L49- introduction to endocrine functions

what is the endocrine system

its the body system that produces and secretes hormones into the bloodstream to regulate physiological functions

the word endocrine means to secrete internally and it a form of signalling mechanism, cell to cell signalling

for endocrine the hormone has to secreted inside the blood and travel to a distant target cell

list some of the main endocrine glands

• hypothalamus

• pituitary gland

• thyroid

• adrenals

• gonads

what type of hormones are released by the endocrine organs

they release hormones that are important in 4 broad areas:

• reproduction

• growth and development

• maintenance of internal environment

• regulation of energy

what are hormones

they are chemical messengers released by the endocrine cells into the blood stream that act of specific target cells with appropriate receptors to regulate physiological process

what are the three major chemical classes of hormones

• amino acids/amines

• peptide sand proteins

• steroids

describe amine hormones

• small hormones made from single amino acids initially

• the two main sources:

• tyrosine ( e.g. adrenaline and noradrenaline ) and tryptophan ( e.g. melatonin )

what are key structural features of the endocrine glands

• they are ductless, compare to salivary glands they don’t have ducts and secrete hormones directly from the cell into the blood

• richly vascularized- they have good blood circulation

• there’s primary and secondary glands

explain the synthesis pathways for amine hormones ( starting with tyrosine- adrenaline )

• they start with tyrosine which is converted into L-Dopa by tyrosine hydroxylase

• the L-DOPA is then converted into dopamine by dopa decarboxylase

• the dopamine then gets converted into noradrenaline by dopamine- beta- hydroxylase

• finally the noradrenaline is converted into adrenaline

what are steroid hormones

• these are hormones that are all derived from cholesterol

• these are hormones such as:

• cortisol, aldosterone, testosterone also vitamin d, sex hormones

explain the synthesis of steroid hormones

• it starts from cholesterol in the mitochondria

• inside the mitochondria the cholesterol is converted into pregnenolone