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Introduction
• The trillions of cells of the body all interact with each other—no cell operates in isolation.
• Hormones are chemical regulators produced by cells in one part of the body that affect cells in another part of the body
http://www.pituitarysociety.org/public/overview/normalpituitary?printablepage=1
Endocrine hormones
• Only small amounts of hormones are needed to affect the target organs
• Endocrine hormones are chemicals produced in glands and secreted directly into the blood
• The circulatory system carries these hormones to the various organs of the body.
Steroid and Protein Hormones
• How do hormones signal cells?
http://www.hcc.uce.ac.uk/physiology/endocrinesystem.htm
Steroid and Protein Hormones
• Specific hormones do not affect all cells. • Cells may have receptors for one hormone but
not another. • The number of receptors found on individual
cells also may vary. • There are two types of hormones, which differ
in chemical structure and action.
Steroid Hormones• Made from cholesterol (a lipid compound)• Includes male and female sex hormones and
cortisol • Steroid molecules are composed of complex rings
of carbon, hydrogen, and oxygen molecules and are not soluble in water but are soluble in fat.
http://www.novatec-id.com/products/hormone-markers/steroid/
Steroid Hormones
• Steroid hormones diffuse from the capillaries into the interstitial fluid and then into the target cells
• they combine with receptor molecules located in the cytoplasm
Steroid Hormones• The hormone–receptor complex then moves
into the nucleus and attaches to a specific site on the DNA
• The hormone activates a gene • Ribosomes begin producing a specific protein
http://163.16.28.248/bio/activelearner/47/ch47c1.html
Protein Hormones
• Includes insulin and growth hormone• These hormones contain chains of amino acids
of varying length and are soluble in water
http://www.nibsc.ac.uk/science/diagnostics/protein_hormones__endocrine_p.aspx
Protein Hormones
• Protein hormones combine with receptors on the cell membrane
• Some of the protein hormones form a hormone– receptor complex that activates the production of an enzyme called adenylyl cyclase.
Adenyly Cyclase
• The adenylyl cyclase causes the cell to convert ATP into cyclic AMP.
• The cyclic AMP functions as a messenger, activating enzymes in the cytoplasm to carry out their normal functions
• For example, when thyroid-stimulating hormone (TSH) attaches to the receptor sites in the thyroid gland, cyclic AMP is produced in thyroid cells.
• The cyclic AMP in the thyroid cell activates enzymes, which begin producing thyroxine, a hormone that regulates metabolism.
The Pituitary Gland: the Master Gland • The pituitary gland exercises control over
other endocrine glands. • This small sac-like structure is connected by a
stalk to the hypothalamus, the area of the brain associated with homeostasis
http://en.wikipedia.org/wiki/File:Pituitary_gland.png
• http://bcs.whfreeman.com/thelifewire/content/chp42/4202s.swf
Pituitary Gland
• The interaction between the nervous system and endocrine system is evident in this hypothalamus–pituitary complex
• The pituitary gland produces and stores hormones
• The hypothalamus stimulates the release of hormones by the pituitary gland by way of nerves.
Pituitary Gland
• The pituitary gland is actually composed of two separate lobes: the posterior lobe and the anterior lobe
• The posterior lobe of the pituitary stores and releases hormones such as antidiuretic hormone (ADH) and oxytocin, which have been produced by the hypothalamus
http://www.neurosurgery.pitt.edu/minc/skullbase/pituitary/index.html
Pituitary Gland
• The hormones travel by way of specialized nerve cells from the hypothalamus to the pituitary
• The pituitary gland stores the hormones, releasing them into the blood when necessary
Pituitary Gland
• The anterior lobe of the pituitary produces its own hormones
• Like the posterior lobe, the anterior lobe is richly supplied with nerves from the hypothalamus
• The hypothalamus regulates the release of hormones from the anterior pituitary
http://ja.wikipedia.org/wiki/%E3%83%95%E3%82%A1%E3%82%A4%E3%83%AB:Pituitary_gland_et_vessel.jpg
Pituitary Gland
• Most of the hormones produced by the hypothalamus activate specific cells in the pituitary, causing the release of pituitary hormones
http://www.becomehealthynow.com/popups/pit_hypothalamus.htm
Hormones of the Pituitary
• Various regulator hormones are stored in the anterior lobe of the pituitary gland.– Thyroid-stimulating hormone (TSH) – Reproductive stimulating hormones– Growth-stimulating hormones– Prolactin– Adrenocorticotropic hormone