Hormones and the Endocrine
System
Chapter 26
The Endocrine System
• Specialized glands throughout the body
• Help maintain homeostasis
– Secrete hormones into blood
• Slow acting
• Long living
• Act on target cells
– Signaling molecules
Controlling Secretion
Negative Feedback
Positive Feedback
Categories of Hormones
• Amino acid based
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Chains of AA’s
Not membrane soluble (hydrophilic)
e.g. oxytocin, insulin, and prolactin
e.g. epinephrine, norepinephrine, and thyroxine
– Derived from AA tryptophan and tyrosine
• Steroids
– Lipids made from cholesterol
– Right through membrane (hydrophobic)
– e.g. testosterone, estrogen, and cortisol
Amino Acid Action
• Dissolve in blood
• Binds to plasma membrane (1)
• Intracellular events (2)
– Change permeability of ion channels
– Change 2nd messenger system
– Activate translation genes
• Change physiology or behavior (3)
– Rapid because all chemicals present
Steroid Action
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Carriers in the blood
Binds in cytoplasm or nucleus (2)
Turns on genes (3)
Synthesizes proteins (4) 
change physiology or behavior
– Slower because chemicals need to
be made
Endocrine Glands
• Pituitary gland
– Posterior
• Vasopressin (ADH)
• Oxytocin
– Anterior
• Growth hormone (GH)
• Thyroid stimulating hormone
(TSH)
• Adrenocorticotropic hormone
(ACTH)
• Follicle stimulating hormone
(FSH)
• Lutenizing hormone (LH)
• Prolactin (PRL)
• Hypothalamus
– Corticotropin releasing
hormone (CRH)
• Thyroid gland
– Thyroid hormones
• Adrenal glands
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Corticosteroids
Glucocorticoids
Sex steroids
Epinephrine/norepineprine
• Pancreas
– Glucagon
• Gonads
– Sex steroids
Pituitary Gland
• Connected to hypothalamus
• Bipartate structure
– Posterior lobe
• Neurosecretory cells signal exocytic release of hormones
– Anterior
• Hormone release to portal system
Posterior Lobe
• Hypothalamic storage
• Neurohormone release
– Oxytocin
• Milk letdown
• Childbirth contractions
• Pair bonding/monogamy (voles)
– Vasopressin
• Water balance and loss
• Alcohol and urination connection
Anterior Lobe
• Hypothalamic control
• Blood portal system
– Releasing or inhibiting
hormones
• Hormones released
– Signal endocrine or
nonendocrine glands
Growth Hormone
• Multiple target cells
• Regulates body growth
– Hypersecretion: gigantism or
acromegaly
– Hyposecretion: pituitary dwarfism
• Artificial HGH can counter in youth
• Artificially created in bacteria
– Abused by athletes
– Meat production and organic foods
Thyroid Stimulating
Hormone
• Stimulates T3 and T4 from
thyroid
• Same effects, different targets
• Most processes in body
• Controls metabolism
– Hyperthyroidism, Graves’ disease
– Hypothyroidism, goiter
• Growth and physical
development
– Cretinism
• Metamorphosis in amphibians
Grave’s Disease
Adrenal Glands
• Bipartite structure
– Stress responses
– Some level for glucose breakdown
•
Peaks in morning
• Adrenal cortex
– Long-term stress responses
• Mineralcorticoids
– Mineral and water balance
• Glucocorticoids (cortisol)
– Stress response
• Sex steroids
– Small amounts
– Adrenocorticotropic
hormone stimulates
• Adrenal medulla
– Short-term stress responses
• Epinephrine
• Norepinephrine
– Hypothalamic neural signal
Gonads
• LH and FSH stimulate
– Produce sex steroids
– Cross BBB easily
• Influence brain activation and organization
• 3 hormone types in both sexes, but ratios vary
– Estrogens (estradiol)
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Maintain female system
Development of 2° sex characteristics
Derived from androgens
Masculinize male brain in early development
– Progestins
• Prepare and maintain uterus
• Breast development
• Can be converted to testosterone
– Androgens (testosterone)
• Maintain and stimulate development of male system
• Development of 2° sex characteristics
• 7th week level determines sex
Pancreas
• No hypothalamic or
pituitary control
• Produces insulin and
glucagon
– Manage energy supply by
regulating blood glucose
– Antagonistic hormones
– Islets of Langerhans
• Beta and alpha cells
Diabetes Mellitus
• Cells can’t absorb glucose from blood
– Insufficient insulin or cells unresponsive
• Cells burning fats and proteins
• Excess absorbed by digestive system = [glucose] in urine is high
• Treatments, but no cure
– Genetic engineering produces synthetic insulin
– W/o causes blindness, dehydration, kidney and cardiovascular disease
• Type 1 (insulin dependent)
– Autoimmune disease
– WBC’s attack beta cells
• Type 2 (non-insulin dependent)
– Older onset
– Obesity is common
• Gestational diabetes
– Can effect any pregnant woman
Prolactin
• Humans
– Mammary gland growth
– Milk production
– Control egg release  evolutionary adaptation?
• Birds
– Nest building behavior (male and female)
– Regulates fat metabolism and reproduction
• Amphibians
– Movement to water to breed
– Metamorphosis
• Fish
– Regulate salt and water balance when environments
change