Organization of the Endocrine System
Chapter 46: Organization of endocrine control
Two major systems evolved to communicate and coordinate body functions
Nervous system
Endocrine system
Hormones are carried through the blod to distant target tissue where they are recognized by specific, high-affinity receptors
These receptors may be located either on the surface of target tissue, within the cytosol, or in the target cell’s nucleus
Once a hormone is recognized by its target tissue or tissues, it can exert its biologic action by a process known as signal transduction
PRINCIPLES OF ENDOCRINE FUNCTIION
Chemical signalling can occur through endocrine, paracrine or autocrine pathways
In classic endocrine signalling, a hormone carries a signal from a secretory gland across a large distance to a target tissue
Hormones secreted into the extracellular space can also resulate nearby cells without ever passing though the systemic circulation
This is referred to as paracrine regulation
Chemicals that bind to receptor on or in the cell that is actually secreting the hormone and thus affect the funciotn of the hormone-secreting cell itself, this is referred to as autocrine regulation
Endocrine glands
Seven classic endocrine glands: pituitary, thyroid, parathyroid, testes, ovary, adrenal, and pancreas
Tissue that are not classically recognized as part of endocrine system produce hormones and play a vital role in endocrine regulation
CNS (hypothalamus), GI tract, liver, heart, kidney and others
Paracrine factors
Interleukins or lymphokines are example of such paracrine factors, growth factors (platelet-derived growth factor, fibroblast growth factor)
These factors are not hormones in the usual senses
They are not secreted by glandular tissue, and their sites of action are usually within the local environment
These signalling molecules share many properties of classic peptide and amine hormones in that they bind to surface receptors and regulate one or more of specific intracellular signalling
Two major systems evolved to communicate and coordinate body functions
Nervous system
Endocrine system
Hormones are carried through the blod to distant target tissue where they are recognized by specific, high-affinity receptors
These receptors may be located either on the surface of target tissue, within the cytosol, or in the target cell’s nucleus
Once a hormone is recognized by its target tissue or tissues, it can exert its biologic action by a process known as signal transduction
PRINCIPLES OF ENDOCRINE FUNCTIION
Chemical signalling can occur through endocrine, paracrine or autocrine pathways
In classic endocrine signalling, a hormone carries a signal from a secretory gland across a large distance to a target tissue
Hormones secreted into the extracellular space can also resulate nearby cells without ever passing though the systemic circulation
This is referred to as paracrine regulation
Chemicals that bind to receptor on or in the cell that is actually secreting the hormone and thus affect the funciotn of the hormone-secreting cell itself, this is referred to as autocrine regulation
Endocrine glands
Seven classic endocrine glands: pituitary, thyroid, parathyroid, testes, ovary, adrenal, and pancreas
Tissue that are not classically recognized as part of endocrine system produce hormones and play a vital role in endocrine regulation
CNS (hypothalamus), GI tract, liver, heart, kidney and others
Paracrine factors
Interleukins or lymphokines are example of such paracrine factors, growth factors (platelet-derived growth factor, fibroblast growth factor)
These factors are not hormones in the usual senses
They are not secreted by glandular tissue, and their sites of action are usually within the local environment
These signalling molecules share many properties of classic peptide and amine hormones in that they bind to surface receptors and regulate one or more of specific intracellular signalling