AP Biology Notes Chapter 45

1. Chemical Signals in Animals
Chapter 45
I.An Introduction to Regulatory Systems
•A. The endocrine system is the hormone secreting system of the body.
–1. Endocrine glands are the organs of this system.
–This system regulates blood sugar, dehydration, reaction to stress, growth, sexual
maturity, among others.
–2.Hormones are released directly into body fluids from the endocrine glands.
• a. Hormones are chemical signals in the body.
• b. Target cells receive the hormone messages.
• c. Tropic hormones affect other endocrine glands.
Many endocrine glands contain special nerve cells called neurosecretory cells which
secrete hormones.
B.Hormones work via signal-transduction pathways which initiate a response from the
target cell
II. Major Glands of the Endocrine System
In the Brain:
•A. Hypothalamus-the “master gland”-receives info from the body and maintains
homeostasis by integrating the endocrine and nervous systems.
•B. Pituitary-oxytocin(milk), ADH-antidiuretic, FSH (follicle), growth hormone,
endorphins(dull pain).
•C.Pineal-melatonin(pigment) and biorhythms.
In the neck and torso:
D.Thyroid-calcitonin-lowers blood calcium levels
E. Parathyroid-PTH-raises blood calcium levels
F.Thymus-thymosin-stimulates t-cells
• In the abdomen:
G.Adrenal-epinephrine and norepinephrine.
These are responsible for the fight or flight response
•H. Pancreas-insulin lowers blood sugar, glucagon raises blood sugar.
•I. Gonads-
– 1.Testes-androgens for sperm formation, sex characteristics.
–2.Ovaries-estrogens and progesterone for uterine lining growth and sex characteristics.