gen physio: physiology

• Cell membrane limits the boundary of the cell.
• The membrane is impermeable to most of the anions in the cell, so the K+ efflux is not accompanied by an equal flux of anions and the membrane is maintained in a polarized state, with the interior of the cell negatively charged and the exterior area positively charged.
• Intercellular bridges fasten the cells to one another and to the surrounding tissues and permit transfer of ions and other molecules from one cell to another.
• Mitochondria are the power-generating unit of the cell.
• Lysosomes contain enzymes which would cause destruction of cellular components once released.
• Microfilaments cause contraction.
• Microtubules make up the skeletal framework of the cell; provide the pathway along which secretory granules move to the cell membrane; play a key role in nerve fiber outgrowth.
• Centrioles are concerned with the movement of the chromosomes during cell division.
• Golgi complex packages cellular products.
• Endoplasmic reticulum contains ribosomes which are the sites of protein synthesis.
• Nucleolus contains RNA which regulates protein synthesis.
• Nucleus contains chromosomes which are the carriers of hereditary traits of the individual.
• Body weight is composed of 60% water, 40% protein, 18% fats, 15% minerals, and 7% in the vascular system, 75% outside V.S.
• Forces producing movements of water and other molecules across membranes or barriers include diffusion, solvent drag, filtration, osmosis, active transport, exocytosis/endocytosis.
• Diffusion is the process by which a gas or a substance, in solution, expands because of the motion of its particles to fill all of the available volume.
• The movement of the particles of a substance dissolved in a solvent are in continuous random movement.
• In regions where they are abundant, particles frequently collide and, therefore, tend to spread from regions of high concentration to regions of low concentration until the concentration is uniform throughout the solution.
• Diffusion is also affected by electric charge and permeability of the barrier.
• Donnan effect states that when there is an ion on one side of a membrane, the distribution of other ions to which the membrane is permeable to is affected.
• Solvent drag occurs when solvent is moving in one direction, the solvent tends to drag along some molecules of the solute.
• Filtration is the process by which fluid is forced through a membrane or other barriers due to a difference in hydrostatic pressure on the two sides; molecules that are smaller in diameter than the pores of the membrane pass through with the fluid and larger molecules are retained.
• The vacuole inside the cell will be mixed with the digestive enzymes of the lysosome.
• The distribution of ions across cell membrane and the nature of this membrane are responsible for the presence of membrane potential.
• Cell membranes are moderately permeable to Na+.
• Ions in the body are hydrated, so although K+ is larger than Na+, hydrated Na+ is larger than hydrated K+.
• Endocytosis is the reverse of exocytosis, one form is phagocytosis or cell eating.
• The passage of Na+ through Na+ channels in excitable tissues such as muscles and nerves is greatly increased by a decrease in membrane potential.
• The unique properties of the cell membranes are responsible for the differences in the composition of the intracellular and interstitial fluid compartments.
• The ease with which ions pass through some of these channels is controlled by voltage.
• Active transport requires energy and is referred to as active transport.
• After a certain time, an equilibrium is reached and Cl influx will be equal to Cl efflux.
• Active transport involves ions and larger non-ionized molecules being transported by carrier molecules in the membrane.
• The ease with which ions pass through some of these channels is also controlled by agents called neurotransmitters which may bind to receptors associated with the ions.
• Those with greater pressure are hypertonic, while those with lesser pressure are hypotonic.
• Ca++ has an intracellular concentration that is very low, therefore, electrical and concentration gradients are both directed inward.
• Solutions that have the same EOP as plasma are said to be isotonic, such as NSS (normal salt solution or 0.9 % NaCl).
• Na+ has a chemical gradient that is inward, an electrical gradient that is inward, and a concentration gradient that is inward.
• The pressure necessary to prevent solvent migration is called effective osmotic pressure of the solution.
• Since the permeability of the membrane to K+ is much greater than it is to Na+ at rest, the passive K+ efflux is much greater than the passive Na+ influx.
• Facilitated diffusion is a process where transport is from an area of greater concentration of the transported molecules to an area of lesser concentration, and no energy is required.