Endocrine System

Endocrine System Regulates overall metabolism, homeostasis, growth and reproduction Glands – are organs that specialize in the secretion of substances needed by an organism Hormones – are the secretions produced by the endocrine glands - released into the bloodstream

Endocrine Glands Hypothalamus – part of the CNS, but it produces hormones that influence the pituitary gland Pituitary Gland – the “master gland” Located at the base of the brain Secretes growth hormone which affects growth of bone and cartilage

Endocrine Glands (continued) Thyroid Gland Located in the neck Secretes thyroxine which regulates the rate of metabolism in the body Parathyroid Gland Embedded in the back of the thyroid Secretes parathormone which controls metabolism of calcium and phosphate

Endocrine Glands (continued) Adrenal Glands Located on top of the kidneys Secrete adrenaline which helps deal with stress and accelerates the heart and breathing rates Islets of Langerhans – specialized cells Located in the pancreas Secrete insulin and glucagon Insulin lowers blood sugar Glucagon raises blood sugar

Endocrine Glands (continued) Gonads – sex glands Male gonads are called testes Located in the scrotum Secrete testosterone which regulates male secondary sex characteristics Female gonads are called ovaries Located in the pelvic region Secrete estrogen and progesterone which regulate female secondary sex characteristics

Feedback Mechanisms Negative Feedback – is when an activity alters a condition in the body, and this triggers a series of events that reverses the altered condition Ex. Body temperature When body temp. goes up, we sweat When body temp. goes down, we shiver Ex. Blood sugar levels When blood sugar goes up, insulin lowers blood sugar When blood sugar goes down, glucagon raises blood sugar

Feedback Mechanisms (continued) Positive Feedback – is when a change initiates a response, and that response intensifies the original change Ex. Contractions of the uterus during childbirth

Disorders Diabetes – is a disease where a person cannot produce insulin Inability of the body to store sugar as glycogen Goiter – is enlargement of the thyroid gland caused by iodine deficiency