What is the spinal cord made up of & what does it do?
- FunnelwebLv 74 years agoFavorite Answer
The spinal cord (as opposed to the spine) is an extension of the central nervous system. So it is made up of the same kind of tissue as the brain, including nerve cells, and the various forms of glial cells found in the brain (oligodendrocytes, astrocytes and microglial cells) as well as blood vessels. It extends from the brain-stem and commences at the level of the foramen magnum (the large hole at the base of the skull). In adults it finishes at the level of the 1st lumbar vertebra. (The first lumbar vertebra is the topmost of the five back bones in the lower back: it is just below the 12th thoracic vertebra. The thoracic vertebra are attached to ribs, the lumbar vertebra are not).
The spinal cord sits in the middle of the spinal canal, and is surrounded by cerebrospinal fluid just like the brain is. On each side 31 nerves come off the spinal cord: each nerve leaves the spinal cord as a dorsal root (which is mainly sensory) and a ventral root (which is mainly motor) and these roots unite just as the nerves leave the spinal canal.
The spinal cord has a number of functions:
1) Motor nerves originate in the spinal cord, which send out processes called axons through the nerves to the muscles in the arms, legs and trunk. These nerves receive input from nerve cells originating in the brain, which is how your brain controls the body. They also receive other input.
2) Sensory nerves pass through the spinal cord conveying sensation for touch, joint position sense, movement sense, pain and temperature from the arms and legs and trunk. Some of these nerves end in the spinal cord, others pass sensation up to the brain.
3) Reflexes occur in the spinal cord. For instance when you tap on the patellar tendon (just below the kneecap) the sensation travels back to the cord. Some of the sensory nerves send impulses to the brain, but others send impulses directly to the motor nerve in the spine, causing a reflex "knee-jerk" before your brain has even had time to think about it. There is also a pain-withdrawal reflex, you might have experienced if you ever put your hand onto hot metal.
4) Many "autonomic" nervous system functions are mediated through the spinal cord. From the thoracic cord comes nerves for the "sympathetic" nervous system, which causes blood vessels to constrict, raises the heart rate, causes sweating, and mediates ejaculation in the male. From the sacral (lowest) part of the cord comes nerves for the "parasympathetic nervous system, which controls operation of the urinary bladder, the genital organs (including erection in the male, and lubrication in the female), and the most distal part of the large intestine.
This is just a brief overview, as whole books could be written bout this topic. Feel free to ask me any questions.
- Cal KingLv 74 years ago
It is a bundle of nerves that transmit signals between the brain and the rest of the body.
- G. WhilikersLv 74 years ago
The spinal cord is all the nerves running from the brain to the limbs, combined into one 'cable' (not a medical term). Its path goes down the spine through the center of the vertebrae, and bundles of nerves branch out at each level to serve a section of the body.
- 4 years ago
Bones and muscles