CHEMICAL SIGNALS IN
ANIMALS
Egg
Larva
Pupa
Adult
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Nervous and endocrine systems are the main internal
communication and regulation systems.
The animal hormone-secreting cells constitute the
endocrine system.
Hormone secreting organs are called endocrine glands
(ductless glands).
Hormone is a chemical signal secreted into blood stream
and regulates communicating messages within the body.
Target cell is the site that reached by the hormone to
which it responds.
Feedback is common in regulation of the activity of
endocrine system
Types of hormones are [ Polypeptide H., Steroid H. or
Amino acid derivatives H ].
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Humans have nine
endocrine glands.
‫الصنوبرية‬
‫النخامية‬
‫الدرقية‬
‫الكظرية‬
Fig. 45.5, Page 960
The hypothalamus integrates endocrine and
nervous function.
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Neurosecretory cells of the hypothalamus produce
hormones.
a)
Releasing hormones stimulate the anterior pituitary
(adenohypophysis) to secrete hormones.
b) Inhibiting hormones prevent the anterior pituitary from
secreting hormones.
Pituitary gland:
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secretes 9 hormones
7 hormones by the anterior part
2 hormones by the posterior part.
A)- Anterior pituitary hormones.
Growth hormone (GH)
2) Prolactin (PRL).
3) Gonadotropins: glyocoproteins.
1)
Follicle-stimulating hormone (FSH).
 Luteinizing hormone (LH) ‫ال ُمحفز لتكوين الجسم األصفر‬.
Thyroid-stimulating hormone (TSH).
Adrenocorticotropic hormone (ACTH).
Melanocyte-stimulating hormone (MSH).
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4)
5)
6)
B)- Posterior pituitary hormones.
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Oxytocin: a peptide.
 Stimulates contraction of the uterus and mammary glands.
 Secretion regulated by the nervous system.
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Antidiuretic hormone (ADH): ‫الهرمون المانع إلدرار البول‬