• 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.

• 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

• 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

• Protein-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

• 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

• 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

Benefits of a 2 ° messenger system signal receptor protein
1
Activated adenylyl cyclase
2 amplification
GTP
3 amplification
G protein
6
Not yet activated
5
4 amplification cAMP protein kinase amplification
Amplification!
enzyme
Cascade multiplier!
7 amplification product

• 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.

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

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

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.

 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)

• 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 posterior pituitary hypothalamus anterior

• 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.

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

Cretinism – lack of thyroxine during fetal life
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

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

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.

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

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

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

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

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