1. Endocrine System

2. Major Hormone Secreting Structures

3. General Information
Integrates and coordinates activities of body cells.
Maintains homeostasis by regulating:
1. metabolism and energy balance
2. water, electrolyte & nutrient balance
3. reproduction, growth and development
4. mobilization of body against stressors
Hormones are secreted into interstitial fluid diffusing into blood or lymph fluid.
Hormones act upon specific target cells.

4. Regulation & Communication
Two systems for regulation:
endocrine system
ductless glandular epithelium
secrete hormones directly into blood
chemical travels to target tissue
target cells have receptor proteins
slow, long-lasting response
nervous system
system of neurons
transmits “electrical” signal & release neurotransmitters to target tissue
fast, short-lasting response
Hormones coordinate slower but longer–acting responses to stimuli such as stress, dehydration, and low blood glucose levels. Hormones also regulate long–term developmental processes by informing different parts of the body how fast to grow or when to develop the characteristics that distinguish male from female or juvenile from adult. Hormone–secreting organs, called endocrine glands, are referred to as ductless glands because they secrete their chemical messengers directly into extracellular fluid. From there, the chemicals diffuse into the circulation.

5. Regulation by chemical messengers
Neurotransmitters released by neurons
Hormones release by endocrine glands
endocrine gland
neurotransmitter
axon
hormone carried by blood
receptor proteins
receptor proteins
Lock & Key system
target cell

6. Classes of Hormones Protein-based hormones Lipid-based hormones
polypeptides
small proteins: insulin, ADH
glycoproteins
large proteins + carbohydrate: FSH, LH
amines
modified amino acids: epinephrine, melatonin
Lipid-based hormones
steroids
modified cholesterol: sex hormones, aldosterone
insulin

7. Animation – Intracellular Receptor Model
Steroid Hormones
Lipid soluble (hydrophobic)
Synthesized from cholesterol
Transported by a protein in bloodstream.
Diffuses inside, binds with DNA to transcribe gene.
Full effect could be minutes to days.
Animation – Intracellular Receptor Model

8. Animation – Second Messenger cAMP
Protein Hormones
Water soluble (hydrophilic)
Binds to receptors on target cell membranes. No diffusion!
Causes second messengers (cAMP) to be activated inside cell.
Cascading effect: a single molecule can activate hundreds of second messengers each which activates thousands of reactions.
Rapid response
Multiplier effect!
Animation – Second Messenger cAMP

9. Benefits of a 2° messenger system1
signal
Activated adenylyl cyclase
receptor protein 2
Not yet
activated
amplification 4
amplification 3
cAMP
amplification 5
GTP
G protein
protein kinase 6
amplification
Amplification!
enzyme
Cascade multiplier! 7
amplification
FAST response!
product

10. Specificity of Hormones
Target cells only respond to a specific hormone by having a unique receptor just for that hormone.
EX: Insulin receptors only respond to insulin not thyroxine.

11. Control of Hormone Secretion

12. Hormone Regulation Hormone secretion is controlled by:
1. Neural stimuli
2. Humoral stimuli (blood chemistry)
3. Hormonal stimuli
Process used to regulate:
FEEDBACK LOOPS!

14. Homeostasis of Blood Glucose

15. Regulation of Blood Sugar
Endocrine System Control
Feedback
Regulation of Blood Sugar
islets of Langerhans beta islet cells
insulin
body cells take up sugar from blood
liver stores glycogen
reduces appetite
pancreas
liver
high
blood sugar level
(90mg/100ml)
low
liver releases glucose
triggers hunger
pancreas
liver
islets of Langerhans alpha islet cells
glucagon

16. Gland A secretes a hormone that stimulates gland B to increase secretion of another hormone. The hormone from gland B alters its target cells and inhibits activity of gland A.

18. Synergistic effect vs. Antagonistic effect
Target Cells
Responsiveness can depend on:
1. Hormone concentration
2. Amount of receptors
a. up-regulation (increasing # of receptors)
b. down-regulation (decreasing # of receptors)
3. Influence of other hormones
Synergistic effect vs. Antagonistic effect
(Glucagon + epinephrine)
(Insulin and Glucagon)

19. Nervous & Endocrine systems linked
Hypothalamus = “master nerve control center”
nervous system
receives information from nerves around body about internal conditions
releasing hormones: regulates release of hormones from pituitary
Pituitary gland = “master gland”
endocrine system
secretes broad range of “tropic” hormones regulating other glands in body
hypothalamus
posterior
pituitary
anterior

20. Hormone Disorders
Most involve the HYPOSECRETION or HYPERSECRETION of a hormone.
Hypersecretion most likely due to a tumor on the gland.
Few cases involve faulty hormone receptors or reduction of receptors.

21. Grave’s Disease Hyperthyroidism Symptoms: Intolerance to heat
Heart palpitations
Sensitivity to light
Weight loss
Appetite increase
Easily agitated
Protruding eyes

22. Hypothyroidism or Myxedema
Early symptoms:
Being more sensitive to cold
Constipation
Depression
Fatigue or feeling slowed down
Heavier menstrual periods
Joint or muscle pain
Paleness or dry skin
Thin, brittle hair or fingernails
Weakness
Weight gain (unintentional)
Late symptoms, if left untreated:
Decreased taste and smell
Hoarseness
Puffy face, hands, and feet
Slow speech
Thickening of the skin
Thinning of eyebrows
Cretinism – lack of thyroxine during fetal life

23. Goiter
Iodine deficiency causes thyroid to enlarge as it tries to produce thyroxine + ✗
tyrosine +
iodine ✗
thyroxines

24. hypersecretion of GH during adulthood, usually a pituitary tumor.
Acromegaly
hypersecretion of GH during adulthood, usually a pituitary tumor.
Only certain bony regions in face, feet and hands are affected by excessive bone deposition.

25. Gigantism
Hypersecretion of GH during childhood If left untreated, acromegaly will occur.

26. Pituitary Dwarfism
Hyposecretion of GH, can be corrected by giving GH hormone
Must be diagnosed before growth plates have closed.
Can be tumor related

27. Gigantism vs. Dwarfism

28. Adrenal Gland Disorders
Cushing’s
Excess Cortisol
Weight gain
Rounded moon face
Fatty hump on back
Fatigue
Addison’s
Hyposecretion of glucocorticoids and mineralcorticoids
Mouth lesions
Hypoglycemia
Strange skin pigmentation
Salt craving

29. Diabetes D. Insipidus “tasteless” Hyposecretion of ADH Extreme thirst
Dehydration
Excessive urination
D. Mellitus
“Sweet tasting”
Hyposecretion of insulin (type 1)
Blood glucose build up
Weight loss
Excessive urination
Sweet smelling breath

30. Adipose and Leptin Leptin is hormone that causes you to feel full.
Obesity may be due to no leptin or not enough or hypothalamus becomes leptin resistant.