1. Endocrine System

2. Endocrine System Overview
Consists of ductless glands
Secrete hormones directly into bloodstream
Affect the function of specific body organs
Regulates many intricate body functions

4. Messenger Molecules
Cells must communicate with one another to coordinate cell processes within tissues and to maintain homeostasis.
Cell-to-cell communication is carried out via messenger molecules.

5. Three types of chemical signals are used for cell-to-cell communication.

6. Four methods of cell-to-cell communication are found in the human body, ranging from direct to remote communication.

7. Endocrine hormones
Produced by endocrine (“ductless”) glands and secreted into the bloodstream.
Endocrine hormones may affect a wide array of target cells to produce multiple effects.
Two types: peptides (small proteins) and steroids (lipids).

8. Hormones and Receptors

9. Peptide Hormones
Peptide hormones do not enter the cell directly. These hormones bind to receptor proteins in the cell membrane.
When the hormone binds with the receptor protein, a secondary messenger molecule initiates the cell response.
Because peptide hormones are water soluble, they often produce fast responses.

10. peptide or amino
acid-derived
hormone
(first messenger)
Hormone–receptor binding
activates an enzyme that catalyzes
the synthesis of a second messenger,
such as cyclic AMP 2
The hormone binds to
a receptor on the plasma
membrane of a target cell 1
cyclic AMP-
synthesizing
enzyme
(cytoplasm)
(extracellular
fluid)
ATP
active
enzyme
receptor
product
cyclic AMP
(second messenger) 4
The activated enzymes
catalyze specific reactions
plasma membrane
inactive
enzyme
reactant
The second
messenger activates
other enzymes 3
nuclear
envelope
(nucleus)

11. Steroid Hormones
Steroid hormones enter through the cell membrane and bind to receptors inside of the target cell.
These hormones may directly stimulate transcription of genes to make certain proteins.
Because steroids work by triggering gene activity, the response is slower than peptide hormones.

12. steroid hormone
(extracellular
fluid)
The hormone binds to a
receptor in the nucleus or to
a receptor in the cytoplasm
that carries it into the nucleus 2
The hormone–receptor
complex binds to DNA and
causes RNA polymerase to
bind to a nearby promoter
site for a specific gene 3
A steroid hormone
diffuses through the
plasma membrane 1
DNA
plasma
membrane
hormone receptor
ribosome
RNA polymerase
The mRNA leaves the
nucleus, then attaches to a
ribosome and directs the
synthesis of a specific protein
product 5
RNA polymerase catalyzes
the transcription of DNA into
messenger RNA (mRNA) 4
mRNA
new protein
gene
nuclear
envelope
(cytoplasm)
(nucleus)

13. Hormones Everywhere!
Many other organs besides the endocrine glands produce hormones.
Kidneys produce several hormones that regulate blood pressure, which is essential for kidney function.
The digestive system produces several hormones that regulate appetite.

15. Role of the Hypothalamus
The thalamus receives sensory information, relays some to the hypothalamus.
Hypothalamus monitors the body for temperature, pH, other conditions.
Hypothalamus signals pituitary gland if conditions need to be corrected.

16. Pituitary Gland Referred to as “master gland”
Secretes hormones that control functions of other glands
Known as hypophysis
Has two distinct lobes with specific functions

17. Role of the Pituitary
The pituitary is the “master gland” that signals other glands to produce their hormones when needed.
The anterior lobe of the pituitary receives signals from the hypothalamus, and responds by sending out the appropriate hormone to other endocrine glands.
The posterior pituitary receives oxytocin or antidiuretic hormone (ADH) from the hypothalamus, relays them to the body as necessary.

18. Pituitary Gland Anterior Pituitary Gland = Adenohypophysis
Secretes Growth Hormone (GH)
Also called Somatotropic Hormone (STH)
Regulates growth of bone, muscle, and other body tissues
Secretes Adrenocorticotropic Hormone (ACTH)
Stimulates normal growth and development of adrenal cortex and secretion of corticosteroids

19. Pituitary Gland Anterior Pituitary Gland
Secretes Thyroid-Stimulating Hormone (TSH)
Promotes and maintains normal growth and development of the thyroid gland
Stimulates secretions of the thyroid hormones
Secretes Lactogenic Hormone (LTH)
Also called Prolactin
Promotes development of breasts during pregnancy
Stimulates secretion of milk from breasts after delivery of baby

20. Pituitary Gland Anterior Pituitary Gland
Secretes Follicle-Stimulating Hormone (FSH)
Stimulates secretion of estrogen and production of eggs in the female ovaries
Stimulates production of sperm in the male testes
Secretes Luteinizing Hormone (LH)
Stimulates female ovulation and the secretion of testosterone in the male
Melanocyte-Stimulating Hormone (MSH)
Controls intensity of pigmentation in pigmented cells of the skin

21. Pituitary Gland Posterior Pituitary Gland = Neurohypophysis
Secretes Antidiuretic Hormone (ADH)
Decreases excretion of large amounts of urine
Increases reabsorption of water by the renal tubules
Secretes Oxytocin (OT)
Stimulates contraction of the uterus during childbirth
Stimulates release of milk from the breasts of lactating women in response to the suckling reflex of the infant

22. Hypothalamus
Located below the thalamus and above the pituitary gland (=epiphysis)
Regulates the pituitary gland secretions through two different mechanisms

23. Hypothalamus - neurohypophysis
1- Neurons, receiving information from receptors, fire APs which travel down to the post pituitary gland and stimulate the release of stored neurohormones – Oxytocin (OT) and anti-diuretic hormone (ADH)

24. Hormones of the posterior pituitary
Regulation
Hormone
Target organ
Action
Pathology
Reflex
Oxytocin
- Uterus (smooth muscle)
- breast tubules (smooth muscles)
labor and delivery
- milk-let down --
Reflex (osmoreceptor)
ADH
(vasopressin)
- DCT in kidney tubules
- promote H2O reabsorption
- not enough: diabetes insipidus
- too much: ↑ BP?

25. Hypothalamus – adenohypophysis
2- Upon stimulation, secretory cells located in the hypothalamus secrete “releasing” hormones which travel down a capillary bed toward the anterior pituitary gland (adenopituitary). Each type of releasing hormones will stimulate the secretion and release of a pituitary hormone.
Hormones which control the secretion of other hormones are tropic hormones (found in hypothalamus and pituitary gland)

26. Anterior pituitary Regulation Hormone Target organ Action Pathology
GHRH and GHIH
Growth hormone (GH)
Many cells (bones..)
Stimulate cell growth and cell division
- not enough: children  pituitary dwarfism
too much: gigantism (children) – acromegaly (adult)
PRH - PIH
Prolactin (PL)
Breast secretory cells
- milk secretion --
TRH
Thyroid stimulating hormone (TSH)
Thyroid gland
- promote thyroid gland secretion (T3 and T4)
- not enough: hypothyroidism (cretinism in children)
- too much: hyperthyroidism
CRH
Adrenocorticotropic hormone (ACTH)
Adrenal cortex (3 layers)
- stimulates secretion of adrenal cortex
- not enough: Addison's disease
- too much: Cushing syndrome
GnRH
Gonadotropin
- Follicle stimulating hormone (FSH)
- Luteinizing hormone (LH)
Stimulate gamete maturation
Stimulate gonadal gland secretion and gamete formation
- infertility
Figure 6.8

27. Pituitary Hormones Pituitary Hormone Functions
Follicle-stimulating hormone
Stimulates egg maturation in the ovary and release of sex hormones.
Lutenizing hormone
Stimulates maturation of egg and of the corpus luteum surrounding the egg, which affects female sex hormones and the menstrual cycle.
Thyroid-stimulating hormone
Stimulates the thyroid to release thyroxine.
Adrenocorticotropic hormone
Causes the adrenal gland to release cortisol.
Melanocyte-stimulating hormone
Stimulates synthesis of skin pigments.
Growth hormone
Stimulates growth during infancy and puberty.
Antidiuretic hormone
Signals the kidney to conserve more water.
Oxytocin
Affects childbirth, lactation, and some behaviors.

28. Mechanism of control
Figure 6.6

29. Hormones of the hypothalamus and anterior pituitary gland
Figure 6.5

30. Pineal Gland Tiny, pinecone-shaped gland
Located behind dorsal aspect of midbrain region
Plays a part in supporting body’s biological clock
Regulation of patterns of eating, sleeping, and reproduction
Secretes melatonin
Induces sleep

31. Thyroid Gland
Located in front of the neck just below the larynx, on either side of the trachea
Consists of a right and left lobe

32. Thyroid Gland Secretes Triiodothyronine (T3)
Helps regulate growth and development of body
Helps control metabolism and temperature
Secretes Thyroxine (T4)
Helps maintain normal body metabolism
Secretes Calcitonin
Helps regulate the level of calcium in the blood

33. The thyroid gland Located in the neck, just below the larynx
Secrete 2 types of hormone:
- thyroid hormones  stimulate cell metabolism, triiodothyronine (T3) and thyroxine (T4) – iodine is needed to synthesize these hormones
- calcitonin  decrease blood calcium
Figure 6.8a

34. Thyroid hormones T3 and T4 secreted by the follicular cells
Stored as colloid
Parafollicular cells (C cells) secrete calcitonin

35. Thyroid Hormones T3 and T4
Target organs: all cells
Role: Increase cell metabolism, oxygen consumption
Permissive role for some other hormones (growth hormone)

36. Thyroid hormone regulation
Figure 6.7

37. Parathyroid Glands
Four tiny rounded bodies located on dorsal aspect of thyroid gland
Secrete Parathyroid Hormone (PTH)
Also known as parathormone
Regulates level of calcium in blood

38. Parathyroid glands
Four nodules located in the back of the thyroid gland
Secreted parathyroid hormone or parathormone or PTH
Action of PTH opposes action of calcitonin
Both hormones play a role in calcium metabolism, regulating the level of calcium in blood.

39. Roles of calcium Most calcium ions are stored in the bones
Calcium is an important cofactor for enzymatic activity, plays a role in blood coagulation and action potentials.
Calcitonin and PTH participate in calcium regulation
Vitamin D helps PTH activity

40. Calcium regulation: Calcitonin promotes blood calcium decrease, by:
1. calcium deposition on bone
2. calcium dumping by the kidney
PTH promotes blood calcium increase by:
1. bone resorption
2. calcium reabsorption by kidney
3. increase calcium absorption by intestine

41. Figure 23-20: Calcium balance in the body
Calcium Metabolism:
Figure 23-20: Calcium balance in the body

42. Figure 19.20

43. Thymus
Single gland located in mediastinum near the middle of the chest, just beneath sternum
Large in fetus and infants, shrinks with age
Secretes thymosin and thymopoietin
Stimulates production of T cells that are involved in the immune response

44. Adrenal Glands Two small glands, one positioned atop each kidney
Also known as suprarenal glands
Consists of an adrenal cortex and an adrenal medulla
Each has independent functions

45. Adrenal Glands Adrenal cortex secretes corticosteroids
Mineralocorticoids
Regulate how mineral salts (electrolytes) are processed in the body
Glucocorticoids
Influence metabolism of carbohydrates, fats, and proteins in the body
Necessary for maintaining normal blood pressure
Have an anti-inflammatory effect on the body
Increase glucose available during “fight-or-flight” responses by the body

47. Adrenal Glands Adrenal cortex secretes Gonadocorticoids
Sex hormones secreted in small amounts
Contribute to secondary sex characteristics in males and females

48. Adrenal Glands Adrenal medulla secretes catecholamines
Epinephrine = adrenaline
Sympathiomimetic agent
Increases heart rate and force of heart muscle contraction
Dilates bronchioles in the lungs
Decreases peristalsis in the intestines
Raises blood glucose levels by causing the liver to convert glycogen into glucose

49. Adrenal Glands Adrenal medulla secretes Norepinephrine = noradrenaline
Known as a sympathomimetic agent
Produces a vasoconstrictor effect on the blood vessels, thereby raising blood pressure

50. Adrenal gland hormones
Regulation
Glands
Hormones
Target organs
Action
Pathology
Reflex
Adrenal medulla
Epinephrine
ANS target organs
Fight/flight
Stress
Blood Pressure
Adrenal cortex
- Mineralocorticoid = aldosterone
DCT from renal tubule
- promote sodium reabsorption
Not enough" Addison disease
CRH  ACTH
Glucocorticoid = cortisone
Many cells
Mobilize fuels – stress adaptation
Excess hormone: Cushing syndrome
GnRH  GN
Estrogen
Testosterone
Sexual organs
- Sex organ maintenance
- Gamete development
Infertility

51. Pancreas Elongated gland located in upper left quadrant of the abdomen
Behind the stomach
Extends horizontally across the body
Beginning at first part of small intestines and ending at edge of spleen
Contains exocrine and endocrine glands
The endocrine function is due to the cells of the islets of the Langerhans
-- α cells  glucagon
-- β  insulin
-- δ  somatostatin

52. The pancreas

53. Pancreas Islets of Langerhans secrete: Glucagon Insulin
Increases blood glucose levels by stimulating liver to convert glycogen into glucose when blood sugar is extremely low
Insulin
Makes it possible for glucose to pass from blood through cell membranes to be used for energy
Promotes conversion of excess glucose into glycogen for storage in the liver for later use

54. Glucose regulation Glucose level controlled by insulin and glucagon
Insulin promotes a decrease in blood glucose
Glucagon promotes an increase in blood glucose

55. Glucose regulation

56. Fate of glucose
Figure 3.21

57. Diabetes mellitus
Type I: autoimmune disease  beta cells of the islets of Langerhans are destroyed by antibodies
Type II: The cells become insulin-resistant  glucose does not enter the cells as readily

58. Ovaries Female sex glands = female gonads Pair of almond shaped glands
Located in upper pelvic cavity, on either side of lateral wall of uterus
Near fimbriated ends of the fallopian tubes
Responsible for producing mature ova and releasing them at monthly intervals during ovulation

59. Ovaries Hormones secreted by the ovaries Estrogen
Promotes maturation of ovum in the ovary
Stimulates vascularization of uterine lining each month to prepare for implantation of a fertilized egg
Contributes to secondary sex characteristic changes in female with onset of puberty
Progesterone
Primarily responsible for changes within the uterus in anticipation of a fertilized ovum
Responsible for development of maternal placenta after implantation of a fertilized ovum

60. Testes Testes = male gonads = testicles
Two small ovoid glands located in scrotum
Primary organs of male reproductive system
Responsible for production of sperm and secretion of androgens (male steroid hormones)
Secrete testosterone
Responsible for secondary sex characteristic changes that occur in male with onset of puberty
Responsible for maturation of sperm

61. Endocrine Hormones Gland Hormones Functions Thyroid Thyroxine
Regulates metabolism
Calcitonin
Inhibits release of calcium from the bones
Parathyroids
Parathyroid hormone
Stimulates the release of calcium from the bones.
Islet cells (in the pancreas)
Insulin
Decreases blood sugar by promoting uptake of glucose by cells.
Glucagon
Increases blood sugar by stimulating breakdown of glycogen in the liver.
Testes
Testosterone
Regulates sperm cell production and secondary sex characteristics.
Ovaries
Estrogen
Stimulates egg maturation, controls secondary sex characteristics.
Progesterone
Prepares the uterus to receive a fertilized egg.
Adrenal cortex
Epinephrine
Stimulates “fight or flight” response.
Adrenal medulla
Glucocorticoids
Part of stress response, increase blood glucose levels and decrease immune response.
Aldosterone
Regulates sodium content in the blood.
Testosterone (in both sexes)
Adult body form (greater muscle mass), libido.
Pineal gland
Melatonin
Sleep cycles, reproductive cycles in many mammals.

62. Homeostasis and Hormones
Examples:
Thyroid and temperature control
Thyroid, Parathyroid, and calcium
Pancreas and glucose control

63. Temperature Control