Endocrine System

Communication through hormones

Hormone • Hormone – a molecule that is released to flow

through blood or lymph to send a signal

Signaling Types• Local regulators – act over short distances

paracrine- target cells are near signaling cells

Autocrine – hormone acts on the cell that released it• Synaptic signaling – nerve cells release hormones

onto target cells• Neuroendocrine signaling – nerve cells release

hormones into the bloodstream to target cells• Pheromones- hormones are released outside the

body.

Water Soluble vs. Lipid-Soluble• Water soluble hormones

deliver signals outside the

cell

• Lipid soluble can get

through the plasma

membrane and go into

cells

Water Soluble• Signal transduction pathway (signal,

transduction, response)

Lipid Soluble• Lipid soluble hormones form a hormone

receptor complex that go directly to the nucleus.

• Usually involved in

gene expression

One Hormone many jobs• Homones can act many ways

• When stressed, Epinephrine:

Causes glycogen to break down when stressed

Causes muscle blood vessels to dilate

Causes intestinal blood vessels to constrict

Negative feedback• Negative feedback – a response reduces the

initial stimulus

Ex. Low duodenum pH

Antagonistic Hormone Pairs• Pairs of hormones often help maintain

homeostasis

• Blood glucose level is usually 90mg/100ml

When it rises insulin is released by the pancreas

When it falls glucagon is release by the pancreas

Diabetes Mellitus• Deficiency of insulin or less response of target cells to

insulin (blood sugar stays to high)• Type I – autoimmune disease, beta cells of the

pancreas are destroyed. Develops during childhood and daily insulin is given.

• Type II – target cells stop responding normally to insulin. Being overweight and lack of exercise increase the risk. Diet and exercise can usually control this. (top ten causes of death in the U.S.)

Glands and Hormones

*

Hypothalamus• In the brain, helps link the endocrine and

nervous system. Controls pituitary glands and other glands through cascade that ways

Posterior pituitary • Water balance in kidneys, uterus contraction in

females

Anterior pituitary• Growth, milk production, gamete production,

stimulates thyroid, stimulates adrenal cortex

Thyroid• Controls metabolism, lowers calcium levels

Parathyroid• Raises calcium levels

Pancreas• Lowers and raises blood glucose level

Adrenal Glands

Adrenal medulla• Stress response, raise blood glucose, constrict

blood vessels

Adrenal Cortex• Long term stress response, increase blood

glucose, blood pressure, and immune suppression

Testes• Sperm formation (spermatogenesis), sex

characteristics, testosterone (androgen)

ovaries• Egg formation (oogenesis), female sex

characteristics, uterine lining growth, estrogen and progesterone

Pineal gland• Regulates body rhythmic cycles (light and

dark), like sleep