1. The Endocrine System
Anatomy & Physiology

2. The Endocrine System The “other” great controlling system of the body
What’s the first?

3. Endocrine vs. Nervous Endocrine Nervous Slower Uses hormones
Responses are continuous or long-term
Nervous
Faster
Uses nervous impulses
Responses are immediate

4. What Are Hormones?
Chemical substances, secreted by cells into extracellular fluids, that regulate the metabolic activity of other cells of the body

5. Target Cells/Hormones
The specific cells or organs a hormone is meant to affect
Each hormone must have a receptor protein present on a cell’s plasma membrane in order to work

6. Types of Hormones
Non-steroidal or amino-acid based: made from proteins, peptides or amines)
Steroidal: made from cholesterol
Includes all sex hormones and hormones made in adrenal cortex

7. How Do They Work? First Mechanism Direct Gene Activation
a. Steroid hormones diffuse through plasma membrane (why?)
b. Enters nucleus
c. Binds to a specific receptor inside nucleus—hormone-receptor complex (HRC)
d. HRC binds to cell’s DNA—
causes transcription of mRNA
e. mRNA translated in cytoplasm—makes new proteins

9. How Do They Work? Second Mechanism Second Messenger System
a. Non-steroidal hormones bind to
receptors on plasma membrane (why?)
b. Reactions go off inside cell activating an
enzyme
c. Enzyme sets off reactions to create a
second messenger (cAMP)
d. Second messenger instills changes in cell

11. Controlling Hormone Release
Negative Feedback Mechanisms
Hormone released triggered by internal or external stimuli
Rising hormone levels in blood inhibits further release
Blood levels of hormones vary within a very narrow range

13. Controlling Hormone Release
Hormone Stimuli
1. Humoral: changing blood levels of
different ions and nutrients
example: PTH in response to calcium levels
2. Hormonal: endocrine organs
stimulated to work due to presence of
other hormones
example: TSH stimulates thyroid

14. Controlling Hormone Release
3. Neural: nerve fibers stimulate
hormone release
example: epinephrine and nor-epinephrine

15. Major Endocrine Organs
Pituitary gland (anterior & posterior)
Pineal Gland (body)
Thymus
Thyroid & Parathyroid
Pancreas
Adrenal glands (cortex & medulla)
Gonads (testes or ovaries)

17. Anterior Pituitary Gland
Secretes 6 Hormones
Found at base of hypothalamus
“Master Endocrine Gland”
Actually regulated by hypothalamus
All non-steroidal
All respond to hormonal stimuli from hypothalamus

18. Anterior Pituitary Gland
1. Growth Hormone
Target cells: skeletal muscles & bones
Function:
to stimulate growth of target cells
Cause fat metabolism, sparing glucose
Hyposecretion disorder: dwarfism
Hypersecretion: kids = gigantism
adults = acromegaly

19. Anterior Pituitary Gland
2. Prolactin
Target cells: the breasts of females
Function:
stimulates & maintains milk production after birth
No associated disorders

20. Anterior Pituitary Gland
3. Adrenocorti-cotropic Hormone (ACTH)
Target cells: adrenal cortex
Function: regulates release of hormones
4. Thyroid-Stimulating Hormone (TSH)
Target cells: thyroid
Function: regulates growth & activity of gland

21. Anterior Pituitary Gland
5. Follicle-stimulating Hormone (FSH)
Target cells: gonads
Functions:
Females: stimulates follicle development
Males: stimulates sperm development
Hyposecretion: sterility

22. Anterior Pituitary Gland
6. Luteinizing Hormone (LH)
Target cells: gonads
Functions:
Females: triggers ovulation
Males: stimulates testosterone production
Hyposecretion: sterility

24. Posterior Pituitary Gland
Stores 2 hormones made by hypothalamus
Non-steroidal hormones
1. Oxytocin
Target cells: uterus & breasts of pregnant women
Functions: stimulates contractions & breast milk ejection

25. Posterior Pituitary Gland
2. Antidiuretic Hormone (ADH)
Target Cells: kidneys
Functions: causes kidneys to reabsorb water—decrease urine volume/ increases blood volume
Hyposecretion: diabetes insipidus
** diuretics inhibit ADH

26. Adrenal Glands 2 bean shaped glands Sit on top of kidneys
Steroidal hormones
2 parts:
Adrenal cortex: outside layer
Adrenal medulla: center

28. Adrenal Cortex
1. Corticosteroids: mineralocorticoids, glucocorticoids, sex hormones
A. Mineralocorticoids: aldosterone
Target cells: kidneys
Function: Regulates water & electrolyte balance
Causes uptake of sodium (and water), release of potassium by kidneys

29. Adrenal Cortex B. Glucocorticoids: cortisol and cortisone
Target cells: all body cells
Function: promote normal cell metabolism
Assist body in coping with long-term stress—increasing blood glucose
Can decrease edema and pain

30. Adrenal Cortex
C. Sex Hormones: aka androgens; released in both males & females all through life.

31. Adrenal Cortex Hormones
Hyposecretion of any adrenal cortex hormone:
Addison’s Disorder
Hypersecrretion of any adrenal cortex hormone:
Cushing’s Syndrome

32. ADRENAL CORTEX DISORDERS
Addison’s Disorder
Cushing’s Syndrome

34. Adrenal Medulla Located in center of adrenal gland
Stimulated by sympathetic nervous system
1. Catecholamines: epinephrine & norepinephrine
Target cells: all body cells
Function: assists body in coping with short-term stressors
increase glucose levels, increase breathing rate
“fight or flight” response

36. Thyroid Gland Located at base of throat
Makes 2 hormones both non-steroidal
1. Calcitonin
Target cells: bones
Function: causes absorption of calcium by bones
decreases blood calcium levels

37. Thyroid Gland
2. Thyroid Hormone (thyroxine, T4, & tri-iodothyronine, T3)
requires iodine
Target cells: all body cells
Function: controls rate of glucose metabolism
Needed for normal tissue growth & development
Hyposecretion: Kids: cretinism, adults: myxedema
Hypersecretion: graves disease

39. Parathyroid Gland Tiny masses of tissue on posterior thyroid
1. Parathyroid Hormone (PTH)
Target cells: bone cells, kidneys & intestines
Function: regulates blood calcium levels
Causes release of calcium from bones
Hyposecretion: tetany
Hypersecretion: massive bone loss

40. Pancreas Located close to stomach in abdominal cavity
Part exocrine gland/ part endocrine gland
Pancreatic Islets—endocrine portion

41. Pancreas 1. Insulin: stimulated by high glucose
Target cells: all body cells
Function: allows for uptake of glucose by cells
Hyposecretion: diabetes mellitus
2. Glucagon: stimulated by low glucose
Target cells: liver
Functions: calls for breakdown of glucogen to glucose.

42. Pineal Gland aka pineal body Small, cone-shaped
Located in diencephalon of brain
1. Melatonin
Target cells: ??
Function: day-night cycle
Peak levels occur at night– drowsiness
Low levels around noon—alertness
“Biological Clock” ???

43. Thymus Located in upper thorax, posterior to sternum
Large in infants and kids—decreases and converts to fat in adults
1. Thymosin
Target cells: t-cells of immune system
Function: assists in maturation of t-cells

44. Gonads Females: ovaries Males: testicles A. Ovaries 1. Estrogen
Target cells: female sex organs
Function: stimulate development of secondary sex characteristics
Assists in preparing uterus for fertilized egg
Help maintain pregnancy and produce milk

45. Gonads 2. Progesterone Target cells: uterus
Function: assists in preparation of uterus for fertilized egg
During pregnancy—quiets contractions of uterine muscle
Hyposecretion of either hormone—inability to conceive and bear children

46. Gonads B. Testes 1. Testosterone (made by interstitial cells)
Target cells: male sex organs
Function: development of male secondary sex characteristics
Growth and development of sex organs
Male sex drive
Production of sperm
Hyposecretion: sterility