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Sectional organization of spinal cord. The spinal cord is the main pathway for information connecting the brain and peripheral nervous system. [3] [4] Much shorter than its protecting spinal column, the human spinal cord originates in the brainstem, passes through the foramen magnum, and continues through to the conus medullaris near the second lumbar vertebra before terminating in a fibrous ...
Area of the human body surface innervated by each spinal nerve. Even mammals, including humans, show the segmented bilaterian body plan at the level of the nervous system. The spinal cord contains a series of segmental ganglia, each giving rise to motor and sensory nerves that innervate a portion of the body surface and underlying musculature ...
The sympathetic trunk (sympathetic chain, gangliated cord) is a paired bundle of nerve fibers that run from the base of the skull to the coccyx. It is a major component of the sympathetic nervous system .
The number of vertebrae in a region can vary but overall the number remains the same. In a human spinal column, there are normally 33 vertebrae. [3] The upper 24 pre-sacral vertebrae are articulating and separated from each other by intervertebral discs, and the lower nine are fused in adults, five in the sacrum and four in the coccyx, or tailbone.
The CSF-filled central chamber is continuous from the telencephalon to the spinal cord, and constitutes the developing ventricular system of the CNS. Because the neural tube gives rise to the brain and spinal cord any mutations at this stage in development can lead to fatal deformities like anencephaly or lifelong disabilities like spina bifida.
Most motor pathways originate in the motor cortex of the brain. Signals run down the brainstem and spinal cord ipsilaterally, on the same side, and exit the spinal cord at the ventral horn of the spinal cord on either side. Motor nerves communicate with the muscle cells they innervate through motor neurons once they exit the spinal cord. [1] [7]
The corticospinal tract originates in several parts of the brain, including not just the motor areas, but also the primary somatosensory cortex and premotor areas. [1] Most of the neurons originate in either the primary motor cortex (precentral gyrus, Brodmann area 4) or the premotor frontal areas.
The ventral spinocerebellar tract will cross to the opposite side of the body first in the spinal cord as part of the anterior white commissure and then cross again to end in the cerebellum (referred to as a "double cross"), as compared to the dorsal spinocerebellar tract, which does not decussate, or cross sides, at all through its path.