1. Endocrine System

2. Endocrine System What is the endocrine system?
The endocrine system is comprised of the hormone producing glands and tissues of the body.
Functioning of the Endocrine System
The endocrine system functions along with the nervous system to help the nervous system to help maintain homeostasis.
Endocrine system functions slower than the nervous system but gives a more sustained effect

3. Mechanisms of Hormone Action
Certain secretory cells release chemical agents (hormones) for the purpose of mediating biologic responses in distant Target Cells.
Hormones sources
Single amino acid (catecholamines)
Chains amino acids (peptide hormones of hypothalamus)
Cholesterol (steroids)

4. Mechanisms of Hormone Action
Hormones control and integrate many body functions with this system.
The endocrine system carries out its functions based upon messages received from the Hypothalamus
The hypothalamus monitors the blood and sends hormones from glands into the blood when needed
Organs await the arrival of hormones
In general, hormonal control regulates the metabolic functions of the body, the types of effects that occur inside the cell and determined the character of the cell itself.
The endocrine system works with the nervous system to regulate: metabolism, water and salt balance, blood pressure, response to stress, and sexual reproduction.

5. Endocrine System
Endocrine System Hormones/Glands whose functions are solely endocrine include:
pituitary (hypophysis)
pineal
thyroid
parathyroids
adrenals
pancreas

6. Types of Glands
Endocrine: ductless glands that secrete hormones directly into blood stream
Exocrine: glands that have ducts and secrete substances such as sweat salvia tears milk or digestive enzymes

7. Endocrine Glands Pituitary Gland Hypothalamus Adrenal Cortex
Adrenal medulla
Thyriod
Parathyroid
Pancreas
Thymus
Kidney
Pineal
Ovaries
Testes

8. Hormones
These are chemicals that circulate throughout the blood and exert some measure of control over most every organ and tissue in the body.
Types of Hormones
Hormones are either Steroidal or Non-steroidal
Steroid Hormones- hormones manufactured from fatty substances called cholesterol.
These substances are fat soluble. Ex. Cortisol

9. Steroid Hormones
Steroid hormones are produced by chemical modification of cholesterol
Major classes steroid hormones
glucocorticoids (cortisol)
mineralocorticoids (aldosterone)
androgens (testosterone)
estrogens (estradiol)
Vitamin D metabolites

10. How steroid Hormones work
These hormones enter a cell and binds to a protein receptor in the cell. This creates a hormone receptor complex.
The hormone receptor complex enters the nucleus where it activates a specific gene in the DNA
Activated gene produces an enzyme(protein) that initiates a chemical reaction within the cell.

11. Non Steroid Hormones
Hormones composed of proteins, peptides or amino acids
These hormones are not fat soluble. They are unable to enter cells because the are not soluble in the membrane.

12. How a Non-Steriod Hormone Works
A hormone called a first messenger binds to receptors on surfaces of target cells. The binding causes ATP to be changed into cyclic AMP(cAMP).
Cyclic AMP(second messenger) causes chemical reactions to occur within the cell.
Ex. Adrenaline, ACTH, LH, FSH, ADH

13. Summary of Steroidal. VS Non Steroidal Hormones
Solubility in cell membrane
Location of Receptors
End Result
Steroidal
Within the cell
Gene produces a protien
Non-steriodal
Surface of cell
cAMP causes chain reaction

14. Types of Hormones Antagonistic Hormones
These are hormones that work against each other or they have opposite effects on the body.
Ex. Insulin and Glucagon
Parathyroid hormone and Calcitonin
Tropic Hormones
These hormones regulate the hormone production of many other glands.
Ex. Thyroid stimulating hormone, HGH

15. Endocrine Hormone Disorders
Problems with most endocrine glands are either caused by Hyposecretion or Hypersecretion of a hormone.
Hyposecretion; under secretion of a hormone within the body
Hypersecretion; A over secretion of a hormone within a body.

16. Feedback Mechanisms and Operation of Hormones
Hormones regulate endocrine function on the basis of feedback mechanisms. There are two types of feedback mechanisms
1. Negative feedback loop:
A loop that works to reverse or decrease changes in the body. When concentration of a hormone rises to above desired levels, a series of steps is taken within the system to cause the concentration to fall. Conversely, steps are taken to increase concentration when the level is too low.
Ex. Hypothalamus-Pituitary-thyroid feedback mechanism operation

17. Positive feedback Mechanism or loop
A loop that serves to increase the effect of an action.
Ex. Oxytocin feedback loop
Diagrams pg 424 figure 13.3
Pg. 432 figure 13.13

18. Feedback Loops
The release of a hormone is often triggered by a change in the concentration of some substance in the body fluids.
Each hormone has a corrective effect, eliminating the stimulus, which then leads to a reduction in hormone secretion.
This process is called a negative feedback homeostatic control system to keep hormones at normal levels. (if levels increased it would be called positive feedback)

20. Hypothalamus and Pituitary
Pituitary has direct neural and blood connection to the hypothalamus
Hypothalamus sends releasing factors to anterior pituitary
Hypothalamus stimulates posterior pituitary via neural pathway

21. Hypothalamus
Hypothalamus can synthesize and release hormones from its axon terminals into the blood circulation.
controls pituitary function and thus has an important, indirect influence on the other glands of the endocrine system.
exerts direct control over both the anterior and posterior portions of the pituitary gland.
regulates pituitary activity through two pathways: a neural pathway and a portal venous pathway.

22. Hypothalamus
Neural pathways extend from the hypothalamus to the posterior pituitary lobe, where the hormones are stored and secreted.
Portal venous pathways connect the hypothalamus to the anterior pituitary lobe, carry releasing and inhibiting hormones

23. Pituitary Gland
Pituitary Gland is located at the base of the skull in an indentation of the sphenoid bone, and is called the Master Gland.
Is joined to the hypothalamus by the pituitary stalk and consists of the anterior pituitary and the posterior pituitary.
Nervous system sends messages to the hypothalamus to exert control over the pituitary

24. Anterior pituitary gland
anterior lobe has direct control over the secretion of:
HGH- Somatotropin or human growth hormone
ACTH - adrenocorticotrophic hormone
TTH - thyrotrophic hormone
FSH - follicle stimulating hormone
LH - leutinizing hormone
PRL- prolactin

25. Posterior pituitary
Stores and secretes hormones made in the hypothalamus and contains many nerve fibers.
ADH (Antidiuretic Hormone/Vasopressin), which controls the rate of water excretion into the urine
Regulates Na+ & K+ reabsorption in the kidneys this influences blood volume & blood pressure
Oxytocin, which, among other functions, helps deliver milk from the glands of the breast.

26. Adrenal Glands Located on top of the kidneys
Adrenal Glands have an outer cortex and an inner medulla.
The adrenal cortex and medulla are major factors in the body's response to stress, and are controlled by the hypothalamus

27. Adrenal Glands
ACTH - Adrenocorticotrophic Hormone causes adrenal cortex to release 3 types of hormones: Cortisol (Glucocorticoids), Aldosterone (Mineral corticoids), and sex hormones
The outer cortex is responsible for the secretion of mineralocorticoids (steroid hormones that regulate fluid and mineral balance) ALDOSTERONE
glucocorticoids (steroid hormones responsible for controlling the metabolism of glucose) Cortisol
androgens (sex hormones).

28. Adrenal Glands
Centrally located adrenal medulla is derived from neural tissue and secretes Epinephrine and Norepinephrine
Epinephrine circulates and acts upon the sympathetic nervous system
Norepinephrine released from sympathetic nerve endings and from adrenal medulla in small amounts

29. Adrenal Mineral Corticoids
ADH - antidiuretic hormone
Regulates Na+ & K+ reabsorption in the kidneys
regulates water retention

30. Adrenal Steroids
Testosterone - masculinizing affects, increase lean body mass
Estrogens - estrodial, estrone, estriol - stimulate breast development and female pattern fat deposition

31. Thyroid Gland
Located in the throat
Butterfly shaped

32. Thyroid Gland
Thyroid function is regulated by the hypothalamus and pituitary, feedback controls an intrinsic regulator mechanism
Hormones produced are:
thyroxine (T4) & triiodothyronine (T3), regulate the metabolic rate of the body and oxygen consumption and increase protein synthesis
It is released from the thyroid gland when stimulated by TSH from the pituitary. TSH---- Thyroid gland---- release Thyroxin
TSH and Thyroxin work on a negative feedback loop.

33. calcitonin, has a weak physiologic effect on calcium and phosphorus balance in the body.
It moves calcium from the blood and into the bones. This lowers the amount of calcium in the blood

34. Thyroid Problems
Thyroid gland enlargement may or may not be associated with abnormal hormone secretion.
An enlarged thyroid gland can be the result of:
iodine deficiency (Goiter)
inflammation, or
benign or malignant tumors

35. Hyperthyroidism Hyperthyroidism or Grave’s Disease
This disease causes excess production of thyroid hormones
Weight loss and exopthalmic goiter

36. Hypothyroidism Caused by a deficiency of thyroxin
Refereed to as Myxedema
Reduced metabolism
Weight gain
Decreased mental capacity

37. Thyroid imbalance can cause cretinism, metabolic disorders, and goiter( due to lack of iodine)

38. Parathyroid Glands
There are 4 parathyroid glands located on the surface of the thyroid.
Parathyroid Glands produce PTH ( parathyroid hormone)
PTH causes bones to release calcium into the bloodstream
Causes kidneys to reabsorb calcium from the blood thus increasing amount of calcium in the body

40. Pancreas Located near the small intestine.
Contains specialized endocrine cells called islets of langerhans
Islets of langerhans is made up of both alpha and Beta cells.
Secretes insulin, glucagon (regulate blood sugar)

41. Diabetes Mellitus
Syndrome when insulin levels are inadequate to keep blood sugar within normal range. Due to:
Inadequate amount of insulin (Insulin-Dependent Diabetes Mellitus). Results from severe insulin deficiency secondary to loss of beta cells. Autoimmune process selectively destroys beta cells.
Inadequate response to normal or high insulin levels (Non-Insulin-Dependent Diabetes Mellitus). More common that IDDM, 90% NIDDM, associated with obesity.

42. Type I (insulin-dependent) diabetes
Autoimmune disease in which pancreatic beta cells are destroyed and thus not enough insulin is produced
Often develops before age 15
Patient requires insulin supplement, often by injection

43. Type II (non-insulin-dependent) diabetes
Pancreatic cells function properly and there are sufficient amounts of insulin produced
Body cells fail to respond to insulin
Accounts for 90% of diabetes cases in the United States
Associated with obesity
Often develops after age 40
Manageable

44. Function of Insulin
Created by the Beta cells of the islets of langerhans
Causes the conversion of glucose into glycogen that is stored in the liver
Causes excess glucose to be changed into fat
Helps regulate blood sugar levels. Insulin and glycogen

45. Pancreas( Islets of Langerhans)
Function of Glucagon(created by the alpha cells of the islets of Langerhans)
Causes the conversion of Glycogen (Liver) into Glucose that is released into the blood as needed.
Operation of insulin and Glucagon in sugar(glucose) regulation.
Insulin and glucagen are antagonistic hormones. They work opposite each other to maintain proper blood sugar levels in a negative feedback loop.
They work by either increasing or decreasing the amount of glucose (sugar) in the blood.

46. Blood Sugar Control
Insulin and glucagon are produced by small groups of cells in the pancreas (islets of Langerhans).
Beta cell make insulin (beta cells) and Alpha cells that make glucagon
Insulin is released when the blood sugar rises too high. Insulin tells the cells to use sugar.
Glucagon is produced when the blood sugar is falling too low. Glucagon tells the liver to release sugar that was stored there when the blood sugar was higher.

48. Insulin Insulin promotes glucose entry into cells
Insulin effects enzymes that rule rate of metabolism of CARBOHYDRATE, FAT, PROTEIN, & ION TRANSPORT
Carbohydrate metabolism
stimulates glucose utilization, storage & also INHIBITS glucose formation
Insulin acts on LIVER depending upon plasma glucose level

49. Glucagon
Secreted in response to: decreased blood glucose levels, increased amino acid levels, or stimulation by growth hormone
primary function is to increase the circulating blood glucose level: converts stored glucose (primarily in the liver) to circulating glucose.
promotes glucose formation (from fat and protein when the need for glucose is greater than the amount that can be mobilized from the liver)

50. Chronic Diabetic Complications
Retinopathy = due to dilations of retinal vessels from microaneurysms.
atherosclerotic process that occludes coronary and other arteries. Leading cause of death in diabetic subjects is coronary heart disease.

51. The gonads secrete sex hormones
Secretion is controlled by the hypothalamus and the pituitary
The steroid hormones are found in both sexes but in different proportions
estrogens
progestins
androgens

52. Gonads Ovaries- found in females Produces estrogen and progesterone
Estrogen controls secondary sex characteristics in females
Prepares the uterus for pregnancy
Progesterone maintains the uterus during pregnancy
Estrogen and progestins

53. Testes
Found in males
Produces testosterone
Controls secondary sex characteristics in males

54. Pineal Gland

55. Pineal Gland Its principal hormone is melatonin.
Synthesis and release of melatonin is stimulated by darkness and inhibited by light.
Levels of melatonin in the blood rises and falls on a daily (circadian) cycle with peak levels occurring in the wee hours of the morning.
Ingesting even modest doses of melatonin raises the melatonin level in the blood. These levels appear: to promote going to sleep and thus help insomnia. Considered to be the biological clock

56. Thymus Gland
Located between the lobes of the lungs in the upper chest. Disappears after puberty
Produces Thymosin
Function of Thymosin:Causes the production and maturation of lymphocytes into T-cells

57. Growth Hormone Problems
Gigantism
Dwarfism

58. GH - Growth Hormone Release of somatomedins from the liver
Uptake of amino acids by tissues
Synthesis of new proteins
Long bone growth
Blunts insulin’s affect on glucose uptake
Induces gluconeogenesis

59. Gigantism
Acromegaly/Gigantism is a very rare disease and syndrome results from a chronic exposure to GH (Growth Hormone) leading to the classic clinical features that the diagnosis seems to be easy
High exposure to GH produces gigantism in youths prior to epiphyseal fusion and acromegaly in adults.
In adults, the syndrome is characterized by local overgrowth of bone (skull, mandible).

61. Dwarfism
Dwarfism results from growth hormone deficiency.  A pituitary dwarf has too little growth hormone.  The achondroplastic dwarf has an orthopedic reason for having short limbs and a short spinal column. 
Cause of this is unknown, a tumor or cyst in the pituitary area may cause dwarfism.

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