Urine Movement

URINE MOVEMENT

● as the bladder fills with urine, pressure increases and micturition reflex is activated by the stretch of the bladder ● action potentials are conducted from the bladder to the spinal cord through the pelvic nerves ● parasymphathetic nerves carries action potentials that causes the bladder to contract ● decreased action potentials carried by the somatic motor nerves causes the external sphincter to relax ● 2 ways on how the micturtion reflex is controlled by higher brain centers: ● in the ascending tract, when the bladder is stretched, there is an increased frequency of action potentials up in the spinal cord to the pons and cerebrum. This increases the conscious desire to urinate ● descending tracts, it carries action potentials from the cerebrum to the sacral region of the spinal cord to stimulate the micturition reflex and when one voluntarily chooses to urinate ● micturition reflex is inhibited by the higher brain centers by sending action poptentials through the spinal cord to decrease the intensity of the autonomic reflex that stimulates nerve fibers that keeps the external urinary sphincter contracted ● the ability to voluntarily inhibit micturition develops at the age of 2-3 years

BODY FLUID COMPARTMENTS adult male – 60% consists of water adult female – 50% consists of water *smaller percentage of the body weight of the adult female consists of water because females generally have a greater percentage of body fats than males 2 major compartments: ● intracellular fluid compartment - fluid inside all the cells of the body

- enclosed by trillions of small compartments - composition and movement of fluid across the cell membrane are equal - 2/3 of all the water in the body

● extracellular fluid compartment - all the fluid outside the cell - 1/3 of total body water - interstitial fluid, plasma and fluid in the lymphatic vessels - separated into subcompartments - includes the aqueous and vitreous humor of the eye, cerebrospinal fluid, synovial fluid, serous fluid and fluid secreted by glands

COMPOSITION OF THE FLUID IN THE BODY FLUID COMPARTMENTS ● intracellular fluid contains relatively high concentration of ions: K+, MG2+, PO43-, SO42● extracellular fluid has a lower concentration of Na, Ca, Cl- and HCO – ● concentration of protein in the intracellular fluid is greater than that in the extracellular fluid ● the extracellular fluid also has a fairly consistent composition from one area of the body to another EXCHANGE BETWEEN BODY FLUID COMPARTMENTS ● cell membranes that separate the body fluid compartments are selectively permeable ● much less permeable to ions dissolve ● water movement is regulated by hydrostatic pressure differences and osmotic differences ● the intracellular fluid can help maintain the extracellular fluid volume if it is depleted ● helps to maintain blood volume ● can help prolong the time a person can survive conditions such as dehydration or cardiovascular shock ● if concentration of ions decreases in the extracellular fluid, water moves from the extracellular fluid into the cells causing the cells to swell