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Ashleigh Sargent
Biology Chapter 42 Section One
Hormones- chemical messenger that travels through blood stream and excretes a
distance from where they are produced
Chemical substance made in one part that effects another part.
Endocrine system- composed of glands that secrete hormones into bloodstream.
Target Cells- cells that have receptors for a particular hormone
Ovaries- produce eggs
Gland- organ that produces a secretion
Secretion- substance made inside a cell and released from that cell.
Testes- produce sperm
Endocrine Glands- major hormone producing organ of the endocrine system, doesn’t
have glands, releases directly into blood stream.
Exocrine glands- another group of glands that release their secretions through tube like
structures called ducts
Islets of Langerhans- hormone producing portion of the pancreas consist of clusters of
Hormones bind to receptors on the cells and affect the cells behaviors.
Body generally responds slower a longer lasting then responding to nerve impulses.
Thyroid Gland
Located at the base of the neck and wraps around the upper part of the trachea just below
the larynx.
- Needs iodine (salt) to secrete
- secretes thyroxine
- Increased levels can cause an increase in cellular respiration rate and cells have more
energy and are more active.
- Decreased levels cause a decrease in cellular respiration and cells have less energy and
are less active.
- If too much is provided a condition called Hyperthyroidism occurs= nervousness,
elevated body temperature, increased heart and metabolic rates, increased blood pressure,
weight loss
- Surgical removal of part of the gland or certain drugs can slow the production.
- If not enough is produced, a condition called hypothyroidism occurs which is a low
metabolic rates and body temperature lack of energy and weight gain.
- In infancy, it can effect skeletal, muscular, and nervous system causing cretinism=dwarfism and mental retardation.
- Thyroxin injections solve this.
Goiter is an enlargement of the thyroid gland
CRETINISM- not enough thyroxin and characterized by dwarfisms and mental
ACROMEGALY- too much GH from pituary gland, causing gigantism
DIABETES TYPE I- little or no secretion of insulin, mostly juvenile onset.
DIABETES TYPE II- mainly in people after 40 cells do no have enough insulin receptors
Pituary gland disorders-if to little GH, it could cause dwarfisms, if too much, it could
cause gigantism
HYPOTHALAMUS- controls the secretions of the Pituary gland.
- neurosecretory cells extend their axons into the posterior pituary which cause hormones
to enter directly into capillaries.
Negative feedback system- occurs when an increase in a substance inhibits the process
leading to the increase
Prostaglandins – fatty acids that cause contractions in smooth muscles like the uterus,
bronchioles, and walls of blood vessels also causes pain
-Polypeptide hormones affect the target cell by means of receptor molecules embedded in
the cell membrane
- Steroid hormones pass through the cell membrane in the cytoplasm, forming a hormone
receptor complex.