1214 Week 14

1214 Week 14

1. Lecture 2

   • Endocrine System
     • controls hormone regulation in the body
     • specialised cells in endocrine glands secrete hormones into the circulation and are transported around the body
     • hormones are deposited at target tissues where they affect cell function
     • hormones also have paracrine and autocrine actions
   • Hormones
     • amino acid derivatives
       • arise from tyrosine - thyroid hormone, catecholamines
       • arise from tryptophan - melatonin
     • peptide derivatives
       • arise from glycoproteins
       • arise from short polypeptides and small proteins
     • lipid derivatives
       • arise from cholesterol (steroid hormones)
       • arise from eicosanoids-lipid derivative of arachidonic acid
   • Hormone Control
     • hormones circulate freely in the blood or are bound to plasma proteins
     • hormones that require binding proteins are able to create reservoirs in the blood which increases their half lives
     • steroid and thyroid hormones use carrier proteins
     • peptide and catacholamines don't use carrier proteins
     • rate of hormone excretion depends on neural and humoral signals each being wirher stimulatory or inhibitory
     • control of blood hormone levels depends on secretion, amount of hormone bound to plase proteins and the rate of hormone metabolism
     • humoral signals include hormones, ions and metabolites
     • abnormal secretion are either hyper or hypo for example - acromegaly is caused by excess growth hormone and insulin dependant diabetes mellitus is caused by a lack of insulin
     • abnormal secretion can be primary - abnormality in the gland - or secondary - problem with the tropic hormone or synthesis of the hormone or its action
   • Hormone Action
     • lipophilic hormones use intracellular receptors
     • lipophobic hormones use extracellular receptors
     • lipophobic hormones have to use secondary messenger systems