The Endocrine System

Endocrine System A set of glands that produce hormones-- chemical messengers that circulate in the blood

Hormone Chemical messengers produced by the endocrine glands and circulated in the blood Similar to neurotransmitters in that they are also messengers Slower communication system, but with longer lasting effects

Endocrine System

Hypothalamus Brain region that controls the pituitary gland Controls homeostasis – the bodies ability to remain at a status quo level

Pituitary Gland The endocrine system’s gland that controls the other endocrine glands Called the “master gland” Located at the base of the brain and connects to the hypothalamus Controls thirst by controlling the amount of water in the body ’ s cells Controls female contractions, and tells the mammary glands to produce milk for newborns May control grooming habits, companionship, and sexual behavior Controls the flow of the human growth hormones – dwarfism and gigantism

Thyroid Gland Endocrine gland that helps regulate the energy level in the body Located in the neck Controls body temperature Controls metabolism – our body ’ s ability to transform the food we eat into usable energy

Adrenal Gland Endocrine glands that help to arouse the body in times of stress Located just above the kidneys Release epinephrine (adrenaline) and norepinephrine (noradrenaline ) Increase heart rate, blood pressure, and blood sugar

Pancreatic Gland Regulates the level of blood sugar in the blood by insulin Insulin is needed in the body to break down sugars in the body

Sex Glands Ovaries (females) and testes (males) are the glands that influence emotion and physical development. Testosterone – primary male hormone Estrogen – primary female hormone Males and females have both estrogen and testosterone in their systems.

Gonads (sex organs) Testicles – release androgens (male hormones) Ovaries – release estrogens (female hormones) The presence of these chemicals influence male and female reproductive characteristics.

Maintaining Homeostasis Homeostasis is the maintenance of a stable internal state within an organism. Organisms detect changes in their environment and respond to these changes in a variety of ways. A feedback mechanism occurs when the level of one substance influences the level of another substance or activity of another organ.

Feedback Mechanisms Three parts of the mechanism –Sensor – something that can detect a change Ex. Structures in the brain detect changes in CO 2 levels –Control Unit – something that knows what the correct level should be Ex. Information in the brain is preset for the correct CO 2 level –Effector – something to take the instructions and make changes Ex. Muscles in the chest used for breathing

Feedback Mechanisms Positive feedback - designed to accelerate or enhance the output created by a stimulus that has already been activated. Designed to push levels out of normal ranges. Example is the release of oxytocin to intensify the contractions that take place during childbirth. –The more oxytocin, the greater and more frequent the contractions, which in turn produces more oxytocin

Feedback Mechanisms Negative feedback – process in which a stimulus produces a response that opposes the original stimulus. Ex. Blood sugar regulation –An increase in blood sugar level triggers the release of the hormone insulin by the pancreas –the hormone insulin lowers blood sugar level restoring the body to its original blood glucose level in two major ways: it increases the ability of body cells to take in glucose from the blood it converts blood glucose to the compound glycogen -- this compound is also called animal starch and is stored in our liver and muscles –A decrease in blood sugar levels triggers the release of the hormone glucagon by the pancreas It causes the liver to release glucose into the blood to regulate blood sugar levels

Endocrine Disorders Diabetes interruption of the feedback system that controls blood sugar. Too little insulin = buildup of sugar in the blood the kidneys use a lot more water to flush it out of the body. extra water comes from surrounding cells, which in turn dehydrates them –leaves the cells vulnerable to infection and poisons. Type I – born with it –Controlled by insulin injections Type II – acquired –Usually occurs in older people –May be controlled with diet

Endocrine Disorders –Hyperactive thyroid- Behaviors may include excitability, insomnia, ADD, agitation, difficulty focusing –Hypoactive thyroid - Behaviors may include sleepiness, reduced muscle tone, overweight –Hypoglycemia - Too much insulin in the body devours all of the sugar in the blood. May appear sluggish and inattentive.