{"id":564,"date":"2015-08-16T14:19:41","date_gmt":"2015-08-16T14:19:41","guid":{"rendered":"http:\/\/sites.msudenver.edu\/haysc\/?page_id=564"},"modified":"2020-03-13T19:38:56","modified_gmt":"2020-03-13T19:38:56","slug":"outline-4-bio-3360-ionic-and-osmotic-balance","status":"publish","type":"page","link":"https:\/\/sites.msudenver.edu\/haysc\/biology-courses\/animal-physiology-bio-3360\/outline-4-bio-3360-ionic-and-osmotic-balance\/","title":{"rendered":"Outline-4, BIO 3360, Ionic and Osmotic Balance"},"content":{"rendered":"

I. Introduction –Kidneys are the main organs controlling ion and water balance, but gills, skin and digestive mucosa also play a role<\/em><\/p>\n

A. Osmotic Regulation<\/strong>–\u00a0The control of tissue osmotic pressure requires the movement of solutes across membranes since animals cannot actively pump water.<\/em><\/p>\n

B. Ionic Regulation<\/strong>–\u00a0The control of ionic composition of body fluids – especially those that are important solutes.<\/em><\/p>\n

C. Nitrogen Excretion\u00a0<\/strong>–Ridding the body of nitrogen waste from protein catabolism in the form of ammonia, uric acid, and urea.<\/em><\/p>\n

D. While some animals maintain osmotic\/ionic balance like their surroundings, most need to regulate ions and osmotic composition.<\/p>\n

1. Marine animals are challenged to expel ions (especially NaCl) against ionic gradients and obtain water against osmotic gradients.<\/p>\n

2. Fresh water animals need to acquire ions from ion-poor water and dispose of excess water.<\/p>\n

3. Terrestrial animals are challenged with a constant threat of dehydration.<\/p>\n

II. Aquatic Environments<\/p>\n

A. Ionoconformer<\/strong>–\u00a0Internal conditions are similar to external conditions even if the external conditions change. ECF resembles seawater in terms of the major cations and anions.<\/em><\/p>\n

1. Typically saltwater animals – typically simple animals such as sea anemones, coral, jellyfish, sea squirts.<\/p>\n

B. Ionoregulator<\/strong>–\u00a0Controls the internal conditions in ECF by using ion absorption and excretion strategies.<\/em><\/p>\n

1. Examples include squid, shark, tuna, killer whale, flounder, sea turtle in saltwater<\/p>\n

2. Examples include freshwater animals<\/p>\n

3. Eases the burden of individual cells to regulate ions<\/p>\n

C. Osmoconformer<\/strong>–\u00a0Internal osmolarity is close to that of external environment even if external environment changes.\u00a0 (Osmolality is the solute concentration that will determine if water moves by osmosis.)<\/em><\/p>\n

1. Examples include marine invertebrates such as clams and primitive vertebrates such as sharks.<\/p>\n

D. Osmoregulator\u00a0<\/strong>–Internal osmolarity is maintained within a narrow range regardless of external environment.<\/em><\/p>\n

1. Marine vertebrates such as flounder, maintain internal osmolarity much below surrounding saltwater<\/p>\n

2. Freshwater vertebrates such as goldfish, and freshwater invertebrates such as the mayfly and clam, maintain an internal osmotic pressure well above that of the surrounding water.<\/p>\n

3. Many different osmoregulatory mechanisms have evolved in different animals.<\/p>\n

III. Water sources –\u00a0all living things need a source of water especially for terrestrial animals<\/em><\/p>\n

A. Aquatic animals have a constant source of water<\/p>\n

B. Diet is a mixture of water and solutes<\/p>\n

C. Water is a metabolic by-product<\/p>\n

IV.Inorganic and Organic Solutes – Potassium, sodium, chloride, sulfate ions, as well as amino acids, glucose, urea<\/p>\n

A. Cell volumes are controlled by transporting solutes in and out of extracellular fluid.\u00a0 Note we transport solutes because water cannot be actively moved.<\/p>\n

1. Regulatory Volume Increase\u00a0<\/strong>(RVI) –\u00a0importing ions causing an influx of water<\/em><\/p>\n

a. Most common mechanism is the Na+<\/sup>\/K+<\/sup>\/2Cl–<\/sup> cotransporter which brings sodium, potassium and chloride into the cell and water follows<\/p>\n

2. Regulatory Volume Decrease<\/strong>(RVD) –\u00a0exporting ions, causing an efflux of water.<\/em><\/p>\n

a. Activation of K+<\/sup> channels cause K+<\/sup> to exit cell resulting in hyperpolarization; Opening of Cl–<\/sup> channels cause Cl–<\/sup> to exit cell in response to hyperpolarization; As K+<\/sup> and Cl–<\/sup>, both solutes exit cell, water follows<\/p>\n

b. K+<\/sup>\/Cl–<\/sup> Cotransporter activation results in both solutes to leave cell and water follows the solutes<\/p>\n

c. Na+<\/sup>\/Ca2+<\/sup> exchanger expels Na+<\/sup> and imports Ca2+<\/sup>; Calcium is then exported via the Ca2+<\/sup> ATPase; water follows<\/p>\n

d. Na+<\/sup>\/K+<\/sup> ATPase exports three sodium for every two potassium entering reducing intracellular osmolarity and water follows the majority of the solutes<\/p>\n

V. Integument –epithelium is an osmotic barrier<\/em><\/p>\n

A. Epithelium with aquaporins are more permeable to water than those without these proteins in the cell membrane<\/p>\n

B. Solutes move by transcellular and paracellular transport (See unit 1)<\/p>\n

C. Mucus (hydrophobic), keratin (protein forming dense envelope), insect cuticle (hydrophobic covering) reduce water loss<\/p>\n

VI. Gills –transport ions into and out of water and the direction depends on the salinity of the water<\/em><\/p>\n

VII. Digestive epithelium –\u00a0digestion involves moving solutes and water across the gut wall<\/em><\/p>\n

VIII. Salt glands –\u00a0most birds and reptiles have salt gland that can excrete hyperosmotic solutions of Na+<\/sup> and Cl–<\/sup> which allows the drinking of hypertonic water. Bird salt gland are found at base of beak and near the eye in reptiles<\/em><\/p>\n

A. Salt gland is a series of secretory tubules that open to the surface and are surrounded by a network of capillaries<\/p>\n

B. Salt can be concentrated in gland by countercurrent multiplier system –if blood moves left to right, it becomes more dilute as the salt escapes the bloodstream to the interstitial space; interstitial fluid is more concentrated with salt to the left and less concentrated to the right; fluid in the tubules moves right to left and are exposed to an increasing concentration of salt and therefore the fluid in the lumen of the tubules becomes increasingly concentrated.<\/em><\/p>\n

IX. Rectal glands –salt excretion glands in sharks<\/em><\/p>\n","protected":false},"excerpt":{"rendered":"

I. Introduction –Kidneys are the main organs controlling ion and water balance, but gills, skin and digestive mucosa also play a role A. Osmotic Regulation–\u00a0The control of tissue osmotic pressure requires the movement of solutes across membranes since animals cannot … Continue reading →<\/span><\/a><\/p>\n","protected":false},"author":270,"featured_media":0,"parent":292,"menu_order":0,"comment_status":"closed","ping_status":"open","template":"","meta":{"_exactmetrics_skip_tracking":false,"_exactmetrics_sitenote_active":false,"_exactmetrics_sitenote_note":"","_exactmetrics_sitenote_category":0,"footnotes":""},"class_list":["post-564","page","type-page","status-publish","hentry"],"_links":{"self":[{"href":"https:\/\/sites.msudenver.edu\/haysc\/wp-json\/wp\/v2\/pages\/564","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/sites.msudenver.edu\/haysc\/wp-json\/wp\/v2\/pages"}],"about":[{"href":"https:\/\/sites.msudenver.edu\/haysc\/wp-json\/wp\/v2\/types\/page"}],"author":[{"embeddable":true,"href":"https:\/\/sites.msudenver.edu\/haysc\/wp-json\/wp\/v2\/users\/270"}],"replies":[{"embeddable":true,"href":"https:\/\/sites.msudenver.edu\/haysc\/wp-json\/wp\/v2\/comments?post=564"}],"version-history":[{"count":0,"href":"https:\/\/sites.msudenver.edu\/haysc\/wp-json\/wp\/v2\/pages\/564\/revisions"}],"up":[{"embeddable":true,"href":"https:\/\/sites.msudenver.edu\/haysc\/wp-json\/wp\/v2\/pages\/292"}],"wp:attachment":[{"href":"https:\/\/sites.msudenver.edu\/haysc\/wp-json\/wp\/v2\/media?parent=564"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}