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The phrenic nerve is a nerve essential for our survival which arises from nerve roots C3, C4 and C5.
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Spinal nerve C1 is called the suboccipital nerve, which provides motor innervation to muscles at the base of the skull.Ĭ2 and C3 form many of the nerves of the neck, providing both sensory and motor control, and include the greater occipital nerve, which provides sensation to the back of the head, the lesser occipital nerve, which provides sensation to the area behind the ears, the greater auricular nerve and the lesser auricular nerve. The first 4 cervical spinal nerves, C1 through C4.Ĭ1 through C4 split and recombine to produce nerves that serve the neck and back of head. In the lumbar and sacral region, the spinal nerve roots travel within the dural sac and they travel below the level of L2 as the cauda equina. In the cervical region, the spinal nerve roots come out above the corresponding vertebrae.įrom the thoracic region to the coccygeal region, the spinal nerve roots come out below the corresponding vertebrae. Nerve roots are named according to the spinal vertebrata which they are adjacent to. In humans, there are 31 pairs of spinal nerves: 8 cervical, 12 thoracic, 5 lumbar, 5 sacral, and 1 coccygeal. Spinal nerves control the functions of the rest of the body. Spinal nerves arise from the spinal cord, usually as a web of interconnected nerves roots that arrange to form single nerves. Spinal nerves are responsible for somatosensory information for the rest of the body. The neuron is the primary component of the nervous system, which transmits messages from sensory receptors all over the body. Sensory receptors are modified ends of sensory neurons modified to deal with specific types of stimulus, thus there are many different types of sensory receptors in the body. The accessory nerve is responsible for innervating the sternocleidomastoid and trapezius muscles, neither of which being exclusively in the head. The vagus nerve, receives sensory information from organs in the thorax and abdomen. There are twelve cranial nerves which mainly control the functions of the anatomic structures of the head with some exceptions.īecause the nuclei of the olfactory nerve and the optic nerves lie in the forebrain and thalamus, respectively, they are not considered to be true cranial nerves.
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In the head and neck, cranial nerves carry somatosensory data. The somatic system includes the sensory nervous system and the somatosensory system and consists of sensory nerves and somatic nerves, and many nerves which hold dual functions. The autonomic nervous system influences the function of organs outside voluntary control, such as the heart rate, or the functions of the digestive system. The autonomic nervous system is a self-regulating system. The sensory nervous system transmits signals from senses such as taste and touch to the spinal cord and brain.
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The sensory nervous system is part of the somatic nervous system. The somatic nervous system transmits signals from the brain to end organs such as muscles. The somatic nervous system under voluntary control. The connection between CNS and organs allows the system to be in two different functional states: sympathetic and parasympathetic. The autonomic nervous system involuntary controls of smooth muscles and glands. The remaining ten cranial nerve axons extend beyond the brain and are therefore considered part of the PNS. The second cranial nerve is not a true peripheral nerve but a tract of the diencephalon.Ĭranial nerve ganglia originated in the CNS. In the somatic nervous system, the cranial nerves are part of the PNS with the exception of the optic nerve, along with the retina. The peripheral nervous system is divided into the somatic nervous system and the autonomic nervous system. The PNS is not protected by the vertebral column and skull, like the CNS, or by the blood–brain barrier.Īs a result the PNS which leaves it exposed to toxins and mechanical injuries. Its main function is to connect the CNS to the limbs and organs, essentially serving as a relay between the brain and spinal cord and the rest of the body. The PNS consists of the nerves and ganglia outside the brain and spinal cord. The peripheral nervous system (PNS) is one of two components that make up the nervous system the other part being the central nervous system (CNS). Peripheral nerves consist of sensory, motor, and autonomic fibers.