1. THE ENDOCRINE SYSTEM
Like the Nervous System, the Endocrine System work through a group of chemical messengers. The endocrine messengers are called hormones.
Hormones: Substances secreted by one group of cells that travel through the blood stream and regulate the metabolic functions of other cells.
Hormones can affect only cells that have receptors that can bind the hormone
Target cells: Those cell types that can be affected by a given hormone

3. FUNCTIONS OF THE ENDOCRINE SYSTEM
The Endocrine System helps to control and integrate:
1- Reproduction
6- Energy balance
2- Growth
7- Cellular metabolism
3- Development
4- Defense against stress
5- Water, electrolyte and nutrient balance
The Endocrine system helps to maintain homeostasis by coordinating and regulating the activities of cells, tissues, organs, and systems throughout the body

4. Homeostasis
It is the ability of the human body to maintain relatively stable internal conditions (temperature, PH, etc) even though the outside world changes continuously.
A good homeostasis is indispensable to maintain the organism in good health. Most diseases can be regarded as a result of disturbance of homeostasis.
Example: The body temperature must be near to 37 C (98.6 F). When temperature increases only three degrees (to 40 C), the organism is in danger. o

5. o o
Temperature: C
Temperature: C
Homeostatic Control Mechanisms maintain the temperature of the bodies near to 37 C, and both men are in good health o

6. F E E D B A C K S Y S T E M S 1- Negative feedback mechanisms:
Causes the variable to change in a direction opposite to that of the initial change. or
2- Positive feedback mechanisms:
Causes the variable to accelerate the change in the same direction that the initial disturbance. or

7. 1- ENDOCRINE SYSTEM IN NEGATIVE FEEDBACK MECHANISMS
First Hormonal Mechanism
Parathyroid hormone is released by parathyroid gland
Stimulates the osteoclasts to resorb bone, releasing calcium to the blood
[Calcium] in blood
[Calcium] in blood
Second Hormonal Mechanism
Calcitonin hormone is released by thyroid gland
Inhibits osteoclasts to resorb bone, and encourages calcium salt deposit in bone matrix
[Calcium] in blood
[Calcium] in blood

8. 2- ENDOCRINE SYSTEM IN POSITIVE FEEDBACK MECHANISMS
Positive feedback mechanisms are used to amplify or perpetuate events. They are referred as “cascades”.
SENSOR
EFFECTOR
HYPOTALAMUS
CONTROL CENTER
Example:
PITUITARY GLAND
Neural electrical impulses
OXYTOXIN
DELIVERY!
Uterine contractions

10. Control of Hormone Secretion
Most of hormone secretions are controlled by the Hypothalamus and the Pituitary gland
Hypothalamus
Pituitary gland

11. Septum pellucidum
Intermediate mass
Corpus callosum
Fornix
Thalamus
Epi- thalamus
Pineal gland
Hypothalamus
Anterior commissure
Pituitary gland
Optic chiasm
Mamillary body

12. Three mechanisms of Hypothalamic Control over Endocrine Function

13. TSH, FSH, LH, ACTH, GH, PRL, MSH
Posterior lobe
Anterior lobe
TSH, FSH, LH, ACTH, GH, PRL, MSH
Oxytoxin and Antidiuretic Hormone (ADH)

14. melanocyte stimulating hormone

15. Hormones produced by the Anterior Lobe or Adenohypophysis (1)2 1 5

16. Hormones produced by the Anterior Lobe or Adenohypophysis (2)4
Gonadotropins 3 3 6
melanocyte stimulating hormone

17. Hormones produced by the Hypothalamus and released by the posterior pituitary

18. Hormonal Control of Water Retention in the Body
The body controls how much water is either sent to the bladder (in urine) or retained in circulation through a hormone called “antidiuretic hormone” (ADH)
When the body needs water, receptors in the hypothalamus sense the increase of solute concentration in the blood, and the hypothalamus orders the release of ADH from the pituitary gland.
ADH works on the distal nephron tubule and the collecting duct increasing their permeability to water. Consequently, more water moves out of the nephron tubule and collecting duct and thus back into circulation

19. Hormonal Control of Water Retention in the Body

20. Neural electrical impulses
HYPOTALAMUS
CONTROL CENTER
SENSOR
OXYTOXIN
EFFECTOR
DELIVERY!
Uterine contractions
PITUITARY GLAND

22. The Thyroid Gland
Isthmus
Right lobe
Left lobe

23. Calcitonin
T4 or Thyroxine
T3 or Triiodothyronine

24. Thyroid Hormones 1- T4 or thyroxine 2- T3 or triiodothyronine
3- Calcitonin
1- T4 or thyroxine
2- T3 or triioodothyronine
Follicular hormones (they are produced by the follicular cells)
1- They increase the rate of oxygen uptake and the basal metabolic rate
2- They enhance the effects of sympathetic stimulation (increasing heart rate, blood pressure, nervousness, and sweating)
3- They help to maintain body temperature
4- They help to regulate growth, development, and intracellular metabolism by increasing protein synthesis and lipid breakdown
5- They stimulate RBC formation, and speed up bone turnover

25. 3- Calcitonin
It is released in response to high levels of calcium in the blood
Calcitonin hormone is released by thyroid gland
Inhibits osteoclasts to resorb bone, and encourages calcium salt deposit in bone matrix
[Calcium] in blood
[Calcium] in blood

26. The Parathyroid Glands
Thyroid gland, posterior view
Parathyroid glands

27. The Parathyroid Hormone
It increases calcium blood levels by targeting bone and kidneys
1- In bones
[Calcium] in blood
Parathyroid hormone is released by parathyroid gland
Stimulates the osteoclasts to resorb bone, releasing calcium to the blood
2- In kidneys
- It increases calcium reabsortion
- It increases formation and secretion of calcitriol
Increases absorption of calcium and phosphate from the intestines

28. Adrenal or Suprarenal Glands

29. (Epinephrine and Norepinephrine)
Medulla (It is considered part of Sympathetic Autonomic nervous System)
Catecholamines
(Epinephrine and Norepinephrine)
Sex hormones
( androgens)
Glucocorticoids
(Cortisol, Cortisone and Corticosterone)
Mineralocorticoids
(Aldosterone)

30. Hormones of the Adrenal Glands
1- Mineralocorticoides (Aldosterone)
-It increases sodium ion and water reabsortion in kidneys
-It increases potassium secretion in kidneys
Aldosterone secretion is regulated by the renin-angiotencin mechanism
Blood pressure or plasma solute concentration
Renin-angiotencin mechanism
Aldosterone secretion
2- Glucocorticoids (Corticosterone and Cortisol)
-They help the body to resist stressors
-They depress the immune system and the inflammatory response

31. 3- Gonadocorticoids or Sex Hormones (Androgens)
-They are masculinizing hormones.
- In females they stimulate sexual drive. After menopause they are converted to estrogens.
4- Catecholamines (Epinephrine and Norepinephrine)
-Blood glucose levels
They increase:
-Cardiac activity
-Blood pressure
-Glycogen breakdown
-Triglyceride breakdown

32. Three mechanisms of Hypothalamic Control over Endocrine Function

33. The Pancreas

34. Endocrine pancreas Exocrine pancreas Islets of Langerhans
Pancreatic acini
They secrete large quantities of an alkaline, enzyme rich fluid
1- Beta cells:
Insulin
2- Alpha cells:
Glucagon
3- Delta cells:
Somatostatin
4- F cells:
Pancreatic polypeptide

35. 1- Glucagon (Released by alpha cells)
-It stimulates the liver to produce glucose
-It stimulates to breakdown glycogen
Glucose in blood
(Alpha cells)
Pancreas
Glucagon
Liver
Glycogen
Glucose

36. Insulin 2- Insulin (Released by beta cells) - High blood glucose
- Parasympathetic stimulation
- High level of some aminoacids
(Beta cells)
Pancreas
Insulin
- It increases the rate of glucose uptake by cells
- It increases cellular metabolism
- It increases the storage of lipid and glycogen
- Increases aminoacids absorption and protein synthesis

37. Secondary spermatocyte
The Gonads
Spermatogonia
Primary spermatocyte
Seminiferous tube
Secondary spermatocyte
Spermatids
Sperm (immature)
Sustentacular or Sertoli cells: Produce Inhibin
Interstitial or Leydig cells: Produce androgens (testosterone)

40. The Development of the Egg
Corpus luteum :
Progesterone
Primary oocytes
Secondary follicles
Tertiary follicles
Primary follicles
Follicles: Estrogens and Inhibin

41. The Pineal Gland Pineal gland Melatonin:
1- Inhibiting reproductive functions
2- Protecting against damage for free radicals
3- Setting circadian rhythms

42. Hormones of the Kidneys
1- Calcitriol:
It stimulates uptake of calcium and phosphate ions from the gut
2- Erythropoietin:
It stimulates the production of red blood cells by red bone marrow
3- Renin:
It converts angiotensinogen into angiotensin-I and starts the cascade of enzymatic changes known as the renin-angiotensin system
Atrial Natriuretic Peptide (ANP)
It is produced by the atrial cells of the heart
It reduces the blood volume and blood pressure