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The Spinal Cord

The spinal cord is of great importance to the nervous system and to the whole body.

The Spinal Cord

Spinal Cord | © BruceBlaus, own work, CC BY 3.0, Wikimedia

From the spinal corddas Rückenmark and the dorsal rootder Stamm, die Wurzel ganglia the central nervous system innervatesanregen, beleben most of the body. The spinal cord transmitsübertragen, übermitteln nerve impulses to and from the brain and is the integrating center for the spinal cord reflexes. The spinal cord lies enclosed within the vertebral canal and is well protected from injuriesdie Verletzung by the vertebral column, the meninges and the cerebrospinal fluid. It extendsetw. verlängern from the foramen magnum to the disc between the first and second lumbar vertebrae. Internally, the spinal cord comprises the gray mattergraue Substanz and the white matterweiße Substanz. The inner gray matter is made up of the cell bodies of motor neurons, sensory neurons and interneurons, as well as synapses and glia cells. The outer white matter comprises of myelinated axons and dendrites of interneurons. Depending on their functions these nerve fibers are grouped into nerve tracts. The one which are ascendingaufsteigen carry the sensory impulses from the peripheral organs to the brain. The ones which are descendingabsteigen carry motor impulses away from the brain to the muscles. The very important cerebrospinal fluid is found in the central canal.

What are spinal nerves exactly?

All together the human body has 31 pairs of spinal nerves. They all get out protrude from the spinal cord and are named according togemäß, nach their respective vertebrae: e.g. 8 cervical pairs, 12 thoracic pairs, 5 lumbar pairs, 5 sacral pairs, and 1 very small coccygeal pair. The 8th cervical nerve is named C 8, the 1st thoracic nerve is called T 1 (always a letter and a number) and so on. The spinal nerves transmit information from the CNS to the muscles and transmit sensory information from the periphery systems, like the skin or the muscle spindles to the CNS.

Which nerve supplies which area?

•    Cervical nerves: the back of the head, neck, shoulders, arms, and the diaphragmdas Zwerchfell

•    Thoracic nerves: the nerves in the arms and the trunk of the body

•    Lumbar and sacral nerves (this area is also called the “horse’s tail“): the nerves of the hips, pelvic cavity and the legs

What functions do the spinal roots have?

Each segment of the spinal cord has two roots, a ventral and a dorsal root. From the roots, the spinal nerves enter or leave the spinal cord.

•    Dorsal root: It is made of sensory neurons which carry impulses to the spinal cord.

•    Ventral root: It is the motor root and made of motor neurons carrying impulses from the spinal cord to muscles or glands.

What does “spinal cord reflex“ mean?

We do not have to think much about reflexes as long as they are working. However, they are very important. A reflex is an involuntaryunwillkürlich response of a part of your body (e. g. a muscle) to a stimulus. Spinal cord reflexes are those that do not depend directly on the brain, although the brain inhibitshemmen them.

There are five essential parts of reflex arcs (pathway of nervous impulses):

•    Receptors (change detection and impulse generation)

•    Sensory neurons (impulse transition from receptors to the CNS)

•    Central nervous system (contains one or more synapses)

•    Motor neurons (impulse transition from the CNS to the effector)

•    Effector (performs its characteristic action).

Among the most famous reflex arcsder Bogen is the patellar (or kneejerk) reflex that is often tested by physicians during routine exams. In this reflex, a tap on the patellar tendon just below the kneecap causes a rapid extension of the lower leg. It is a stretch reflex, which means that a stretched muscle automatically contracts.

The flexor reflex (or withdrawal reflex) is another type of spinal cord reflexes. The stimulus activating the reflex is often something painful, and the response is to then avoid this stimulus. For instance, if you touch a hot stove, you will immediately pull your hand away due to your flexor reflex. Flexor reflexes are three-neuron reflexes including sensory neurons, inter neurons and motor neurons. The sensory neurons synapse with the inter neurons in the spinal cord, which synapse with motor neurons. However, the brain does not have to make any active decision in order to protect the body.

 

BIBLIOGRAPHY

1.     Gilroy AM: Anatomy – An Essential Textbook: An Illustrated Review, Thieme Verlag 2013.
2.     http://dict.leo.org.
3.     www.dict.cc.
4.     www.webster-dictionary.org.

 

EXERCISE:

1. Which of the following transmits information from the spinal cord to the extremities of the body?
a. dorsal roots
b. ventral roots
c. ventral root ganglia

2. Cerebrospinal fluid is found only in the brain
a. True
b. False

3. How many lumbar vertebrae do we have?
a. 5
b. 4
c. 7
d. 12

4. How many cervical vertebrae do we have?
a. 12
b. 4
c. 7
d. 5

You‘ll find the answer on:
tinyurl.com/weiterbildung-englisch

 

Die Autorin:

Carmen Lobitz
Carmen Lobitz ist freie Trainerin, Lehrerin und MTA. Sie gründete 1998 in Berlin lobitz seminare, die unter anderem Englischseminare für Health Professionals anbieten.
Kontakt: mail@lobitz-seminare.de, www.lobitz-seminare.de

 

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