Which of the following parts of a spinal nerve carries sensory information only?

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Purves D, Augustine GJ, Fitzpatrick D, et al., editors. Neuroscience. 2nd edition. Sunderland (MA): Sinauer Associates; 2001.

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The arrangement of gray and white matter in the spinal cord is relatively simple: The interior of the cord is formed by gray matter, which is surrounded by white matter (Figure 1.11A). In transverse sections, the gray matter is conventionally divided into dorsal (posterior) lateral and ventral (anterior) “horns.” The neurons of the dorsal horns receive sensory information that enters the spinal cord via the dorsal roots of the spinal nerves. The lateral horns are present primarily in the thoracic region, and contain the preganglionic visceral motor neurons that project to the sympathetic ganglia (see Figure 1.10C). The ventral horns contains the cell bodies of motor neurons that send axons via the ventral roots of the spinal nerves to terminate on striated muscles. The white matter of the spinal cord is subdivided into dorsal (or posterior), lateral, and ventral (or anterior) columns, each of which contains axon tracts related to specific functions. The dorsal columns carry ascending sensory information from somatic mechanoreceptors (Figure 1.11B). The lateral columns include axons that travel from the cerebral cortex to contact spinal motor neurons. These pathways are also referred to as the cortico-spinal tracts. The ventral (and ventrolateral or anterolateral) columns carry both ascending information about pain and temperature, and descending motor information. Some general rules of spinal cord organization are (1) that neurons and axons that process and relay sensory information are found dorsally; (2) that preganglionic visceral motor neurons are found in an intermediate/lateral region; and (3) that somatic motor neurons and axons are found in the ventral portion of the cord.

Figure 1.11

Internal structure of the spinal cord. (A) Transverse sections of the cord at three different levels, showing the characteristic arrangement of gray and white matter in the cervical, thoracic, and lumbar cord. (B) Diagram of the internal structure of (more...)

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Copyright © 2001, Sinauer Associates, Inc.

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Introduction[edit | edit source]

Formation of spinal nerve from roots of spinal cord

Spinal nerves are bundles of nerve fibers connected to the spinal cord that carry information to and away from the spinal cord. Spinal nerves supply all the areas of the body except most head and neck region (see cranial nerves) with a few exceptions eg neck muscles are supplied by the spinal nerves.

Spinal nerves are mixed nerves sending motor, sensory, and autonomic signals between the CNS and the body and they belong to the peripheral nervous system (PNS).[1][2]

Spinal nerves are essential for the control of body parts by the higher centres of the nervous system.

• If the spinal nerve is cut, trapped, injured, or is involved in a disease process, the areas of the body supplied by that nerve escape the control of CNS.
• If spinal nerves are impacted by injuries it will lose its functional ability and will cause pain, weakness and loss of sensation and may dies. eg A nerve entrapment occurs when there is pressure or compression of a spinal nerve, and it is the most common spinal nerve disorder; a nerve can be lacerated resulting in cessation of function.[3]

Anatomy[edit | edit source]

Humans have 31 left–right pairs of spinal nerves, each roughly corresponding to a segment of the vertebral column: eight cervical spinal nerve pairs, 12 thoracic pairs , five lumbar pairs, five sacral pairs, and one coccygeal pair.[4][1].[2]

Cervical vertebra, spinal nerve.

Each spinal nerve is formed by the combination of nerve fibers from the dorsal and ventral roots of the spinal cord.

1. The dorsal roots carry afferent sensory axons
2. The ventral roots carry efferent motor axons.

The spinal nerve emerges from the spinal column through in the intervertebral foramen between adjacent vertebrae, where it is surrounded by the dura mater.[5]

Each spinal nerve is a mixed nerve that contains afferent and efferent, somatic and autonomic fibers.

Rami[edit | edit source]

Once outside the vertebral column, the nerve divides divides.

1. The Dorsal Ramus contains nerves that serve the dorsal portions of the trunk carrying visceral motor, somatic motor, and somatic sensory information to and from the skin and muscles of the back.
2. The Ventral Ramus contains nerves that serve the remaining ventral parts of the trunk and the upper and lower limbs carrying visceral motor, somatic motor, and sensory information to and from the ventrolateral body surface, structures in the body wall, and the limbs.

The meningeal branches branch from the spinal nerve to re-enter the intervertebral foramen to innervating the ligaments, dura, blood vessels, intervertebral discs, facet joints, and periosteum of the vertebrae.[1]

The spinal nerves have a variable course, horizontal in the cervical region and increasingly oblique in an inferolateral direction as the spinal cord descends (due of the growth discordance between the spinal cord and the spine).

Plexi[edit | edit source]

The spinal nerves form within a few centimeters of the spine on each side. Some groups of spinal nerves merge with each other to form a large plexus. Some spinal nerves divide into smaller branches, without forming a plexus.

A plexus is a group of nerves that combine with each other. There are five main plexi formed by the spinal nerves:

1. Cervical Plexus
2. Brachial Plexus
3. Lumbar Plexus
4. Sacral Plexus
5. Coccygeal Plexus: Composed of the merging of nerves S4 through Co1, this plexus supplies motor and sensory control of the genitalia and the muscles that control defecation.[3]

Physiotherapy Relevance[edit | edit source]

Spinal nerves can be affected by a number of conditions. These situations can cause pain, sensory changes, and/or weakness. eg:

• Disc Herniation
• Herpes Zoster (Shingles)
• Guilliane Barre Disease
• Trauma eg falls, whiplash
• Neuropathy
• Cancer in or near the spine can infiltrate/ compress the spinal nerves, causing dysfunction. eg Spinal malignancy [3]

References[edit | edit source]

1. ↑ 1.0 1.1 1.2 Lumen learning Spinal nerves Available: https://courses.lumenlearning.com/boundless-ap/chapter/spinal-nerves/(accessed 6.2.2022)
2. ↑ 2.0 2.1 Musculoskeletal key Spinal nerves Available: https://musculoskeletalkey.com/nerves-innervation-of-the-spine/(accessed 6.2.2022)
3. ↑ 3.0 3.1 3.2 Very well health Spinal Nerves Available: https://www.verywellhealth.com/spinal-nerves-anatomy-4682599(accessed 6.2.2022)
4. ↑ Brain made simple Spinal nerves Available: https://brainmadesimple.com/spinal-nerves/(accessed 7.2.2022)
5. ↑ Britannica Spinal nerves Available: (accessed 6.2.2022)

Which of the following parts of a spinal nerve carries sensory?

What part of the spinal cord carries sensory information?

Which of the following would carry only sensory information?

What part of the spinal nerve carries only motor information?