Endocrine system maintains homeostasis by releasing hormones and provide slow, but long lasting control.
Secrete products into ducts that transport the products into body cavities.
Secrete products into extracellular space surrounding the secretory cells (ductless glands)
Primary endocrine glands of the body and their locations.
Pituitary gland - beneath the brain: Thyroid and Parathyroid glands - in the neck; Adrenal glands - on top of each kidney, the pancreas, and behind the stomach; Sex glands - testes in males, ovaries in females.
Minor role endocrine glands
Pineal gland - in the brain; Thymus gland - above the heart
What happens when a hormone unites with receptor on target cell membrane?
May change the rates of enzyme activities, secretion, protein synthesis or rates at which materials are transported.
Chemical signals in the bloodstream cause endocrine glands to adjust its rate of secretion.
How do negative feedback systems work?
When hormones reach a certain level in the blood either the hormone itself or chemicals provide a response working in the opposite direction of the stimulus.
What is an example of a negative feedback system?
PTH released by the parathyroid gland stimulates the release of Ca ions from the bones. A high blood calcium level provides a stimulus to the parathyroid gland to stop production of PTH so high chemical levels in the blood inhibits further hormone production.
How do positive feedback systems work?
Positive feedback systems by causing a response in the same direction as the stimulus. They tend to by unstable and uncommon.
What is an example of a positive feedback system?
Oxytocin (OT) release by the pituitary stimulates contractions during childbirth which stimulates more oxytocin release until birth is accomplished.
GH - various tissues, including liver to convert glycogen to glucose; TSH - thyroid, TSH is tropic hormone because it stimulates the thyroid to 2 more hormones, regulation of cell metabolism; ACTH - adrenal cortex, stress affects its release; FSH and LH - ovaries/testes, gonadotropic hormone because it targets gonads, LH w/estrogen stimulates release of egg; PL - secretion and ejection of breast milk.
Important roles in metabolism and growth. together they stimulate the rate of metabolism, promote protein synthesis, increase the rate of glucose uptake, promote lipid metabolism, and accelerate actions of the nervous system.
How are concentrations regulated?
Negative feedback between the hypothalamus and anterior lobe of the PG- thyroid hormone levels in the blood drop, hypothalamus secretes a releasing hormone (TRH) which triggers PG to secrete TSH.
4 or 5 pea shaped masses of glandular epithelium embedded within the posterior thyroid gland. Secrete parathyroid hormone (PTH).
What role does PTH play in the body?
Maintains blood levels of Ca and PO4 which opposes CT release by the TG - prompts osteoclasts to break done bone matrix (bone resorption). Also stimulates conversion of precursor molecules to form vitamin D in kidneys.