(ANS Receptors) Cholinergic and Adrenergic Neurons and Receptors

Overview

• ANS uses ACh and NE and stimulate or inhibit

• Cells release ACh = cholinergic, target cells have cholinergic receptors

  • all ANS preganglionic neurons

  • PNS ganglionic neurons

  • SNS ganglionic neurons innervating sweat glands + BV in skm

• Cells release NE = adrenergic neurons, target cells have adrenergic receptors

  • most SNS ganglionic neurons

Cholinergic Receptors: Nicotinic

• all ganglionic neurons and adrenal medulla cells, skm

• ACh binds to nicotinin receptor = open cation channel → Na+ into cell → depolarization → ESPS

• receptors at neuromuscular junctions blocked by curare, receptors on ganglionic neurons are not

Cholinergic Receptors: Muscarinic

• all SNS and a few PNS

  • sympathetic effectors = sweat glands and BV in skm

• all muscarinic receptors use second messengers, different subtypes have different effect

  • ACh binds in smooth muscle in GI = contract more

  • ACh binds in cardiace muscle = heart rate decreases

Adrenergic Receptors

• NE = catecholamine

  • chemical subtype of biogenic amines

    • ligands bind membrane receptors

    • NE and epinephrine catecholamines bind to adrenergic receptors

• two main types: alpha, beta

  • alpha stimulate by NE

  • beta stimulate or inhibited by NE

Adrenergic Receptors: Alpha

• alpha 1

  • receptors on smooth muscle cells

  • BV, arrector pili, uterus, ureters, internal urethral sphincter, dilator pupillae

• alpha 2

  • throughout CNS

  • pancreas, GI tract sphincters

Adrenergic Receptors: Beta

• beta 1

  • stimulatory

  • heart and kidney

• beta 2

  • inhibitory

  • smooth muscle of vessels to hear, liver and skm; lung’ uterine and GI tract; detrusor muscle of bladder

• beta 3

  • stimulator or inhibitory

  • adipose, urinary bladder smooth muscle