BSC 2086 1st Edition Lecture 5 Outline of Last Lecture I Equilibrium and Hearing II Intro to Endocrine System III Intercellular Communication in the Endocrine System Outline of Current Lecture I Hormones II Pituitary Gland Current Lecture I Hormones a Can either travel freely or attached to special carrier proteins b Amino acid derivatives i Structurally related to amino acids ii Derivatives of Tyrosine 1 Thyroid hormones 2 Catecholamines epinephrine and norepinephrine iii Derivatives of Tryptophan 1 Used to make many hormones and neurotransmitters 2 Dopamine melatonin pineal gland and serotonin c Peptide Hormones i Chains amino acids synthesized as prohormones 1 Pro means inactive 2 Converted to active hormones before or after secretion ii Glycoproteins 1 More than 200 amino acids long with carb side chains chains 2 Thyroid stimulating hormone TSH 3 Luteinizing hormone LH 4 Follicle stimulating hormone FSH iii Short chain polypeptides antidiuretic hormone ADH and oxytocin OXT 1 Each 9 amino acids long iv Small proteins 1 Growth hormone GH and prolactin PRL 2 GH 191 amino acids 3 PRL 198 amino acids d Lipid Derivatives i Eicosanoids 20 carbon fatty acid derived from arachidonic acid 1 Paracrine factors that coordinate cell activities and play a role in enzymatic processes such as blood clotting 2 Prostaglandins direct local cell activities a Sometimes converted to thromboxanes and prostacyclins ii Steroid hormones 1 Originate from cholesterol 2 Released as a Androgens by testes b Estrogens and progestins by the ovaries c Corticosteroids by adrenal glands d Calcitriol by the kidneys 3 Remain in circulation longer than peptide hormones because they are bound to specific transport proteins e Secretion and distribution of free hormones i Go out of bloodstream and bind to target cell receptors ii Cells in liver or kidneys as well as enzymes in plasma membrane or in interstitial fluids break down and absorb the free hormones f Thyroid and steroid hormones i Stay in circulation longer due to more than 99 of them binding to carrier proteins ii Intracellular receptors affect rate of DNA transcription in nucleus which will change pattern of protein synthesis 1 Affects metabolic activity and structure of target cell g Mechanisms of Hormone Action i Hormone receptors 1 Hormonal sensitivity determined by presence or absence of receptors different tissues have different receptor combinations 2 One cell can respond to different hormones as long as they have receptors for it ii Catecholamines and peptide hormones 1 Cant penetrate plasma membrane not lipid soluble 2 Bind to extracellular receptors on outer surface of plasma membrane iii Eicosanoids 1 Can penetrate plasma membrane 2 Bind to intracellular receptors iv First and Second Messengers 1 First messenger hormone must stimulate second messenger to cause change in a cell 2 Use intermediary to have effect on activities within target cell 3 Second messengers include a Cyclic AMP cAMP i ATP which has been converted into cyclic form b Cyclic GMP cGMP c Calcium Ions i Important in muscle systems 4 G Proteins involved in the link between first and second messenger a Adenylate cyclase enzyme activated when hormone binds to receptor and changes concentration of cyclic AMP i Increased cAMP acceleration of metabolic activity ii Converts ATP to cAMP b G proteins and calcium ions i Activated G protein opens calcium ion channels which released calcium ions ii G protein activates phospholipase C PLC which is an enzyme triggers receptor cascade iii Calmodulin may be activated which will cause more changes v Amplification 1 Binding of small amount of hormone molecules to receptors which leads to thousands of second messengers 2 Amplifies the effect of the hormone vi Regulation 1 Down regulation when there is a high presence of a hormone which leads to decreased sensitivity and less hormone receptors a Ex Cocaine usage need more and more to get the same high 2 Up regulation when there is a low presence of hormones which leads to increased sensitivity and more hormone receptors h Hormone Control by Endocrine Reflexes i Counterpart of neural reflexes ii Usually controlled by negative feedback stimulus triggers hormone production the effects of the hormone will reduce intensity of stimulus iii Can be triggered by 1 Humoral stimuli different signals found in blood which cause change in composition of extracellular fluid 2 Hormonal stimuli Addition or removal of specific hormone 3 Neural stimuli signal coming from nervous system through neurotransmitters at neuroglandular junctions iv Types 1 Simple endocrine reflex only one hormone involved a Controls secretion of hormones by the heart digestive system pancreas and parathyroid gland 2 Complex endocrine reflex two or more hormones II v Hypothalamus highest level of endocrine control vi Neuroendocrine Reflexes both neural and endocrine components vii Complex commands are given by changing amount of hormone secreted and the pattern of release 1 Pituitary and hypothalamic hormones are released in random bursts Pituitary Gland a Also known as hypophysis b Located within sella turcica of the sphenoid bone and is connected to the infundibulum under the hypothalamus i Sellar diaphragm holds pituitary in position and isolates it from the cranial cavity c Releases 9 important peptide hormones which bind to intracellular receptors i cAMP second messenger d Anterior Lobe i Aka adenohypophysis ii Endocrine glands and other organs are turned on by hormones iii Tropic hormone causes release of other hormones by endocrine glands iv Hypothalamic control 1 Releasing hormones RH a Promotes synthesis and secretion of one or more hormones at anterior lobe 2 Inhibiting hormones IH a Prevents synthesis and secretion of hormones from anterior lobe 3 Secretion rate controlled by negative feedback v Hormones 1 Thyroid stimulating hormone TSH a thyrotropin b Increases secretion of TH by thyroid gland 2 Adrenocorticotropic hormone ACTH a corticotropin b Stimulates release of steroids from adrenal cortex 3 Follicle stimulating hormone FSH a follitropin b Promotes follicle development and estrogen secretion in women 4 Luteinizing hormone LH a lutropin b Starts ovulation and secretion of estrogens and progestins in women 5 Growth hormone GH a Accelerates rate of protein synthesis by starting cell growth and replication in most cell types 6 Prolactin PRL a mammotropin b starts development of mammary gland milk production e Hypophyseal Portal
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