1. Chemical Signaling within the
Body

2. • Maintenance of homeostasis involves coordinating
activities of organs and systems throughout the body
• The nervous system and endocrine system work
together to monitor and adjust physiologic activities

3. •The nervous system performs short-term very specific
responses to environmental stimuli
- chemical messengers are neurotransmitters
(NTs)
•The endocrine system regulates longer-term, ongoing
metabolic processes throughout the body
- chemical messengers are hormones (‘to excite’)
Nervous System vs Endocrine System

4. Endocrine System
• Endocrine cells are
glandular secretory
cells that release
hormones directly into
the interstitial fluids,
lymphoid system, or
blood
• Hormones alter the
metabolic activities of
many different tissues
and organs

5. ‘Pure’ endocrine
glands: pituitary,
pineal, thyroid,
parathyroid, and
adrenal
Organs containing
endocrine cells:
pancreas, thymus,
gonads, and
hypothalamus

8. Thyroid Releasing
Hormone

9. HYPOTHALAMUS
1) The hypothalamus acts
as an endocrine organ,
releasing the hormones
ADH and oxytocin into the
circulation at the
neurohypophysis
(posterior lobe)
2) The hypothalamus
contains autonomic
centers that have direct
neural control over the
endocrine cells of the
adrenal gland.

11. Hypothalamic Control over Endocrine Organs

12. Hypothalamus and pituitary gland
• Hypothalamus- important homeostatic control center
– Regulates water balance, hunger and satiety, body
temperature, water balance
– Controls the pituitary gland
• Composed of 2 bodies of glandular tissue of different
embryologic origin
– Anterior pituitary-secretes at least 6 different hormones in
response to releasing factors from the hypothalamus
– Posterior pituitary- stored ADH and oxytocin which are actually
produced in the hypothalamus
» Diabetes insipidus- inability to produce ADH
» Oxytocin -causes uterine contractions and milk letdown in
lactation

13. The Pituitary Gland
• Or hypophysis lies in the sella turcica
- resembles a golf club with a stalk or infundibulum that
extends from the hypothalamus and the head of the club
as the gland
• 2 lobes: the adenohypophysis (anterior lobe) and
the neurohypophysis (posterior lobe)
- 9 important peptide hormones are released by the
pituitary

14. The Pituitary Gland
• Neurohypophysis
ADH and Oxytocin
• Adenohyposphysis
ACTH – adrenocorticotropic hormone
TSH – thyroid-stimulating hormone
GH – growth hormone
PRL – prolactin
FSH – follicle-stimulating hormone
LH – luteinizing hormone

15. The Pituitary Gland
Fig 19.3 Gross Anatomy -Histological Organization of the Pituitary Gland
and Its Subdivisions
Copyright © 2009 Pearson Education, Inc., publishing as Pearson Benjamin Cummings

16. 20-16
• Anterior pituitary
– Hypothalamus controls anterior pituitary by
hypothalamic-releasing hormones and in
some cases hypothalamic-inhibiting
hormones
• 3 anterior pituitary hormones have target effect on
other glands
– TSH-thyroid stimulating hormone stimulates thyroid
gland to produce thyroid hormone
– ACTH-adrenocorticotrophic hormone stimulates the
adrenal cortex to produce glucocorticoids
– Gonadotrophic hormones stimulate the gonads to
produce estrogen and testosterone

17. Pituitary Hormones and Their Targets

18. 20-18
Hypothalamus and pituitary gland
• Anterior pituitary cont’d.
– 3 anterior pituitary hormones do not affect other
glands
• MSH- melanocyte stimulating hormone stimulates the
pigment producing melanocytes of the skin
• Growth hormone stimulates bone and muscle growth,
increases protein synthesis and fat metabolism
• Prolactin stimulates the mammary glands to synthesize milk
• Effects of growth hormone (GH)
– Greatest production occurs during childhood
• Lack of GH- pituitary dwarfism
• Excess- gigantism
– Excess production in adulthood- acromegaly
• Growth plates of bone have closed so no increased growth in
height
• Feet, hands, and face become “heavy” in appearance

19. Same Individual with Acromegaly
(evolution over 20 years)

20. Pituitary
Disorders

21. The Thyroid Gland
• Sits on thyroid cartilage of the larynx
- butterfly-like appearance
• Consists of 2 main lobes connected by the
isthmus
• Controls metabolism
- Thyroxine (T4) and Triiodothyronine (T3)
• Involved in calcium homeostasis
- calcitonin

22. The thyroid gland
– TSH from pituitary stimulates thyroid to produce
thyroxine (T4) and triiodothyronine (T3)
• increase metabolic rate
• Stimulate all body cells
• More glucose is utilized to form ATP
• Necessary for normal growth and nervous system
function
– Thyroid requires iodine to produce these hormones
• Iodine deficiency causes simple goiter

23. • T3 and T4 secreted by the
follicular cells
-stored as colloid
THYROID HORMONES
Parafollicular cells (C
cells) secrete calcitonin

24. The Regulation of Thyroid Secretion
Negative Feedback Loop

25. Goiter due to
hypothyroidism
Grave’s disease-hyperthyroidism
• Causes exophthalmic goiter-edema behind eyes causes
bulging
• Hyperactivity, arrythmias

26. Cretinism- results from abnormal thyroid development
• Short, stocky body type
• Severe hypothyroidism
• Mental retardation
• Treatment must begin in first 8 weeks of life
Myxedema
• Hypothyroidism in
adults-lethargy,
weight gain, loss of
hair

27. The Parathyroid Glands
• Lie on the posterior surface of the thyroid gland surrounded by
CT capsules (number varies)
• Regulates calcium homeostasis
- PTH increases calcium levels and is essential to life:
1) stimulates osteoclasts to release calcium from bones
2) decreases secretion of calcium by the kidney
3) activates vit D, which stimulates uptake of Ca by the
intestine

28. parathyroid hormone - ↑ level of
calcium in blood
Hypocalcemia can result if
parathyroids are removed or
destroyed.

29. The Thymus
• Secretes many
chemicals that help T
cells of the immune
system develop
(thymosins)
• Atrophies as one ages
Largest and most active in
childhood
Produces melatonin
Sleep-wake cycle
Circadian rhythms
Regulates sexual
development

30. Adrenal glands
• Adrenal gland structure
– Outer cortex and inner medulla
– Distinctly different in origin and function
• Cortex is under the control of ACTH
• Medulla is a neurosecretory structure
• Adrenal medulla
– Hypothalamus initiates neural impulses which travel
through brain stem, cord, and then sympathetic fibers to
the medulla
– Epinephrine and norepinephrine released
• Fight or flight responses
• Provide a short-term, immediate response to stress

32. Adrenal glands
• Adrenal cortex
– Long-term stress response
– Produces 2 main groups of hormones
• Mineralocorticoids
– Regulate salt and water balance
– Aids in regulation of blood volume and pressure
• Glucocorticoids
– Under control of ACTH
– Regulates carbohydrate, protein, and fat metabolism
» Causes increase in blood glucose
– Anti-inflammatory
– Also produces small amounts of the sex hormones

35. • Malfunction of the adrenal cortex
– Addison’s disease
• ACTH accumulates and causing bronzing of the skin from
stimulation of melanocytes
• Without cortisol, there is no mobilization of glucose under
stress
– Can be life-threatening
• Hyposecretion of aldosterone-most serious
– Can cause hyperkalemia (elevated blood potassium) which can
cause cardiac arrest

36. Adrenal glands
• Malfunction of the
adrenal cortex
– Cushing’s syndrome
• Hypersecretion of the
adrenal cortex
• Excess cortisol is
primary problem
– Diabetes mellitus
from increased blood
glucose
– Subcutaneous fat
deposited in
midsection
– High blood pressure

37. The Pancreas
• Contains endocrine and exocrine cells
• Exocrine acinar cells, form most of the gland
- secrete digestive enzymes into the small intestine
• Endocrine cells are contained in spherical bodies
- pancreatic islets or islets of Langerhans
- about 1 million scattered among the exocrine cells

38. • Each islet contains 4 major cells
• Alpha cells – glucagon
• Beta cells – insulin
• Delta cells – somatostatin (growth-hormone inhibiting
hormone)
• F cells – pancreatic polypeptide (PP)

39. • Insulin
– Released after eating
– Stimulates uptake of glucose by cells
• Especially muscle, liver, and adipose cells
• Decreases blood glucose
• Glucagon
– Released before eating when glucose is low
– Targets liver and adipose tissue
– Increases blood glucose

41. 20-41
Pancreas
• Diabetes mellitus
– Type 2 diabetes mellitus
• Insulin-resistant
• Obesity- adipose tissue produces a substance that
impairs insulin receptor function
• Insulin levels are often low, and cells may not have
sufficient insulin receptors
• Controlled by diet, exercise, medications
• Long term complications of diabetes
mellitus
– Blindness, kidney disease, cardiovascular
disorders

42. Endocrine Tissue of the Reproductive System
• Testes:
- Interstitial cells produce androgens (testosterone)
promotes production of functional sperm, maintains
secretory glands, influences 2nd
sexual characteristics, and
stimulates muscle growth
• Ovaries
- Follicular cells produce estrogens and secrete inhibin
- Corpus luteum releases progestins and relaxin

43. The Pineal Gland
• Small pine-cone shaped gland (or epiphysis
cerebri) - part of the epithalamus
• Contains neurons, glial cells, and special secretory
cells called pinealocytes
- synthesize the hormone, melatonin
- melatonin slows the maturation of sperm, oocytes, and
reproductive organs
- production rates rises at night and declines during the day

45. GENERAL ADAPTATION SYNDROME
ALARM
RESISTANCE
EXHAUSTION
STRESS
hypothalamus
C-RF secretion increased sympathetic activity increased blood pressure
ACTH norepinephrine
epinephrine
---------------------------------------------------------------------------------------------------------------------------------
glucocorticoids increased blood pressure
continued
decreased inflammatory response
increased blood glucose
altered protein and fat metaoblism
---------------------------------------------------------------------------------------------------------------------------------
decreased immune response + decreased energy reserves
decreased resistance to
disease
hypertension
cardiac failure and renal failure
DEATH