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 emergency situation.

Horner's Syndrome: damage of the superior cervical sympathetic ganglion leads to: Ptosis. Miosis. Anhydrosis. Vasodilatation.

Origin and distributio n of parasympa thetic 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.

The most widely distributed transmitters are acetylcholine (ACH) and noradrenalin. acetylcholine cholinergic nerve cholinergic receptors. noradrenalin adrenergic nerve adrenergic receptors. adrenergic receptors : there are ά and β receptors, ά receptors are divided into ά 1 and ά 2 receptors. Subtypes of cholinergic receptor are nicotinic and muscarinic receptors.

Site of release of acetylcholine (the cholinergic nerve fibers): I- Central cholinergic fibers: a) All the preganglionic sympathetic. b) All the preganglionic parasympathetic. 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 autoimmunity. * It is a disease of the neuromuscular junction characterized by weakness and easy fatigability of skeletal muscles autoimmunity. decreasing the receptor area * Destruction of the cell membrane over the motor end plate decreasing the receptor area for acetyl choline.

Is the chemical transmitter of most of the postganglionic sympathetic nerves. ADRENERGIC RECEPTORS: ; ά and β. ά 1, ά 2, β 1 β 2 There are 2 main types of adrenergic receptors; ά and β. In each type there are 2 subtypes. So, there are ά 1, ά 2, β 1 and β 2 adrenergic receptors. Different adrenergic receptors produce different actions in target organs.