This preview shows pages 1–3. Sign up to view the full content.
This preview has intentionally blurred sections. Sign up to view the full version.View Full Document
Unformatted text preview: Chapter 7 Regulation of Potassium Balance Potassium Homeostasis Why is it essential to maintain K + balance in the body?- Recall the role of K + ions in the maintenance of the resting membrane potential and the role of voltage-gated Na + and K + channels for the events of the action potential. In a 70 Kg individual, total body K + is 50 mEq/Kg of body weight, or 3500 mEq - 98% of total K + content is in cells (150 mEq/L) - 2% in the ECF (4.5 mEq/L) - This large K + concentration gradient is maintained by which pump? ________________- High K + needed for many cell functions: cell growth, cell division, volume regulation. - Hyperkalemia:- Hypokalemia:- Cardiac arrhythmias are produced by both hypokalemia and hyperkalemia It is a challenge to maintain low extracellular K + concentration 1. Large amount of intracellular K + a shift can produce a change The distribution of K + across cell membranes is called the internal K + balance- What factors may alter this distribution and thus alter the extracellular K + concentration? - 2. Variation in dietary K + intake Varies _______________________ To maintain balance, urinary excretion of K + must be equal to dietary K + intake- In other words, K + excretion must be capable of varying from ______________________________ The renal mechanisms that allow for this variability are called the ______________________________ Internal K + Balance Ingested K + is absorbed by GI tract and enters ECF within minutes after a meal. K Ingested during a Normal Meal = 33 mEq 33 /14L (ECF) = 2.4 mEq/L K (Potentially Lethal K Conc.) All of the absorbed K + must be excreted by the kidneys. - Done slowly (6 hours) - In this time period, buffering K + by cells is important to prevent life-threatening hyperkalemia The amount of K + remains constant. What factors may affect the internal K + balance? _______________________________ Hormones Which hormones increase K + uptake into skeletal muscle, liver, bone and RBC?- How?- Insulin Stimulates K + uptake into cells after ingestion of K + in a meal Hyperkalemia: Acute therapy for hyperkalemia in diabetic patients: Epinephrine Catecholamines affect K + distribution across cell membranes- Done by activating -adrenergic receptors - What might happen if K + is released from liver cells?...
View Full Document
- Winter '11