Nervous system Ⅱ Wei yuanyuan
Neurotransmitter Definition : a small molecules released by presynaptic neuron into synaptic cleft that cause a change in post synaptic potential
Neurotransmitter Synthesized and released from neurons Found at the presynaptic terminal Same effect on target cell when applied in vitro Blocked by same drugs that block synaptic transmission in vitro Removed in a specific way Break down reuptake
Neurotransmitter ACh ChE Choline and acetic acid reuptake NE Peptide NT. zymolysis
Classification of neurotransmitter Neurotransmitter in CNS Neurotransmitter in PNS
Neurotransmitter in PNS Acetylcholine (ACh) Noradrenaline (NA) or nor-epinephrine(NE) Peptide
Acetylcholine (ACh)
Cholinergic fiber Sympathetic and parasympathetic pre-ganglionic fiber （ N 1 R ） Parasympathetic postganglionic fiber Sympathetic cholinergic fibers to the sweat glands,muscular blood vessels Sympathetic vasodilator nerve fibers of the muscles (defensive response) Motor nerve fibers （ N 2 R)
Acetylcholine (ACh) The life cycle of ACh
Cholinergic Agonists Direct agonists Muscarine –MR(M1~M5) Nicotine—NR(N1,N2) Indirect agonists ACh E Inhibitors: organophosphorus pesticide
Cholinergic Receptor Muscarinic receptor (MR) Muscarine –like action G-protein-coupled receptor Subtypes:M1~5 M1: postganglionic nerve and stomach M2:heart M3:vascular smooth muscle, endocrine and exocine gland, e.g. salivary glands and stomach. M4 and 5:CNS
Muscarinic – like action Muscarinic effect Inhibition of heart contract the SM in bronchus, GIT, urinary bladder ， iris circular muscle Increase the secretion of digestive gland salivary gland and sweat gland Blood smooth muscle in skeletal muscle relax Antagonists: Atropine mydriatic
If atropine is applied, what will happen ?
2. Nicotine receptor (NR) ligand-gated ion channel
Tubocurare is alkaloid obtained from the bark of the South American plant Chondrodendron tomentosum, a climbing vinealkaloidChondrodendron tomentosum Curare had been used as a source of arrow poison by South American natives to hunt animalsarrow poison skeletal muscle relaxant
Nicotinic – like action Skeletal muscle contraction (low dosage ACh) Blocking the signal transmission in autonomic nervous ganglion (high dosage ACh)
Neurotransmitter receptors Receptors, ligands (agonist and antagonist)
Norepinephrine Epinephrine
Norepinephrine (NE) Adrenergic fibers Most sympathetic post-ganglionic fibers
Adrenergic receptor 1. αR Antagonist:Phentolamine: Subtype: α 1 R :smooth muscle α 2 R: presynaptic membrane
α 1 receptor:smooth muscle contraction. Antagonist:prazosin 1.vasoconstriction in skin gastrointestinal system,renal artery and brain. 2.Other areas of smooth muscle contraction are : ureter and urethral sphicter arrector pili muscles uterus (when pregnant) brochioles (although minor due to the relaxing effect of β 2 receptor on bronchioles) blood vessels of ciliary body (stimulation causes mydriasis)mydriasis
Specific actions of the α 2 receptor : Antagonist: yohimbine agonist ： Clonidine Inhibition ofinsulin release. Induction of glucagon release from the pancreas. Contraction of sphincters of the gastrointestinal tract presynaptic inhibition of noradrenalin release in CNS
Propranolol:
β 1 R: heart β 2 R: blood smooth muscle in liver and skeletal muscle β 3 R: adipose tissue NE α 1 R: contraction of smooth muscle β 1 R: contraction of cardiac muscle β 2 R: relaxation of smooth muscle
The sympathetic nervous system is responsible for the fight-or-flight response, which includes widening the pupils of the eye, mobilizing energy, and diverting blood flow from non-essential organs to skeletal muscle.fight-or-flight responseskeletal muscle
Neurotansmitters in CNS
Nervous reflex
Types Conditioned reflex (Pavlov, Russia) Unconditioned reflex （ primitive reflex ）
Tendon reflex
Cross flexor reflex
Recurrent connection: basic structure of negtive feedback, positive feedback after discharge
Summary Neurotransmitter Conditioned reflex Describe the cholinergic fiber and receptor of the body