Question

Myelinated nerve fibre is found in (a) Spinal nerve (b) Cranial nerve (c) Both (a) and (b) (d) None of these

Short answer

Myelinated nerve fibre is found in Both (a) Spinal nerve and (b) Cranial nerve.

Step-by-step solution

Understand myelinated nerve fibre

Myelin is a protective sheath that covers nerves, including those in the brain and spinal cord. The term 'myelinated nerve fibre' refers to a nerve that's covered by this sheath.

Know nerve types

Spinal nerves are part of the peripheral nervous system (PNS) that carry motor and sensory messages between the spinal cord and the body. Cranial nerves are also part of the PNS and emerge directly from the brain. Both types of nerves can be myelinated.

Choose the correct answer

Since both spinal nerves and cranial nerves can be myelinated, the answer is option (c) Both (a) and (b).

Key concepts

Spinal Nerves

Spinal nerves are crucial components of the peripheral nervous system (PNS). They branch out from the spinal cord and extend to different parts of the body. Each spinal nerve consists of both sensory and motor fibers which are responsible for sending signals from your body to the spinal cord and vice versa.

A typical human has 31 pairs of spinal nerves and each pair emerges from the spinal cord through spaces between the vertebrae. These nerves play a significant role in synchronizing muscular functions and sensation in your body.

• Sensory nerves carry information from the body to the brain, informing about sensations like touch, pain, and temperature.
• Motor nerves send signals from the brain to different body parts, controlling muscles and movements.

The myelinated fibers within these spinal nerves greatly enhance the speed and efficiency of nerve signal transmission. This myelination is essential, as it ensures that communication between the brain and the body is swift and precise.

Cranial Nerves

Cranial nerves are another vital part of the peripheral nervous system, originating directly from the brain, rather than the spinal cord. There are 12 pairs of cranial nerves, each with specific functions related to sense and movement, contributing to various head and neck functions.

They are essential for sensory inputs like vision, hearing, taste, and smell, along with motor functions like facial expressions and eye movements. Examples include:

• Optic nerve, responsible for vision.
• Olfactory nerve, responsible for smell.
• Facial nerve, controlling the muscles of facial expression.

Like spinal nerves, several cranial nerves contain myelinated fibers which allow them to transmit signals rapidly and efficiently. This myelination helps in maintaining the accurate function of these cranial nerves, ensuring that sensory and motor signals are correctly interpreted and acted upon.

Peripheral Nervous System

The peripheral nervous system (PNS) encompasses all the nerves that lie outside the brain and the spinal cord. Its primary function is to connect the central nervous system (CNS) to the limbs and organs. The PNS is divided into two main parts:

• Somatic Nervous System, which controls voluntary movements and transmits sensory information to the CNS.
• Autonomic Nervous System, which manages involuntary body functions like heartbeat and digestion.

The PNS is equipped with both spinal and cranial nerves that ensure the efficient relay of information between your brain and different parts of your body. Myelinated nerve fibers in the PNS allow for quicker transmission of nerve signals, aiding in swift reflexes and responses to environmental changes. Thus, the PNS is fundamental for maintaining the body's homeostasis and supporting mobility and sensory perception in your everyday life.