1. The Endocrine System
Chapter 12
A&PI

2. Endocrine System Group of glands that produce hormones
Hormones are regulatory chemicals
Endocrine & nervous system work together to control & coordinate all other systems of the body
Nervous system – rapid responses using chemical & electrical stimuli
Endocrine – slower effects over longer time period using chemical stimuli only

4. Hormones
Regulatory chemicals that have specific effects on certain cells or organs (target tissue)
Some hormones affect many tissues
Some hormones affect only specific tissues
Released directly into the surrounding tissue and diffuse into the bloodstream that carry them throughout the body
Attach to receptors on plasma membrane of target tissues

5. Hormone Chemistry Amino acids – protein compounds
Almost all hormones fall into this category except those of the adrenal cortex and the sex glands
Steroids – lipid compounds made of cholesterol
Adrenal hormones & sex hormones are steroids
End in the suffix –one, as in progesterone, testosterone

6. Hormone Regulation
Hormone levels in the blood are generally kept within a specific range using a negative feedback loop
Exception; oxytocin, which allows the uterus to contract during pregnancy, responds to a positive feedback loop (hormone promotes further hormone release)
In negative feedback, the hormone itself (or the result of its action) controls further hormone secretion
Hormone release may also be rhythmic
Adrenal cortex hormones follow a 24 hour cycle
Female hormones follow a 28 day cycle

7. Methods of Hormone Regulation
Negative Feedback Loop –Pituitary & Thyroid Glands

8. Endocrine Glands Pituitary Gland Thyroid Parathyroid Adrenal Gland
Anterior & posterior
Thyroid
Parathyroid
Adrenal Gland
Medulla & cortex
Pancreas
Testes
Ovaries
Thymus
Pineal gland

9. Pituitary Gland aka Hypophysis
Master gland – pituitary hormones affect the working of other glands
Connected to brain at the hypothalamus
Infundibulum – stalk that connects pituitary with hypothalamus
Sits in a depression in sphenoid
Two lobes of pituitary gland:
1. Anterior pituitary gland
GH, TSH, ACTH, PRL, LH
2. Posterior pituitary gland
ADH

10. Chemical messengers called releasing hormones (RH) arrive from the hypothalamus.
RH travel to the anterior pituitary by way of a special type of circulatory pathway called a portal system.
As the blood circulates through the capillaries, it delivers the hormones that stimulate the release of anterior pituitary secretions.

11. Pituitary Gland

12. Control of the Anterior Pituitary Gland
Releasing hormones – chemical messages from the hypothalamus stimulate the anterior pituitary to produce hormones
GH-RH is growth hormone releasing hormone
GH-IH is growth hormone inhibiting hormone
Portal system – circulatory pathway between the hypothalamus & the anterior pituitary

13. Control of the Posterior Pituitary Gland
Posterior pituitary hormones are produced by the hypothalamus and stored in the posterior pituitary; ADH & oxytocin
Posterior pituitary hormone release is controlled by nerve impulses that travel over nervous tracts between the hypothalamus & the posterior pituitary

14. Anterior Pituitary Hormones
GH – growth hormone aka somatotropin
Acts directly on most body tissues, promoting growth
Produced throughout life
TSH – thyroid stimulating hormone; thyrotopin
Stimulates production of hormones in the thyroid gland
ACTH – adrenocorticotropic hormone
Stimulates production of hormones in the adrenal cortex
PRL – prolactin – stimulates milk production
Gonadotropins – hormones that act on the reproductive systems
FSH – follicle sitmulating hormone
Stimulates egg & sperm development
LH – leutinizing hormone
Causes ovulation in females & sex hormone secretion in men & women

15. Posterior & Anterior Pituitary

16. Posterior Pituitary Hormones
ADH – antidiuretic hormone
Promotes H2O reabsorption from the kidneys
Contracts blood vessels; increasing blood pressure
Oxytocin
Causes uterine contractions

17. Pituitary Disorders Anterior Pituitary Posterior Pituitary
Childhood increased GH – gigantism
Adult increased GH – acromegaly; thickened features
Posterior Pituitary
Decreased ADH – diabetes insipidus; excessive water loss

18. Acromegaly

19. Thyroid Gland Largest endocrine gland in body
2 lobes separated by an isthmus
Covered with a connective tissue capsule

20. Hormones of the Thyroid Gland
Two Thyroid hormones increase metabolic rate
Require iodine
T4 - Thyroxine
T3 - Triiodothyronine
Calcitonin – active in calcium metabolism. Calcitonin lowers the amount of calcium circulating in the blood by promoting the deposit of calcium in bone tissue

21. Thyroid Disorders; underactivity
Hypothyroidism – underactivity
Cretenism; infants & children usually due to failure of thyroid forming during development
Myxedema; thyroid wasting in an adult resulting in sluggishness, hair & skin changes, swollen face

22. Thyroid Disorders; Overactivity
Hyperthyroidism – overactivity
Graves disease – enlarged thyroid, exopthalmosis (bulging eyes), nervousness, weight loss
Thyroid storm – sudden onset of hyperthyroidism which can be fatal if untreated

23. Thyroid Disorders
Goiter – enlarged thyroid which may or may not cause altered secretions
Hashimoto disease – autoimmune inflammation of the thyroid

24. Parathyroid 4 glands embedded in posterior capsule of thyroid
PTH – parathyroid hormone regulates calcium levels in blood
Promotes calcium release from bone tissue
Stimulates kidney to conserve calcium
Tetany – muscle spasms as a result of low PTH levels which result in low calcium levels
PTH works with calcitonin from the thyroid gland to regulate calcium metabolism. When calcium is high, calcitonin is produced; when calcium is low, PTH is produced.

25. Adrenal Glands 2 small glands on top of the kidneys
2 parts to each adrenal gland
Adrenal medulla
Epinephrine/adrenaline
Norepinephrine/noradrenaline
Adrenal cortex
Glucocorticoids
Mineralcorticoids
Sex hormones

26. Adrenal Medulla Hormones
Fight or flight hormones; can be released from nerve endings as well, making them neurotransmitters
Adrenaline/epinephrine
Noradrenaline/norepinephrine
Stimulates arteriole contraction, raising blood pressure
Converts glycogen to glucose
Increases heart rate, metabolic rate
Dilates bronchioles, increasing respiration

27. Adrenal Cortex Hormones
Glucocorticoids – maintain carbohydrate reserve of the body; suppress body’s inflammatory response
Stress increases production of these hormones
Cortisol aka hydrocortisone
Mineralcorticoids – regulate electrolyte balance
aldosterone
Sex hormones – secreted in small amounts; little effect on body

28. Adrenal Glands

29. Pancreas – Endocrine & Exocrine Gland
Islets of Langerhans – small groups of cells throughout pancreas that secrete
Insulin
glucagon
Insulin – transports glucose across plasma membrane for use by cells; promotes conversion of excess glucose into fatty acids – decreases blood sugar
Glucagon – works with insulin to regulate blood sugar levels; causes liver to release stored glucose - increases blood sugar

31. Diabetes Mellitus – Type I
Type I - Islets of Langerhans fail to produce enough insulin
Usually brought on by infection or autoimmune disorder destroying islets
Insulin dependant
More severe
Usually <30 yoa onset

32. Diabetes Mellitus – Type II
Type II - Body cells become resistant to insulin & glucose remains in the blood instead of being transported across plasma membrane
Non-insulin dependant, although many will use insulin
Retain ability to secrete insulin but body becomes resistant due to excessive weight
Adult onset

33. Gestational Diabetes
During pregnancy, usually disappears after childbirth
Familial pattern, obesity, older age at conception
Complications for both mother and baby

34. Long Term Complications of Diabetes
Abnormal fat metabolism, increasing blood levels of fat and accelerating atherosclerosis
Arterial damage, especially in the retina, heart & kidneys
Peripheral nerve damage
Decreased ability to utilize amino acids, resulting in poor tissue repair & reduced resistance to infection

35. Sex Glands – Ovaries & Testes
Hormones needed for the maintenance of reproductive system
Responsible for secondary sex characteristics, those features that typify male vs female but are not involved with reproduction (i.e. deep voice)
Androgens – male sex hormones
Estrogens & progesterone – female sex hormones

36. Thymus Gland Behind the sternum superior to heart
Lymphoid tissue important in immunity
Thymosin – hormone secreted to assist in developing some white blood cells known as T cells (T lymphocytes)

37. Pineal Gland
Small structure attached to the roof of the 3rd ventricle in the brain
Melatonin – produced during the night & influences sleep-wake cycles

38. Other Hormone Producing Tissues
Hormones are considered any substance that has a regulatory function, either locally or distant from its site of secretion
Stomach & small intestine secrete hormones that regulate digestive action
Kidneys produce erythropoietin which stimulate RBC formation in the bone marrow

39. Prostaglandins Hormones produced by most body tissues
Produced, act & are deactivated at a local level
Involved in the inflammatory process
Involved in sensitizing pain receptors
Aspirin & other NSAIDs counteract prostaglandins

40. Hormones in Medical Treatment
Growth Hormone – to strengthen & build body mass in weakened or elderly
Insulin – treatment of diabetes
Adrenal steroids – inflammation relief
Epinephrine – anaphylactic shock treatment
Progesterone & estrogen – oral contraceptives

41. Hormones & Stress
Stress activates the fight or flight response of the autonomic nervous system
Hypothalamus of the brain is stimulated to release hormones
Prolonged stress causes prolonged elevated hormone levels which can lead to decreased immunity & stress related health problems