Question

1. Mrs. Robinson is hospitalized for dehydration. Somehow, medical orders are mixed up, and Mrs. Robinson is infused with a low-potassium intravenous solution meant for another patient. Mrs. Robinson's potassium levels are normal before the I.V. is administered, but, due to an undiagnosed kidney problem, she is not able to retain potassium. She soon begins to complain of numbness in her extremities (a) What will happen to the resting potential of Mrs. Robinson's sensory neurons, which are responsible for the numbness? Please explain your reasoning. (b) Based on A, what will happen to her sensory neuron's ability to produce action potentials? (c) Taken together, propose a mechanism for why Mrs. Robinson's kidney issue produces her chief complaint of numbness in her extremities

Answer 1

a)The resting membrane is altered.As Mrs.Robinson is nit able to retain potassium, it means that her blood potassium levels are low and this condition is known as  hypokalemia. Hypokalemia leads to hyperpolarization of the resting membrane potential and therefore the resting membrane potential becomes more negative as a result of the altered potassium gradient.Due to this, the nerve signalling is weakened and a greater than normal stimulus will be required for depolarization of the membrane so as to initiate an action potential or in other words the cells become less excitable and this is responsible for the numbness.

b)The sensory neuron's ability to produce an action potential is weakened and a greater than normal stimulus will be required to produce an action potential.

c) Mrs Robinson has a kidney issue and this might be due to an adrenal disorder known as Cushing syndrome in which the adrenal glands secrete more of the hormone aldosterone causing the kidneys to excrete large amounts of potassium as a result of which the blood potassium levels go down affecting the resting membrane potential and numbness in her extremities.