The Endocrine System

Elisa Barkan Jaume Ros

ENDOCRINE SYSTEM• Glands that release their products

into bloodstream– These send messages throughout

the body• Hormones: chemicals that send

the messages.

HORMONES

• Chemicals that travel through bloodstream and affect activities of other cells.

• Bind to specific chemical receptor on that cell

• Target cells: cells with receptors for particular hormone

GLANDS • Organ that produces and releases substance or

secretion. Two types of glands Exocrine glands: release secretions through tub

like structures called ducts. Release: Sweat Tears digestive juices.

Endocrine glands: release secretions directly into bloodstream

Major Glands

• Pituitary gland• Hypothalamus gland• Thyroid gland• Parathyroid glands• Adrenal glands• Pancreas• Reproductive glands

HORMONE ACTION

Steroid hormones: produced from lipid called cholesterol

Nonsteroid hormones: include proteins, small peptides and modified amino acids

STEROID HORMONES

• Can cross cell membranes, pass directly into the cytoplasm and even into nucleus. 1. Enters cell by passing across cell membrane

STEROID HORMONES CONTINUED

2. Binds to steroid receptor protein ( only found in its target cells) to form hormone receptor complex 3. Hormone receptor complex enters nucleus and binds to DNA control sequence. 4. Binding initiates passing of specific genes to messenger RNA

STEROID HORMONES CONTINUED

5. The RNA moves into the cytoplasm and directs protein synthesis

NONSTEROID HORMONES

1. Hormone binds to receptors on cell membrane

2. Binding of the hormone activates enzyme on inner surface of cell membrane

3. Enzyme activates secondary messengers that carry the message inside the cell.

4. Once released these second messengers can activate or inhibit many other cell activities

CONTROL OF THE ENDOCRINE SYSTEM• Endocrine system regulated by feedback

mechanisms• function to maintain homeostasisExample: • Thyroid releases thyroxin• if thyroxin level in blood low hypothalamus releases

the TRH hormone – stimulates TSH which releases thyroxin– starts cycle again.

Maintaining Water Balance • Hypothalamus contains cells that are sensitive

to concentration of water in blood• As you exercise and loose water the

concentration of dissolved materials in the blood rises

• Hypothalamus releases hormone called ADH– carried to kidney where the removal

of water from the blood is slowed down.

• Next you experience thirst and take in 1-2 liters of fluid.

• Most of that fluid is directly absorbed by the walls of the digestive system and into the bloodstream.

• If there is too much water in the bloodstream the hypothalamus sends less ADH levels and the equilibrium is restored.

• Glands scattered throughout body

• Generally no connections to one another

• Improper functioningendocrine gland mayresult in disease or disorder

GLANDS

Pituitary Gland• Bean sized structure dangles slender stalk tissue at

base of skull• Divided in two parts:– Anterior pituitary– Posterior pituitary

• Secretes 9 hormones– Regulate many body

functions– Control actions of

several other endocrineglands

Pituitary Gland Continued

• Normal function gland essential to good health

• Example: gland produces too much growth hormone (GH) body grows too quickly– Condition called gigantism

• Example: too little GH during childhood – condition called pituitary dwarfism– Treated with growth hormones

Hypothalamus• Part of brain above attached to posterior

pituitary• Controls secretions of pituitary gland• Influenced by: – levels of hormones in blood– Sensory information

collected other parts central nervous system

• Interactions between nervous and endocrine systems take place at hypothalamus

Posterior Pituitary• Made up of axons belonging to

neurosecretory cells– Cell bodies in hypothalamus

• when stimulated axons release hormones

• Posterior pituitary extension of hypothalamus

Hypothalamus Continued

• Also indirect control of anterior pituitary

• Produces small amounts chemicals (releasing hormones)– Secreted into blood vessels

Thyroid Gland• Located base of neck • Wraps around upper trachea• Major role regulating body’s

metabolism• Cells in gland produce

thyroxine– Made of amino acid tyrosine and

mineral iodine• Increased levels tyrosine

increase cellular respiration rate– Cells release more energy

Thyroid Gland Continued• Other cells secrete calcitonin– Hormone decreases level calcium in blood

• hypothyroidism– Nervousness, elevated body temperature, increased

heart and metabolic rates, increased blood pressure and weight loss

• hypothyroidism– Lower metabolic

rates and body temperature, and weight gain

Thyroid Gland Continued• Improper activity; parts of world food

lack iodine for thyroid produce normal amounts thyroxin

• Iodine-deficient infants: condition called cretinism– Neither skeletal nor nervous system

develop properly• Two effects: dwarfism and severe

mental retardation

Parathyroid Glands• Four parathyroid glands• Found on back surface of thyroid gland• Hormones from thyroid and parathyroid maintain

homeostasisin blood calcium levels

• Glands secrete PTH– Regulates calcium

levels blood increasing reabsorption calciumkidneys and increasinguptake calcium digestive system

Adrenal Glands• Two pyramid-shaped structures sit on top of

kidneys• Help body prepare for and deal with stress• Outer part:– Adrenal Cortex

• Inner part:– Adrenal Medulla

• Contain different types tissues

Adrenal Cortex• 80% adrenal gland• Produces +two dozen hormones called corticosteroids• Aldosterone regulate reabsorption sodium ions and

excretion potassium ions by kidneys• Cortisol control rate metabolism of carbohydrates, fats and

proteins

Adrenal Medulla• Release hormones regulated by sympathetic

nervous system• Releases two hormones:– Epinephrine: more powerful, 80% secretions– Norepinephrine– Increase heart rate, blood pressure, and blood flow

to muscles• “fight or flight” response to stress– Feeling when excited o frightened

Pancreas• Located right side and behind stomach• Digestive organ, enzyme secretions break

down food– Exocrine gland

• Different cells inside release hormones

• Clusters cells resembleislands– Islets of Langerhans• Include beta cells

(insulin) and alpha cells (glucagon)

Pancreas Continued• Insulin and glucagon help

keep level glucose in blood stable

• Insulin stimulates cells (liver and muscles) remove sugar from blood and store as glycogen or fat

• Glucagon stimulate liver break down glycogen and release glucose into blood

Pancreas Continued• Too little insulin: diabetes mellitus– Amount glucose in blood rise so high kidneys excrete

glucose in urine– Can damage organs and tissues

• Juvenile-onset diabetes (Type I)– Before age 15– Little or no secretion of insulin

• Adult-onset diabetes (Type II)– After age 40– Low to normal amount of insulin– Unable properly respond to hormone: interaction insulin

receptors and insulin is insufficient

Reproductive Glands• Gonads• Serve two important fuctions:– Production of gametes– Secretion of sex hormones

• Female gonads: ovaries– Produce eggs (ova)

• Male gonads: testes– Produce sperm

Other Vocab

• Thymus: releases thymosin –stimulates T cell development– during childhood

• Thyroid: produces thyroxine – regulates metabolism

Endocrine song!

• http://www.youtube.com/watch?v=h58x_oJXKsg