; ↓ L- and N-type Ca++ channel influx; ↑ PLC → ↑ IP3, DAG, Ca++
Alpha 2 action on vascular smooth muscle
Response
Mechanism
Response - contracts smooth muscle
Mechanism - Gi and Gq. ↓ AC → ↓ cAMP; ↑ K+ channel efflux; ↓ L- and N-type Ca++ channel influx; ↑ PLC → ↑ IP3, DAG, Ca++
Alpha 2 action on platelets
Response
Mechanism
Response - aggregation
Mechanism - Gi and Gq. ↓ AC → ↓ cAMP; ↑ K+ channel efflux; ↓ L- and N-type Ca++ channel influx; ↑ PLC → ↑ IP3, DAG, Ca++
Beta 1 tissues of action
Heart and kidney (JG cells)
Beta 1 action on heart
Response
Mechanism
Response - increased HR, conduction velocity, and contractility (opposite as M2)
Mechanism - Gs: ↑ AC → ↑ cAMP → ↑ PKA → ↑ L-type Ca++ channel influx
Beta1 predominate in heart 100:1 compared to beta2
Beta 1 action on kidney
Response
Mechanism
Response - JG cells secrete more renin Ang II (via renin release) --> vasoconstriction Mechanism - Gs: ↑ AC → ↑ cAMP → ↑ PKA → ↑ L-type Ca++ channel influx
Beta 2 tissues of action
SM (eye, bronchioles, GI, urogenital, vascular), heart, liver, skeletal muscle, pancreatic beta cells
Beta 2 action on SM
Types
Response
Mechanism
Types - eye, bronchioles, GI, urogenital, vascular
Response - relaxes smooth muscle
Mechanism - Gs: ↑ AC → ↑ cAMP; in smooth muscle, inhibits MLCK → ↓ myosin-PO4 → relaxation
Beta 2 action on heart
Response
Mechanism
Response - increase HR and contractility
Mechanism - ↑ AC → ↑ cAMP
Beta 2 action on liver / skeletal muscle
Response
Mechanism
Response - increased glycogenolysis and GNG (liver)
Mechanism - ↑ AC → ↑ cAMP; in smooth muscle, inhibits MLCK → ↓ myosin-PO4 → relaxation
Beta 2 action on pancreatic beta cells
Response
Mechanism
Response - increased insulin release
Mechanism - ↑ AC → ↑ cAMP; in smooth muscle, inhibits MLCK → ↓ myosin-PO4 → relaxation
D1
Tissues
Response
Mechanism
Tissues - vascular SM, especially renal
Response - vasodilation –> increased GFR
Mechanism - Gs
D2
Tissues
Response
Mechanism
Tissues - Axon terminals (autoreceptors) and cholinergic neurons in gut
Response - Decrease DA release and GI motility (via inhibited Ach release)
Mechanism - Gi: ↓ AC → ↓ cAMP; ↑ K+ efflux; ↓ Ca++ influx
Pupil diameter
M3 → iris circular muscle contraction → miosis (smaller)
B2 → circular muscle relaxation → mydriasis (larger)
A1 → iris radial muscle contraction → mydriasis
Lens shape
M3 → ciliary muscle contraction (relaxes ligament) → accommodation (more round)
B2 → ciliary muscle relaxation → flattens lens
Lacrimal glands
M3 → tear secretion
Bronchial smooth muscle
M3 → bronchoconstriction. B2 → bronchodilation
Blocking M3 and stimulating B2 aids in COPD / asthma
Bronchial glands
M3 → mucous secretion. B2 → water secretion via CFTR
Heart
M2 → Gi → close funny Na channels → decreased SA / AV node conductivity → bradycardia and decreased atrial contractility. Acts via vagus nerve.
B1 & 2 → Gs → cAMP opens Ca channels → increased SA / AV node automaticity / conductivity → tachycardia
Vascular system
- M3 → relaxes endothelial cells → decreased BP
- A1 & 2 → SM constriction → increased BP
- A1 are #1 control of increasing vascular resistance.
- B2 → vasodilation in liver & skeletal muscle → increased flow
- D1 → dilation of renal arteries / arterioles → increased flow
Intestine
- M3 → contraction of circular / longitudinal muscles → peristalsis
- A1 & B2 → relaxation of intestinal muscles → decreased peristalsis
- Hyperpolarizatoin / relaxation caused by activation of Ca-dependent K channels
GI sphincters
- M3 → relaxation → increased motility
* A1 → contraction → decreased motility
GI secretions
- M3 → increased acid secretion from parietal cells, increased intestinal secretions, and gall bladder contraction
- B2 → decreased acid secretion, increased gall bladder relaxation, but increased amylase secretion
Kidney / Bladder
- D1 → vasodilation → increased GFR
- B1 → renin release from JG cells
- M3 → contracts detrusor, relaxes trigone & sphincter → urination
- B2 → relax detrusor → urinary retention
- A1 → constricts trigone & sphincter → urinary retention
Penis
- M3 → vasodilation → erection (parasympathetic)
* A1 → contracts seminal vesicles, prostatic capsule, and vas deferens → ejaculation (sympathetic)
Uterus
- B2 → uterus relaxation
- A1 → uterus contraction
- M3 → uterus contraction
General secretions
- M3 → watery secretions from salivary, nasopharyngeal, pulmonary, GI, and eccrine sweat glands (used for temp control).
- A1 → viscous salivary secretions and apocrine sweat glands (axilla and groin)
Metabolism
- A2 → decreased insulin release from pancreatic beta cells
- B2 → increased insulin release, glycogenolysis & GNG in liver, glycogenolysis & K+ uptake in skeletal muscle. Good for fight / flight.
