Animal Form and Function-1 COMMUNICATION_III The Endocrine System and Chemical Messenger Lecture Content: 1-Introduction of chemical messenger 2-Chemical Messengers 3-Biochemistry of hormones 4-Characteristics of hormones 5-Feedback control of hormone secretion 6-Mechanism of hormone action (I,II)

1. Endocrine System and Chemical Messenger
Lec-1
Mr. Hassan Hameed
University of Education Lahore, Pakistan
(Multan Campus)

2. Lecture Content
Introduction of chemical messenger
Chemical Messengers
Biochemistry of hormones
Characteristics of hormones
Feedback control of hormone secretion
Mechanism of hormone action (I,II)

3. Introduction of Chemical Messenger
Communication
Maintenance of homeostasis in an animals
body.
Body’s response to various stimuli
One time of chemical messenger is a hormone
Only those cells that have specific receptors
for a hormone can respond to that hormone

4. Hormones work with nerves to communicate,
coordinate, and integrate activities with in the
body of an animal
Almost every invertibrate produces hormone
The major endocrine glands of vertebrates
include; Hypothalamus, Pituitary, Thyroid
parathyroid, Adrenals, Pineal, Thymus,
Pancreas and Gonads.

5. Various other tissues, however, such as the
kidneys, heart, digestive system and placenta
also secrete hormones.

6. Chemical Messengers
The development of most animals commences
with fertilization and the susequent division of
zygote
Further development then depends on continued
cell proliferation, differentiation and growth.
Integration, communicationn and coordination of
all physiological processes such as metabolism,
respiration, excretion, movement and
reproduction, depends on chemical messengers.

7. The chemical messengers are the molecules that
are synthesized and secreted by specialized cells.
Categorized;
- Local chemical messengers
(Lumones, Histamine)
- Neurotransmitters
(acetylcholine)
- Neuropeptides
- Hormones (thyroxin, insulin)
- Pheromones

9. Biochemistry of Hormones
Proteins (insulin)
Derrivatives of A.A (TSH)
Steroids (Sex hormones)
F.A derivates (postgladins)

10. Positive
- Oxytocin
Negative
- Thyroxin

11. Feedback control of hormone secretion
Feedback system is defined as the system in
which the controlling mechanism is itself
controlled by the product of the reaction it is
controlling. e.g iron
The endocrine system is controlled by complex
feedback mechanism in which the secretion of
a hormone is turned on or off (depends on its
concentration)
It may be Positive or Negative.

13. Mechanism of Hormone Action
Fixed-receptor mechanism;
Endocrine cells > secrete > water soluble hormone>
at target cells > hormones binds specific receptor
site on target cell membrane > comlexed formed >
hormone-receptor complex > complex activate
adenylate cyclase > convert ATP to AMP cyclic >
AMP then activate protein kinase > phosphorylates
cell specific proteins > that tiger biochemical
reaction> lead to cell respose.

14. After function > phosphodiesterase inactivates
cyclic AMP.
Meantime, receptor on the plasma membrane
loses the first messenger and now becomes
available for new reaction.

16. Mobile-receptor mechanism;
Steroid hormone molecules diffuses from blood
to a target cell > in cytoplasm binds to receptor
protein > steroid-protein complex >carries to
nucleus > trigers transcription of specific gene
region of DNA > mRNA translated to protein in
cytoplasm> this new protein the mediate the
cells response.

18. Endocrine System of Mammals
• Hypothalamus,
• Pituitary,
• Thyroid,
• Parathyroid,
• Adrenals,
• Pineal,
• Thymus,
• Pancreas,
• Testes,
• Ovraries.

21. Pituitary Gland
Hypophysis > below hypothalamus
Two distinct lobes:
- Anterior lobe (large, pituicytes)
- Posterior lobe (nerve endings)

22. Hormones of Adenohypophysis
6 different hormones
Two types of hormone;
- Tropic (Primary target > another EG)
(TSH, ACTH, LH, FSH)
- Non-Tropic
(GH, Prolactin)

23. Tropic hormone
TSH; > thyroid gland > thyroxin
ACTH; Hypothalamus>CRF> pituitary>ACTH
Female; LH>stimulate ovulation > mature ova,
LH also stimulate corpus luteum > ovaries, in
response release sex hormone > estrogen and
progesterone.
FSH…..?
LH; (Male) stimulate> leyding cells >
testosterone.
FSH,LH; Gonadotropins

24. Non-Tropic Hormone
GH; (Somatotrophic hormone), Affect all
body part concerned with Growth, induces cell
division.
Influence protein synthesis, RNA synthesis,
ribosome activity.
Prolactin; Role in reproduction such as
- stimulate reproductive migration
- mammary gland development, milk
production

25. Neurohypophysis Hormone
Two Hormone;
- ADH; Regulate urine secretion
- Oxytocin; Stimulate uterine contraction,
also promote milk ejection

26. Pineal Gland
Third eye
Darkness makes PG to produce melatonin.
Wake/sleep and seasonal changes modulation
Light inhibit enzyme need for melatonin synthesis
Affect our physiological process to adapt to
seasonal and diurnal cycles
In human, decreased melatonin secretion, triger
puberty onset
Regulate sleep pattern

27. Thyroid Gland
Thyroxine(T4);
Tri-iodothyronine(T3);
- Both influence growth, development,
metabolic rates.
Calcitonin; help to control extracellular level
of Ca ions.
Thyroid disorder; hyperthyrodism,
hypothyrodism,

28. Parathyroid Gland
Secrete parathormone(PTH) > regulate conc.
of Ca , Phosphate ions in blood. That may
absorb from intestine or released by bone
tissues.

30. Adrenal Glands
Two gland top of kidney
Eeach gland have two part(cortex and medula)
Adreanl Cortex; secretes three hormone
1. Glucocorticoids; Cortisol > regulate
metabolism, blood sugar, also function as
defense against infection
2. Mineralocorticoids (Aldosterone) > maintain
solute conc. In extracellular fluid
3. Sex hormones (androgens, estrogens)

31. Adrenal medulla;
Epinephrine, Norepinephrine > both control
heart rate and carbohydrate metabolism.

33. Pancreas
Synthesize,store and secrete hormone insulin
and glucagon
Somatostatin; inhibit glucagon and insulin
secretion
Pancreatic polypeptide >inhibit somatostatin
secretion

36. Testes
Male > testosterone secrete, which act with
LH and FSH > spermatogenesis
Testosterone necessary for growth and
maintenance of male sex organs, sex behavour,
stimulate growth of facial and pubic hair.
Testes also produce inhibin which inhibit FSH
secretion

37. Overies
Estrogens; regulate menstrual and estrus
cycle,mammary gland development, sec.sex
character
Progestin; placenta formation
Relaxin; soften uterus opening in delivery
Inhibin; inhibits FSH

38. Thymus
Behind breastbone
Role in immune and endocrine system.
Active until puberty
Produce hormone thymosin > stimulate WBC
development (T-cells).