Homeostasis and the Endocrine System

Endocrine System Endocrine system: consists of ductless glands that release hormones into the blood Hormones~ chemical signals that are transported in blood (communicates regulatory messages) (Option H) Target cells~ body cells that respond to specific hormone (Option H) Feedback mechanisms Essential idea: Hormones are used when signals need to be widely distributed.

Homeostasis and Negative Feedback Homeostasis = maintaining the internal environment of the body within limits (a steady state). Negative feedback maintains homeostasis Level of the hormone has an effect that controls the hormone’s secretion Ex. If ADH levels are high, secretion of ADH slows. If ADH levels are low, secretion of ADH increases.

The Hypothalamus Brain Region that links nervous and endocrine system. Controls the pituitary gland (the body’s “master gland”

Hormone Examples: Insulin and Glucagon Islets of Langerhans– clusters of endocrine cells in pancreas Alpha (α) cells: •glucagon~ raises blood glucose levels Beta (β) cells: •insulin~ lowers blood glucose levels Negative feedback!.

Diabetes mellitus Two types: Blood glucose homeostasis is NOT effectively maintained in diabetes How the disease was named: Greek diabainein (to pass through), refers to excessive urination of diabetics. Latin mellitus (honey-sweet) http://www.healthline.com/galecontent/diabetes-mellitus-5 Two types:

Type I diabetes mellitus Onset: childhood autoimmune disorder (immune system destroys beta cells) insulin-dependent (Beta cells produce insufficient insulin) Insulin injections required

Type II diabetes mellitus http://www.hivandhepatitis.com/hep_c/hepc_news_insulin.html Type II diabetes mellitus Onset: later in life (usually after childhood non-insulin-dependent reduced responsiveness to insulin (insensitivity) Can usually be controlled with low carb diets (insulin injections usually not needed)

Thyroid Gland Thyroxin is secreted by the thyroid gland to regulate the metabolic rate and help control body temperature.

Leptin is secreted by cells in adipose tissue and acts on the hypothalamus of the brain to inhibit appetite.

Application: Testing of leptin on patients with clinical obesity and reasons for the failure to control the disease. Most cases of obesity are caused by an unresponsiveness to leptin and not a leptin deficiency  An obese and healthy mouse are given leptin in both of these experiments, but the end result is different. Why?

Pineal Gland and Melatonin Melatonin is secreted by the pineal gland to control circadian rhythms. Application: Causes of jet lag and use of melatonin to alleviate it.

Utilization: • Hormones are used in a variety of therapies such as replacement therapies. Aim 8: Scientists are aware that the drugs women take in fertility treatment pose potential risks to health. Should scientific knowledge override compassionate considerations in treating infertile couples?

Sex hormones Discussed in reproduction system ppt.

End of IB

Vertebrate Endocrine System http://www.youtube.com/watch?v=rS7SM4vzs18 Tropic hormones ~ a hormone that has another endocrine gland as a target Hypothalamus~pituitary Pituitary gland Pineal gland Thyroid gland Parathyroid glands Thymus Adrenal glands Pancreas Gonads (ovary, testis) http://health.howstuffworks.com/adam-200091.htm

The Anterior Pituitary Anterior pituitary hormones: Growth (GH)~bones √gigantism/dwarfism √acromegaly (abnormal growth of bones in head, hands, feet in adults) Prolactin (PRL)~mammary glands; milk production Follicle-stimulating (FSH) & Luteinizing (LH)~ gonadotropins (affect ovaries/testes) Thyroid-stimulating (TSH)~ stimulates thyroid gland Adrenocorticotropic (ACTH)~ stimulates adrenal cortex to secrete hormones Melanocyte-stimulating (MSH)– regulates pigmented cells, fat metabolism Endorphins~natural ‘opiates’; brain pain receptors

The posterior pituitary Oxytocin~ uterine muscle contraction during childbirth and mammary gland milk secretion Antidiuretic (ADH)~ retention of water by kidneys

The pineal, thyroid, & parathyroid glands Melatonin~ pineal gland; biological rhythms Thyroid hormones: Calcitonin~ lowers blood calcium (opposite effects of PTH—see below Thyroxine~ regulates metabolic processes (speeds up metabolism) Parathyroid hormone (PTH)~ raises blood calcium (reabsorption in kidneys, release of calcium from bone)

The adrenal glands Adrenal medulla (catecholamines): •epinephrine & norepinephrine~ increase basal metabolic rate (blood glucose and pressure) Adrenal cortex (corticosteroids): •glucocorticoids (cortisol)~ raise blood glucose •mineralocorticoids (aldosterone)~ reabsorption of Na+ and K+, and water

The gonads Steroid hormones: precursor is cholesterol androgens (testosterone)~ sperm formation; male secondary sex characteristics; gonadotropin estrogens (estradiol)~uterine lining growth; female secondary sex characteristics; gonadotropin progestins (progesterone)~uterine lining growth and maintenance

Local regulators: cells adjacent to or near point of secretion Growth factors ~ proteins for cell proliferation Nitric oxide (NO) ~ neurotransmitter; cell destruction; vessel dilation Prostaglandins ~ modified fatty acids secreted by placenta and immune system; cause uterine contractions during labor, induce inflammation