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

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• 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 or shuts down the original stimulus.

Endocrine DisordersDiabetes

• 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.