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ENDOCRINE SYSTEM
Honors Biology
Introduction
• Glands that transmit chemical messengers
throughout the body
• Hormones: chemical messengers
– Circulate through body
– Affect many body cells
GLAND TYPES
• Gland: organ made of cells that secrete
materials
– Exocrine glands: secrete nonhormonal
chemicals into ducts and transport to
locations inside and outside the body; i.e.
sweat, mucous, saliva, digestive
– Endocrine glands: ductless and throughout
body; secrete hormones into bloodstream
through fluid surrounding cells
HORMONE TYPES
• Hormones:
– Compounds that are secreted into
bloodstream and affect activity of distant cells
– Diffuse into blood
• 2 Categories
– Amino acid-base hormones: derived from
amino acids (epinephrine)
– Steroid hormones: lipids derived from
cholesterol (estrogen and testosterone)
HORMONE ACTION
• Each hormone only affects certain cells
called target cells
PROSTAGLANDINS
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Group of hormone like lipids
Regulate cell activities
Not made by specific endocrine glands
Made by cells throughout body
Made and travel locally
ENDOCRINE GLANDS
• JIGSAW ACTIVITY
– Pituitary Glands
– Thyroid Gland
– Adrenal Gland
– Gonads
– Pancreas (done for you)
OTHER ENDOCRINE GLANDS
• Thymus Gland:
– Located beneath sternum and between lungs
– Development of immune system and T cells
• Pineal Gland:
– Near base of brain
– Secretes melatonin; cycle regulate sleep
patterns
OTHER ENDOCRINE GLANDS
• Parathyroid Glands
– 4 parathyroid glands
– Back of thyroid gland
– Secrete parathyroid hormone: Increase concentration
of calcium ions in blood
• Digestive (in walls)
– Gastrin: stimulates release of digestive enzymes
– Secretin: in small intestine; stimulates release of
digestive enzymes from pancreas and bile from liver
FEEDBACK MECHANISMS
• Last step of a series controls the first step
– Negative: shuts off
– Positive: makes more (going into labor!)
• Homeostasis
– Insulin and glucagon work together to balance
blood glucose
– Antagonistic hormones
FEEDBACK MECHANISMS
NEGATIVE FEEDBACK
• Final step inhibits first step; thermostat
• Example:
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Hypothalamus secretes LH releasing hormone
Stimulates LH from anterior pituitary
LH released into blood and transported
LH binds to target cells in tests
Stimulate cAMP production
Stimulate testosterone secretion
Testosterone binds to target cells
If high testosterone concentration; LH releasing
hormone is inhibited