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Biology 30: Endocrine Themes
Endocrine Themes: Metabolism & Calcium Homeostasis
Homeostatic themes: Composed of a GLAND – HORMONE – TARGET – FUNCTION
Example: hGH feedback loop
APG – hGH – Somatic Cells – Growth & Repair
 A typical loop has a start point to “turn it on” and to “turn it off”
 Growth & Repair is a daily thing usually as we sleep & rest for the next day
THEME #1 – Metabolism:
 This includes how your body maintains body temperature (higher rate in winter; lower
rate in summer), rate of which the body burns fuels, rate at which we grow, rate at
which we convert food into body tissue
 GLANDS: Hypothalamus, APG & Thyroid
 HORMONES: TRH, TSH & Thyroxin
 TARGETS: APG, Body Cells
 FUNCTIONS: Let’s See
You are Cold  Hypothalamus  TRH  _______  TSH  _______  In Presence of ______
 Thyroxin Release  Somatic Cells stimulated to burn fuels  We warm up

What will the Hypothalamus due as body temperature rises?

Is this Positive Feedback or Negative Feedback?

What would happen to levels of TRH & TSH if the Thyroid fails to respond?
THEME #2 – Calcium:
 Calcium is used in the body to build up Bones & Teeth
 Calcium is also stored in the bones when the body needs it for blood clotting & delivery
to muscles who need it to function properly.
Consume Calcium:
Absence of Calcium in blood:
SWITCH ON: Chemoreceptors detect rise in
blood calcium
SWITCH ON: Chemoreceptors detect low
blood calcium
GLAND: Thyroid
GLAND: Parathyroid Gland
HORMONE: Calcitonin is released into blood
HORMONE: PTH released into blood
TARGET: Bones & Teeth are activated
TARGET: Bones & Teeth are activated
FUNCTION: Bones & Teeth absorb blood
calcium. Calcium levels DROP!
FUNCTION: Bones & Teeth release calcium
into the blood. Calcium levels RISE!
RESPONSE: Thyroid slows Calcitonin release!
RESPONSE: Parathyroid continues until diet
supplies calcium!
Biology 30: Endocrine Themes
Endocrine Themes: Sugar & Water Homeostasis
Homeostatic themes: Composed of a GLAND – HORMONE – TARGET – FUNCTION
Example: Milk Production & Release


APG – Prolactin – Mammary Gland – Milk Production
PPG – Oxytocin – Mammary Gland – Milk Release
A typical loop has a start point to “turn it on” and to “turn it off”
Milk Production is stimulated by baby “latching onto its mother” & continues until weaning.
THEME #3 – Sugar:
 Sugar is the primary fuel of the body
 The body stores excess glucose as either fat (long term) or as glycogen (short term)
 If needed, the body can use the glucose that is stored


Consume Glucose:
Hunger, After exercise or between meals:
SWITCH ON: Chemoreceptors detect rise in
blood sugar
GLAND: Pancreas
SWITCH ON: Chemoreceptors detect low blood
sugar
GLAND: Pancreas
HORMONE: Insulin release into blood
HORMONE: Glucagon release (glucose is gone)
TARGET: somatic cells (absorb & burn/convert
to fat; Liver & Muscle absorb glucose
TARGET: Liver & Muscle
FUNCTION: Glucose stored as Glycogen
FUNCTION: Glycogen releases Glucose into
blood
RESPONSE: BS Pancreas slows insulin release
RESPONSE: BS Pancreas slows glucagon release
THEME #4 – Water & Salt Retention:
Water cannot be stored in the body, only conserved!
Diuretics increase urine output (alcohol, caffeine, some medications, excess fluid consumption
Thirst:
Consume a Diuretic:
SWITCH ON: Osmoreceptors in Hypothalamus
detect low water levels
GLAND: Pituitary (PPG)
SWITCH ON: Excess fluids in the blood
GLAND: Pituitary (PPG)
HORMONE: ADH release into blood
TARGET & FUNCTION: Kidneys pass more
fluids
TARGET: Kidneys
FUNCTION: Kidneys retain water
RESPONSE: Less urine, continues until you drink
Salt Retention:


G
H
HORMONE: No/less ADH release
T/G
RESPONSE: Continues until Blood fluid levels
normalize!
F/H
T
F
Low BP  APG  ACTH  Adrenal Cortex  Aldosterone  Kidney  Retain Salts
Water will follow salt back into the blood, BP will be maintained
Biology 30: Endocrine Themes
GLAND
HORMONE
Pineal
Melaonin
APG
T
A
G
F
L
M
P
PPG
O
A
Thyroid
T
C
Parathyroid
P
Pancreas
I
G
Adrenal Cortex
C
A
Adrenal
Medulla
A
N
Testes
T
I
Ovary
E
P
R
Chorion
HCG
Hypothalamus
(chemoreceptors)
TRH
Hypothalamus
(chemoreceptors)
GnRH
TARGET
Thalamus
FUNCTION
Makes me drowsy