Endocrine System

The Importance of the Endocrine System

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

http://kasper-achs-block3.wikispaces.com/General+Info+on+Glands+and+Hormones

Homework

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