ENDOCRINE SYSTEM Functions of the Endocrine System Radio

ENDOCRINE SYSTEM

Functions of the Endocrine System “Radio Station” sends messages using chemicals Different parts of the body are “tuned” to different “stations” Can reach thousands of customers! Chemical messages (“Radio Waves/Stations”) = Hormones Helps maintain homeostasis

Glands: part of the endocrine system Glands: an organ that produces & releases a substance (i. e. secretions) 2 types of glands: Exocrine: release secretions into ducts (tubes) to the outside or into the digestive system Example: sweat glands Endocrine: release secretions directly into the blood Example: ovaries

Hormones: the chemical messengers Deliver messages throughout the body Released in 1 part of the body Travel in the blood Affect cells in other parts of the body

Target Cells with a receptor for a particular hormone AKA: they are a target for that hormone If no receptors hormone DOES NOT affect that cell Prevents cells from reacting to messages meant for others! “Like phone numbers!”

Role of Hormones in Homeostasis Responses to hormones are slower and longer lasting How does this compare to a nerve? Hormones act in pairs, like a tug of war! One may start a reaction The other will stop it This results in your body staying balanced in the middle

Feedback Loops Act to referee the Tug of War Example of a Feedback Loop: Alerts your Brain Sweating, Dehydration Brain releases hormone (ADH) STOP! Producing ADH! Increase Thirst Decrease Urine Body now OK

Another Example: Blood Glucose insulin & glucagon control sugar Both are produced in the Pancreas Insulin stimulates storage of sugar Glucagon stimulates release of sugar Diabetes: Body fails to produce insulin (TYPE I) Receive OR injections of insulin fails to respond to it (TYPE II) Control with diet/exercise

Notes on the Hormones There are many other hormones, but these are some that I think you should know (also refer to worksheet!).

Hormones of the Ovaries Estrogen: Stimulates female sexual development/female characteristics (widening the hips, breast development) Helps regulate the menstrual cycle Bone growth Sex drive Progesterone Stimulates the growth and development of the uterine lining Maintains the uterus in pregnancy

Hormones of the Pituitary Growth Hormone: Stimulates protein synthesis and growth in cells Affects growth in childhood

Hormones of the Thyroid Gland Calcitonin: Controls calcium absorption by promoting absorption into the bones Thyroxine Increases metabolic rate of cells Cells become more active, use more energy, produce more heat Requires Iodine to work properly

Hormones of the Adrenal Gland Epinephrine: Commonly called adrenaline Increases heart rates, blood pressure Stimulates air passages to open widely Stimulates release of glucose

Hormones of the Testes Testosterone: Stimulates male development/secondary sex characteristics (deep voice, facial hair etc) Bone growth Sex drive Linked to aggression

WHEN GOOD HORMONES GO BAD! This is for interest only – I won’t test you on these!

Where can it go wrong? Message doesn’t get sent Feedback doesn’t work! Message isn’t heard!

Diabetes: do you remember? Which hormone is involved? Insulin Type I: ? No insulin Type II? Can’t respond to insulin

Acromegaly or Gigantism Excessive growth hormone Excessive height Enlarged hands, feet, jaws

Cretinism Low levels of thyroxine because low levels of Iodine Skeletal & nervous systems don’t develop properly Picture Cretinism skull & normal skull

Goiters Enlargement of the thyroid gland Sign of Hypothyroidism Not enough thyroxine produced Lack of energy, low body temp, weight gain

Hyperthyroidism Too much thyroxine Symptoms: Fast heart beat Tremors, anxiety Speedy digestive system weight loss, diarrhea

Hyperprolactinemia Too much prolactin produced Prolactin = milk production Can cause: Lack of menstrual period Spontaneous milk production

Turner’s Syndrome Caused primarily by genetics Side effect is low estrogen Causes: no secondary sex characteristics Short stature No periods or puberty