CHAPTER 45 CHEMICAL SIGNALS IN ANIMALS. Egg. Larva. Pupa. Adult. Introduction. Nervous and endocrine systems are the main internal communication and regulation systems. The animal hormone-secreting cells constitute the endocrine system.
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CHEMICAL SIGNALS IN ANIMALS
See Fig. 45.2, Page 957
Most chemical signals bind to plasma-membrane proteins, initiating signal-transduction pathways.
Mechanism of chemical signaling:
The chemical signals secreted by a cell either:
I): Protein hormones:
Bind to a receptor protein on the surface of the target cell whichwill trigger signal transduction pathway.
Fig. 45.3a, Page 959
Penetrate the cell and bind to a receptor protein inside the target cell. This also will trigger signal transduction pathway (for triggering mRNA transcription for synthesizing a specific protein).
Fig. 45.3b, Page 959
1)- Pituitary gland:secrets 9 hormones( 7 hormones by the anterior part and 2 hormones by the posterior part).
Also called gonadotropine hormones هرمونات المناسل
The anterior pituitary gland hormones
Fig. 45.6b, Page 963
Fig. 45.6a, Page 963