Kcl Injection, Hyperkalemia

1) a. When KCl is injected into the bloodstream of the patient, the K+ gradient across the membrane is reduced. This results in depolarization where cells generate an action potential. Voltage-gated Na+ channels open in response to depolarization and close by inactivation for a refractory period and remain closed until repolarization. In this new setting, less K+ leaks out of the intracellular space and the cell is unable to return to its resting membrane potential (ie. The cell stays slightly depolarized) as the voltage-gated Na+ channels have closed. This means that only low-sensitivity channels will function and a stronger stimulus is needed to induce equal excitation in the sensory neuron and spinal nerves. b. The increase in KCl increases potassium channel conductance and delays outward potassium current, resulting in depolarization and expediting repolarization. The basal membrane potential increases (more positive), making it easier to reach threshold and fire an action potential. Sensory neurons fire sooner and more easily, further activating other neurons and allowing both neurons in the heart and sweat glands to fire quickly and spontaneously. c. The increase in K+ concentration reduces the ratio of intracellular to extracellular potassium and decreases the resting membrane potential, making it more positive and closer to threshold potential. The action potential required for contraction is made easier to reach and over-stimulation of muscle cells by neurons cause muscle cramping and fatigue. 2) A hyperkalemic solution is one that elevates the K+ concentration in the bloodstream and provides myocardial protection. It is used in cardiac surgery to induce elective cardiac arrest in cases where a relaxed and still operating field is required. An increase in K+ concentration depolarizes the resting membrane potential. Once the resting membrane potential shifts to about -65mV (or K+ concentrations of ~10mmol/L), the voltage-gated Na+