Dr. Mohd Nazam Ansari

Nervous System which consists of is divided into that make up which is divided into The Nervous System Sensory nerves (Afferent Nerves) Motor nerves (Efferent Nerves) Autonomic nervous system Somatic nervous system Central nervous system Peripheral nervous system Sympathetic nervous system Parasympathetic nervous system

 Nervous structures outside the brain and spinal cord  NERVES that connect the central nervous system to the rest of the body  Nerves allow the CNS to receive information and take action 1. Motor (efferent) Division – impulses from CNS to muscles or glands  Two Parts:  Somatic Nervous System  Autonomic Nervous System 2. Sensory (afferent) Division – transmits impulses from sense organs to CNS

 It is known as sensory or receptor neurons which carry nerve impulses from receptors or sense organs toward the central nervous system.sensory neuronsnerve impulsesreceptorscentral nervous system  It is known as motor or effector neurons which carry nerve impulses away from the central nervous system to effectors such as muscles or glandsmotorneuronsnerve impulsescentral nervous systemmusclesglands

EFFERENT NERVOUS SYSTEM Somatic nervous system (voluntary) Skeletal muscle Autonomic nervous system (involuntary) Heart, blood vessels, glands, other visceral organs, smooth muscle

 Effects of Sympathetic Activation  Generalized response in crises  Increased alertness/energy  Increased cardiovascular activity  Increased respiratory activity  Increased muscle tone  Effects of Parasympathetic Activation  Relaxation  Food processing  Energy absorption  Brief effects at specific sites

Neurotransmitter: A chemical that transmits signals from one neuron to another or from a neuron to an effector cell. Electrical Stimulation (impulse) Chemical (neurotransmitter) Chemical (intracellular messengers) Electrical (membrane ion channels) Physiological functions

1- Cholinergic, 2- Adrenergic, and 3- Dopaminergic

 It means related to the neurotransmitter Acetylcholine.neurotransmitter Acetylcholine  The parasympathetic nervous system is entirely cholinergic. Neuromuscular junctions, preganglionic neurons of the sympathetic nervous system, and the sweat glandsparasympathetic nervous system sympathetic nervous system

 It means "having to do with adrenaline (epinephrine) and/or noradrenaline (norepinephrine)". adrenaline noradrenaline

 It means related to the neurotransmitter dopamine. For example, certain proteins such as the dopamine transporter (DAT), vesicular monoamine transporter 2 (VMAT2)neurotransmitter dopamineproteinsdopamine transportervesicular monoamine transporter 2

Definition of Agonist and Antagonist Agonist: A structural analog that is capable of stimulating a biological response. Antagonist: A receptor-specific blocker (e.g., enzyme inhibitor) or a physiologic agent (e.g., hormone), that prevents the action of another molecule.

Classes of cholinergic stimulants Direct-acting Receptor agonists Choline esters ACETYLCHOLINE BETHANECOL Alkaloids PILOCARPINE Cholinesterase inhibitors Carbamates PHYSOSTIGMINE NEOSTIGMINE PYRIDOSTIGMINE EDROPHONIUM Phosphates ISOFLUROPHATE Antidote PRALIDOXIMINE Indirect-acting

Acetylcholine Preganglionic synapses of both sympathetic and parasympathetic ganglia Parasympathetic postganglionic neuroeffector junctions All somatic motor end-plates on skeletal muscle

NANC (non-noradrenergic, non-cholinergic transmitter)

 Similar to those of parasympathetic stimulation  (M1): CNS, PNS, gastric parietal cells  (M2): conducting tissue  (M3): exocrine glands; smooth muscle

 Similar to those induced by nicotine  Stimulation of all autonomic ganglia (Nn)  Stimulation of voluntary muscles (Nm)  Secretion of epinephrine from the adrenal medulla (Nn)

 A synapse is the junction between 2 neurones.  There is a very narrow gap of about 20nm between neurones called the synaptic cleft.  An action potential cannot cross the synaptic cleft, so nerve impulses are carried by chemicals called neurotransmitters.

 Pre-synaptic neurone = neurone sending impulse  Post-synaptic neurone = neurone receiving impulse

 Neurotransmitter is made by the pre-synaptic neurone and is stored in synaptic vessels at the end of the axon.  The membrane of the post-synaptic neurone has chemical-gated ion channels called neuroreceptors. These have specific binding sites for neurotransmitters.

 Acetylcholine is a common transmitter.  Synapses that have acetylcholine transmitter are called cholinergic synapses.  Some neurones form more than 1 synapse.  This is an electron micrograph of synapses between nerve fibres and a neurone cell body.

 An action potential arrives at presynaptic membrane. Voltage gated calcium channels in the presynaptic membrane open, calcium ions enter the presynaptic neurone.

 Calcium ions cause synaptic vesicles to fuse with the presynaptic membrane, releasing acetylcholine into the synaptic cleft.

 Acetylcholine diffuses cross the synaptic cleft and binds to specific neuroreceptor sites in the post synaptic membrane.

 Sodium channels open. Sodium ions diffuse into the postsynaptic membrane causing depolarisation, which may initiate an action potential.

 Acetylcholinesterase breaks down acetylcholine. The products diffuse back into the presynaptic neurone where acetycholine is resynthesised using ATP from the mitochondria.

 Same stages as cholinergic synapses, but in this case the postsynaptic membrane is the muscle fibre membrane, (Sarcolemma). Depolarisation of the sarcolemma leads to contraction of muscle fibre.

 Drugs which have molecules of similar shape to transmitter substances can affect protein receptors in postsynaptic membranes.  Drugs that stimulate a nervous system are called AGONISTS  Drugs that inhibit a nervous system are called ANTAGONISTS.

 A synapse is the point where 2 nerve cells meet. Tiny gap = synaptic cleft.  Chemical transmitter released from presynaptic neurone diffuses across synaptic cleft & fits into receptors on postsynaptic membrane. May cause postsynaptic neurone to depolarise & set up action potential.  Neuromuscular junction = motor neurone connects with muscle fibre – similar to a synapse.  Many drugs affect synapses.