The document discusses the two systems of internal communication and regulation in animals: the nervous system and the endocrine system. The nervous system uses electrical signals along neurons, while the endocrine system uses hormones secreted into the bloodstream by endocrine glands. Hormones are chemical signals that target specific cell types. Signaling involves reception, signal transduction, and a cellular response. Hormones are classified as steroid hormones, which are lipid-soluble and diffuse through cell membranes, or non-steroid hormones, which bind to cell surface receptors and trigger secondary messengers. Group 1 hormones bind to intracellular receptors, while Group 2 hormones bind to cell surface receptors and stimulate secondary messengers.

1. Presented by Ena Athaide
MSc -1,Sem-2
Institute of Science, Mumbai

2. oAnimals have two systems of
internal communication and
regulation:
•The nervous system
•The endocrine system

3. o The Nervous system conveys high-speed
electrical signals along specialized units
called Neurons.
o The Endocrine system, made up of endocrine
glands, secretes hormones that coordinate
slower but longer-acting responses to stimuli.

5. o A Hormone is a chemical signal that is
secreted into the circulatory system and
communicates regulatory messages
within the body.
o Hormones may reach all parts of the
body, but only certain types of cells,
target cells, are equipped to respond.

6. o Signaling by any of these molecules involves
three key events
-Reception
-Signal transduction
-Response

7. o Steroids
o Non steroid
-Protein and polypeptides
-Tyrosine-derived
-Eicosanoids
-Vitamins

8. o Steroid Hormones:
-Lipid soluble
-Diffuse through cell membranes
-Endocrine organs
-Adrenal cortex
-Ovaries
-Testes
-Placenta

9. o Non-steroid Hormones:
-Not lipid soluble
-Received by receptors external to the cell
membrane
-Endocrine organs
-Thyroid gland
-Parathyroid gland
-Adrenal medulla
-Pituitary gland
-Pancreas

11. o Group 1 Hormones- binds to Intracellular
receptors, to form receptor complexes,
mediate biochemical functions. Mostly
lipophilic in nature.
o Group 2 Hormones- binds to cell surface
receptors and stimulate the release of
secondary messengers which in turn perform
biochemical functions.Thus, hormones itself
is the first messengers.

12. o Group 2 hormones are subdivided into three
categories based on chemical nature of the
second messenger .i.e. cAMP and
phosphatidylinositol/calcium ,
o Some cases second messenger is unknown.