The Spinal Cord
Spinal cord has two main functions:
1). SC connects a large part of the peripheral nervous system to the brain.
2) SC acts as a minor coordinating centre responsible for some simple reflexes (e.g withdrawal reflex).
• 31 pairs of spinal nerves arise along the spinal cord
Peripheral Nervous System
•31 pairs of Spinal nerves
–Join together to form Plexuses
•12 pairs of Cranial nerves
•Autonomic Nervous System
Sensory and Motor Pathways
Sensory
Conduct sensory impulses from the body to various parts of the Brain.
Motor
Conduct motor impulses from the brain to the body via the spinal Cord.
Sensory and Motor systems - pain
Reflex
Rapid (and unconscious) response to changes in the internal or external environment needed to maintain homeostasis.
e.g. Knee jerk reflex
Reflex Arc
The neural pathway over which impulses travel during a reflex. The components of a reflex arc include:
1 - Receptor - responds to the stimulus.
2 - Sensory neuron - transmits impulse into the spinal cord.
3 - Central Nervous System - the spinal cord processes information.
4 - Motor neuron - transmits impulse out of spinal cord.
5- Effector - a muscle or gland that receives the impulse from the motor neuron & carries out the desired response.
Lesions/Damage to the Nervous System
Any localised damage to spinal cord or spinal roots will attribute to some form of functional loss.
- Paralysis: |
(loss of motor function) |
- Parasthesias: |
(loss of senses) |
The effects of disease or injury upon the CNS and periphery depend on the:
-severity of the damage
-type of neurones involved
-position of neurones involved
Damage to the Brain
•The most common causes of damage to the brain are:
-Stroke
-Tumour
-Trauma (caused by a fall or a blow)
-Multiple sclerosis (destruction of Myelin
sheath) |
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- Cerebral palsy (defect or injury to the brain that |
occurs at |
or shortly after birth) |
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- Metabolic disorder (interferes with body's ability |
to |
maintain itself). |
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Damage to the Spinal Cord
- Tumour
- Herniated disk (also called a ruptured or slipped disk)
- Spondylosis (a disease that causes stiffness in the joints of the spine)
-Rheumatoid arthritis of the spine
-Neurodegenerative disease (a disease that damages nerve cells)
-Multiple sclerosis.
Cerebrovascular Accident (Stroke)
•CVAs are: Bleeds into the brain
Obstruction of blood supply to brain.
•CVAs often affect the motor cortex and its major pathways.
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These tracts cross in the medulla, therefore: |
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• |
(Stroke on right side of brain) |
Left hemiplegia |
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• |
(Stroke on left side of brain) |
Right hemiplegia |
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