Endocrine System

Maintaining a constant internal environment, despite changes in the external environment Carried out by both endocrine and nervous system

The body responds to a stimulus, and the response alters the original stimulus

• optimum nutrients, ions, gases, and water • constant temperature • optimum pressure

• stimulus • receptor • modulator • effector • response • feedback

secretes substance into the bloodstream eg. hormones

secretes substances onto a surface through a duct

secreted from an endocrine gland, transported by blood, affects target cells/organs, specific as they bind to certain receptors

“local hormones”; chemicals secreted by all cells, used to communicate with adjacent cells

attach to receptors on the cell membrane, causes secondary messengers to activate cellular enzymes

attach to internal receptors on organelles, activates genes that control protein production (hormone-receptor complex)

activate genes to produce enzymes or proteins, denature enzymes, change rate of enzyme or protein production

one hormone molecule can activate thousands of enzyme molecules - only a small amount of hormones are needed

target cells, liver, kidney

produced by nervous system to trigger hormone production by endocrine glands (anterior pituitary)

Regulates body temp, water balance, heart rate

joined to the hypothalamus by the infundibulum; secretes hormones that regulate activity of endocrine glands

connected to hypothalamus by blood vessels; inhibiting and releasing factors secreted by hypothalamus trigger production of of hormones

Hormones pass from the hypothalamus to posterior pituitary through nerve impulses

gonadotrophins, growth hormone, thyroid stimulating hormone, adrenocorticotrophic hormone, prolactin

releases oxytocin, antidiuretic hormone

produces thyroxine, calcitonin

regulates metabolic rate by regulating energy production from cell respiration - increases body temperature

promotes storage of calcium in the bones, reducing blood calcium levels

both exocrine and endocrine; secretes digestive enzymes, insulin, glucagon