AP Biology
Notes Ch. 45 Endocrine
Do the activities on the Campbell website for:
Ch. 11 Cell Communication. Activities and Activities Quiz
Ch. 45 Endocrine Activities: Ch.45.2 Nonsteroid (Peptide) Hormones
45.2 Steroid Hormones
45.4 How do Thyroxin and TSH Affect Metabolism?
45.4 Investigation: Human Endocrine Glands and Hormones
Activity Quiz
Nonsteroid Hormones: Water-Soluble Hormones
 Derived from amino acids
o examples: oxytocin and epinephrine
 Do NOT enter the cell. (Lipid nature of bilayer repels them)
 Bind a receptor protein embedded in membrane
 Creates a signal transduction pathway
 activates or inhibit proteins in cells.
 creates an immediate response in target cells
 by turning cell components on or off.

Steroid Hormones: Lipid-Soluble
Lipid molecule consisting of multiple fused rings
 Sex Hormones
o testosterone
o estrogen
 Act by diffusing across the cell’s membrane
o binding a receptor protein in the cytoplasm
o enters nucleus binding regulatory sites on DNA.
o acts as a transcription factor—gene activator
o turning genes on or off
o mRNA transcribed
o translated into protein (enzyme for example)
o this protein alters the function of the target cell.
 Steroids act slowly
 Takes time to build up or deplete
Mrs. Loyd 
cloyd@waukee.k12.ia.us
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Ch. 44 Osmoregulation/Endocrine
Do Ch.44 activities and Activities Quiz
Negative Feedback:
Most common control mechanism of homeostasis, whereby a change in a physiological variable that is being monitored
triggers a response that counteracts the initial fluctuation.
Example
Hormones regulate water reabsorption by the nephron tubule
After sweating:
 blood solute concentration rises
 brain (osmoreceptors in hypothalamus) signals the posterior pituitary to increase its output of
 ADH: anti-diuretic hormone
 ADH makes walls of collecting duct more permeable to water
 water reenters the blood
After extensive hydration:
 blood becomes more dilute
 brain decreases secretion of ADH
 collecting duct of nephron becomes less permeable
 less water is reabsorbed
 more water is excreted as dilute urine
Diuretics
 chemicals can increase water loss in urine
o caffeine
o alcohol
 Not based on osmolarity of blood
 Can cause dehydration
 Always hydrate with water when thirsty!
Positive Feedback:
Involves a change in some variable that triggers mechanisms that amplify rather than reverse the change.
Example:
Childbirth
 Oxytocin stimulates contractions causing pressure of the baby’s head against receptors near the opening of the uterus
 stimulates uterine contractions which cause greater pressure against the uterine opening
 heightening the contractions, etc.
 positive feedback brings childbirth to completion.
Investigation 45.4 How do Thyroxine and TSH affect metabolism?
Ch. 45 Insulin and Glucagon: Control of Blood Glucose
Another example of Negative Feedback:
Read about the pancreas. It has important functions in both the
endocrine and digestive systems.
Pancreas produces hormones and secretes into the circulatory system:
 glucagon (-cells) / insulin (-cells)
 antagonistic hormones
 glucose is vital as fuel and carbon skeleton for organic molecules.
 blood glucose concentration must remain near set-point
(90 mg/100mL) in humans. (< 70mg / 100mL is hypoglycemic)
 When blood glucose conc. exceeds this, insulin is released, (“It’s
a sugar rush! Store sugar as glycogen!”) lowering blood
glucose concentration.
 When blood glucose conc. drops below set-pt, glucagon released,
(“Digest glycogen, We need sugar!”) raising blood glucose
levels.
Insulin shock occurs when the level of your blood sugar drops quickly
and leads to unconsciousness. It is a severe form of hypoglycemia (low
blood sugar.) What would a diabetic do to cause this condition?
Diabetic Coma: Diabetic coma is a serious complication that can
happen to a person with type 2 diabetes who is ill or stressed. Diabetic
coma occurs when the blood sugar gets too high and the body becomes severely dehydrated.
Mrs. Loyd 
cloyd@waukee.k12.ia.us
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7/12/16
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