1. Chapter 10
The Endocrine System

2. The Endocrine System FIGURE 10.2
The endocrine system. The endocrine system is made up of endocrine glands and of organs that contain some endocrine tissue. Here, the hormones are listed under the endocrine gland or organ that produces them.

3. Endocrine System Characteristics
Each hormone acts only on specific cells (target cells)
Only target cells have receptors for specific hormones
Endocrine control slower than nervous system
Endocrine and nervous systems complement each other

4. Endocrine Functions: Hormones
Come from endocrine glands
Circulate in the blood stream
Act on specific cells in the body

5. FIGURE 10.1b
Exocrine and endocrine glands. (a) Exocrine glands, such as this oil gland, secrete their products into ducts. (b) Endocrine glands release their products, called hormones, into the fluid just outside cells. The hormones then diffuse into the bloodstream to be transported throughout the body.

6. Exocrine Gland Figure: 10-01a Title: Exocrine glands. Caption:
(a) Exocrine glands secrete their products into ducts that open onto the surface of the body, into the spaces within organs, or into cavities within the body.

7. Classification of Hormones: Steroid Hormones

8. Lipid-soluble and water-soluble hormones interact differently with target cells
Steroid Hormones:
Lipid soluble, chemically derived from cholesterol
Bind to receptors inside target cells
Activate specific genes to produce specific proteins

9. How Steroid Hormones Act
FIGURE 10.3
Mode of action of steroid hormones

10. Characteristics of Non-steroid Hormones
Water soluble
Bind to receptors on target cell membranes
Work through intermediate mechanisms (second messengers) to activate existing enzymes
Faster action than steroid hormones; time to action = seconds to minutes

11. How water-soluble hormones act FIGURE 10.4
Mode of action of some water-soluble hormones: the second messenger system of cAMP. Because water-soluble hormones cannot cross the plasma membrane, they must affect the activities of target cells indirectly.

12. Hormone Receptors All hormones work through receptors
Target cells (and only target cells) for a hormone contain receptors for that hormone
Example: Estrogen Receptor Knockout (ERKO) mouse (and human)

13. In order for a hormone to work on a cell (or tissue):
Receptors are useful but not essential
Receptors for that hormone must be present

14. FIGURE 10.6
The two lobes of the pituitary gland and the hormones they secrete

15. Feedback mechanisms regulate the secretion of hormones
Refer to in-class worksheet

16. Hypothalamus and Pituitary Glands
Hormones from the hypothalamus regulate the pituitary gland
Neurosecretory cells: part neuron; part endocrine organ
Pituitary hormones often prompt other glands to release hormones

17. FIGURE 10.5a
Location and structure of the pituitary gland. (a) Side view of the pituitary gland. (b) Close-up of the pituitary gland showing how it is attached to the hypothalamus by a short stalk.

18. FIGURE 10.5b
Location and structure of the pituitary gland. (a) Side view of the pituitary gland. (b) Close-up of the pituitary gland showing how it is attached to the hypothalamus by a short stalk.

19. The Hypothalamus and Anterior Pituitary Gland
Connection to hypothalamus: releasing (and inhibiting) hormones from hypothalamus travel to pituitary through pituitary portal vessels
No nerve connection to hypothalamus

20. FIGURE 10.6
The two lobes of the pituitary gland and the hormones they secrete

21. Neurosecretory Cells From the Hypothalamus Control the Pituitary

22. True/False
Neurosecretory cells have characteristics of both hormone secreting cells and neurons

23. Hormones of the Pituitary Gland

24. Hypothalamus and the Posterior Pituitary Gland
Connection to hypothalamus: hormones made in hypothalamus, stored in posterior pituitary
Neurosecretory cells project to post. pit.

26. Hypothalamus and the Posterior Pituitary Gland
Posterior pituitary Hormones (protein)
Antidiuretic hormone (ADH): conserves water in kidneys, regulates water balance in body
Regulated by:
High/Low water intake
Alcohol

27. Hypothalamus and the Posterior Pituitary Gland
Posterior pituitary Hormones (protein)
Oxytocin induces:
Uterine contractions during labor
Milk ejection through neuroendocrine reflex
Behavioral Effects: Love/Trust/Bonding

28. Oxytocin
FIGURE 10.10
The steps by which OT stimulates uterine contractions during childbirth

29. Oxytocin Human Sexual Response:
Oxytocin may have a role in sexual arousal, orgasm & sexual satiety/satisfaction
CNS: Penile erection, copulatory behavior
Trust/Love
Pair bonding
Maternal Behavior:
Oxytocin induces maternal behavior in female rats

30. Oxytocin
FIGURE 10.11
The steps by which OT stimulates milk ejection from the mammary glands

31. Oxytocin and ADH (antidiuretic hormone)
Are synthesized and released from the anterior pituitary gland
Are synthesized and released from the posterior pituitary gland

32. Posterior Pituitary Disorder
Diabetes Insipidus: hyposecretion of ADH, inability to conserve water appropriately

33. Anterior Pituitary Disorders
Gigantism: hypersecretion of growth hormone (during growth phase)
Pituitary Dwarfism: hyposecretion of growth hormone (during growth phase)

34. FIGURE 10.7
Robert Wadlow, a pituitary giant, was born in 1918 at a normal size but developed a pituitary tumor as a young child. The tumor caused increased production of GH. Robert never stopped growing until his death at 22 years of age, by which time he had reached a height of 8 feet 11 inches.

36. Anterior Pituitary Disorders
Acromegaly: hypersecretion of growth hormone after bones have stopped growth

37. Acromegaly Symptoms Bony changes alter facial features:
The brow and lower jaw protrude
Spacing of the teeth increases
Enlarged jaw (prognathism), lips, nose & tongue

38. Acromegaly Symptoms Enlarged hands and/or feet
Soft tissue swelling of the hands & feet is often an early feature, with patients noticing a change in ring or shoe size
Widened fingers or toes due to skin overgrowth with swelling, redness, & pain

39. Why is Growth Hormone an Abused Drug?
Role of GH in Normal Adults
Increases muscle growth
Decreases fat stores

40. Thyroid Gland

41. FIGURE 10.12a
Location and structure of the thyroid gland and parathyroid glands. (a) The thyroid gland lies over the trachea, just below the larynx. (b) Section through thyroid tissue. Note the follicular cells that produce the precursor to thyroid hormone. (c) Diagram showing structure of thyroid tissue. In addition to the follicular cells, note the parafollicular cells, which produce CT.

42. Thyroid Gland Secretes thyroid hormones:
Thyroxine (T4) and Triiodothyronine (T3)

43. Thyroid Gland
Secretion: regulated by hypothalamus (TRH) & pituitary (TSH) hormones
Action of T4 & T3
Increase metabolic rate & heat prodn.
Development of fetal nervous system (cretinism results from lack of T4 & T3)

44. Disorders of the Thyroid Gland
Hypothyroidism:
Children: cretinism
Adults: myxedema
Low BMR, Lethargy, Weight gain, Low body temp.
Hyperthyroidism: Graves Disease
Increased BMR
Hyperactivity, nervousness, agitation
Weight loss
Exophthalmos

45. Hypothyroidism and Goiter
Causes of Goiter
Low iodide intake
Genetic mutation
Diet
Direct cause is
excess TSH secretion

47. Low Iodide Goiter

48. Goiters can be caused by:
Too little iodide in the diet
Too much iodide in the diet

49. Too little iodide in the diet causes a goiter because:
Not enough T3/T4 is produced
Not enough negative fdbk of T3/T4 on the pituitary/hypothalamus
Excess secretion of TSH (Thyroid Stimulating Hormone)

50. The factor that most often is the direct stimulus that causes a goiter is excess:
Iodide
T3/T4
TSH (Thyroid Stimulating Hormone)

51. Exophthalmos and Hyperthyroidism
Exophthalmos is caused by oversecretion of the thyroid hormone which leads to accumulation of fluid behind the eyes causing the eyes to bulge out.

52. Hyperthyroidism Patient
Normal

53. Hypothyroidism and Cretinism
Cretinism is characterized by mental retardation, dwarfism and delayed
sexual development and is caused by undersecretion of thyroid hormone during fetal life or infancy.