· Network of nerve cells and fibres which transmits nerve impulse between parts of the body.
Classification of nervous system
Motor: carry neuronal impulse away from CNS to different parts.
Sensory: Carry impulse from sensory stimuli towards the CNS and Brain.
· Fight or flight condition.
· Increase BP, HR, Glucose, perfusion to skeletal muscle, mydriasis, Bronchodilator.
· Rest and digest
· Decrease HR, BP, Bronchial secretion, Insulin release, Digestion, excretion
Introduction to Autonomic Nervous System Drugs
· Neurohumoral transmission implies that nerves transmit their message across synapses and neuroeffector junctions by the release of humoral (Chemical) message.
Steps in Neurohumoral transmission
1. Impulse conduction
· Resting transmembrane potential -70mv (inside) (High concentration K+ ion).
· Electrical impulse causes increase in Na+ conductance so depolarization occur.
· Now the voltage become +20mv.
· K+ ion then move out in the direction of their concentration and repolarization achieved.
· The ionic distribution is normalized during the refractory period by activation of Na+ K+ pump.
· The action potential thus generated set of local circuit currents which active ionic channel at the next excitable part of the membrane.
2. Impulse release
· Transmitted stored pre-junctional nerve ending with synaptic cleft.
· Entry of Ca2+: all contents of the vesicle are extruded.
3. Transmitter action on post-junctional member
· Release transmitter combine with specific receptor on post junctional membrane and depending on its nature induce an excitatory postsynaptic potential (EPSP) or inhibitory post-synaptic potential (IPSP.)
· Increase permeability of cations, so that Na+ Ca2+ influx
· Increase permeability of anions (Cl– ion move inside)
· Increase in permeability to K+ ions, which moves out carrying positive charges.
4. Post junctional activity
· EPSP: propagated post junctional AP results nerve impulse secretions.
· IPSP: stabilize the post junctional membrane. It resist depolarization stimuli.
5. Termination of transmitter action
· The transmitter locally degraded or partly taken back into pre-junctional neuron (e.g. Ach).
· Specific carrier protein e.g. NET (Norepinephrine transporter), DAT (Dopamine transporter), SERT (Serotonin transporter), Amino acid transporter, Enkephalins, VIP (Vasoactive intestinal peptides), NPY (Neuropeptide-y).
· The co-transmitter is stored in the pre-junctional nerve terminal along with primary but in separate vesicle.
· Nerve impulse releases both the transmission concurrently.
· It may also act on pre-junctional receptors and modulate release of the transmitters.
Hi….!! My name is Smrutiranjan Dash, From Odisha, India. Professionally I am Assistant Professor at The Pharmaceutical College, Barpali, Odisha, department of Pharmacology.