13.1 The Glands and Hormones of the Endocrine System

endocrine system

system of glands that produce/release hormones into bloodstream to regulate body functions (growth, metabolism, reproduction, stress responses, homeostasis)

endocrine glands

secrete hormones directly into the bloodstream, which then transports hormones throughout body

hormones

chemical messengers produced by endocrine glands; travel through bloodstream to target cells where they regulate growth, metabolism, reproduction and homeostasis

negative feedback

maintains homeostasis by reversing a change in the body and returning it back to normal

positive feedback

increases/amplifies a change without reversing it

antidiuretic hormone (ADH)

promotes the retention of water by the kidneys

hypothalamus

connects the nervous and endocrine systems. releases hypothalamic hormones which regulate anterior pituitary glands

endocrine system signal

chemical

endocrine system speed

relatively slow (minutes to days)

endocrine system duration

longer lasting

endocrine system target(s)

cells all over the body

endocrine system action(s)

causes changes in metabolic activity

lipid based hormones

easily diffuse through cell membrane; binds to receptor proteins within target cell

water soluble hormones

cannot diffuse through cell membrane; binds to receptor proteijs on cell surface and start a cascade of reactions within target cell. impact of hormone is amplified

examples of lipid based hormones

steroid hormones (estrogen, testosterone, cortisol)

examples of water soluble hormones

hGH, epinephrine, thyroxine, insulin

regulation of ADH in hypothalamus

1. blood plasma becomes too concentrated 2. receptors in hypothalamus detect this and send neural signals to posterior pituitary gland 3. ADH released which targets kidney nephrons 4. causes tubules to he permeable to water 5. as a result, more water is reabsorbed; body excretes less urine (but more concentrated) urine and blood pressure increases

tropic hormones

target and control other endocrine glands, stimulating them to release their own hormones