Spinal cord injuries
If the spinal cord is damaged in an accident, the sections below the injury will be cut off from the circuit of information to and from your brain. This means, all nerves - and all body parts - linked to these areas of the spinal cord will also be disconnected from your brain and will stop functioning. Well protected
To minimise the risk of such an injury, your spinal cord is well protected: Three tough envelopes called meninges surround your spinal cord A clear fluid, that acts as a shock-absorber, circulates in the space between your outer and middle meninge Your backbone surrounds your spinal cord, the shock-absorbing fluid and the meninges Causes of Paraplegia
Note: The cervical spinal nerves exit the vertebrae above the cervical vertebrae, except for C7, where the C8 spinal nerve exits below the C7 vertebrae. All spinal nerves then exit below the thoracic, lumbar and sacral vertebrae. Paraplegia due to a spinal cord injury results in an impairment in motor or sensory function of the lower half of a person's body. The condition occurs due to damage to the cellular structure of the spinal cord within the spinal canal. The area of the spinal cord which is affected in paraplegia is either the thoracic, lumbar, or sacral regions of the spinal column. If the arms are also affected by paralysis, quadriplegia/tetraplegia is the correct terminology. Symptoms of Paraplegia
Injury to the spinal cord at the thoracic level and below result in paraplegia, with the arms and hands not affected. People with injuries to the spinal cord segments T-1 to T-8 usually retain control of the arms and hands but have poor trunk control and balance due to the lack of abdominal muscle control. Lower thoracic injuries (T-9 to T-12) retain good truck control and good abdominal muscle control. The sitting balance of people with lower spinal cord injuries is usually very good. Lumbar and Sacral injuries result in decreased control of the hip flexors and legs.
Central Nervous System
The central nervous system (CNS) is made up of the brain and spinal cord.
Branching out of the CNS are nerves. Each nerve contains a bundle of neurones, surrounded by an insulating layer.
Information is passed from receptors to the brain along sensory neurones.
The brain then coordinates a response and sends a message along a motor neurone to aneffector organ, which could be a muscle or a gland.
2. motor pathway
BASIC MOTOR PATHWAY
A. An overview:
The motor pathways are pathways which originate in the brain or brainstem and descend down the spinal cord to control the -motor neurons. These large neurons in the ventral horns of the spinal cord send their axons out via the spinal roots and directly control the muscles. The motor pathways can control posture, reflexes, and muscle tone, as well as the conscious voluntary movements that we think of when we hear "motor system". The most famous pathway is the so called "pyramidal system", which begins with the large pyramidal neurons of the motor cortex, travels through the pyramids of the brainstem, (somewhere in here there is a coincidence), and finally ends on or near the -motor neurons. This system is extremely important clinically, as strokes often affect the motor system. Therefore it is crucial to understand the anatomy of the motor pathway. B. The anatomy:
The primary motor pathway is also called the corticospinal pathway. As all such pathways are named from beginning to end, this pathway starts in cortex and ends in the spine. Specifically, it starts in the precentral gyrus, the fold of cortex just anterior to the central sulcus.
The precentral gyrus has many names: primary motor cortex, Brodmann's area 4, M1, etc. It provides the bulk of the corticospinal tract, but other cortical areas contribute as well. One such area is area 3a, part of primary somatosensory cortex, which is hidden down inside the central sulcus.
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