1. The Endocrine System and Hormone Function--An Overview Define hormone and target organ. Describe how hormones bring about their effects in the body. Explain how various endocrine glands are stimulated to release their hormonal products. Define negative feedback and describe its role in regulating blood levels of the various hormones. The Major Endocrine Organs Describe the difference between endocrine and exocrine glands. On an appropriate diagram, identify the major endocrine glands and tissues. List hormones produced by the endocrine glands and discuss their general functions. Discuss ways in which hormones promote body homeostasis by giving examples of hormonal actions. Describe the functional relationship between the hypothalamus and the pituitary gland. Describe major pathological consequences of hypersecretion and hyposecretion of the hormones considered in this chapter. Other Hormone-Producing Tissues and Organs Indicate the endocrine role of the kidneys, the stomach and intestine, the heart, and the placenta.

2. Define hormone and target organ
Hormone: A chemical substance produced in the body that controls and regulates the activity of certain cells or organs.
Target organ: A tissue or organ upon which a hormone exerts its action; generally, a tissue or organ with appropriate receptors for a hormone.

3. Describe how hormones bring about their effects in the body.
Changes in plasma membrane permeability or electrical state
Synthesis of proteins, such as enzymes
Activation or inactivation of enzymes
Stimulation of mitosis
Promotion of secretory activity

4. The Chemistry of Hormones
Hormones are classified chemically as
1. Amino acid–based, which includes
Proteins, Peptides, Amines
2. Steroids—made from cholesterol; sex hormones made by gonads & hormones of adrenal cortex
Local Hormones:
Prostaglandins—made from highly active lipids released by nearly all cell membranes

5. Direct Gene Activation (Steroid Hormone Action)
Diffuse through the plasma membrane of target cells
Enter the nucleus
Bind to a specific protein within the nucleus
Bind to specific sites on the cell’s DNA
Activate genes that result in synthesis of new proteins

6. Second-Messenger System (Nonsteroid Hormone Action)
Hormone binds to a membrane receptor
Hormone does not enter the cell
Sets off a series of reactions that activates an enzyme
Catalyzes a reaction that produces a second-messenger molecule
Oversees additional intracellular changes to promote a specific response

7. Explain how various endocrine glands are stimulated to release their hormonal products
Hormonal Stimuli- Endocrine glands are activated by other hormones
Humoral Stimuli-Changing blood levels of certain ions stimulate hormone release
3. Neural Stimuli-Nerve impulses stimulate hormone release; Most are under the control of the sympathetic nervous system

8. Hormonal Stimuli of Endocrine Glands
Most common stimuli
Endocrine glands are activated by other hormones
Examples:
Anterior pituitary hormones
Figure 9.2a

9. Humoral Stimuli of Endocrine Glands
Changing blood levels of certain ions stimulate hormone release
Humoral indicates various body fluids such as blood and bile
Examples:
Parathyroid hormone
Calcitonin
Insulin
Figure 9.2b

10. Neural Stimuli of Endocrine Glands
Nerve impulses stimulate hormone release
Most are under the control of the sympathetic nervous system
Examples include: the release of norepinephrine and epinephrine by the adrenal medulla
Figure 9.2c

11. Define negative feedback and describe its role in regulating blood levels of the various hormones.
Includes most homeostatic control mechanisms
Shuts off the original stimulus, or reduces its intensity
Hormone secretion is triggered by a stimulus or low hormone levels in the blood triggers the release of more hormone
Hormone release stops once an appropriate level in the blood is reached

12. Describe the difference between endocrine and exocrine glands.
Two major gland types
Endocrine gland
Ductless since secretions diffuse into blood vessels
All secretions are hormones
Exocrine gland
Secretions empty through ducts to the epithelial surface
Include sweat and oil glands

13. On an appropriate diagram, identify the major endocrine glands and tissues.

14. List hormones produced by the endocrine glands and discuss their general functions.
Pituitary gland
Thyroid gland
Parathyroid glands
Adrenal glands
Pineal gland
Thymus gland
Pancreas
Gonads (Ovaries and Testes)
Hypothalamus

18. Hormones of the Anterior Pituitary
Figure 9.4

19. Hormones of the Posterior Pituitary
Figure 9.6

20. Thyroid Gland Calcitonin Thyroid hormone
Decreases blood calcium levels by causing its deposition on bone
Antagonistic to parathyroid hormone
Produced by parafollicular cells
Parafollicular cells are found between the follicles
Thyroid hormone
Major metabolic hormone
Composed of two active iodine-containing hormones
Thyroxine (T4)—secreted by thyroid follicles
Triiodothyronine (T3)—conversion of T4 at target tissues
Figure 9.7a

21. Hormones of the Adrenal Cortex
Hormones of the Adrenal Medulla
Two similar hormones (catecholamines)
Epinephrine (adrenaline)
Norepinephrine (noradrenaline)
Hormones of the Adrenal Cortex
Mineralocorticoids (mainly aldosterone)
Glucocorticoids (cortisone and cortisol)
Sex hormones(Mostly androgens (male sex hormones) some estrogens (female sex hormones)
Figure 9.11

22. Hormones of the Adrenal Cortex
Mineralocorticoids (mainly aldosterone)
Produced in outer adrenal cortex
Regulate mineral content in blood
Regulate water and electrolyte balance
Target organ is the kidney
Production stimulated by renin and aldosterone
Production inhibited by atrial natriuretic peptide (ANP)
Figure 9.12

23. Hormones of the Adrenal Cortex
Glucocorticoids (including cortisone and cortisol)
Produced in the middle layer of the adrenal cortex
Promote normal cell metabolism
Help resist long-term stressors
Released in response to increased blood levels of ACTH

24. Hormones of the Adrenal Cortex
Sex hormones
Produced in the inner layer of the adrenal cortex
Small amounts are made throughout life
Mostly androgens (male sex hormones) are made but some estrogens (female sex hormones) are also formed

25. Hormones of the Adrenal Medulla
Produces two similar hormones (catecholamines)
Epinephrine (adrenaline)
Norepinephrine (noradrenaline)
These hormones prepare the body to deal with short-term stress (“fight or flight”) by
Increasing heart rate, blood pressure, blood glucose levels
Dilating small passageways of lungs

26. Roles of the Hypothalamus and Adrenal Glands in the Stress Response
Short term
More prolonged
Stress
Hypothalamus
Nerve impulses
Adrenal cortex
Releasing hormone
Corticotropic cells of anterior pituitary
ACTH
Mineralocorticoids
Glucocorticoids
Retention of sodium and water by kidneys
Increased blood volume and blood pressure
1. Proteins and fats converted to glucose or broken down for energy
2. Increased blood sugar
3. Suppression of immune system
Long-term stress response
Short-term stress response
Spinal cord
Adrenal medulla
Preganglionic sympathetic fibers
Catecholamines (epinephrine and norepinephrine)
1. Increased heart rate
2. Increased blood pressure
3. Liver converts glycogen to glucose and releases glucose to blood
4. Dilation of bronchioles
5. Changes in blood flow patterns, leading to increased alertness and decreased digestive and kidney activity
6. Increased metabolic rate
Figure 9.13

27. Pineal Gland Found on the third ventricle of the brain
Secretes melatonin
Helps establish the body’s wake and sleep cycles
Believed to coordinate the hormones of fertility in humans

28. Thymus Gland Located posterior to the sternum
Largest in infants and children
Produces thymosin
Matures some types of white blood cells
Important in developing the immune system

29. Pancreatic Islets
The pancreas is a mixed gland and has both endocrine and exocrine functions
The pancreatic islets produce hormones
Insulin—allows glucose to cross plasma membranes into cells from beta cells
Glucagon—allows glucose to enter the blood from alpha cells
These hormones are antagonists that maintain blood sugar homeostasis

30. Gonads Ovaries Testes Produce eggs
Produce two groups of steroid hormone
Estrogens
Progesterone
Testes
Produce sperm
Produce androgens, such as testosterone

31. Hormones of the Ovaries
Estrogens
Stimulate the development of secondary female characteristics
Mature female reproductive organs
With progesterone, estrogens also
Promote breast development
Regulate menstrual cycle
Progesterone
Acts with estrogen to bring about the menstrual cycle
Helps in the implantation of an embryo in the uterus
Helps prepare breasts for lactation

32. Hormones of the Testes Produce several androgens
Testosterone is the most important androgen
Responsible for adult male secondary sex characteristics
Promotes growth and maturation of male reproductive system
Required for sperm cell production

33. Discuss ways in which hormones promote body homeostasis by giving examples of hormonal actions.
Homeostasis—maintenance of a stable internal environment

34. Hormonal Regulation of Calcium in Blood
Calcium homeostasis of blood 9–11 mg/100 ml
Rising blood Ca2+
levels
Thyroid gland releases calcitonin
Osteoclasts degrade bone matrix and release Ca2+ into blood
PTH
Calcitonin
Calcitonin stimulates calcium salt deposit in bone
Parathyroid glands release parathyroid hormone (PTH)
Thyroid gland
Parathyroid glands
Falling blood Ca2+ levels
Imbalance
Figure 9.10

35. Hormonal Regulation of Blood Glucose

36. Describe the functional relationship between the hypothalamus and the pituitary gland.
Hormonal release by pituitary is regulated by releasing and inhibiting hormones produced by the hypothalamus
Hypothalamus produces two hormones
These hormones are transported to neurosecretory cells of the posterior pituitary
Oxytocin
Antidiuretic hormone
The posterior pituitary is not strictly an endocrine gland, but does release hormones

37. Describe major pathological consequences of hypersecretion and hyposecretion of the hormones considered in this chapter.
Growth hormone (GH) disorders
Pituitary dwarfism results from hyposecretion of GH during childhood
Gigantism results from hypersecretion of GH during childhood
Acromegaly results from hypersecretion of GH during adulthood
Thyroid Gland
Goiters
Thyroid gland enlarges due to lack of iodine
Salt is iodized to prevent goiters
Cretinism
Caused by hyposecretion of thyroxine
Results in dwarfism during childhood
Myxedema
Caused by hypothyroidism in adults
Results in physical and mental slugishness
Graves’ disease
Caused by hyperthyroidism
Results in increased metabolism, heat intolerance, rapid heartbeat, weight loss, and exophthalmos

38. Adrenal cortex disorders Addison’s disease
Adrenal Glands
Adrenal cortex disorders
Addison’s disease
Results from hyposecretion of all adrenal cortex hormones
Bronze skin tone, muscles are weak, burnout, susceptibility to infection
Hyperaldosteronism
May result from an ACTH-releasing tumor
Excess water and sodium are retained leading to high blood pressure and edema
Cushing’s syndrome
Results from a tumor in the middle cortical area of the adrenal cortex
“Moon face,” “buffalo hump” on the upper back, high blood pressure, hyperglycemia, weakening of bones, depression

39. Indicate the endocrine role of the kidneys, the stomach and intestine, the heart, and the placenta.

40. Table 9.2 (2 of 2)

41. Thyroid Hormones controlled by negative feedback
The thyroid gland is part of the hypothalamic-pituitary-thyroid axis, and control of thyroid hormone secretion is exerted by classical negative feedback.
Thyroid-releasing hormone (TRH) from the hypothalamus stimulates TSH from the pituitary, which stimulates thyroid hormone release (T3 and T4)
As blood concentrations of thyroid hormones increase, they inhibit both TSH and TRH, leading to "shutdown" of thyroid epithelial cells.
Later, when blood levels of thyroid hormone have decayed, the negative feedback signal fades, and the system wakes up again.

42. Regulation of thyroid hormone production
To prevent the overproduction or underproduction of thyroid hormones, the pituitary gland can sense how much hormone is in the blood and adjust the production of hormones accordingly.
For example, when there is too much thyroid hormone in the blood, TRH and TSH production are both decreased. The sum effect of this is to decrease the amount of TSH released from the pituitary gland and to reduce production of thyroid hormones from the thyroid gland to restore the amount of thyroid hormone in the blood to normal

43. Feedback loops are used extensively to regulate secretion of hormones in the hypothalamic-pituitary axis. An important example of a negative feedback loop is seen in control of thyroid hormone secretion. The thyroid hormones thyroxine and triiodothyronine ("T4 and T3") are synthesized and secreted by thyroid glands and affect metabolism throughout the body. The basic mechanisms for control in this system (illustrated to the right) are:
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. This is an example of "negative feedback".
Inhibition of TRH secretion leads to shut-off of TSH secretion, which leads to shut-off of thyroid hormone secretion. As thyroid hormone levels decay below the threshold, negative feedback is relieved, TRH secretion starts again, leading to TSH secretion.