How Does The Endocrine System In Regulating And Maintaining Homeostasis

Submitted By kyrajo4
Words: 951
Pages: 4



To work alongside the Nervous
System in regulating and maintaining homeostasis. 



The NS regulates body activities by responding rapidly using nerve impulses
The endocrine system regulates and responds by releasing hormones.



Function - Helps maintain homeostasis
HOW???










Regulate chemical composition and volume of internal environment Help regulate metabolism and energy balance
Help regulate contraction of smooth and cardiac muscle fibers and secretion of glands
Regulate some activities of immune system
Play role in smooth, sequential integration of growth and development
Contribute to basic process of reproduction

How does the endocrine system keep its fingers in
EVERYTHING???

HORMONES

Endocrine System


Endocrine organs








Pituitary gland
Pineal gland
Thyroid gland
Parathyroid glands
Adrenal: 2 glands
 Cortex
 Medulla

Endocrine cells in other organs





Pancreas
Thymus
Gonads
Hypothalamus

What induces hormone release???
Mechanisms of Hormone Release
-humoral: in response to changing levels of ions or nutrients in the blood
-neural: stimulation by nerves
- hormonal: stimulation received from other hormones

General Characteristics


System of ductless glands that secrete hormones
 Hormones are “messenger molecules”
 Circulate in the blood
 exceptions: paracrine, autocrine hormones
 Act on distant target cells
 exceptions: paracrine, autocrine hormones
 Target cells respond to the hormones for which they have receptors  The effects are dependent on the programmed response of the target cells
 Hormones are just molecular triggers

Circulating Hormones

Paracrine Hormones

Autocrine Hormones



Lipid-soluble


Steroids


Lipids structurally similar to cholesterol






Synthesized from cholesterol
Released by male and female reproductive organs, adrenal glands and kidneys

Thyroid hormones
Nitric oxide (gas) – both hormone and neurotransmitter What is the significance of lipid soluble????

Steroid Hormones



Water-soluble Hormones


Amines
Structurally similar to amino acids
 Released by adrenal medulla, thyroid, and pineal gland
 Most are synthesized from amino acid tyrosine




Water-soluble Hormones


Peptide hormones



Chains of amino acids (30 49 each)
Largest class and includes all hormones secreted by hypothalamus, pituitary gland, heart, thymus, digestive tract, and pancreas

Oxytocin



Water-soluble Hormones


Eicosanoids



Small molecules with 5- carbon ring at one end
Includes prostaglandins and leukotrienes, important paracrine factors

Derived from a 20 carbon fatty acid







For hormone to affect target cell, it must first interact with appropriate receptor
Hormone receptors may be on cell membrane or inside cell
Water soluble hormones- cannot penetrate cell membrane 



Hence, receptors for catecholamines, peptide hormones, and eicosanoids are found on cell membranes Lipid soluble hormones pass into cell and bind to receptors in cell nucleus

Action of Lipid Soluble Hormones
1. Released from transport protein in blood Note: receptor is in the cell

2. Diffuses into cell binds to receptor in nucleus 3. Activates gene expression

End result: synthesis of new proteins that alter cell activity

Mechanism of action of the water-soluble hormones






Hormone (1st messenger) released from endocrine gland bloodstream
Travels thru the body, passes out of capillary and binds to cells with the appropriate receptor.
Receptor binding induces appearance/ action of a 2nd messenger




2nd messengers include: enzyme activators, inhibitors, or cofactors (net result is change in rates of various metabolic reactions)

Most important second messengers are cyclic AMP, cyclic GMP, and calcium ions



Hormones and cell membranes


Binding of hormone to receptors may lead to release of many (thousands) of 2nd messengers--called amplification



G-protein- common link between 1st and 2nd messengers 

an integral membrane