Sympathetic nervous system definition

Tyrosine is a (crystalline) amino add with the formula HOQH4CH2CH(NH2) COOH. It results from the hydrolysis of proteins, that is, the reaction of proteins with water. The -C6H4- group within the compoimd denotes a ring-type stmcture. Another definition provided is that tyrosine is found in most proteins and can be synthesized metabolically from phenylalanine. Furthermore, tyrosine is a precursor for thyroid hormones, melanin (the dark pigment of body parts, notably, the skin), and catecholamines (that affect the sympathetic nervous system). 

The drugs discussed in this section are primarily, but not exclusively, those that have a depressant effect somewhere in the sympathetic nervous system. The diuretics that have definite antihypertensive properties (as well as beneficial effects in CHF) are dealt with separately in this chapter. 

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