Pharmacology of Autonomic Nervous System PDF

Manar Zraikat PhD Pharmacology of Autonomic Nervous System The autonomic nervous system division of the peripheral nervous system that influences the function of internal organs is a control system that acts largely unconsciously and regulates bodily functions ...

Manar Zraikat PhD Pharmacology of Autonomic Nervous System The autonomic nervous system division of the peripheral nervous system that influences the function of internal organs is a control system that acts largely unconsciously and regulates bodily functions  The nervous system central nervous system the peripheral (CNS) nervous system brain efferent (motor) Neurons From CNS to cells Spinal cord afferent (sensory) Neurons From cells to CNS  The peripheral efferent System autonomic nervous system (1) smooth muscle, somatic nervous system (2) cardiac muscle, skeletal muscle cells and (3) exocrine glands Sympathetic Parasympathetic the function of the autonomic nervous system is to maintain the constancy of the internalenvironment (homeostasis). Both somatic and autonomic effectors may be re-flexly excited by nerve impulses arising from the same sensory end organs  Anatomic and neurotransmitter features 7 The axon of a somatic motor neuron leaves the CNS and travels without interruption to the innervated effecter cell. In contrast, two neurons are required to connect the CNS and a visceral effector cell of the autonomic nervous system Anatomy of the Autonomic Nervous System  parasympathetic neurons 9 and synapses Preganglionic neurons have their cell bodies in the brainstem and in the sacral region of the spinal cord Long Synapse with postganglionic neurons at or near organ Release acetylcholine (ACH) to activate nicotinic receptors on postganglionic neurons  parasympathetic neurons and synapses Postganglionic neurons Short Synapse on the target organ Release acetylcholine (ACH) to activate muscarinic receptors on the target organ parasympathetic preganglionic neurons are extremely limited in their distribution  sympathetic neurons and synapses Preganglionic neurons have their cell bodies in the thoracic and lumbar regions of the spinal cord Short branches a number of times after entering a ganglion Synapse with postganglionic neurons near spinal cord Release acetylcholine (ACH) to activate nicotinic receptors on postganglionic neurons  sympathetic neurons and synapses Postganglionic neurons Long Synapse on the target organ Release norepinephrine to activate adrenergic receptors on target organs Exceptions Are the Sweat glands which involved with thermoregulation the Postganglionic neurons release acetylcholine Neurotransmission in the PNS occurs at three major sites: (1) preganglionic synapses in both parasympathetic and sympathetic ganglia, (2) parasympathetic and sympathetic postganglionic neuro effector junctions, (3) all somatic motor end plates on skeletal muscle Acetylcholine is the transmitter released at all of these sites and called cholinergic neurons. Except the majority of sympathetic neuro effector Junctions Norepinephrine is the transmitter released and called adrenergic or noradrenergic neurons neurons Except the sweat glands receive sympathetic innervation but have muscarinic acetylcholine receptors. Second, chromaffin cells of the adrenal medulla receive stimulation via acetylcholine to release catecholamines such as epinephrine and norepinephrine  receptors for acetylcholine and related drugs (cholinoreceptors) receptors for norepinephrine and related drugs (adrenoceptors)  The effects of acetylcholine on visceral effectors known as the muscarinic action of acetylcholine effects of acetylcholine on the autonomic ganglia and adrenal medulla Known as the nicotinic action of acetylcholine respective receptors are called the muscarinic and nicotinic cholinoreceptors the cholinoreceptor on skeletal muscle is a nicotinic receptor. Acetylcholine can stimulate a whole family of receptors.  Cholinergic receptors October 24 17 types of adrenoceptors exist including α1, α2 and β1, β2 adrenoceptors α1 located at postjunctional (postsynaptic) sites α2 located presynaptic The β1 adrenoceptors are found chiefly in the heart and adipose tissue β2 adrenoceptors are located in a number of sites, including bronchial smooth muscle , skeletal muscle and blood vessels INNERVATION OF VARIOUS ORGANS BY THE SYMPATHETIC AND PARASYMPATHETIC NERVOUS SYSTEMS Constriction of radial muscle causing dilation (mydriasis) Contraction of circular muscle (miosis) Contraction of ciliary muscle producing accommodation for near vision October 24 Autonomic Munir Gharaibeh MD, PhD, MHPE 21