Which of the following components of a neuron is an insulative covering necessary for effective transmission of nerve impulses?
Myelin
Synapse
Axon
Dendrite
The Correct Answer is A
A. Myelin is a fatty substance that wraps around axons in many neurons. It acts as an insulative covering that speeds up the transmission of nerve impulses by enabling the signal to jump between gaps in the myelin (called nodes of Ranvier). This is the correct answer.
B. The synapse is the junction between two neurons where signals are transmitted. It is not involved in the insulative covering of a neuron.
C. The axon is the long, slender part of a neuron that transmits electrical signals, but it requires myelin to efficiently conduct those signals.
D. Dendrites are branched extensions of a neuron that receive signals from other neurons. They do not have an insulative function.
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Related Questions
Correct Answer is B
Explanation
A. The trachea is the windpipe that carries air to the lungs. While it plays a role in respiration, it does not protect the airway during swallowing.
B. The epiglottis is a flap of cartilage that covers the trachea during swallowing, preventing food or liquid from entering the airway and directing it to the esophagus.
C. The uvula is part of the soft palate that helps in the swallowing process but does not directly protect the airway. It assists in preventing food from entering the nasal cavity.
D. The pharynx is the passageway for both air and food, but it does not provide protection to the airway during swallowing. The epiglottis is the main structure responsible for this protection.
Correct Answer is B
Explanation
A. In a hypertonic solution, water moves out of the cell into the surrounding fluid, causing the cell to shrink. Therefore, the volume of the cell does not increase.
B. A hypertonic solution has a higher concentration of solutes than the inside of the red blood cell. As a result, water moves out of the cell, causing it to shrink or decrease in volume.
C. The permeability of the cell membrane is not directly affected by the tonicity of the solution. The change in cell volume is due to the movement of water, not a change in membrane permeability.
D. The permeability of the cell membrane is not typically affected by a hypertonic solution, but rather the osmotic pressure that drives water movement across the membrane. The main effect is on the cell's volume, not its membrane permeability.
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