The spinal cord - class-X

The spinal cord has a central H-shaped core of grey matter (cell bodies) surrounded by an outer layer of white matter (myelinated axons).

This describes a reflex arc. The stimulus is detected by a receptor, transmitted to the spinal cord via sensory neurons, and then to the muscles via motor neurons to trigger a response.

The anterior horn of the spinal cord contains the cell bodies of motor neurons. Damage to these cells disrupts the transmission of signals to muscles, resulting in the loss of voluntary motor control.

The grey matter of the spinal cord is organized into ten distinct layers known as Rexed laminae, which are numbered I through X.

The spinal cord is characterized by a central H-shaped or butterfly-shaped region of grey matter, which is surrounded by white matter.

Lateral funiculi are part of white matter of spinal cord having myelinated nerve fibres. Cell bodies/ganglia occur in grey matter that lies inside and in horns of spinal cord.

White matter is a component of the central nervous system, in the brain and spinal cord, and consists mostly of glial cells and myelinated axons that transmit signals from one region of the cerebrum to another and between the cerebrum and lower brain centers.

As a matter of fact, the central nervous system is one of the best-protected systems in the entire body, defended by the bones of the skull and spinal column. Unfortunately, when these bones are injured or fractured they can compromise the soft tissue in the spinal cord, causing permanent damage. If you strain a muscle, it repairs itself. But the spinal cord is different. That's because some of the cells in the central nervous system are so complex and specialized that they don't have the ability to regenerate. 

The ventral root (motor root) of each spinal nerve consists of axons from motor neurons, whose cell bodies are found within the grey matter of the spinal cord. A ventral root and a dorsal root unite to form a spinal nerve, which passes outward from the vertebral canal through an intervertebral foramen.

The grey matter, in the center of the spinal cord, is shaped like a butterfly and consists of cell bodies of interneurons and motor neurons, as well as neuroglia cells and unmyelinated axons. Projections of the grey matter (wings) are called as horns. Together, the grey horns and the grey commissure form the "grey H."

A posterior root ganglion (spinal ganglion) (also known as a dorsal root ganglion), is a cluster of nerve cell bodies (a ganglion) in a posterior root of a spinal nerve. The axons of posterior root ganglion neurons are known as afferents. The posterior root ganglia lie along the vertebral column by the spine. The nerve endings of posterior root ganglion neurons have a variety of sensory receptors that are activated by mechanical, thermal, chemical, and noxious stimuli.

In cross-section, the peripheral region of the cord contains neuronal white matter tracts containing sensory and motor neurons. Internal to this peripheral region is the grey matter.

The sympathetic nervous system is also known as the thoracolumbar outflow because its preganglionic neurons originate in the thoracic and lumbar segments of the spinal cord.

Afferent (sensory) neurons carry information toward the spinal cord. Their cell bodies are located in the dorsal root ganglia, which are clusters of neurons outside the spinal cord.

The dorsal root or the posterior root is the main bundle of nerve fibers that branch off from the spinal cord to enter other areas of the body. This combines with the ventral root to form the spinal nerve. and becomes the afferent sensory root and is responsible for carrying and transmitting the sensory information from the body to the brain for processing the signals by the brain. If the dorsal root is broken, then the transfer of information will not be possible. Thus, the correct answer is option D.

The spinal cord is the extension of the medulla oblongata that runs down through the foremen of magnum. The lowest part of the spinal cord is narrow and it is called the conus medullaris. The conus medullaris is present at the L$ _{1}$ vertebrae. The terminal part of the conus medullaris is a thread-like structure that is made up of fibrous connective tissue called the filum terminale. It is the non-nervous part of the spinal cord that can be seen in the lumbar vertebrae.

The filum terminale is an extension of the pia mater from the conus medullaris. The internal part is covered by pia mater, while the external part (filum terminale externum) is covered by a sheath of dura mater.

The spinal cord begins at the occipital bone and extends down to space between the first and second lumbar vertebrae. The terminal portion of the spinal cord is called the conus medularis. It is tapperd and located near the lumbar vertebrae.

A unipolar neuron is a type of neuron in which only one protoplasmic process (neurite) extends from the cell body. A pseudounipolar neuron is a kind of sensory neuron in the peripheral nervous system. This neuron contains an axon, that has split into two branches; one branch runs to the periphery and the other to the spinal cord.

The spinal cord is a thick cord of the nervous tissue that forms the central nervous system along with the brain. It extends from the brain down through the spine and is protected within the bony vertebral column which is made of bones called the vertebrae. It ends at the second lumbar vertebrae. It is divided into the regions according to the vertebral column as cervical, thoracic and lumbar. The bunch of nerve fibres at the end of the spinal cord is called the cauda equina. It forms a horse tail-like structure. The nerves from this region supply to the pelvic region and lower limbs.

The cavity or system of cavities in the interior of the vertebrate central nervous system comprising the central canal of the spinal cord and the ventricles of the brain is called as neurocoel. 

A dorsal root ganglion (or spinal ganglion) (also known as a posterior root ganglion), is a cluster of nerve cell bodies (a ganglion) in a posterior root of a spinal nerve.
The cell bodies of peripheral neurons are often found grouped into clusters called ganglia. On the basis of the type of nerve cell bodies found in ganglia, they may be classified as either sensory or motor. Sensory ganglia are oval swellings located on the dorsal roots of spinal nerves and on the roots of certain cranial nerves.

The fourth ventricle present between the brainstem and the cerebellum is called the metacoel. It continues to the spinal cord in the form of the central canal to form the cavity of the spinal cord filled with the cerebrospinal fluid. The central canal is also called the neurocoel.