Human Physiology ❮ 191Hormones of the adrenal glandare
Cortisol Stress hormone released in response to physiological challenges. Increases
the blood glucose level in response to chronic stress.
Aldosterone Regulates blood sodium concentration and blood volume by controlling
the renal excretion of sodium.
Epinephrine Raises blood glucose level, increases metabolic activity—“fight or flight”
hormone. Also known as adrenaline.Pancreatichormones are
Insulin Secreted in response to high blood glucose levels to promote glycogen
formation. Lowers blood sugar.
Glucagon Stimulates conversion of glycogen into glucose. Raises blood sugar.Theparathyroidhormone (PTH) increases serum concentration of Ca^2 +, assisting in the
process of bone maintenance.Sexhormones are
Progesterone Regulates menstrual cycle and pregnancy.
Estrogen Stimulates development of secondary sex characteristics in women.
Secreted in ovaries. Induces the release of LH, including the LH surge of
the menstrual cycle. With progesterone, helps maintain the endometrium
during pregnancy.
Testosterone Stimulates secondary sex characteristics and the production of sperm in
men. Secreted in testes.Thyroidhormones are
Calcitonin Lowers blood calcium. Works antagonistically to PTH.
Thyroxine Stimulates metabolic activities.
The thymus hormone is thymosin,a hormone involved in the development of the T cells of
the immune system.
The pineal gland hormone is melatonin,a hormone that is known to be involved in our bio-
logical rhythms (circadian). It is released at night.
How is the hormone secretion process of the body regulated? The two main types of
regulation with which you should be familiar are negative feedback and positive feedback.
Negative feedbackoccurs when a hormone acts to directly or indirectly inhibit further
secretion of the hormone of interest. A good example of negative feedback involves insulin,
which is secreted by the pancreas. When the blood glucose gets too high, the pancreas is
stimulated to produce insulin, which causes cells to use more glucose. As a result of this
activity, the blood glucose level declines, halting the production of insulin by the pancreas.
Positive feedbackoccurs when a hormone acts to directly or indirectly cause increased
secretion of the hormone. An example of this feedback mechanism is the LH surge that
occurs prior to ovulation in females. Estrogen is released as a result of the action of FSH,
and travels to the anterior pituitary to stimulate the release of LH, which acts on the ovaries
to stimulate further secretion of estrogen.BIG IDEA 3.D.1
Activity within
individual cells
supports function
for an entire
organism (e.g.,
epinephrine stimu-
lation of glycogen
breakdown).
BIG IDEA 3.D.2
Cells communicate
with each other
from a distance via
hormones.
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