1. Chapter 13 Endocrine System
Endocrine glands are ductless
Exocrine glands have ducts

2. Major Endocrine Glands

3. General Characteristics
Includes the cells, tissues, and organs that secrete hormones into body fluids
The exocrine system secretes into tubes or ducts which lead to internal or external body surfaces
Ex: sweat and sebaceous glands

4. Endocrine glands and their hormones help regulate metabolic processes: control the rates of some chemical reactions, aid in transporting substances through cell membranes, and help regulate water balance, electrolyte balance, and blood pressure.
Play vital roles in reproduction, development, and growth

5. Comparison of Nervous System and Endocrine System
Neurons release neurotransmitters into a synapse, affecting postsynaptic cells
Glands release hormones into the bloodstream
Only target cells of hormone responds

6. Comparison of Nervous System and Endocrine System

7. Hormone Types
A hormone is a biochemical secreted by a cell that affects the function of another cell.
Five general types: steroids, amines, peptides, protein hormones, glycoproteins (last four are also called nonsteroidal)

8. Steroids
lipids that include complex rings of carbon and hydrogen atoms
derived from cholesterol
ex: estrogen and testosterone

9. Amines Derived from amino acids Produced by neurons
Ex: epinephrine and norepinephrine
Also synthesized from the adrenal medulla from tyrosine

10. Peptides Short chains of amino acids
Ex: oxytocin and antidiuretic hormone

11. Protein hormones Long chains of amino acids
Ex: growth hormone and parathyroid homone

12. Glycoprotiens A protein joined to a carbohydrate
Ex: follicle-stimulating hormone

13. Types of Hormones

14. Prostoglandins
Paracrine substances that regulate only neighboring cells (local action)
Lipids that are made from a type of fatty acid
Found in the liver, kidneys, heart, lungs, thymus, pancreas, brain, and reproductive organs
Regulates the formation of cAMP (2nd messenger)

15. Actions of hormones
Hormones bind to specific receptors on target cells
Each hormone receptor is a protein or glycoprotein that has a binding site for a specific hormone
The more receptors a hormone binds, the greater the cellular response

16. Steroid hormones Soluble in cell membranes
Can diffuse easily into target cells
Once inside they bind to receptors (usually in the nucleus)

17. Specific genes are activated which are transcribed into mRNA
mRNA goes to the cytoplasm and directs the synthesis of specific proteins
Proteins then cause the cellular changes associated with the hormone

18. Actions of Steroid Hormones
hormone crosses membranes
hormone combines with receptor in nucleus
synthesis of mRNA activated
mRNA enters cytoplasm to direct synthesis of protein

19. Nonsteroid hormones
Combines with specific receptors on the target cell membrane
Receptor binding alters the function of enzymes or membrane transport mechanisms which changes the concentration of other cellular components
The first messenger is the hormone that triggers the activity

20. Second messengers are the biochemicals that cause the changes in response to the hormones
Many hormones use cyclic AMP as a second messenger
Many second messenger molecules can be activated in response to just a few hormone-receptor complexes
Cells are highly sensitive to changes in the concentration of nonsteroid hormones

21. Actions of Nonsteroid Hormones
hormone binds to receptor on cell membrane
ATP converted to cAMP
cAMP acts as a 2nd messenger
cAMP promotes a series of reactions leading to cellular changes
Takes place in cytoplasm

22. Actions of Nonsteroid Hormones

23. Control of Hormonal Secretions
primarily controlled by negative feedback mechanism

24. Negative Feedback

25. Major Endocrine Glands

26. Pituitary Gland About 1 cm in diameter
Attached to the hypothalmus by the pituitary stalk (infundibulum) and lies in the stella turcica of the sphenoid bone
Consists of an anterior lobe (adenohypophysis) and a posterior lobe (neurohypophysis)
Anterior lobe secretes GH, TSH, ACTH, FSH LH, and PRL

27. Posterior lobe cells (pituicytes) do not synthesize any hormones
ADH and OT are secreted by the nerve endings of special neurons into the bloodstream in posterior lobe
Cell bodies of neurosecretory cells are in the hypothalmus

28. Substances secreted by the hypothalmus are carried directly to the anterior lobe
hypothalmus is an endocrine gland and it also controls other endocrine glands
Anterior pituitary also controls other endocrine glands

29. Most hypothalmic releasing hormones act on specific cells of the anterior pituitary(AP)
some actions are inhibitory
most stimulate the AP to release hormones that then stimulate other endocrine gland secretions
negative feedback regulates hormone levels in the bloodstream – fig 13.8 page 496

30. Pituitary Gland Two distinct portions
anterior pituitary (adenohypophysis)
posterior pituitary (neurohypophysis)

31. Pituitary Gland Control
Hypothalamic releasing hormones stimulate cells of anterior pituitary to release hormones
Nerve impulses from hypothalamus stimulate nerve endings in the posterior pituitary gland to release hormones

32. Anterior Pituitary Hormones
AP lobe is enclosed in a dense capsule of connective tissue and consists of epithelial tissue arranged around
thin blood vessels
Five types of secretory cells within the epithelial tissue
Table 13.6 page 503

33. Posterior Pituitary Hormones
Posterior lobe consists mainly of nerve fibers and neuroglial cells (pituicytes)
Pituicytes support nerve fibers that originate in the hypothalmus
Table 13.6 page 503

34. Hormones of the Pituitary Gland

35. Hypothalamic Hormones

36. Thyroid Gland Very vascular
Made of 2 large lateral lobes connected by a broad isthmus
Located just below the larynx on either side and anterior to the trachea
Removes iodine from the blood

37. Structure of the thyroid gland
It is covered by connective tissue made of follicles (secretory parts)
Follicles produce and secrete hormones
Extrafollicular cells(C cells) lie outside the follicles
Center filled with a clear viscous glycoprotein called colloid

38. Thyroid Gland

39. Thyroid Hormones
Follicular cells synthesize thyroxine (T4)and triiodothyronine (T3) which affect the metabolic rates of cells
Follicular cells need iodine salts to produce T3 and T4
thyroid enlarges (goiter) if not enough iodine
C cells produce calcitonin

40. Thyroid Gland Hormones

41. Disorders of the Thyroid Gland

42. Disorders of the Thyroid Gland
Graves Disease
Hyperthyroidism
Cretinism
Infantile hypothyroidism

43. Parathyroid Gland
Located on the posterior surface of the thyroid gland
Usually 4 of them
Each gland is a small, yellowish brown structure covered by a thin capsule of connective tissue
Body consists of many tightly packed secretory cells associated with capillary networks

44. Parathyroid Glands

45. Parathyroid Hormone
PTH increases blood calcium ion concentration and decreases blood phosphate ion concentration through actions in the bones, kidneys, and intestines
PTH stimulates bone resorption by osteocytes and osteoclasts
Ca and PO4 ions are released into blood

46. PTH causes kidneys to conserve blood Ca ions and excrete more PO4 ions in the urine
PTH helps kidneys convert Vitamin D into an active form which controls the absorption of Ca ions from the intestines

47. Parathyroid Hormone

48. Parathyroid Hormone
Mechanism by which PTH promotes calcium absorption in the intestine

49. Disorders of the Parathyroid Glands

50. Adrenal Glands Sits atop each kidney
Embedded in adipose tissue that encloses each kidney

51. Structure of the Adrenal Glands
Shaped like pyramids
Very vascular
Consists of a central portion (adrenal medulla) and an outer portion (adrenal cortex)

52. Adrenal Glands

53. Hormones of the Adrenal Medulla
Impulses arriving on the sympathetic nerve fibers stimulate the adrenal medulla to release its hormones
These impulses originate in the hypothalamus in response to stress
Hormones work with the sympathetic division of the autonomic NS to prepare for energy expending action (fight or flight)

54. Two closely related hormones, epinephrine (adrenalin) and norepinephrine (noradrenalin)
Ratio of the 2 is usually about 80% epinephrine secreted and 20% norepinephrine
Effects of the two are similar, but certain effectors respond differently to them
Table page 510 – functions

55. Hormones of the Adrenal Medulla

56. Hormones of the Adrenal Cortex
Cells of the adrenal cortex produce more than 30 steroids, including several hormones (corticosteroids)
Some are vital for survival
The 3 most important adrenal cortical hormones are aldosterone, cortisol, and adrenal androgens

57. Hormones of the Adrenal Cortex
Table page 512 – functions
- Aldosterone helps maintain Na ion concentration and
blood volume
- Cortisol helps keep blood glucose concentration
normal between meals
ACE inhibitors treat high blood pressure – page 511
Cortisol (hydrocortisone) and related compounds are used to reduce inflammation – page 513

58. Hormones of the Adrenal Cortex

59. Hormones of the Adrenal Cortex

60. Hormones of the Adrenal Cortex

61. Pancreas
Functions as an exocrine gland that secretes digestive fluid through a duct
Functions as an endocrine gland that releases hormones into body fluids

62. Structure of the Pancreas
Elongated and somewhat flattened
Posterior to the stomach and behind the parietal peritoneum
Attached to the first section of the small intestine

63. Endocrine portion consists of groups of cells called islets of Langerhans that have 3 types of hormone secreting cells
alpha cells – secrete glucagons
beta cells – secrete insulin
delta cells – secrete somatostatin

64. Pancreas

65. Hormones of the Islets of Langerhans
Table Page 515
Insulin and glucagon function together to help maintain a relatively stable blood glucose concentration
Negative feedback controls both hormones Fig Page 514
Diabetes Mellitus – clinical application page 516

66. Hormones of the Pancreatic Islets

67. Insulin and Glucagon
Insulin and glucagon function together to stabilize blood glucose concentrations

68. The Pancreas
Endocrine portion consists of groups of cells called islets of Langerhans
Insulin is produce by beta cells
Insulin is needed in order for glucose to enter cells (it lowers blood glucose concentration)
Glucagon is produced by alpha cells
Glucagon increases blood glucose concentration

69. Diabetes Characterized by hyperglycemia (high blood sugar)
Type I caused when the beta cells do not produce enough insulin
Type II is caused by body cell receptors that do not respond to insulin (insulin resistance)

70. Type I Diabetes Can be controlled by insulin injections or pump
Is an autoimmune disease – body’s own immune system attacks and destroys beta cells
Less than 10% of diabetics have this type
Often develops in children or young adults but can develop in people of any age

71. Type II Diabetes Controlled by diet (medication also possible)
90% of diabetics have this type
Often associated with genetic history, obesity, lack of exercise, advanced age, or certain ethnic groups (ex. Native Americans)

72. Uncontrolled Diabetes
Can cause damage to the retina leading to blindness
Can cause kidney failure
Can cause nerve damage
Increases the risk of cardiovascular disease
Can cause poor wound healing
Can damage blood vessels and lead to poor circulation

73. Pineal Gland Small oval structure
Located deep between the cerebral hemispheres where it is attached to thalamus

74. Secretes melatonin which regulates circadian rhythms (repeated cycles of day and night)
sleep/wake cycles
seasonal cycles of fertility in many mammals
helps regulate human female menstrual cycle
may control the onset of puberty

75. Thymus Gland Located posterior to the sternum between the lungs
Large in children but gets smaller with age
Secretes thymosins that affect production and differentiation of certain white blood cells (T lymphocytes)
Important role in immunity

76. Reproductive Glands Ovaries secrete estrogen and progesterone
Placenta produces estrogens, progesterone, and a gonadotropin
Testes produce testosterone

77. Digestive Glands
- Secrete hormones associated with the linings of the stomach and small intestines
Other Hormone Producing Organs
Heart
Kidneys

78. Stress and Its Effects
Stressors are factors that cause increased activity of the sympathetic NS in an attempt to maintain homeostasis
Stress is the condition stressors produce in the body

79. Types of Stress 1. Physical – threatens tissues
Ex: extreme heat or cold, decreased O2 concentration, injuries, infections, prolonged heavy exercise, loud sounds

80. 2. Psychological – results from thoughts about real or imagined dangers, personal losses, unpleasant social interactions, or any factors that threaten a person
may also stem from pleasant stimuli
factors vary from person to person
3. Combination of physical and psychological

81. Response to Stress Controlled by the hypothalamus
Called the general stress (adaptation) syndrome
Attempts to maintain homeostasis
Fight or flight response is activated

82. Fight or Flight and General Stress Syndrome
Fig Page 518
Table Page 519 – major events

83. Responses to Stress

84. Stress

85. Life-Span Changes endocrine glands decrease in size
muscular strength decreases as GH levels decrease
ADH levels increase due to slower break down in liver and kidneys
calcitonin levels decrease; increase risk of osteoporosis
PTH level changes contribute to risk of osteoporosis
insulin resistance may develop
changes in melatonin secretion affect the body clock
thymosin production declines increasing risk of infections

86. Clinical Application Growth Hormone Ups and Downs
Gigantism - hypersecretion of GH in children
Acromegaly – hypersecretion of GH in adults
Dwarfism – hyposecretion of GH in children
Figure shows oversecretion of GH in adulthood as changes occur in the same person at ages (a) nine, (b) sixteen, (c) thirty-three, and (4) fifty-two