1. The Endocrine System Controls many body functions
exerts control by releasing special chemical substances into the blood called hormones
Hormones affect other endocrine glands or body systems
Secretion of most hormones is regulated by a negative feedback system
Derives its name from the fact that various glands release hormones directly into the blood (vs. exocrine)

2. I. Nervous vs. Endocrine system
Type of signal
Rate of signal
Duration of action
Electrical
Neurotransmitter
Hormone
Fast (seconds)
Slower
Short
Longer
***Both systems work to maintain homeostasis.

3. Hormonal Control
The secretion of hormones work on a negative feedback system under the control of the nervous system.
Negative feedback occurs when there is a drop in the level of the hormone.
The drop triggers a chain reaction of responses to increase the amount of hormone in the blood.

4. Endocrine System Control x 3

5. Chemical Classificaton of Hormones
Steroid Hormones: formed from cholesterol
Lipid soluble
Diffuse through cell membranes
Endocrine organs
Adrenal cortex
Ovaries
Testes
placenta

6. Chemical Classification of Hormones
Nonsteroid Hormones: formed from amino acids
Not lipid soluble
Received by receptors external to the cell membrane
Endocrine organs
Thyroid gland
Parathyroid gland
Adrenal medulla
Pituitary gland
pancreas

7. Hormone Actions
“Lock and Key” approach: describes the interaction between the hormone and its specific receptor.
Receptors for nonsteroid hormones are located on the cell membrane
Receptors for steroid hormones are found in the cell’s cytoplasm or in its nucleus

8. Major Endocrine Glands

9. Pineal Gland
Shaped like a tiny pine cone (hence its name), and is located near to the center of the brain, between the two hemispheres, tucked in a groove where the two rounded thalamic bodies join. Produces the hormone Melatonin.
Melatonin - helps regulate other hormones and plays a critical role in determining when we fall asleep and when we wake up.
In dark, melatonin

11. The Endocrine System
The two segments are:
Posterior Pituitary:
produces oxytocin (OT) and antidiuretic hormone (ADH)
Anterior Pituitary:
produces thyroid-stimulating hormone (TSH)
growth hormone (GH)
adrenocorticotropin (ACTH)
follicle-stimulating hormone (FSH)
The Pituitary Gland is divided into 2 areas, which differ
structurally and functionally
each area has separate types of hormone production.

13. The Endocrine System And even more…
Posterior Pituitary
Oxytocin – stimulates uterine contractions during childbirth
ADH (vasopressin) causes the kidney to retain water.
And even more…
luteinizing hormone (LH)
Prolactin (PRL)
Let’s go over these one at a time...

14. The Endocrine System Anterior Pituitary
Primarily regulates other endocrine glands
rarely a factor in endocrinological emergencies
TSH stimulates the thyroid gland to release its hormones, thus  metabolic rate
PRL – stimulates production of breast milk
Anterior Pituitary…
Growth hormone (GH)
 glucose usage
 consumption of fats as an energy source
Stimulates growth and cell reproduction
ACTH stimulates the adrenal cortex to release its hormones
FSH & LH/ICSH (males) stimulates maturation & release of eggs from ovary.

15. Pituitary Disorders Gigantism – hyperfunction (secreting too much GH)
Acromegaly - produce excess growth hormone (GH) after epiphyseal plate closure.
Dwarfism – hypofunctioning (secreting too little) pituitary gland

17. The Endocrine System The Thyroid Gland
Within the colloid are the thyroid hormones:
thyroxine (T4)
triiodothyronine (T3)
When stimulated (by TSH or by cold), these are released into the circulatory system and  the metabolic rate.
“C” cells within the thyroid produce the hormone calcitonin.
The Thyroid Gland
lies in the anterior neck just below the larynyx.
Two lobes, located on either side of the trachea, connected by a narrow band of tissue called the isthmus.
Sacs inside the gland contain colloid

19. The Endocrine System
Calcitonin, when released, lowers the amount of calcium in the blood.
Inadequate levels of thyroid hormones = hypothyroidism, or Myxedema.
Myxedema symptoms:
Facial bloating
weakness
cold intolerance
lethargy
altered mental status
oily skin and hair
TX: replacement of thyroid hormone.

21. The Endocrine System
Increased thyroid hormone release causes hyperthyroidism, commonly called Graves’ disease.
Signs and symptoms:
overeating
tachycardia
hypertension
restlessness
weight loss ,
Long term hyperthyroidism:
Exopthalmia
bulging of the eyeballs
In severe cases - a medical emergency called thyrotoxicosis can result.

23. The Endocrine System Parathyroid Glands
small, pea-shaped glands, located in the neck near the thyroid
usually 4 - number can vary
regulate the level of calcium in the body
produce parathyroid hormone -  level of calcium in blood
Hypocalcemia can result if parathyroids are removed or destroyed.

25. Calcitonin and PTH Calcitonin PTH
Decreases above-normal blood calcium concentrations
Inhibits osteoclasts
Kidneys excrete calcium
PTH
Increases a below-normal blood calcium concentration
Stimulates osteoclasts
Kidneys conserve blood calcium
Stimulates calcium absorption in the intestines

26. The Endocrine System Pancreas Islets of Langerhans
a key gland located in the folds of the duodenum
has both endocrine and exocrine functions
secretes several key digestive enzymes
Islets of Langerhans
specialized tissues in which the endocrine functions of the pancreas occurs
include 3 types of cells:
alpha ( )
beta ()
delta ()
each secretes an important hormone.

28. Pancreas Hormones Glucagon Insulin
Stimulates liver to convert noncarbohydrates into glucose
Raises blood sugar concentrations
Insulin
Inhibits conversion of noncarbohydrates into glucose
Decrease blood sugar concentrations

29. Pancreas Disorders Diabetes mellitus Type I
Polyuria – excessive urination
Polydypsia – excessive thirst
Polyphagia – excessive hunger
Weight loss
Blurred vision
Possible diabetic coma
Insulin deficiency causes glucose to accumulate in bloodstream

30. Pancreas Disorders Type II
Gradual onset
Most common in adults over age 45
Feelings of tiredness or illness
Frequent urination, especially at night
Unusual thirst
Frequent infections and slow healing of sores
90 – 95 % of all diabetics, 16 million Americans have diabetes, ½ do not know they have the disease.

31. The Endocrine System Increase heart rate Increase breathing rate
Adrenal Glands
2 small glands that sit atop both kidneys.
Each has 2 divisions, each with different functions.
The Adrenal Medulla secretes the catecholamine (fight-or-fight) hormones
Norepinephrine - neurotransmitter that is important for attentiveness, emotions, sleeping, dreaming, and learning. Norepinephrine is also released as a hormone into the blood, where it causes blood vessels to contract and heart rate to increase.
Epinephrine (Adrenaline) –
Increase heart rate
Increase breathing rate
Decrease digestive activity

33. Adrenal Cortex Hormones
Aldosterone
Helps regulate electrolyte concentrations (sodium & potassium)
Cortisol
Help regulate blood glucose concentrations
Adrenal sex hormones
Produce male hormones, but some are converted to female hormones
Supplement sex hormones from gonads
Stimulates development of reproductive organs

34. Thymus Lies posterior to the sternum and between the lungs.
Larger in young children and shrinks with age.
Secretes a group of hormones called thymosins. Affect the production and differentiation of certain white blood cells.
Immunity