Anatomy Chapter 12 Part 2 Spinal Cord
6. Gray Matter
Gray Matter consists of neuron cell bodies, dendrites, associated glia, and blood vessels. -The cerebral cortex is composed of gray matter. -Looks like the letter H or a butterfly, consists of mirror image lateral gray masses connected by a crossbar of gray matter, the gray commissure, that encloses the central canal.
9. Sensory (afferent) tract
The Sensory (afferent) tracts ascend to higher levels of the nervous system. -The ascending pathways conduct sensory impulses upward, typically through chains of three successive neurons to various areas of the brain.
8. Pia Mater
The Pia mater, meaning "Gentle mother", is composed of delicate connective tissue and contains tiny blood vessels, to supply the brain. -The pia mater is the only part of the meninges that touches the brain. -Small arteries entering the brain tissue carry ragged sheaths of pia mater inward with them for short distances.
1. Arachnoid Mater
The Arachnoid mater is the middle meninx which forms a loose brain covering, which nevers dips into the sulci at the cerebral surface. - It is seperated from the dura mater by a narrow serous cavity, the subdural space which contains a film of fluid. - Because the Arachnoid mater is fine and elastic, the largest blood vessels in the cerebrospinal fluid are poorly protected.
2. Central Canal
The Central Canal is a cerebrospinal fluid filled space that runs longitudinally through the length of the entire spinal cord. - The Central Canal is continuous with the ventricular system of the brain.
3. Dorsal Root
The Dorsal Root carries impulses from the peripheral receptors. -The cell bodies of the associated sensory neurons are found in an enlarged region of the dorsal root called the dorsal root ganglion.
4. Dura mater
The Dura mater is the strongest part of the meninges. -The deeper meningeal layer forms the true external covering of the brain and continues caudally in the vertebral canal as the spinal dura mater. -The Dura mater surrounds the brain, and is a two layered sheet of fibrous connective tissue.
5. Ganglion
The Ganglion is an enlarged region of the dorsal root where cell bodies of the associated sensory neuron are found. -Afferent fibers carrying impulses from peripheral sensory receptors form the dorsal roots of the spinal cord that fan out as the dorsal rootlets before they enter the spinal cord.
7. Motor(efferent) tract
The Motor (efferent) tracts descend to the spinal cord from the brain or descend lower down the spinal cord. -The descending pathways that deliver efferent impulses from the brain to the spinal cord are divided into two groups: the direct pathways, equivalent to the pyramidal tracts or the indirect pathways, essentially all others. -The motor tract transmits nerve impulses from the brain to the muscles and glands.
10. Spinal Cord
The Spinal cord provides a two-way conduction pathway to and from the brain and is the major reflex center. -Spinal reflexes are initiated and completed at the spinal cord level. -Like the brain, the spinal cord is protected by bone, meninges, and cerebrospinal fluid.
11. Spinal Nerves
The Spinal nerves are 31 pairs of nerves that originate from the spinal cord and supply all parts of the body except the head and neck areas. -Each spinal nerve connects to the spinal cord by a dorsal root and a ventral root. -Spinal nerves are named according to where they issue from the spinal cord.
12. Ventral Root
The Ventral root contains motor fibers that arise from the ventral horn and extend to the skeletal muscles. -The ventral roots are very short and fuse laterally with the dorsal roots to form spinal nerves.
13. White Matter
White Matter is composed of myelinated and non-myelinated nerve fibers that allow communication between different parts of the spinal cord and between the cord and brain. -The white matter on each side of the cord is divided into three white columns, or funiculi, named according to their position as dorsal (posterior), lateral and ventral (anterior) funiculi.