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The Nervous System #
chap 5 continued
Question | Answer |
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Blood Supply for the Brain: comes from branches 2 major arteries | Internal carotid Vertebral artery |
Spinal Cord: | A continuation of the medulla and runs within the vertebral canal from the foramen magnum to the conus medullaris (around 2 lumbar vertebra) and ending with the cauda equina (horse tail) around Sacral vertebra 5. |
Spinal Cord: logistics | Its around 17" long and is enclosed with the same 3 protective layers (membranes) as the brain.As with brain has cerebral spinal fluid b/w arachnoid and pia matter. |
Vertebra | Consist of a body and neural arch.The body is the weight bearing portion.The neural arch consists of the pedicle, transverse process, lamina and spinous process. The opening between the body and neural arch is the vertebral formen through which sp passes |
Intervertebral foramen | formed by the superior vertebral notch of the vertebra below and the inferior vertebral notch of the vertebra above. This opening is where the spinal nerve root exits the vertebral canal. |
spinal cord reveals | Gray matter in middle in a butterfly shape - contains neuronal cell bodies and synapses. Top portion of the shape is the posterior horn which transmits sensory impulses and lower portion is the anterior horn which transmits motor impulses. |
spinal cord posterior columns | (dorsal columns) located in the posterior medial portions of the spinal cord transmit sensations of proprioception, pressure and vibration |
White matter | contains ascending sensory and descending motor fiber pathways. Each pathway carries a particular type of impulse such as touch from and to a specific area. |
White matter various pathways | cross over from one side of the body to the other at various levels. This is why with a CVA with right brain damage will have affects the left side of the body. |
Corticospinal pathway | Significant pathway in motor control. They synapse in the anterior horn just before leaving the spinal cord. |
Corticospinal pathway levels | . Motor neurons which synapse above this level are called upper motor neurons. Ones that synapse at or below the anterior horn are called lower motor neurons. |
Corticospinal pathway upper lesion | If lesion occurs b/w brain and spinal cord proximal to the anterior horn it is an upper motor neuron lesion. |
Corticospinal pathway lower lesion | If it between the anterior horn of the spinal cord and periphery it is a lower motor neuron lesion. |
Upper motor neuron lesions | spinal cord injuries, MS, parkinsonism, CVA, Various types of head injuries. |
Lower motor neuron lesions | - MD, poliomyelitis, Myasthenia gravis, and peripheral nerve injuries. |
Spinal nerves | 31 pairs. 8 cervical, 12 thorasic, 5 lumbar and 1 coccygeal. They exit the vertebral column over the corresponding vertebra through C7, there are 8 cervical nerves so the 8th one exits over T1 and T1 nerve exits under T1 vertebra and so on. |
Cranial nerves - 12. | Named and numbered. They have origins in the brain and are motor and sensory nerves. |
The Peripheral Nervous System - | all the nervous tissue outside o the vertebral canal. |
Branches of the spinal nerves | Posterior (dorsal) ramus -Anterior (ventral) ramus |
Anterior (ventral) ramus | innervates all muscles and skin not innervated by the posterior ramus. |
Posterior (dorsal) ramus | supplies deep muscles of the back and skin covering these muscles. |
Dermatomes: | Area of skin supplied with the sensory fibers of a spinal nerve. There is overlap so have damage 2 dermatomes to have lost function. One will result in decreased or altered sensation. |
spinal cord level: | Spinal nerves exits above the vertebra in cervical region-Starting with C8 they come out below. Starting with C8 they come out below. |
spinal cord level:nerve pathway | Starting with T1 all spinal nerves below T1 come out below the same numbered vertebra. |
muscles innervation | Most muscles take innervation from more than one spinal level. May weaken muscles but, some function remains |
Plexus formation:Cervical - C1-C4 | innervates the muscles of the neck |
Plexus formation:Brachial - C5-T1 | innervates upper limb |
Plexus formation:Lumbrosacral - L1-S5- | thigh, leg and foot |
Brachial plexus: | formed from C5-T1 nerves. It splits and joins several times before ending in 5 main peripheral nerves: musculocutaneous, axillary, radial, median, ulnar |
Functional Significance of Spinal Cord Level: | most muscles take innervations from more than one spinal level, therefore an injury at one level may weaken a muscle but some function will remain |