endocrine system chapter 16. endocrine glands ductless glands that produce hormones that are...
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ENDOCRINE GLANDS
Ductless glands that produce hormones that are released directly into the bloodstream and are transported throughout the body to regulate the metabolic function of other cells in the body.
Types of hormones: Paracrine Autocrine
Chemical Nature of Hormones
Amino-acid based hormones Amines=simple hormones derived from tyrosine
(example: Epinephrine) Protein and peptides=chains of amino acids hooked
together (example: ADH or Oxytocin)
Steroid-based hormones Progesterone Testosterone
Eicosanoids Hormone-like substances that act only on cells in the
immediate vicinity (example: prostaglandin)
Mechanisms of Hormone Action
Lipid-soluble hormones Diffusion occurs Binds to intracellular
receptors Forms hormone-receptor
complexes Hormone-receptor complex
binds to specific receptor proteins on DNA
Initiates transcription of certain genes
Mechanisms of Hormone Action
Cyclic AMP signaling Hormone binds to cell
membrane receptor Hormone-receptor complex
binds to inactive G protein G protein becomes active by
GTP to GDP G protein binds adenylate
cyclase producing Cyclic AMP
Cyclic AMP activates protein kinase enzymes
Mechanisms of Hormone Action
PIP-calcium signaling Hormone binds to cell
membrane receptor Hormone-receptor
complex binds to inactive G protein
G protein becomes active and binds to phospholipase
Phospholipase splits to form IP3 and DAG which activate protein kinases and calcium
Control of Hormones
Feedback Mechanisms Negative feedback Positive feedback
Responsiveness to target cells Concentrations of hormones Number of receptors Interaction of other hormones
Major Endocrine Glands
Pituitary Gland
Thyroid Gland
Parathyroid Gland
Adrenal Gland
Thymus Gland
Pineal Gland
Other endocrine tissue
Thyroid Gland
Follicles and follicle cells
Thyroglobulin
Colloid
Thyroxine (T4)
Triiodothyronine (T3)
Calorigenic effect
Calcitonin produced by parafollicular cells
Parathyroid Gland
Produces parathyroid hormone (PTH)
Regulates calcium levels by targeting: Bones Intestine Kidneys
Adrenal Gland
Adrenal Cortex Zona glomerulosa
produces mineralcorticoids
Zona fasciculate produces glucocorticoids
Zona reticularis produces androgens or adrenal sex hormones
Adrenal Gland (continued)
Adrenal Medulla Chromaffin cells Epinephrine Norepinephrine Associated with stress
or “Fight or Flight” responses
Thymus and Pineal Gland
Thymus Gland Thymosin stimulates
T-cell maturation Immune system
Pineal Gland Pinealocytes Melatonin
Pancreas
Alpha Cells Produce glucagon Glycogen>>Glugacon>>Glucose
Beta Cells Produce insulin Enhances uptake of glucose by cells
as well as inhibits glycogenolysis and gluconeogenesis
Delta Cells Somatostatin
Acinar Cells Produces pancreatic enzymes but
are exocrine
Other Endocrine Tissues
Ovaries=produce estrogen and progesterone
Testes=produce testosterone and inhibin
Placenta=produces HCG
Heart=secretes ANP
Kidneys=secrete erythropoietin
Skin=produces choleocalciferol
Adipose tissue=releases leptin
Gastrointestinal tract=releases gastrin, secretin, serotonin, cholecystokinin and others
Homeostatic Imbalances
GigantismAcromegalyProgeriaPituitary dwarfismGalactorrheaGynecomastiaMyxedemaGoiterCretinism
Grave’s diseaseHyperparathyroidismHypoparathyroidismDiabetes insipidusDiabetes mellitusAldosteronismAddison’s diseaseCushing’s diseaseMasculinization