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Chapter 11
The Endocrine System
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Endocrine vs. Exocrine
Exocrine – have ducts (tubes)
Endocrine - ductless
Secreted directly into body fluids
Regulated by NS and ES
Target cells
Steroid hormones – link to cell, bind to
nucleus, activate genes to make specific
proteins
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Responding to hormones
• Lock and key system
– hormone fits receptor on “target” cell
target
cell
secreting
cell
can’t
read
signal
nontarget
cells
can’t
read
signal
Prostaglandins
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Made from organs
Act locally
Potent
Produced just before released
Produce diverse and opposite effects
Control of Hormonal Secretions
• Negative feedback
• Hypothalamuspituitaryother endocrine
glands
• NSglands directly
• Changes in internal environmentglands
• Example: pancreas
Feedback
Maintaining homeostasis
hormone 1
lowers
body condition
gland
high
specific body condition
low
raises
body condition
gland
hormone 2
Glands
Pituitary –
base of brain, anterior and posterior
lobes, **master gland
• **Growth Hormone (GH) – stimulates size and
division increases
• Pituitary dwarfism and giantism
• http://www.youtube.com/watch?v=Ebhf1qKVA9A
• http://www.youtube.com/watch?v=WoYeU6onK3g
• Prolactin (PRL) – stimulates and sustains milk
production
• Effect in males not understood
• TSH – controls thyroid secretions
• **FSH – follicle-stimulating hormone
Thyroid – in neck
• **Thyroxine – regulates metabolism of
carbohydrates, proteins, and lipids
• **Requires iodine to make
• Hyper and hypo
• Calcitonin – regulates blood calcium and
phosphate
• As calcium goes up, calcitonin increases
• This triggers osteoblasts and kidneys.
Goiter
Why we use iodized salt
Thyroid Gland (thyroxin)
• Hypo Secretion
(too little)
– Low metabolic rate
– Person is tired and
often over weight
• Hyper Secretion
(too much)
– High metabolic rate
– Person is “Hyper” and often thin
Parathyroids – in thyroid
• **Parathyroid hormone (PTH) – increases
calcium in blood
• Triggers osteoclasts and kidneys
• Hyper – bones soften and easily fracture,
kidney stones
• Hypo – tetanic contractions
Pancreas – inferior to stomach
• Exocrine and endocrine
• Islets of Langerhans
• http://bcs.whfreeman.com/thelifewire/conte
nt/chp50/5002s.swf
• Alpha cells – glucagon – increases blood
sugar – how?
• Beta cells – insulin – decreases blood sugar
– how?
Endocrine System Control
Feedback
Regulation of Blood Sugar
insulin
body
cells take
up sugar
from blood
pancreas
high
liver stores
sugar
reduces
appetite
liver
blood sugar level
(90mg/100ml)
low
triggers
hunger
liver
releases
sugar
liver
pancreas
glucagon
Diabetes: insulin deficiencyresults in an elevated blood sugar
level (glucose)
Diabetes Mellitus
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Type I – insulin-dependent (IDDM)
Immune system destroys beta cells
Usually before age 20
Type II – non-insulin-dependent (NODDM)
Beta cells function, but body cells lose
sensitivity to insulin
• Usually after age 40