BIO 137 Case Study Kaly Barren is a 16-year-old sprinter on the high school trac
ID: 262041 • Letter: B
Question
BIO 137 Case Study Kaly Barren is a 16-year-old sprinter on the high school track team. Recently, after completing her events, she felt extremely weak and her legs became "like rubber". After the most recent event, she was unable to walk and had to be carried from the track on a stretcher. Her parents were very alarmed and made an appointment for Kaly to be evaluated by her pediatrician. As a part of the workup, the pediatrician measured Kaly's serum K concentration, which was normal (4.5 mEq/L). However, because the pediatrician suspected a connection with K', the measurement was repeated immediately after a strenuous exercise treadmill test. After the treadmill test, Kaly's serum K was alarming low (2.2 mEq/L). Kaly was diagnosed as having an inherited disorder called primary hypokalemic periodic paralysis and subsequently treated with K' supplements. QUESTIONS 1. In what body fluid is most of our K located? 2. What is the role of K in the resting membrane potential of neurons? 3. How does exercise lower Kt in body fluids? If less K is available to cells, will this cause the development of action potentials to occur faster or slower? 4. 5. What other excitable tissues does a decrease in K' affect? 6. How does taking K supplements improve Kaly's condition? 7. What other cation plays a role in maintaining the electrochemical gradient? 8. In what body fluid is most of this cation found? 9. In what phase of an action potential does this other cation participate? 10. Will taking supplements of this cation cause the development of action potentials to occur faster, slower or no change?Explanation / Answer
1. Potassium ions are predominantly concentrated in the intracellular fluid (ICF) present in cells. ICF is the component of the cytosol. It makes up 60% of the total fluid in the body.
2. A neuron at rest is negatively charged as the internal environment of the cell is 70mV more negatively charged than the outside of the cell. This negatively charged voltage is called resting membrane potential of the neuron. The concentration of positively charged K+ ions inside and outside of the cell determines the resting membrane potential. When neurons are at rest, K+ ions will move across the membrane along the concentration gradient and will accumulate inside the cell. As sodium ions are not permeable in these resting neurons, the concentration of Na+ ions increase outside the cell.
Neurons however, have leaky potassium channels that will allow more free diffusion of K+ ions to the outside of the cell. This creates a negatively charged membrane potential as the interior of the cell is more negative as compared to outside of the cell due to diffusion of K+ ions. Thus, K+ ions play an important role in resting membrane potential of neurons.
3. Potassium is used by the body for muscle activity as it is required for muscle stimulation and contraction. It is involved in transmission of nerve impulses to the muscles. After exercise, potassium levels are lowered as the potassium is used up for muscle activity.
4. Decreasing the Extracellular K+ concentration will cause rapid efflux of K+ ions from the inside of the cell to the outside. As a result, the cell will hyperpolarize due to cell potential becoming more negative. Hyperpolarization of membrane will decrease the action potential. Action potential will develop slower.
5. Kidneys secrete excess potassium outside the body. When potassium levels are low, kidneys will not excrete potassium. Hence, a salt and potassium imbalance is created. This may cause Bartter syndrome or Gltelman syndrome. As there is a salt imbalance, blood levels of potassium will be further affected causing increased blood pressure. High blood pressure will affect the heart causing arrythremias.
6. Sodium is another ion that is involved in electrochemical gradient. The sodium potassium ATPase pump transports 3 sodium ions outside the cell and two potassium ion inside the cell. This transport requires ATP.
7. Sodium is found in high concentration in blood and extracellular fluid (ECF). ECF is the fluid that bathes the tissues and cells of the body. It helps to keep the balance of body fluids.
As per Chegg’s rules, only one question needs to be answered.
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