Spinal Cord
Together with the Brain, the spinal cord constitutes an important part of the central nervous system. It conducts impulses between the brain and the rest of the body and is a center for reflex activity. The spinal cord is present in the vertebral column of all vertebrate animals, running from the brain stem to the tail.
The spinal cord consist of a tube about 1 cm (0.4 in) thick with a small central canal. Cerebrospinal fluid flows through this canal and around the spinal cord. The cord is encased in three membranes called meninges: the pia mater, the arachnoid, and the dura mater. In cross section, the spinal cord has centrally positioned butterfly-shaped gray matter, consisting of unmyelinated cell bodies of nerve cells (neurons), surrounded by the myelinated axonal fibers, or white matter.
A cell body contains the nucleus of the nerve cell, and it sends out a single axon and numerous fibrous extensions known as dendrites. In the spinal cord, dendrites receive stimuli from the axons of other neurons whose cell bodies are located either elsewhere in the central nervous system or in the peripheral nervous system.
In human there are 31 pairs of spinal nerves, and each pair divides into two segments: a dorsal sensory root and a ventral motor root. The ventral root located at the front side of the spinal cord, carry the initial segment of motor neuron axons. Ventral roots stem from ventral horns, which contain the cell bodies of motor neurons. These carry impulses from the spinal cord to the body. The dorsal roots, located at the back side of the cord, carry the terminal segment of sensory neurons. The dorsal horns are where the sensory neuron form synapses with dendrites of neurons carrying information to the brain, or with motor neurons. Lateral horn present only in the thoracic and lumbar regions, are situated between the dorsal and ventral horns: they protrude laterally and contain cell bodies of neurons from the autonomic nervous system. The axons of motor neurons are carried, together with the axon of motor neuron in the ventral roots. The cell bodies of the sensory neurons are found in a spinal ganglion adjacent to the cord, and their dendrites are located in the skin, the muscles, the soft organ tissues, and blood vessels.
Traumatic injuries to the neck or back can causes spinal cord damage, including paralysis if the spinal cord is cut. Tumors can grow in the spinal cord, about 40 percent of these tumors are cancerous, but they can be treated with corticosteroid drugs. If the tumor is around but not within the spine, it may be surgically removed.
The spinal cord consist of a tube about 1 cm (0.4 in) thick with a small central canal. Cerebrospinal fluid flows through this canal and around the spinal cord. The cord is encased in three membranes called meninges: the pia mater, the arachnoid, and the dura mater. In cross section, the spinal cord has centrally positioned butterfly-shaped gray matter, consisting of unmyelinated cell bodies of nerve cells (neurons), surrounded by the myelinated axonal fibers, or white matter.
A cell body contains the nucleus of the nerve cell, and it sends out a single axon and numerous fibrous extensions known as dendrites. In the spinal cord, dendrites receive stimuli from the axons of other neurons whose cell bodies are located either elsewhere in the central nervous system or in the peripheral nervous system.
In human there are 31 pairs of spinal nerves, and each pair divides into two segments: a dorsal sensory root and a ventral motor root. The ventral root located at the front side of the spinal cord, carry the initial segment of motor neuron axons. Ventral roots stem from ventral horns, which contain the cell bodies of motor neurons. These carry impulses from the spinal cord to the body. The dorsal roots, located at the back side of the cord, carry the terminal segment of sensory neurons. The dorsal horns are where the sensory neuron form synapses with dendrites of neurons carrying information to the brain, or with motor neurons. Lateral horn present only in the thoracic and lumbar regions, are situated between the dorsal and ventral horns: they protrude laterally and contain cell bodies of neurons from the autonomic nervous system. The axons of motor neurons are carried, together with the axon of motor neuron in the ventral roots. The cell bodies of the sensory neurons are found in a spinal ganglion adjacent to the cord, and their dendrites are located in the skin, the muscles, the soft organ tissues, and blood vessels.
Traumatic injuries to the neck or back can causes spinal cord damage, including paralysis if the spinal cord is cut. Tumors can grow in the spinal cord, about 40 percent of these tumors are cancerous, but they can be treated with corticosteroid drugs. If the tumor is around but not within the spine, it may be surgically removed.
