The endocrine system regulates activities in the body through chemical signals called hormones. It consists of endocrine glands that secrete hormones directly into the bloodstream, targeting specific organs. The hypothalamus and pituitary gland control hormone production. The pituitary gland secretes hormones that regulate other glands like the thyroid, adrenals, ovaries and testes. Imbalances in hormone levels can cause disorders like diabetes, dwarfism, and thyroid issues. Hormones work in feedback loops to maintain homeostasis.

1. UNIT 4: ENDOCRINE
SYSTEM
(CHEMICAL
COORDINATION)
(Campbell et.al, 2010 – CHAPTER
45)

2. ENDOCRINE SYSTEM
 The nervous system and the
endocrine system work together
 To regulate the activities of the other
systems in the body.
 Both systems use chemical signals
when they respond to changes.
 But they have different means of
delivering the signals

3. Differences between the CNS and
the endocrine system
Central nervous
system
Endocrine system
Transmits electrical
impulses
Transmits chemical
biological
messengers
Impulse send through
neurons through
neurotransmitters
Transmits message
through bloodstream
by means of
hormones
Fast reaction Slow reaction

4. ENDOCRINE GLANDS
 Endocrine system consist of different
endocrine glands in the body.
 Endocrine glands are ductless .
 And produce and secrete hormones.
 That are transported through the
blood in the blood vessels of the
body.
 Towards a specific target organ

5. ENDOCRINE GLANDS
 The target cells only respond to
specific hormones secreted by
specific endocrine glands.
 If the cell can respond to the hormone,
the hormone and the receptor proteins
bind together as a key fits into a lock.

6. EXOCRINE GLANDS
 Exocrine glands have ducts and
secrete chemicals like enzymes into
these ducts which takes it to the
lumen of organs or to the outside of
the body.

7. HORMONES (CHEMICAL
SIGNALS)
• Hormones are biological chemical
messengers that help cells, body parts
and even individuals to communicate
with one another.
• Most hormones are proteins, but the
steroids are fats.
• Hormones can inhibit or stimulate a
reaction.
• Hormones are temperature, pH and

8. ENDOCRINE GLANDS
1. PITUITARY GLAND
2. THYROID
3. ADRENAL GLAND
4. PINEAL GLAND
5. PARATHYROID GLAND
6. THYMUS
7. PANCREAS
8. GONADS

9. ENDOCRINE GLANDS

10. HYPOTHALAMUS AND
PITUITARY GLAND
 The hypothalamus controls the glandular
secretions of the pituitary gland

11. PITUITARY GLAND
 Attached to a stalk onto the
hypothalamus.
 Consist of a posterior- and anterior
pituitary.
 Posterior- (Pars nervosa) produce and
secrete the following hormones: ADH
and Oxytocin.
 Anterior- (Pars distalis) produce and
secrete the following hormones: TSH,

12. Posterior pituitary gland
hormones: ADH and Oxytocin
 ADH: Regulate the water reabsorption
through the kidneys by changing the
permeability of the renal tubules.
 Oxytocin: Stimulates the uterus wall to contract
during the process of giving birth and stimulates
milk production during pregnancy.

13. How ADH functions

14. Anterior pituitary gland
hormones: TSH
ACTH
prolactin
growth hormone
FSH
LH.

15. TSH (THYROID STIMULATING
HORMONE)
 Stimulates the thyroid gland to
secrete thyroxin.
 Function by means of a negative
feedback reaction.

16. TSH (THYROID STIMULATING
HORMONE)

17. ACTH (Adrenocorticotropic
hormone)
 Stimulates the adrenal cortex to produce
glucocorticoid that is released during
stress.

18. PROLACTIN
 Control milk production in females

19. Growth hormone
 Promotes skeletal and
muscular growth.
 It stimulates the rate at
which amino acids enter
cells and protein
synthesis occurs.
 It promotes fat
metabolism as opposed to
glucose metabolism.

20. Growth hormone

21. DISORDERS CAUSED BY THE
UNDERSECRETION OF
GROWTH HORMONE
 When a too little GH has
been produced during
childhood.
 Normal proportions but
small stature.
 Low blood pressure.
 Can be rectified by injecting
the child with growth
PITUITARY DWARFISM

22. DISORDERS CAUSED BY
THE OVERSECRETION OF
GROWTH HORMONE
 If too much GH have been
produced during childhood.
 Excessive growth of
muscles and bones.
 Usually have diabetes.
 Much taller than normal
children/adults.
GIGANTISM

23. Disorder of GH :
ACROMEGALY
 Caused by
overproduction of
GH in adults.
 Enlargement of
bones in the face,
fingers and toes as a
person ages.

24. FEEDBACK MECHANISMS
CAUSED BY HORMONE ACTION
 NEGATIVE FEEDBACK MECHANISM

25. FSH (follicle stimulating
hormone) and LH
 Stimulates the gonads (testis and
ovaries) to produce sex hormones
and gametes.

26. THYROID GLAND
 Located in the neck
around the trachea.
 Red – high blood
volume
 2 lobes connected by
isthmus.
 Uses Iodine to produce
the hormone thyroxin
 Thyroxin production is
stimulated by TSH
secreted by the
Hypophysis
 Also secretes the
STRUCTURE OF THYROID
GLAND

27. FUNCTIONS OF THYROXIN
 Increase the metabolic rate of a
person.
 No specific target organ, they stimulate
all cells of the body to metabolize at a
faster rate.
 Promotes the metabolism of glucose
so that more energy is released.

28. DISORDERS OF THE THYROID
GLAND
 Disorder caused by the
lack of Iodine in the
diet.
 Without iodine the
thyroid is unable to
produce thyroxin and
continued anterior
pituitary stimulation
 Retarded growth
during infancy.
 Body is short and
stocky with mental
retardation
SIMPLE GOITER
CONGENITAL
HYPOTHYROIDIS
M

29. Disorder of Thyroid Gland:
Exophthalmic goiter
 This goiter is due to an overactive
thyroid gland
 The eyes of a person protrudes
because of edema in the eye socket
tissue
 Person is hyperactive, nervous,
irritable, suffers from insomnia.
 Sweat excessively and is heat
sensitive.
 Enlarged thyroid can be surgically

30. FUNCTIONS OF CALCITONIN
 Regulates the Calcium level in the blood.
 Calcitonin brings about the deposit of calcium
in the bones when the level of calcium in the
blood is too high.
 When the blood calcium level lowers to normal,
the release of calcitonin by the thyroid is
inhibited.
 This lower level of calcium in the blood,
stimulates the release of parathyroid
hormone (PTH) by the parathyroid glands.

31. PARATHYROID GLAND
 4 parathyroid glands are located on the thyroid.
 Secretes the hormone: Parathyroid Hormone
(PTH)
 PTH corrects a low blood calcium level
 PTH promotes the release of calcium by the
bones
 PTH promotes the reabsorption of calcium
from the kidneys
 PTH brings about the activation of Vitamin D.

32. PARATHYROID GLAND

33. DISORDERS OF THE
PARATHYROID GLAND
 Insufficient PTH
secreted.
 Dramatic drop in
blood calcium
levels.
 The body
shakes from
continuous
 The blood
calcium level
becomes
abnormally high.
 Bones become
soft and fragile.
 Person irritable
and prone to get
TETANY
HYPERPARATHYROID
ISM

34. CALCITONIN AND PTH –
ANTAGONISTIC HORMONES
 These 2 hormones (Calcitonin and PTH) are
antagonistic.
 Both hormones work together regulate the
blood calcium level.
 When the blood calcium level is high – the
thyroid gland secretes calcitonin.
 When the blood calcium level is low – the
parathyroid gland releases PTH

35. ADRENAL GLAND
 Located ontop of the
kidneys.
 Consist of an inner part
the adrenal medulla and
outer part called the
adrenal cortex.
 The adrenal medulla
secretes 2 hormones:
adrenalin and nor-
adrenalin.
STRUCTURE

36. FUNCTIONS OF ADRENALIN
AND NOR-ADRENALIN
 Brings about all the bodily changes that
occur when an individual reacts to an
emergency situation.
 Effect of this hormone is short term.
 Released during fright, anxiousness and
anger.
 Increase heart rate.
 Increase blood flow and blood pressure.
ADRENALIN and NOR-
ADRENALIN

37. FUNCTIONS OF ADRENALIN
AND NOR-ADRENALIN
 Muscles absorb glucose for energy to
react.
 More blood (oxygen) to brain.
 Actions of the digestive system
inhibited.
 Pupils dilate to observe clearly
ADRENALIN and NOR-ADRENALIN

38. MALFUNCTION OF THE
ADRENAL CORTEX
 Bronzing of the skin
 Excess amount of
ACTH.
 This lead to a buildup
of melanin.
 Excess cortisol in
blood
 Sub-cutaneous
fat deposits.
ADDISON DISEASE CUSHING SYNDROME

39. PANCREAS
 The pancreas consist of exocrine tissue with
ducts that produce and release digestive juice
(pancreatic sap) into the duodenum, and
endocrine tissue without ducts that secrete
hormones directly into the bloodstream.
 The endocrine tissue is know as the Islets of
Langerhans and it secretes two hormones:
Insulin and glucagon (antagonistic
hormones).

40. PANCREAS

41. FUNCTIONS OF INSULIN IN THE
PANCREAS
 If blood sugar (glucose) level is high.
 Insulin is secreted.
 Insulin stimulates the uptake of glucose by the
cells (liver, muscle and adipose)
 In the liver and muscles it is stored as
glycogen.
 Muscle cells break it down for energy.
 Fat cells convert it to glycerol for the forming of
fat.

42. FUNCTIONS OF GLUCAGON
 When the blood sugar
level is low.
 Glucagon is secreted
into the blood.
 Glucagon stimulates the
liver cells to convert
glycogen into glucose
for energy production.
 Therefore glucagon
raises the blood sugar

43. DIABETES MELLITUS
 Type 1 Diabetes:
 Pancreas is not
producing insulin
 Islets of Langerhans
damaged.
 Glucose accumulate in
blood.
 Coma results if not
treated with insulin
injections.
 Treatment of
Diabetes:
 Self study

44. TESTIS AND OVARIES
 Testis produce
testosterone
(male sex
hormone)
 Stimulates the
formation of male
traits during
puberty
 Stimulates oil and
sweat glands.
 Stimulates
hairloss
 Ovaries produce estrogen and
progesterone (female sex
hormones)
 Estrogen stimulates growth of the
uterus and vagina during puberty
and secondary sexual female
traits.
 Stimulate egg production and
preparation of the uterus for
pregnancy.
 Progesterone prepare the uterus
wall for possible implantation of an
HORMONES
PRODUCED BY THE
TESTIS
HORMONES PRODUCED BY THE
OVARIES

45. Effects of testosterone on
males
Effects of estrogen and
progesterone in females