intracellular fluid

Examples of intracellular fluid in the following topics:

• Body Fluid Composition

  • The cytosol or intracellular fluid consists mostly of water, dissolved ions , small molecules, and large water-soluble molecules (such as proteins).
  • The pH of the intracellular fluid is 7.4.
  • The concentrations of the other ions in cytosol or intracellular fluid are quite different from those in extracellular fluid.
  • Ocular fluid in the eyes contrasts cerebrospinal fluid by containing high concentrations of proteins, including antibodies.
  • Describe the composition of intracellular and extracellular fluid in the body

• Fluid Compartments

  • The major body fluid compartments include: intracellular fluid and extracellular fluid (plasma, interstitial fluid, and trancellular fluid).
  • The intracellular fluid of the cytosol or intracellular fluid (or cytoplasm) is the fluid found inside cells.
  • Although water forms the large majority of the cytosol, its mainly functions as a fluid medium for intracellular signaling (signal transduction) within the cell, and plays a role in determining cell size and shape.
  • It is the intravascular fluid part of extracellular fluid (all body fluid outside of cells).
  • Examples of this fluid are cerebrospinal fluid, and ocular fluid, joint fluid, and the pleaural cavity which contain fluid that is only found in their respective epithelium-lined spaces.

• Water Content in the Body

  • A significant percentage of the human body is water, which includes intracellular and extracellular fluids.
  • Water also provides a fluid environment for extracellular communication and molecular transport throughout the body.
  • The water in the body is distributed among various fluid compartments that are interspersed in the various cavities of the body through different tissue types.
  • In diseased states where body water is affected, the fluid compartments that have changed can give clues to the nature of the problem.

• Introduction to Osmoregulation

  • The intake is balanced by more or less equal excretion of fluids by urination, defecation, sweating, and, to a lesser extent, respiration.
  • The solutes in body fluids are mainly mineral salts and sugars.
  • The body's fluids include blood plasma, the cytosol within cells, and interstitial fluid, the fluid that exists in the spaces between cells and tissues of the body.
  • Mammalian systems have evolved to regulate osmotic pressure by managing concentrations of electrolytes found in the three major fluids: blood plasma, extracellular fluid, and intracellular fluid.
  • Water movement due to osmotic pressure across membranes may change the volume of these fluid compartments.

• Types of Receptors

  • Receptors, either intracellular or cell-surface, bind to specific ligands, which activate numerous cellular processes.
  • The toxin then enters these intestinal cells, where it modifies a G-protein that controls the opening of a chloride channel and causes it to remain continuously active, resulting in large losses of fluids from the body that can lead to potentially fatal dehydration.
  • Enzyme-linked receptors are cell-surface receptors with intracellular domains that are associated with an enzyme.
  • In some cases, the intracellular domain of the receptor itself is an enzyme or the enzyme-linked receptor has an intracellular domain that interacts directly with an enzyme.
  • Many intracellular receptors are transcription factors that interact with DNA in the nucleus and regulate gene expression.

• Short-Term Chemical Control

  • When stimulated a signal transduction cascade leads to increased intracellular calcium from the sarcoplasmic reticulum through IP3 mediated calcium release, as well as enhanced calcium entry across the sarcolemma through calcium channels.
  • The rise in intracellular calcium complexes with calmodulin, which in turn activates myosin light chain kinase.
  • Once elevated, the intracellular calcium concentration is returned to its basal level through a variety of protein pumps and calcium exchangers located on the plasma membrane and sarcoplasmic reticulum.
  • Localized tissues utilize multiple ways to increase blood flow including releasing vasodilators, primarily adenosine, into the local interstitial fluid which diffuses to capillary beds provoking local vasodilation.
  • Dephosphorylation by myosin light-chain phosphatase and induction of calcium symportersand antiporters that pump calcium ions out of the intracellular compartment both contribute to smooth muscle cell relaxation and therefore vasodilation.

• Microbial Growth at Low or High pH

  • The pH of different cellular compartments, body fluids, and organs is usually tightly regulated in a process called acid-base homeostasis.
  • Most acidophile organisms have evolved extremely efficient mechanisms to pump protons out of the intracellular space in order to keep the cytoplasm at or near neutral pH.
  • Therefore, intracellular proteins do not need to develop acid stability through evolution.

• Type IV (Delayed Cell-Mediated) Reactions

  • Historically, the immune system was separated into two branches: humoral immunity, for which the protective function of immunization could be found in the humor (cell-free bodily fluid or serum) and cellular immunity, for which the protective function of immunization was associated with cells.
  • 1. activating antigen-specific cytotoxic T-lymphocytes that are able to induce apoptosis in body cells displaying epitopes of foreign antigen on their surface, such as virus-infected cells, cells with intracellular bacteria, and cancer cells displaying tumor antigens
  • It is most effective in removing virus-infected cells, but also participates in defending against fungi, protozoans, cancers, and intracellular bacteria.
  • Activated CD8+ T cells destroy target cells on contact, whereas activated macrophages produce hydrolytic enzymes and, on presentation with certain intracellular pathogens, transform into multinucleated giant cells.

• Endocytosis

  • The pocket pinches off, resulting in the particle being contained in a newly-created intracellular vesicle formed from the plasma membrane.
  • This literally means "cell drinking" and was named at a time when the assumption was that the cell was purposefully taking in extracellular fluid.
  • In reality, this is a process that takes in molecules, including water, which the cell needs from the extracellular fluid.
  • Instead, it will stay in those fluids and increase in concentration.
  • In pinocytosis, the cell membrane invaginates, surrounds a small volume of fluid, and pinches off.

• Polycystic Kidney Disease

  • The cysts are numerous and are fluid-filled, resulting in massive enlargement of the kidneys.
  • Gene PKD-1 is located on chromosome 16, and codes for a protein involved in regulation of cell cycle and intracellular calcium transport in epithelial cells; it is responsible for 85% of the cases of ADPKD.
  • As the cysts accumulate fluid, they enlarge, separate entirely from the nephron, compress the neighboring renal parenchyma, and progressively compromise renal function.
  • Under the function of gene defect, epithelial cells of renal tubule turn into epithelial cells of cyst wall after phenotype change and begin to have the function of secreting cyst fluid, which leads to continuous cysts enlargement.