Endocrine System

The making and sending of hormones

How it works

• Sends signals directly into blood stream (remember, takes less than a minute for blood to circulate through entire body!)

• Signals are specific shape, and will bind to cells that have the proper receptor shape

• Signal tells cell to do a specific function

Hormones vs. neurotransmitters

• Neurotransmitters released into small space called synapse between two nerves. ONLY ACTS IN THIS AREA

• Hormones released in larger levels into blood stream to tell whole body what to do

Receptor Proteins

• Proteins embedded into cell membrane, each with specific shape receptor

• Designed to receive a specific signal in blood stream

– *many drugs act by blocking these receptors so certain signals (ex. Pain) cannot be received OR by blocking the receptors responsible for breaking down a message, keeping that message in the body for longer)

Target Cells

• Certain cells within the body that are supposed to react when a signal is sent out

• Example- pancreas and liver communication– Pancreas senses too much glucose in blood, sends out

insulin– Liver gets insulin signal, reacts by storing glucose away

as glycogen– If too little glucose, glucagon sent out and glycogen is

broken down by liver

Negative Feedback

• The response to the original signal gets to a certain concentration and causes the organ to stop reacting– Example- when enough insulin is in the blood

stream, insulin turns the pancreas off, telling it to stop making insulin.

– *This keeps the body at a level state (homeostasis) since it can monitor how much of each chemical is in your body and make sure that there is never too much released at one time.

Glands

• Adrenal gland• Testes• Ovaries• Pineal gland• Pituitary gland• Thymus• Thyroid• Pancreas

Adrenal

• Located above kidneys

• Releases stress hormones into blood stream– Corticosteroids– Epinepherine

• Fight or flight response

Sex glands

• Testes- primarily makes testosterone, responsible for development of male characteristics

• Ovaries- release estrogen and progesterone. – Estrogen- results in development of female

characteristics– Progesterone- works with estrogen to regulate

menstrual cycle

Birth Control Pills

• A combination of estrogen and progesterone keep female ovulating each month counteracting the chemicals given off by any fertilized egg

– Also thicken cervix and thin uterine wall to prevent sperm from reaching egg and to prevent egg from implanting in uterus

Pineal

• Near base of brain, just above cerebellum

• Make serotonin and melatonin, regulating sleep cycles

Pituitary

• Below hypothalamus

• Makes many hormones to regulate homeostasis in the body– Growth hormone– Hormones in menstrual cycle (FSH, LH)– Stress hormones

Thymus

• Lobed, behind breastbone

• Site of creation of T-Cells– Where they are “educated”

• Creates hormones that stimulate antibody production during immune responses

Thyroid

• In neck

• Produces chemicals regulating metabolism

• Chemicals produced by iodine and tyrosine (an amino acid)

Pancreas

• At base of stomach

• Releases insulin and glucagon, controlling amount of glucose in blood stream

• Makes digestive enzymes

Abuse of Endocrine System

• Steroids

– Body makes version of HGH, tells everything inside to “get bigger”

– In children, bone growth– In adults, muscle development

• New MLB contract requires blood testing for HGH– Barry Bonds, etc. have been accused of using this

Barry Bonds Comparison

Diseases of…

• Diabetes• Hyperthyroidism• Osteoporosis• Klinefelter’s and Turner‘s Syndromes• Goiters

Diabetes

• Type I- you are born with- a genetic defect causes body to not be able to make insulin properly– Body cannot regulate glucose levels

• Type II

Hyperthyroidism

• Thyroid producing too much hormone– Results in metabolic rate speeding up – Can lead to rapid weigh loss, increased heart rate,

etc.

Osteoporosis

• Largely result of estrogen or testosterone production decreasing– Tends to affect those around age 50– Sex chemicals change levels of calcium and

phosphate available to can be used in making new bone tissue

• Result- brittle bones that are easily broken

Klinefelter’s and Turner’s Syndroms

• Klinefelter’s- XXY or XXX– More common- xxy- develop as male but over time begin

to develop female characteristics like breasts– Result of change in hormone levels- drop in T, increase in

FSH, estrogen, etc.• Turner’s- X only

– Develop as female, but usually have non-working ovaries

• Both result of error in meiosis- second most common disorder involving chromosome nondisjunction

Goiters

• Result of low iodine levels

• Thyroid cannot make hormones without iodine, so gets bigger to compensate

• Solution- iodized salt