1. What is the primary role of myelin in neural transmission? - A) To generate electrical impulses - B) To insulate axons and increase the speed of transmission - C) To release neurotransmitters - D) To regulate ion exchange Answer: B) To insulate axons and increase the speed of transmission Rationale: Myelin, a fatty substance that surrounds axons, serves as an insulator to prevent signal loss and speeds up the transmission of electrical impulses along the nerve cells. 2. Which ion's influx is most directly responsible for the depolarization phase of an action potential? - A) Sodium (Na+) - B) Potassium (K+) - C) Calcium (Ca2+) - D) Chloride (Cl-) Answer: A) Sodium (Na+) Rationale: During the depolarization phase of an action potential, sodium channels open, allowing Na+ to flow into the neuron, causing the interior to become more positive. 3. What is the significance of the sodium-potassium pump in maintaining the resting membrane potential? - A) It pumps sodium and potassium ions in equal quantities - B) It contributes to the hyperpolarization of the neuron - C) It expels three sodium ions for every two potassium ions it brings into the cell - D) It is only active during the action potential Answer: C) It expels three sodium ions for every two potassium ions it brings into the cell Rationale: The sodium-potassium pump is essential for maintaining the resting membrane potential by actively transporting three Na+ out of the neuron and two K+ into the neuron against their concentration gradients. 4. In synaptic transmission, what is the role of calcium ions (Ca2+) at the presynaptic terminal? - A) They initiate the repolarization phase - B) They trigger the release of neurotransmitters into the synaptic cleft