Fluid and Electrolyte Balance (Physiology)

Chapter 20 -- Fluid and Electrolyte Balance **[20.1 Fluid and Electrolyte Homeostasis]** **REVIEW INTO MATERIAL** \- Renal, respiratory, & cardiovascular system control fluid & electrolyte balance \- renal compensation is slower than respiratory and cardiovascular \- renal/kidneys = under endoc...

Chapter 20 -- Fluid and Electrolyte Balance **[20.1 Fluid and Electrolyte Homeostasis]** **REVIEW INTO MATERIAL** \- Renal, respiratory, & cardiovascular system control fluid & electrolyte balance \- renal compensation is slower than respiratory and cardiovascular \- renal/kidneys = under endocrine/neuroendocrine control \- respiratory & cardiovascular system = neural control \- **high osmolarity = low water volume less urine** **- low osmolarity = high water volume more urine volume** \- kidney = primary route of ion & water excretion A diagram of blood flow Description automatically generated 1\. SKIP [2. Explain how the countercurrent multiplier in the loop of Henle is the key to the regulation of urine concentration] - Creates **high osmolarity** in the interstitial fluid of medulla by **active transport** of Na+, Cl-, & K+ out of the nephron. - This occurs in the thick [ascending limb] - Necessary for making concentrated urine as filtrate flows through collecting duct - Pumping ions = establishes a gradient so other things can follow it passively - [Vasa recta] capillaries form a **countercurrent exchanger** that [removes water] leaving the nephron so water won't dilute the medulla interstitial fluid - **Urea** plays a large role in increasing interstitial osmolarity  A diagram of a complex number Description automatically generated with medium confidence **[20.2 Water Balance]** **[3. Map in detail the reflex pathway through which vasopressin controls water reabsorption in the kidney]** - **[Vasopressin / arginine vasopressin (AVP) / antidiuretic hormone (ADH)]** - Controls **collecting duct permeability** to water in a **graded fashion** - Increases aquaporins on apical membrane of collecting duct - **Graded effect** -- matches urine concentration to body's water volume need - As plasma osmolarity rises (from dehydration or solute intake) the body releases more vasopressin to retain water & attempts to lower osmolarity by increasing water absorption - When vasopressin is absent = water permeability is nearly zero - Lots of ADH/vasopressin lots of water reabsorption very concentrated urine - Low ADH low water reabsorption dilute urine - [Increase in ECF osmolarity, decrease atrial stretch from low blood volume, or a decrease in blood pressure **stimulates vasopressin release** from **the posterior pituitary**] - Osmolarity is monitored by **hypothalamic osmoreceptors** - Blood pressure and blood volume are sensed by receptors in the **carotid and aortic baroreceptors,** & in by **atrial stretch receptors** in the heart  A diagram of a blood vessel Description automatically generated 4\. Diagram the cellular mechanism of action of vasopressin on principal cells  - Receptor is on basolateral side - Binding activates cAMP **[20.3 Sodium Balance and ECF Volume]** **[5. Map the homeostatic responses to salt ingestion]** A diagram of a flowchart Description automatically generated **[6. Diagram the cellular mechanism of aldosterone action at principal cells]** - Aldosterone = steroid hormone made on demand - Made in **adrenal cortex** - Stimulated by: - low BP (via renin) - high K+ (hyperkalemia) - [Natriuretic peptides inhibits if ECF osmolarity is very high] - Has cytosolic receptor - **Makes new ion channels and pumps** - **Increased Na+ absorption & increased K+ secretion** - Acts on principal cells of Renal collecting duct - **Enhances Na+/K+ ATPase activity** - **Increases open time of leak channels** - Aldosterone secretion is also stimulated by angiotensin II - In response to low blood pressure granular cell in kidney secretes **renin** converts **angiotensinogen** in blood to **angiotensin I** Angiotensin-converting enzyme (**ACE**) Converts ANG I to ANG II - **Renin** release signal is either directly/indirectly related to low blood pressure  **\*\*\*Aldosterone controls potassium levels in the body** A diagram of a cell cycle Description automatically generated **REVIEW THIS SO WELL** **[7. Map the renin-angiotensin-aldosterone system (RAAS), including all the responses initiated by ANG II and aldosterone]** - Aldosterone secretion is also stimulated by angiotensin II - In response to low blood pressure granular cell in kidney secretes **renin** converts **angiotensinogen** in blood to **angiotensin I** Angiotensin-converting enzyme (**ACE**) Converts ANG I to ANG II - **Renin** release signal is either directly/indirectly related to low blood pressure  **Low blood pressure results in renin production... 3 ways:** - Increasing sympathetic activity causing granular cells to produce renin - Granular cells themselves directly sense stretch... from low BP - Low GFR results in less NaCl transport... causing maculla densa to release paracrines A diagram of a diagram Description automatically generated **REVIEW SO WELL** **- ultimately raises BP** **[8. Describe the release of natriuretic peptides and their effects on sodium and water reabsorption]** - Atrial natriuretic peptide (ANP) and brain natriuretic peptide (BNP) - Made in the brain - Enhance Na+ excretion and urinary water loss by - increasing GFR, - inhibiting tubular reabsorption of NaCl - inhibiting release of renin, aldosterone, and vasopressin  A diagram of a chemical reaction Description automatically generated - **ANP does almost opposite of ANG 2** \*ANP is the only one released in response to high blood pressure **[20.4 Potassium Balance]** \- potassium homeostasis keeps plasma K+ concentrations in a narrow range \- **Hyperkalemia** = too much potassium in blood \- can lead to cardiac arrhythmias \- **Hypokalemia** = too little potassium in blood \- muscle weakness and failure of respiratory muscles & the heart 9\. SKIP **[20.5 Behavioral Mechanisms in Salt and Water Balance]** 10\. SKIP \- Thirst is triggered by [hypothalamic osmoreceptors] and relieved by drinking \- **Salt appetite** is triggered by [aldosterone and angiotensin] **[20.6 Integrated Control of Volume, Osmolarity, and Blood Pressure]** - Homeostatic changes follow the Law of mass balance - Fluid and solute added to body must be removed - Fluid and solute lost from body must be replaced **[11. Diagram the appropriate homeostatic compensations for different combinations of volume and osmolarity disturbances]** - **Osmolarity and volume can change independently** - Dehydration triggers homeostatic response - Compensation involves cardiovascular, ANG II, vasopressin, and thirst  **REVIEW SO WELL** **[20.7 Acid---Base Balance]** - CO2 from respiration is the biggest source of acid - CO2 combines with water H+ and HCO3- with the help of carbonic anhydrase [12. Compare and contrast the three mechanisms by which the body copes with minute-to-minute changes in pH] - 3 mechanisms the body uses to cope for pH - **Buffers systems** include proteins, phosphate ions, and HCO3- - Moderate changes in pH by combining with or releasing H+ - HCO3- is the best extracellular buffer in the body - Buffers organic acids produced by metabolism - **Ventilation** can compensate for pH disturbances - Corrects 75% of disturbances & can also cause disturbances - Ventilation changes plasma pCO2 affects H+ and HCO3- - **Kidneys** - Use ammonia and phosphate buffers to buffer urine - Proximal tubule secretes H+ and reabsorbs HCO3- - Distal nephron can secrete or reabsorb H+ and HCO3- to regulate pH of extracellular fluid - Abnormal pH affects the nervous system: - Acidosis -- neurons become less excitable CNS depression - Alkalosis -- neurons become hyperexcitable; if severe muscle tetanus **[13. Diagram the reflex pathways and cellular mechanisms involved in respiratory compensation of pH changes]** A diagram of a diagram of a person\'s face Description automatically generated [14. Diagram the mechanisms by which the kidneys compensate for pH changes] - Just know kidney info from above - Intercalated cells = in **collecting duct**; responsible for fine pH regulation - **Acidosis** - [Type A intercalated cells HELP correct ACIDOSIS] - Kidneys secrete/excretes H+ - reabsorbs HCO3- and K+ - **Alkalosis** - [Type B intercalated cells HELP correct AKALOSIS] - Kidneys secrete/excrete HCO3- and K+ - H+ is reabsorbed