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General functions of the sympathetic nervous system: (The alarm response or stress response) In emergency conditions : e.g. in cases of fight, flight, muscular exercise, emotions, pain and cold, generalized sympathetic excitement occurs (the alarm response or stress response):
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General functions of the sympathetic nervous system: (The alarm response or stress response) In emergency conditions: e.g. in cases of fight, flight, muscular exercise, emotions, pain and cold, generalized sympathetic excitement occurs (the alarm response or stress response): • Acceleration of the heart. • Dilatation of bronchi. • Vasoconstriction in inactive regions.
Sweat secretion. • Delay muscle fatigue. • Contraction of spleen. • Glycogenolysis. • Adrenal secretion. All the above reactions prepare the body for fight or flight or to face an emergencysituation.
Horner's Syndrome: damage of the superior cervical sympathetic ganglion leads to: • Ptosis. • Miosis. • Anhydrosis. • Vasodilatation.
The Parasympathetic Nervous System Origin and distribution of parasympathetic nervous system
General functions of parasympathetic system: • Parasympathetic functions are anabolic and energy preserving • Its function becomes most apparent in a person at rest after a meal and reading a newspaper.
CHEMICAL TRANSMITTERS The most widely distributed transmitters are acetylcholine (ACH) and noradrenalin. • acetylcholinecholinergic nerve cholinergicreceptors. • noradrenalinadrenergic nerveadrenergic receptors. • adrenergic receptors : there are ά and β receptors, ά receptors are divided into ά1 and ά 2 receptors. • Subtypes of cholinergic receptor are nicotinic and muscarinic receptors.
Acetylcholine Site of release of acetylcholine(the cholinergic nerve fibers): I- Central cholinergic fibers: a)All the preganglionicsympathetic. b) All the preganglionicparasympathetic. c) All the somatic motor fibers supplying the skeletal muscles.
II- Peripheral cholinergic fibers: a) All the parasympathetic postganglionic fibers. b) Sympathetic postganglionic secretary fibers to sweat glands. c) Sympathetic postganglionic vasodilator fibers to blood vessels of skeletal muscle.
Actions of acetylcholine: • "the nicotine-like actions"nicotinic receptors. • "the muscarine-like actions" muscarinic receptors.
Myasthenia Gravis * It is a disease of the neuromuscular junction characterized by weakness and easy fatigability of skeletal musclesautoimmunity. * Destruction of the cell membrane over the motor end plate decreasing the receptor areafor acetyl choline.
Catecholamines Is the chemical transmitter of most of the postganglionic sympathetic nerves. ADRENERGIC RECEPTORS: • There are 2 main types of adrenergic receptors; ά and β. In each type there are 2 subtypes. So, there are ά1, ά2, β1andβ2 adrenergic receptors. • Different adrenergic receptors produce different actions in target organs.