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A&P Lecture 18
| Question | Answer |
|---|---|
| Diabetes insipidus | this differs from diabetes mellitus as blood glucose levels are normal, but kidneys cannot properly concentrate urine |
| Septic shock | vasopressin is a potent vasopressor (causes constriction of blood vessels) for improved organ perfusion during septic shock |
| Blood clotting disorders | reduces bleeding through vasopressor activity |
| ADH binds to its membrane receptor which is a | GPCR (g-aS) |
| ADH receptor is a G alpha S, meaning | ligand binding stimulates the enzyme adenylate cyclase to synthesize cAMP (a second messenger) |
| cAMP then promotes insertion of aquaporin 2 into the apical membrane of the DCT and collecting ducts, thereby | increasing permeability |
| Water exits the lumen and enters the | tubule cells through this newly inserted channel |
| Water then exits the tubule cells and is reabsorbed through | aquaporin-3 and 4 located on basal membrane |
| The Renin-Angiotensin-Aldosterone-System (RAAS) | critical regulator of BP, electrolyte balance, and systemic vascular resistance |
| Renin is what Secreted into where? | an enzyme secreted into blood by kidneys following a drop in BP or fluid volume |
| Angiotensinogen is secreted by | liver |
| Renin then cleaves | angiotensinogen into angiotensin 1 |
| ACE (angiotensin-converting enzyme) is released from | lungs and further cleaves angiotensin 1 into angiotensin 2 |
| Angiotensin 2 is the active form of this molecule which circulates to: | Blood vessels where it directly stimulates vasoconstriction Adrenal cortex to stimulate release of aldosterone. Aldosterone acts on kidneys to stimulate reabsorption of water |
| BOTH a and b help to | increase BP and maintain homeostasis |
| Effects of aldosterone on kidney | critical modulators of gene expression during water conversation |
| Aldoserone is secreted by the | adrenal cortex under low blood pressure conditions. |
| Aldosterone is a | steroid hormone that binds to nuclear receptors which change gene expression |
| Aldosterone elicits responses at the DCT, but its effects are strongest and most well studied at the | collecting ducts |
| Aldosterone binds to its nuclear receptor increasing | the synthesis of Na/K pumps (mobilized to basal membrane) and the Na antiporters (mobilized to apical membrane facing the lumen) |
| These new transport proteins: (they increase 2 things) | Increase secretion of K+ AND Increase absorption of Na+ and water Water travels with Na+ due to osmotic pressure changes! |
| Increased water retention increases | blood pressure |
| ACE inhibitors are a class of mediation used primarily for the | treatment of high blood pressure and heart failure |
| ACE inhibitors inhibit the activity of angiotensin-converting enzyme, which is | an important component of the renin-angiotensin system which converts angiotensin 1 to angiotensin 2 |
| Drugs such as Benazepril, Captopril, and Lisinopril are used to treat | Acute myocardial infarction (heart attack) Heart failure (left ventricular systolic dysfunction) High BP associated with diabetes mellitus (diabetic nephropathy) by means of decreasing the BP and increasing perfusion in glomerular arterioles |
| Atrial natriuretic hormone (ANH) | a hormone secreted by cells in the right atrium when they are stretched higher than usual |
| ANH is also called | ANP (atrial natriuretic peptide) and functions opposite that of ADH |
| ANH is released when | BP or volume increases. This detected by mechanoreceptors in the right atria |
| ANH decreased | Na+ and water reabsorption in the DCT. More urine |
| ANH inhibits | ADH secretion from posterior pituitary |
| ANH dilates | arteries which reduces peripheral resistance |
| Together, these effects reduce | BV and BP. Thus venous return of blood to right atria no longer stimulates release of ANS |
| Fluid homeostasis: | water accounts for at least half of the total body weight of the human body This percentage varies with developmental stage, biological sex, and body composition. For example, in infants, 75% of their total weight is water |
| The total amount of water in the body is separated into 2 fluid compartments | The intracellular fluid compartment The extracellular fluid compartment (interstitial fluid) |
| Each fluid compartment is composed of | water, ions called electrolytes, and other solutes. These are specific electrolyte distributions in the intracellular fluid compared with the extracellular fluid |
| ***Maintaining a relative constant concentration of solutes is crucial for cellular function | |
| Solutes concentrations drop when | sweating and when hyperhydrated |
| Hyperhydration aka water poisoning: | Extreme water poisoning caused swelling in the brain, seizures, and heart failure Mild symptoms include headache, confusion, and nausea Easily avoided with electrolytes or a small amount of food |
| Dehydration | occurs when body fluid volume drops below its set point, increasing its osmolarity |
| One early sign of dehydration is | thirst, triggered when plasma osmolarity rises or blood volume falls. |
| As dehydration develops | water loss often exceeds solute loss, increasing extracellular fluid solute concentration (hypertonic ECF). |
| Cells exposed to a hypertonic extracellular environment lose water by osmosis | causing cells to shrink and potentially function abnormally. |
| Severe dehydration is often treated with | fluids containing water and electrolytes, rather than plain water alone, to restore both volume and electrolyte balance and avoid dilutional hyponatremia. |
| Acid-Base Balance | Hydrogen ions affect the activity of the enzymes and interact with many electrically charged molecules |
| ***pH is the measure of the acidity or basicity of a solution. This is calculated by the inverse logarithmic concentration of the hydrogen (H+) ions | |
| Acids ______ H+ into a solution (high H+ concentration= low pH) | releases |
| Bases ______ H+ from a solution (low H+ concentration= high pH | removes |
| Maintaining the H+ concentration within a narrow range of values is essential for normal metabolic reactions. Body fluids contain buffers that prevent extreme changes in pH These include | phosphate buffer and bicarbonate buffer |
| Regulation of Acid-Base Balance: there are 2 major mechanisms for regulation of H+ concentration. | Chemical buffer systems Physiological buffer systems. |
| Chemical buffers act | directly on H+ ions to almost instantaneously resist changes in the pH of body floods These bicarbonate and phosphate buffer systems that act to neutralize excess H+ ions and stabilize pH |
| Physiological buffers are | slow and include 2 principle systems: The respiratory system The renal system |
| The respiratory system | provides short-term changes in acid-base balance through exchange of CO2 at respiratory membre. This response takes place within a few minutes |
| The renal system: provides long-term and more substantial changes in acid-balance. It responds within hours to days. This is accomplished through the altering secretion and reabsorption of H+ and HCO3- (bicarbonate) | |
| Alkalosis | blood pH rises above 7.45 due to excess bicarbonate or loss of acid |
| Alkalosis Physiological Effects | CNS and muscular excitability (twitches, spasms) Hypoventilation Possible hypokalemia (Low K+) Severe cases: arrhythmia, seizures |
| Alkalosis Common causes | Vomiting (loss of stomach acid) hyperventilation/anxiety Excess antacid use Diuretic use |
| Alkalosis Treatment | Treat the cause, normalize breathing, give fluids, and lower potassium (if present) |
| Acidosis | blood pH falls below 7.35 due to excess acid or loss of bicarbonate |
| Acidosis Physiological effects | CNS depression ( fatigue, confusion, lethargy) Hyperventilation Possible hyperkalemia (High K+) Severe cases: coma, arrhythmia |
| Acidosis Common causes | Diabetic ketoacidosis (DKA) Kidney failure Severe diarrhea COPD |
| Acidosis Treatment | Treat the cause, normalize breathing, give fluids, and increase potassium (if present) |
Created by:
liladdoyle