1. Endocrine System

2. Endo crine System “inside” “secrete”
Odd organ system
Compared to nervous sys. & digestive sys.
Endocrine glands usually not connected
Considered a “system” because of functional similarity
Secrete chemical messages called hormones to target cells “to excite”
Know the names of the glands and their positions from this picture. Figure 16.1 Page 605
Also skin, heart, GI tract, placenta, kidneys, adipose tissue

3. Principal functions of the endocrine system
Maintenance of the internal environment in the body (maintaining the optimum biochemical environment).
Integration and regulation of growth and development.
Control, maintenance and instigation of sexual reproduction and development.
Homeo/homo = same
Stasis = arrest/fixation
Endocrine system maintains homeostasis by releasing chemicals to control or prolong continuous processes
Glands with a sensing and signaling system which regulates the duration and magnitude of hormone release via feedback from the target cell. 3

4. Types of hormones
Hormones are categorized into four structural groups, with members of each group having many properties in common:
Peptides and proteins (polypeptides)
Amino acid derivatives
Steroids (cholesterol based)
Fatty acid derivatives - Eicosanoids (mostly paracrines, i.e. leukotrines, prostaglandins)
What are the 4 organic compounds necessary for life?
What are the monomers and polymers? 4

5. Types of hormones: Proteins
Peptides
Water soluble
Largest # of hormones
Hypothalamus
Pituitary (Ant. & Post.)
Islets of Langerhans
Parathyroid hormone
Digestive system hormones
How and where are proteins synthesized?

6. Types of hormones Amino Acid Based Tyrosine derivatives
Thyroid hormones
Thyroxine (T4)
Triiodothyronine (T3)
Catecholamines/Adrenal medulla
Epinephrine
Norepinephrine
Both neurohormones & neurotransmitter
Tryptophan derivatives (precursor to serotonin and the pineal hormone melatonin)
Glutamic acid (converted to histamine)
Histamine neurotransmitter or paracrine

7. Types of hormones: Lipids
Steroids
Derivatives of cholesterol differing in side chains
Lipid soluble (freely diffuse, not stored, not packaged)
Examples
Glucocorticoids (cortisol major representative in mammals)
Mineralocorticoids (aldosterone most prominent)
Androgens (i.e. testosterone)
Estrogens (i.e. estradiol and estrone)
Progestogens (i.e. progestins)
Eicosanoids
derived from polyunsaturated fatty acids.
The principal groups of hormones of this class are prostaglandins, prostacyclins, leukotrienes (inflammation) and thromboxanes (platelet aggregation).
Only gonadal and adrenocortical hormones are steroids

8. Mechanisms of Hormone Action
Lipid-soluble steroids & thyroid hormones
Diffuse through plasma membrane
Enter nucleus
Forms “hormone-receptor complex”, binds as TFs to chromosome to activate/ inactivate gene(s)
Peptides & water-soluble amines
Hormone (A) binds to receptor on cell surface
Activates G- protein
Activates adenylate cyclase
Converts ATP to cAMP
cAMP activates protein kinases, which produce final effect.
Hormone receptor binds to a region of DNA that is specific—a hormone response element
Receptors are bound up by chaperones when not bound to hormone to prevent them from proteolysis. Binding of hormone releases the chaperone.
Hydrophobix/nonpolar/tails
Hydrophilic/polar/heads
Orientations of phospholipids in and out of cells
Signal Transduction Pathway Animation Transduction Pathway Epinephrine

9. Hormone Targets
A cell is a target because is has a specific receptor for the hormone
Most hormones circulate in blood, coming into contact with essentially all cells. However, a given hormone usually affects only a limited number of cells, which are called target cells.
A target cell responds to a hormone because it bears receptors for the hormone. 9

10. Which diagram represents…
Steroid hormones?
Lipid hormones?
Peptide hormones?

11. Target cell
concept
Receptor
Target cell
Hormone

12. Target cell concept Not all hormones find their target
How are chemical signals sent to cells?

13. Types of cell-to-cell signaling
Classic endocrine hormones travel via bloodstream to target cells
Neurohormones are released via synapses and travel via the bloostream
Paracrine hormones act on adjacent cells
Autocrine hormones are released and act on the cell that secreted them
Intracrine hormones act within the cell that produces them 13

14. Response vs. distance traveled
Endocrine action: the hormone is distributed in blood and binds to distant target cells.
Paracrine action: the hormone acts locally by diffusing from its source to target cells in the neighborhood.
Autocrine action: the hormone acts on the same cell that produced it. 14

15. Ways of influencing target cells
Within beside/near self close to

17. Create a Venn diagram comparing the nervous & endocrine systems

18. Endocrine vs. Nervous System
Major communication systems in the body
Integrate stimuli and responses to changes in external and internal environment
Both are crucial to coordinated functions of highly differentiated cells, tissues and organs
Unlike the nervous system, the endocrine system is anatomically discontinuous. 18

19. Nervous Sys. vs Endocrine Sys.
The nervous system exerts point-to-point control through nerves, similar to sending messages by conventional telephone. Nervous control is electrical in nature and fast.
The endocrine system broadcasts its hormonal messages to essentially all cells by secretion into blood and extracellular fluid. Like a radio broadcast, it requires a receiver to get the message - in the case of endocrine messages, cells must bear a receptor for the hormone being broadcast in order to respond.

20. Regulation of hormone secretion
Sensing and signaling: a biological need is sensed, the endocrine system sends out a signal to a target cell whose action addresses the biological need. Key features of this stimulus response system are:
·        receipt of stimulus
·        synthesis and secretion of hormone
·        delivery of hormone to target cell
·        evoking target cell response
·        degradation of hormone 20

21. Receipt of Stimulus Humoral in response to changing blood levels
i.e. PTH regulation of Ca2+ via parathyroid
Neural in response to nerve fibers
i.e. catecholamines (norepinephrine & epinephrine) from adrenal medulla
Hormonal in response to other hormones
i.e. GHRH secreted by hypothalamus which regulates GH secretion by anterior pituitary 21

22. Inputs to endocrine cells22

23. Control of Endocrine Activity
The concentration of hormone as seen by target cells is determined by three factors:
Rate of production
Rate of delivery
Permissiveness/Synergism/Antagonism
Upregulation (insipidus)/downregulation (Type II, melitus)
Rate of degradation and elimination
What is a feedback loop?
Permissiveness—thyroid hormone is necessary for normal timely development of the reproductive structures.
Synergism—both glucagon and the epinephrine cause the liver to release glucose. Together they lead to release of 150% of what is released if either acted alone.
Antagonism—insulin antagonizes the effects of glucagon. Example of down regulation is the action between estrogen and progesterone. Progesterone induces loss of estrogen receptors in the uterus. Estrogen causes the same cells to increase progesterone receptors. 23

24. Components of an automatic control system
Variable characteristic of the internal environment that is controlled by this mechanism (internal temp in this example)
Sensor (receptor) detects changes in variable and feeds that information back to the integrator (control center) (thermometer in this example)
Integrator (control center) integrates (puts together) data from sensor and stored "setpoint" data (thermostat in this example)
Setpoint "ideal" or "normal" value of the variable that is previously "set" or "stored" in memory
Effector  mechanism (furnace in this example) that has an "effect" on the variable (internal temperature in this example)

26. Feedback Control of Hormone Production
Feedback loops are used extensively to regulate secretion of hormones
Negative feedback occurs when a change in a physiological variable triggers a response that counteracts the initial fluctuation 26

27. Negative Feedback
Neurons in the hypothalamus secrete thyroid releasing hormone (TRH), which stimulates cells in the anterior pituitary to secrete thyroid-stimulating hormone (TSH)
TSH binds to receptors on epithelial cells in the thyroid gland, stimulating synthesis and secretion of thyroid hormones, which affect probably all cells in the body
When blood concentrations of thyroid hormones increase above a certain threshold, TRH-secreting neurons in the hypothalamus are inhibited and stop secreting TRH.
Negative Feedback feedback that tends to stabilize a process by reducing its rate or output when its effects are too great

28. Feedback control Positive & Negative Feedback
Negative feedback is most common: for example, LH from pituitary stimulates the testis to produce testosterone which in turn feeds back and inhibits LH secretion
Positive feedback is less common: examples include LH stimulation of estrogen which stimulates LH surge at ovulation
Positive & Negative Feedback 28

29. A steroid hormone affects target cells by directly binding with:
A. cAMP
B. nuclear receptors which activate genes
C. protein receptors on the target cell’s surface
D. The RER
E. The second messenger B

30. 30

31. Endocrine Glands Islets of Langerhans Hypothalamus Pituitary Gonads
Ovaries
Testes
Pineal gland
Thymus
others
Hypothalamus
Pituitary
Anterior lobe
Posterior lobe
Thyroid gland
Parathyroid glands
Adrenal Glands
Cortex
Medulla
Hormonal Communication 31

32. Hypothalamus Part of brain
Regulates ANS, emotions, feeding/satiety, thirst, body temperature, etc.
Hormones related to these functions
“Releasing hormones”
Axonal transport to posterior lobe
ANS autonomic
The posterior lobe is part of the brain.  It derives from downgrowth of the hypothalamus and maintains neural connections to the hypothalamus.
The anterior lobe derives from superior outpocketing of the oral mucosa and is formed from epithelial tissue. Once it touches the posterior lobe it loses connection to the oral mucosa and adheres to the posterior lobe. 
There is a vascular connection with the hypothalamus and the nervous system. Regulates body temp., water balance, metabolism and limbic (thirst/appetite/pleasure/pain) system 32

33. Anterior Pituitary “Releasing” hormones regulate AP aka
adeno hypo physis “glands” “under” “growth”
All proteins
TSH (thryoid stimulating hormone/thyrotropin)
ACTH (adrenocorticotropic hormone)
FSH (gonadotropin)
LH (gonadotropin)
Tropins/tropic hormones
GH (growth hormone)
Prolactin-releasing H
GHRH
GHIH TRH
Hypothalamic Pituitary Axis Animation : IP Web 33

34. Anterior Pituitary 34

35. 35

36. 36

37. Parathyroid Glands Four small glands embedded in posterior of thyroid
Parathyroid hormone (PTH)
Stimulates osteoclasts to free Ca2+ from bone
Stimulates Ca2+ uptake from intestine by stimulating conversion of vitamin D to calcitrol
Stimulates Ca2+ reuptake from kidney
Typically 4 glands but amount varies up to 10.
PTH = antagonist to Cacitonin
Hormonal Regulation of Calcium 37

38. Feedback Loop
Negative feedback in calcium homeostasis. A rise in blood Ca2+ causes release of calcitonin from the thyroid gland, promoting Ca2+ deposition in bone and reducing reabsorption in kidneys.
A drop in blood Ca2+ causes the parathyroid gland to produce parathyroid hormone (PTH), stimulating the release of Ca2+ from bone.
PTH also promotes reabsorption of Ca2+ in kidneys and uptake of Ca2+ in intestines. 38

39. 39 Eustress is a good stress that allows us to meet challenges
Distress is harmful.
Something that causes stress is a stressor.
Prolonged stress leads to the stress response or general adaptation syndrome (GAS)
Initial fight or flight response
Initiated through input from hypothalamus-SNS acts on adrenal medulla to cause release of NE and EPI, which leads to large amounts of glucose and oxygen to the organs needed to respond to danger (skeletal muscles, heart, lungs) other organs not essential to response are inhibited (urinary and digestive organs) Increased flow of blood to kidneys leads to release of renin which activates RAA pathway (Na + levels and water retained, BP goes up
A slower resistance reaction—corticotropin releasing hormone (CRH), GHRH and TRH are released. CRH leads to release of ACTH from pituitary which stimulates release of cortisol from the adrenal gland. Cortisol stimulates gluconeogenesis in liver, breakdown of glycogen to glucose, and lipolysis. hGH and TSH supply additional ATP for active cells
Exhaustion--prolonged exposure to cortisol leads to wasting muscles, suppression of the immune system, ulceration of the GI tract, failure of pancreatic beta cells and other pathological changes. 39

40. Pancreas
Consists of two major types of secretory tissues which reflects its dual function
Exocrine gland
secretes digestive juice
localized in the acinar cells
Endocrine gland
releases hormones
localized in the islet cells (islets of Langerhans) 40

41. Pancreatic Islets “About a million” embedded in pancreas
Control centers for blood glucose
Insulin from beta cells
Glucagon from alpha cells
99% of the cells are arranged in clusters called acini, which produce digestive enzymes which are the exocrine glands that glow into the gastrointestinal tract through a system of ducts
Pancreatic islets or islets of Langerhans contain the other 4 cell types
Alpha cells (17%) secrete glucagon
Beta cells (70%) secrete insulin
Delta cells (7%) secrete somatostatin, same peptide as secreted by hypothalamus
F cells (6%) secrete pancreatic polypeptide 41

42. Insulin Glucagon 42

43. Islets of Langerhans Insulin stimulates glucose uptake, glycogenesis
Glucagon stimulates glycogenolysis, glucose release from liver (vs gluconeogenesis) 43

44. 44

45. Feedback Loop
A rise in blood glucose causes release of insulin from beta cells the pancreas, promoting glucose uptake in cells and storage as glycogen in the liver.
A fall in blood glucose stimulates alpha cells in the pancreas to secrete glucagon, which causes the liver to break down glycogen and release glucose. 45

46. Pancreas Homeostatic Imbalances Diabetes “siphon” mellitus mel= “honey”
Symptoms:
Polyuria
Polydipsia
Polyphagia
Blood Level Regulation in Diabetics 46

47. Non-Endocrine Gland Hormones
Stomach (gastrin)
Small intestine (duodenumintesetinal gastrin, secretin, cholecystokinin)
Heart (atrial natriuretic peptide)
Kidneys (erythropoietin, active vitamin D3)
Adipose tissue (leptid, resistin)
Skin
Placenta (human chorionic gonadotropin, human placental lactogen, relaxin) 47

48. Functions regulated by the Endocrine System
Growth
Healing
Water balance & Blood Pressure
Calcium Metabolism
Energy Metabolism
Stress
Regulation of other Endocrine Organs 48

49. 1. Juvenile diabetes mellitis (type 1) is:
a. insulin dependent
b. Non-insulin dependent
c. Diabetes insipidus
d. Goiter associated
e. Caused by thyroid deficiency
2. Which of the following processes is not regulated by adrenal cortical hormones:
Adaptatoin to stress
Blood pressure
Glucose utilization
Labor and delivery
Sodium/potassium balance A D 49

50. a. Cells communicate by cell-to-cell contact.
Essential knowledge 3.D.2: Cells communicate with each other through direct contact with other cells or from a distance via chemical signaling.
a. Cells communicate by cell-to-cell contact.
b. Cells communicate over short distances by using local regulators that target cells in the vicinity of the emitting cell.
c. Signals released by one cell type can travel long distances to target cells of another cell type.
1. Endocrine signals are produced by endocrine cells that release signaling molecules, which are specific 50

51. Resources Endocrinology Questions: Endocrinology Quiz:
Pathophysiology of the Endocrine System:
Endocrine Surgery:
Dr. Ross BIO 218 A&P:
McGraw Hill Tutorial:
Lion Den:
Medical Mneumonics:
Peptide Hormone Signal Transduction Animation:
106 Animated Tutorials:
BIOMedia:
Signal Transduction Pathway:
Human Physiology U of Colorado:
Textbook in Medical Physiology And Pathophysiology:   
Pituitary Tumors: