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Week 7
| Question | Answer |
|---|---|
| in precise order, the ionic and voltage-gated channel events underlying the phases of an action potential. | 1. Depolarization threshold reached (~–55 mV): Voltage-gated Na⁺ channels open. 2. Rapid depolarization: Na⁺ influx drives membrane potential toward +30 mV. 3. Na⁺ channel inactivation occurs at peak depolarization. 4. Repolarization: Voltage-gated |
| Compare the biophysical mechanisms of continuous propagation and saltatory conduction, including their effects on conduction velocity and metabolic efficiency. | Continuous propagation: • In unmyelinated axons, each adjacent segment of the membrane depolarizes sequentially. • Slower and more energy-demanding, as Na⁺/K⁺ exchange must occur along the entire axon. • Saltatory conduction: • In myelinated axons |
| What event initiates the depolarization phase of an action potential? | A. Opening of voltage-gated K⁺ channels B. Opening of voltage-gated Na⁺ channels C. Activation of Na⁺/K⁺ pumps D. Closing of voltage-gated Ca²⁺ channels Explanation: Once threshold (≈ –55 mV) is reached, Na⁺ channels open rapidly, causing Na⁺ influx a |
| Which feature is unique to electrical synapses? | A. Direct ion flow through gap junctions B. Neurotransmitter release into the synaptic cleft C. One-way signal transmission only D. Slower and easily modifiable communication Explanation: Electrical synapses allow instantaneous, bidirectional current |
| Which of the following disorders involves demyelination of neurons in the central nervous system? | A. Multiple sclerosis B. Myasthenia gravis C. Parkinson’s disease D. Guillain-Barré syndrome Explanation: MS is an autoimmune disease that destroys CNS myelin, impairing conduction. |
| Parkinson’s disease is primarily associated with | A. Degeneration of dopaminergic neurons in the substantia nigra B. Loss of acetylcholine receptors at the neuromuscular junction C. Immune attack on myelin in the PNS D. Overproduction of serotonin in the brain Explanation: Dopamine deficiency disrupt |
| . Which of the following is TRUE regarding action potential propagation? | A. It is unidirectional due to Nat channel inactivation. B. It moves equally in both directions along the axon. C. It depends solely on chemical diffusion. D. It occurs only at synaptic terminals. Explanation: Inactivation of Na* channels behind the d |
| Which component of a chemical synapse directly binds neurotransmitters? | A. Synaptic vesicle membrane B. Postsynaptic receptor proteins C. Presynaptic terminal boutons D. Axon hillock Explanation: Neurotransmitters bind to receptor proteins on the postsynaptic membrane to generate a response. |
| Spatial summation occurs when: | A. One presynaptic neuron releases neurotransmitter rapidly over time. B. Multiple presynaptic neurons fire simultaneously at different locations on the postsynaptic membrane. C. Postsynaptic potentials cancel each other completely. D. A single presyna |
Created by:
Johnsonreta