The endocrine system sends hormones into the bloodstream to regulate many metabolic processes including digestion, growth, and reproduction. The pancreas secretes endocrine hormones (insulin and glucogen) and exocrine digestive enzymes (sent directly into the digestive tract via ducts). This is a long-range form of cell signaling vs. paracrine signaling which is localized. Signaling pathways involve three steps: reception, transduction, and response. Major classes of hormones include steroids (from cholesterol), peptides, and amines. The anterior pituitary gland secretes a number of hormones that stimulate other organs (thyroid, adrenals, etc.) rather than impacting the body as a whole. It also secretes growth hormone, which has a more direct effect. Important components of the endocrine system include the pancreas, the hypothalamus and posterior pituitary (oxytocin and others), adrenals, thyroid, parathyroids, and reproductive organs.
Endocrine glands secrete
hormones into the bloodstream. Hormones exert effects on target
The pancreas produces insulin
and glucagon. Insulin decreases the level of glucose in the blood,
whereas glucagon increases the level of glucose in the blood.
The secretion of hormones by
the anterior pituitary gland is regulated by the hypothalamus. The
hypothalamus also produces oxytocin and antidiuretic hormone (ADH),
which are stored in and secreted by the posterior pituitary.
The anterior pituitary secretes
hormones, called tropic hormones, that act on other endocrine glands
as well as hormones with direct physiological effects.
The adrenal cortex secretes
mineralocorticoids and glucocorticoids. The adrenal medulla secretes
epinephrine and norepinephrine, which trigger the fight or flight
The thyroid produces thyroxine,
which increases the metabolic rate, and calcitonin, which lowers
blood calcium levels.
Parathyroid hormone is released
by the parathyroid glands in response to decreased blood calcium
levels. PTH stimulates the release of stored calcium from the
The ovaries produce estrogen
and progesterone. Estrogen is responsible for the development of
secondary sex characteristics in females. Progesterone maintains
The testes secrete
testosterone, which stimulates the development of male secondary sex
The Endocrine System
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The book and CD package include two full length practice exams that are presented with all questions answered and explained. The author also presents detailed reviews of all test topics and includes multiple-choice and free-response questions with answers at the end of each topic's chapter.
This book includes a review of the AP Biology exam format and scoring, proven strategies for answering multiple-choice questions, and hints for tackling the essay questions. The practice tests include answers and explanations and there is also proven test-taking strategies for both the multiple choice and essay parts.