Final answer:
Ion movement during different membrane potential stages includes Na+ influx causing depolarization and K+ efflux for repolarization, with active transport restoring resting potential. Sound travels from the outer ear, through the middle ear to the inner ear, where it is converted to neural signals and sent via auditory nerve to the brain.
Step-by-step explanation:
The movement of ions across the cell membrane is crucial for the generation of action potentials, which are the electrical signals used for communication in neurons. During the resting potential, the membrane is relatively impermeable to sodium (Na+) and potassium (K+) ions, with K+ slowly leaking out of the cell, leading to a negative charge inside the cell. Once a threshold potential is reached due to a stimulus, voltage-gated Na+ channels open allowing Na+ to rush into the cell, causing depolarization.
This influx of Na+ makes the inside of the cell more positive. Following depolarization, K+ channels open and K+ begins to exit the cell, which brings the membrane potential back toward the resting level, known as repolarization. Lastly, active transport mechanisms, particularly the Na+/K+ pump, restore the resting potential by moving Na+ out of the cell and K+ back in, requiring chemical energy to do so.
The pathway of sound involves a journey from the outer ear through to the brain. Sound waves enter through the outer ear (pinna and ear canal) and cause the tympanic membrane (eardrum) to vibrate. These vibrations travel through the middle ear bones (ossicles), which amplify the sound. The vibrations are then transmitted to the cochlea in the inner ear, where they are converted into neural signals by hair cells. These signals are carried by the auditory nerve to the brain, where they are interpreted as sound.