Each pair of nerves corresponds to a segment of the cord and they are named accordingly. This means there are 8 cervical nerves, 12 thoracic nerves, 5 lumbar nerves, 5 sacral nerves, and 1 coccygeal nerve.
Each spinal nerve is connected to the spinal cord by a dorsal root and a ventral root. The cell bodies of the sensory neurons are in the dorsal root ganglion, but the motor neuron cell bodies are in the gray matter. The two roots join to form the spinal nerve just before the nerve leaves the vertebral column. Because all spinal nerves have both sensory and motor components, they are all mixed nerves. The autonomic nervous system is a visceral efferent system , which means it sends motor impulses to the visceral organs.
It functions automatically and continuously, without conscious effort, to innervate smooth muscle , cardiac muscle , and glands. It is concerned with heart rate , breathing rate, blood pressure , body temperature, and other visceral activities that work together to maintain homeostasis.
The autonomic nervous system has two parts, the sympathetic division and the parasympathetic division. Many visceral organs are supplied with fibers from both divisions. In this case , one stimulates and the other inhibits. This antagonistic functional relationship serves as a balance to help maintain homeostasis. The neurons are essentially the cells which make up the central nervous system and the peripheral nervous system.
The structure of neurons allows it to receive and carry messages effectively to other neurons and throughout the body. It contains a soma cell body , which is the core of the neuron, responsible for ensuring that everything is functioning efficiently. The axon is a tail-like structure of the neuron which functions in carrying signals away from the soma to the end of the neuron, for the purpose of transmitting signals to other neurons. The dendrites of the neurons are tree-root shaped, located at the end of the neuron.
Their function is to receive and pass on information through their synapses to other neurons nearby. The nerves are essentially bundles of thousands of individual axons all wrapped in a protective membrane in the PNS. Messages are sent along each of the axons to the peripheral organs of the body and send back information to the CNS.
Each axon within the nerve is an extension of an individual neuron. Within the PNS, there are some nerves that are attached to the spinal cord spinal nerves and others which are attached directly to the brain cranial nerves. Spinal nerves are relatively large nerves that serve all of the body below the neck, conveying sensory and motor information from the body and carrying messages to the muscles and glands.
The spinal nerves carry signals from receptors around the body to the spinal cord. These signals are then transmitted to the brain for processing. The PNS is made up of 31 pairs of spinal nerves, which radiate out from the spinal cord, operating different locations of the body:. Each spinal nerve exits the spinal cord by traveling through openings at the right and left sides of the vertebrae of the spine. These nerves divide and subdivide to form a network connecting the spinal cord to every part of the body.
The longest nerve in the human body, the sciatic nerve from the lumbar region networks off until it reaches the tips of the toes, measuring up to a meter or more in length. The cranial nerves primarily coordinate the muscle and sense receptors of the head and neck. These nerves are different to the spinal nerves as they do not enter through the spinal cord to reach the brain, instead, they are directly linked to the brain.
Cranial nerves allow sensory information to transmit from the organs of the brain ears, eyes, nose, and mouth , as well as conveying motor information from the brain to these organs. For instance, when eating food, the brain will transmit motor messages through the nerves to move the mouth in order to chew and swallow. When tasting the food, the sensory information gets sent back to the brain through a set of cranial nerves.
Olivia has been working as a support worker for adults with learning disabilities in Bristol for the last four years. Guy-Evans, O. Peripheral nervous system PNS definition, parts and function. Simply Psychology. Dorland, W. Elsevier Health Sciences. Goldstein, D. Adrenal responses to stress. It helps the body return to normal activity after an emergency. Next Endocrine System. Removing book from your Reading List will also remove any bookmarked pages associated with this title.
Are you sure you want to remove bookConfirmation and any corresponding bookmarks?
0コメント