Download Endocrine Regulation

Biology 12
Endocrine Regulation
 Glands release hormones into blood stream
 Hormones are chemical messengers that react with target cells to stimulate a reaction
o Target cell: cell with specific proteins that react to hormones.
 Types of hormones;
o Protein hormones:
 Made by protein synthesis
 Are polar, thus not able to enter cells; thus require second messenger (ie. Cyclic
AMP)
o Steroid Hormones:
 Made by enzymes modifying cholesterol in adrenal cortex and gonads.
 Are non-polar, thus are able to enter a target cell directly.
 Important glands;
o Adrenal Gland: secretes hormones that help the body deal with stress.
o Ovary: matures oocytes into ova and secretes estrogen and progesterone
o Pancreas: produces insulin to reduce the amount of sugar in the blood and enzymes that aid
in digestion.
o Pineal Gland: secretes melatonin, a hormone that affects moods and reproductive processes
o Pituitary Gland: controls the functioning of other glands in the body
o Testis: form spermatozoa and secrete androgens
o Thymus: matures blood stem cells to become activated T-helper cells.
o Thyroid Gland: produces thyroxin to control the basal metabolic rate.
 Regulation of hormones
o Feedback: the levels of hormones influence the release of other hormones
 Types of feedback;
 Positive feedback:
o when a decrease in a hormone causes a decrease in another.(-/-)
or
o When an increase in a hormone causes an increase in another.(+/+)
 Negative feedback:
o When an increase of one hormone causes another to decrease(+/-)
or
o When a decrease in one hormone causes an increase in another.(/+)
 Metabolism:
o (-)thyroxine, hypothalamus secretes Thyrotropin Releasing Hormone(TRH) to pituitary gland
o (+)TRH causes pituitary to secrete Thyroid Stimulating Hormone(TSH) that acts on the
thyroid
o (+)TSH causes thyroid to release more thyroxine
o High levels of thyroxine cause the hypothalamus to release less TRH which then affects the
levels of the other hormones.
o Low levels of thyroxine cause hypothalamus to increase the release of TRH which the affects
the levels of other hormones.
 Reproduction:
o Male: check out the diagram from pp.394 (understand and explain pathway)
o Female: check out the diagram from pp.398 (understand and explain pathway)
o Necessary hormones;
 Gonadotropin Releasing Hormone(GnRH);
 Acts on pituitary gland to release gonadotropins
 Gonadotropin Hormones;
 Follicle Stimulating Hormone(FSH);
o Stimulates development of gametes
 Male: meiosis and sperm development
 Female: development of follicle
 Luteinizing Hormone(LH)
o Males: stimulates production of testosterone by Leydig cells
o Females: stimulates the maturing of follicle and production of
estrogen
 Testosterone: stimulates spermatogenesis
 Estrogen: stimulates formation of endometrium
o Menstrual Cycle:
 Flow Phase: release of endometrium and unfertilized ovum
 Signifies the beginning of next cycle
 Follicular Phase: maturing of ovum and formation of endometrium
 Ovulation: release of ovum
 Luteal Phase: formation of corpus luteum and increased secretion of progesterone
for maintaining endometrium.