Question

All of the following are associated with the myelin sheath EXCEPT A. faster conduction of nervous impulses. B. nodes of Ranvier forming gaps along the axon. C. increased energy output for nervous impulse conduction. D. saltatory conduction of action potentials.

Short answer

Option C: increased energy output for nervous impulse conduction.

Step-by-step solution

Identify What Myelin Sheath is Responsible For

The myelin sheath is a protective covering that surrounds fibers called axons. It aids in the rapid transmission of electrical signals.

Analyze Each Option

Go through each option to determine if it is related to the role of the myelin sheath.

Evaluate Option A

Option A states that myelin sheath is responsible for faster conduction of nervous impulses. This is true because myelin insulates the axon and speeds up the transmission.

Evaluate Option B

Option B states that the nodes of Ranvier form gaps along the axon. This is true as these gaps are necessary for the saltatory conduction of nerve impulses.

Evaluate Option C

Option C states that there is increased energy output for nervous impulse conduction. This is false because myelin actually reduces the energy required for nerve impulse transmission.

Evaluate Option D

Option D states that there is saltatory conduction of action potentials. This is true as the presence of myelin sheath allows for action potentials to 'jump' from one node of Ranvier to another, speeding up signal transmission.

Conclusion

All other options (A, B, D) are directly associated with the function of the myelin sheath except for Option C.

Key concepts

nodes of Ranvier

The nodes of Ranvier are small gaps in the myelin sheath of an axon. These gaps are crucial for the proper functioning of the nervous system. Without them, the transmission of electrical signals along the axon would be much slower.

Let's break this down further. The nodes of Ranvier are not just random gaps; they are strategic points where the axon membrane is exposed to the external environment. This exposure allows for the exchange of ions, which is vital for the generation and propagation of electrical signals known as action potentials.

• The myelin sheath insulates the axon, preventing the loss of electrical signals.
• The nodes of Ranvier enable the action potential to be regenerated at each gap.
• This regeneration prevents the signal from degrading as it travels along the axon.

In summary, the nodes of Ranvier play a key role in maintaining the speed and efficiency of nervous impulse transmission.

saltatory conduction

Saltatory conduction is a process that significantly speeds up the transmission of electrical signals along an axon. The term 'saltatory' comes from the Latin word 'saltare,' which means 'to jump.' This is exactly what happens during saltatory conduction—the electrical signal 'jumps' from one node of Ranvier to the next.

Because the myelin sheath insulates most of the axon, the action potentials cannot travel through the myelin. Instead, they leap from one node of Ranvier to the next. This jumping mechanism is much faster than the slow, wave-like transmission of action potentials along an unmyelinated axon.

• Saltatory conduction reduces the overall time it takes for a signal to travel along an axon.
• This process is energy-efficient, as less energy is required to maintain the action potentials.
• The myelin sheath and nodes of Ranvier work together to make this rapid transmission possible.

By understanding saltatory conduction, we can see why the myelin sheath is so crucial for fast and efficient nervous impulse transmission.

nervous impulse transmission

Nervous impulse transmission refers to the way electrical signals are sent along neurons to communicate information throughout the nervous system. This process is essential for everything from reflex actions to complex thoughts.

Here's how it works:

1. **Resting Potential:** At rest, a neuron has a negative charge inside the axon and a positive charge outside.

2. **Depolarization:** When a signal is received, sodium channels open, allowing positive sodium ions to rush into the neuron, making the inside positive.

3. **Action Potential:** This change in charge generates an action potential, an electrical signal that travels along the axon.

4. **Repolarization:** After the action potential passes, potassium channels open, allowing positive potassium ions to leave the neuron, restoring the negative charge inside.

Myelin sheaths and nodes of Ranvier work together to facilitate this process. Without them, nervous impulse transmission would be slower and less efficient.

• The myelin sheath insulates the axon, preventing the leaking of electrical signals.
• The nodes of Ranvier are points where the action potential is regenerated.
• Saltatory conduction enables the action potential to 'jump' from one node to the next, speeding up transmission.

Understanding these components helps us appreciate the sophisticated mechanisms that allow our nervous system to function at its best.