Human Physiology
Endocrine System
• Chemical
Communcations in
the Body
1
Endocrine Glands (internal Secretions)
Endocrine system composed of hormone-secreting
glands (i.e., ‘internal secretions’)
Secreted hormones enter blood stream (vein) and
target specific tissues & organs
Gland
Hormone
Target Tissue
(activated by
the hormone)
Blood Stream
Endocrine Glands (External Secretions)
Exocrine system composed of glands which secrete
substances into a duct network (I.e., ‘external
secretions’)
Exterior
Gland
Duct
system
Interior
Secreted Substances
E.g., milk
tears
saliva
sweat
sebum
G/I juice
semen
Endocrine System
 Second messenger system of the body
 Uses chemical messages (hormones)
that are released into the blood
 Hormones control several major
processes
 Reproduction
 Growth and development
 Mobilization of body defenses
 Maintenance of much of homeostasis
 Regulation of metabolism
Chemistry of Hormone
 Steroids – made from cholesterol
 Non-steroids:
 Amino acid-based hormones
 Proteins
 Peptides
 Amines
 Prostaglandins – made from highly
active lipids
Control of Hormone Release
 Hormone levels in the blood are maintained by negative
feedback
 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
Negative Feedback
Control of Hormone Release
Positive Feedback
Hormonal Stimuli of Endocrine Glands
 Endocrine glands
are activated by
other hormones
Humoral Stimuli of Endocrine Glands
 Changing blood
levels of certain
ions stimulate
hormone release
Location of Endocrine Glands
Anatomy of Pituitary Gland
 Master gland of the body
 Size of a grape
 Has two functional lobes
 Anterior pituitary (adenohypophysis) –
glandular tissue- 75%
 Posterior pituitary (neurohypophysis) –
nervous tissue- 25%
Anatomy of Pituitary Gland
Hormones:
Human growth hormone- hGH
Thyroid stimulating - TSH
Follicle stimulating- FSH
Leutinizing hormone - LH
Prolactin
Adrenocorticotropin - ACTH
Melanocyte stimulating - MSH
Hormones of the Anterior Pituitary
Hormones of the Anterior Pituitary
Growth Hormone
 General metabolic hormone
 Major effects are directed to growth of
skeletal muscles and long bones
 Causes amino acids to be built into proteins
 Causes fats to be broken down for a source
of energy
Pituitary Glands Disorders
• Hyposecretion during childhood = pituitary
dwarfism
• Hypersecretion during childhood = giantism
– very tall,
• Hypersecretion as adult = acromegaly
– growth of hands, feet, facial features & thickening of
skin
Hormones of the Anterior Pituitary
 Prolactin (PRL)
 Stimulates and maintains milk production
following childbirth
 Function in males is unknown
 Adrenocorticotropic hormone (ACTH)
 Stress stimulates ACTH release, which in turn
stimulates cortisol release
 Thyroid-stimulating hormone (TSH)
 Influences growth and activity of the thyroid
 Melanocyte Stimulating hormone (MSH)
 Increases Skin Pigmentation
Hormones of the Anterior Pituitary
 Gonadotropic hormones
 Regulate hormonal activity of the gonads
 Follicle-stimulating hormone (FSH)
 In females, FSH initiates follicle development
and secretion of estrogens in the ovaries
 In males, FSH stimulates sperm production in
the testes
Hormones of the Anterior Pituitary
 Gonadotropic hormones (continued)
 Luteinizing hormone (LH)
 In females, LH stimulates secretion of estrogen
by ovarian cells to result in ovulation
In males, LH stimulates the interstitial
cells of the testes to secrete testosterone
Hormones of the Posterior Pituitary
• Does not synthesize
hormones
• It does store and release
oxytocin (OT) and
antidiuretic hormone
(ADH)
• These hormones are
made by the
hypothalamus and stored
in the Posterior pituitary
Hormones of the Posterior Pituitary
 Oxytocin
 Stimulates contractions of the uterus during
labor
 Causes milk ejection
 Antidiuretic hormone (ADH)
 Can inhibit urine production
 In large amounts, causes vasoconstriction
leading to increased blood pressure
(vasopressin)
Thyroid Gland
• On each side of trachea is lobe of thyroid
• Weighs 1 oz & has rich blood supply
Actions of Thyroid Gland
• T3 & T4 = thyroid hormones
responsible for our
metabolic rate, synthesis of
protein, breakdown of fats,
use of glucose for ATP
production
• Calcitonin = responsible for
building of bone & stops
reabsorption of bone (lower
blood levels of Calcium)
Thyroid Gland Disorders
• Hyposecretion during infancy results in
dwarfism & retardation called cretinism
• Hypothyroidism in adult produces sensitivity
to cold, low body temp. weight gain &
mental dullness
• Hyperthyroidism (Grave’s disease)
– weight loss, nervousness, tremor &
exophthalmos (edema behind eyes)
• Goiter = enlarged thyroid (dietary)
Parathyroid Gland
• 4 pea-sized glands found on back of thyroid gland
Parathyroid Hormone (PTH)
• Raise blood calcium levels
– increase activity of osteoclasts
– increases reabsorption of Ca+2 by kidney
– promote formation of calcitriol (vitamin D3) by
kidney which increases absorption of Ca+2 and
Mg+2 by intestinal tract
• Opposite function of calcitonin
Adrenal Glands
• One on top of each kidney
• 3 x 3 x 1 cm in size and weighs 5 grams
• Cortex produces 3 different types of hormones from 3
zones of cortex
• Medulla produces epinephrine & norepinephrine
Adrenal Glands
Adrenal Cortex
• Secretes over 30 different steroid hormones
(corticosteroids)
– Mineralocorticoids
• Aldosterone: maintains electrolyte balance
– Glucocorticoids
• Cortisol:
– Stimulates gluconeogenisis
– Mobilization of free fatty acids
– Glucose sparing
– Anti-inflammatory agent
– Gonadocorticoids
• testosterone, estrogen, progesterone
Adrenal Glands
Adrenal Medulla
– Situated directly atop each kidney and stimulated by
the sympathetic nervous system
– Secretes the catecholamines
• Epinephrine: elicits a fight or flight response
– Increase H.R. and B.P.
– Increase respiration
– Increase metabolic rate
– Increase glycogenolysis
– Vasodilation
• Norepinephrine
– House keeping system
Anatomy of Pancreas
• Organ (5 inches) consists of head, body & tail
• Cells (99%) in acini produce digestive enzymes
• Endocrine cells in pancreatic islets produce hormones
Cell Types in the Pancreatic Islets
•
•
•
•
Alpha cells (20%) produce glucagon
Beta cells (70%) produce insulin
Delta cells (5%) produce somatostatin
F cells produce pancreatic polypeptide
Regulation of Glucagon & Insulin Secretions
• Low blood glucose
stimulates release of
glucagon
• High blood glucose
stimulates secretion of
insulin
Ovaries and Testes
• Ovaries
– estrogen, progesterone, relaxin & inhibin
– regulate reproductive cycle, maintain pregnancy &
prepare mammary glands for lactation
• Testes
– produce testosterone
– regulate sperm production & secondary sexual
characteristics
Thymus Gland
• Important role in maturation of T cells
• Hormones produced by gland promote the
proliferation & maturation of T cells
– thymosin
– thymic humoral factor
– thymic factor
– thymopoietin
1. Difference between endocrine and exocrine system?
2. Define Hormone?
3. Write the important functions of Hormone?
4. What it the chemical nature of Hormone?
5. Write the mechanism of action of steroid hormone?
6. Write the mechanism of action of non-steroid hormone?
7. How is hormone levels maintained?
8. Give the location of pituitary gland?
9. Write the anatomy of pituitary gland?
10. Write about the types of cells found in the anterior pituitary gland
and the glands produced by them?
11. Write the function of growth hormone?
12. What do you mean by dwarfism, gigantism and acromegaly?
13. Write the function of prolactin hormone and name the gland which
produces it?
14. Write the function of ACTH and name the gland which produces it?
15. Write the function of TSH and name the gland which produces
it?
16. Write the function of MSH and name the gland which produces
it?
17. Write the function of gonadotropic hormone?
18. Write the function of FSH and LH hormone?
19. Name the hormones of posterior part of pituitary gland and the
location from where they are synthesized?
20. What is the other name for antidiuretic hormone?
21. Write the function of oxytocin and vasopressin?
22. Give the location of thyroid gland?
23. Name the hormone produced by thyroid gland and the cell
which produces them?
24. Write the function of T3 and T4?
25. Write the function of calcitonin?
26. Write short notes on cretinism, Grave’s disease and goiter?
27. Where is parathyroid gland located?
28. Write the function of parathyroid hormone?
29. How is the level of calcium regulated by parathyroid hormone
and calcitonin?
30. Give the location and anatomy of adrenal gland?
31. What are the hormones produced by adrenal cortex?
32. What are the hormones produced by adrenal medulla?
33. What are catecholamines?
34. Give the function of Epinephrine?
35. Name the cells types and the hormone produced by pancreatic
islets?
36. How is the level of glucose regulated by glucagon and insulin?
37. Write the name and function of hormone produced by ovaries
and testis?