Drugs Affecting the Autonomic Nervous System BY : DR ISRAA OMAR

Organization of the Peripheral Nervous System Three major divisions: Efferent Somatic (motor) Autonomic Sympathetic and Parasympathetic Afferent Sensory

Some Basic Plumbing: The Peripheral Nervous System Sensory Motor Sympathetic Parasympathetic

Basic anatomy of the ANS The ANS comprises 2 divisions : sympathetic and parasympathetic The basic 2 neuron pattern consist of preganglionic neuron cell body in the CNS and post ganglionic neuron cell body in the autonomic ganglia The parasympathetic system is connected to CNS via: Cranial nerves outflow 10, 9, 7, 3 and sacral outflow

Basic anatomy of the ANS Parasympathetic ganglia usually lies close to the or within the effector organ Sympathetic outflow leave the CNS in the thoracic and lumbar roots. Sympathetic ganglia form 2 paravertebral chains, plus some midline ganglia Adrenal medulla is considered to be modified sympathetic ganglia

Functions of the autonomic nervous system(sympathetic division) Increase the heart rate and blood pressure Increase blood flow to skeletal muscle and heart, while diverting flow from skin and internal organs Increases the secretion of adrenaline and NE by adrenal medulla Dilation of pupils and bronchioles Relaxation of the GIT and bladder In sexual process the SNS is responsible of ejaculation, in female it relaxes the uterus

Fight or flight response The changes experienced by the body during emergencies have been referred to as fight and flight response These reaction are triggered by stimulation of the nervous system and stimulation of the adrenal medulla to release adrenaline and to some extent noradrenaline which in turn produce response in the system contain adrenergic receptors

Fight or flight response SNS often discharges as a complete system-for example, during sever exercise or in reaction to fear Although this system involved in wide array of physiological activities it is not essential for life

Functions of the parasympathetic nervous system Decrease the heart rate, contractility Constriction of pupils and contraction of the ciliary muscle( accommodation for near vision) Increase motility and secretion in the GIT and stimulate contraction of the bladder In sexual process the PSNS is responsible of erection Bronchial muscle constriction and increase secretion, increase secretion of watery saliva from SG

Functions of the parasympathetic nervous system It maintain essential body function such as digestion and elimination of waste This division of the ANS is essential for life It is generally dominant in rest and digest situation over the SNS It is not a functional entity and doesn’t discharge as a complete system

Functions of the parasympathetic nervous system If it did, it will lead to massive, unpleasant, undesirable symptoms Instead fibers are stimulated separately, and the system function to affect specific organ, such as stomach or eyes

Innervation of the ANS Dual innervation: most organs are innervated by both division of ANS. Thus, vagal stimulation slows the heart rate, and sympathetic stimulation increase the heart rate This type of antagonism is fine-tuned at any given time to control homeostatic organ functions

Organs receiving only sympathetic innervation Adrenal medulla Kidneys( secretion of renin) Pilomotor muscles Sweat glands Blood pressure is also mainly under sympathetic control, with essentially no participation of PSNS

Preganglionic Nerves Sympathetic Parasympathetic Sympathetic AND Parasympathetic preganglionic fibers release Acetylcholine (ACh) Postganglionic nerves have Nicotinic receptors ACh

Postganglionic Nerves Sympathetic Parasympathetic Sympathetic post ganglionic neurons release Norepinephrine except in the sweat gland they secrete ACh Parasympathetic post ganglionic neurons release ACh Norepinephrine binds to adrenergic receptors ACh binds to Muscarinic receptors ACh NE

What Happens at the Effectors? NE from postganglionic sympathetics binds to Adrenergic Receptors ACh from postganglionic parasympathetics binds to Muscarinic Receptors NE ACh Adrenergic Receptor Muscarinic Receptor Sympathetic Parasympathetic

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REFERNCES LIPPINCOTTS PHARMACOLOGY RANG AND DALE PHARMACOLOGY