THE CNS AND PNS: THE MAIN DIVISIONS OF THE NERVOUS SYSTEM
It is connected to the peripheral nervous system (PNS) which includes the nerves in our extremities. But, there are big differences between the. The nervous system is the most important organization which Controls and integrates the different body functions and it maintains stability or. Describe the hierarchical structure of the nervous system . The peripheral nervous system (PNS) provides the connection between internal or external stimuli.
The autonomic nervous system is a 'self-regulating' system which influences the function of organs outside voluntary control, such as the heart rateor the functions of the digestive system.
Somatic nervous system[ edit ] See also: List of nerves of the human body 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 both functions. In the head and neckcranial nerve s carry somatosensory data. There are twelve cranial nerves, ten of which originate from the brainstemand mainly control the functions of the anatomic structures of the head with some exceptions.
The nuclei of the olfactory nerve and the optic nerve s lie in the forebrain and thalamus, respectively, and are thus not considered to be true cranial nerves. One unique cranial nerve is the vagus nervewhich receives sensory information from organs in the thorax and abdomen.
The accessory nerve is responsible for innervating the sternocleidomastoid and trapezius musclesneither of which being exclusively in the head. For the rest of the body, spinal nerves are responsible for somatosensory information.
These arise from the spinal cord. Usually these arise as a web "plexus" of interconnected nerves roots that arrange to form single nerves.
Difference between CNS and PNS
These nerves control the functions of the rest of the body. In humans, there are 31 pairs of spinal nerves: These nerve roots are named according to the spinal vertebrata which they are adjacent to. In the cervical region, the spinal nerve roots come out above the corresponding vertebrae i. From the thoracic region to the coccygeal region, the spinal nerve roots come out below the corresponding vertebrae.
Difference between CNS and PNS
It is important to note that this method creates a problem when naming the spinal nerve root between C7 and T1 so it is called spinal nerve root C8.
The brain contains about 86 billion nerve cells neurons and trillions of "support cells" called glia. The spinal cord is about 43 cm long in adult women and 45 cm long in adult men and weighs about grams. The vertebral column, the collection of bones back bone that houses the spinal cord, is about 70 cm long.
Therefore, the spinal cord is much shorter than the vertebral column. For brain weights of other animals, see brain facts and figures. A stegosaurus dinosaur weighed approximately 1, kg but had a brain that weighed only approximately 70 grams 0. Therefore, the brain was only 0.
The difference between centre and periphery
In contrast, an adult human weighs approximately 70 kg and has a brain that weighs approximately 1. This makes the brain to body ratio of the human times greater than that of the stegosaurus. Peripheral Nervous System The peripheral nervous system is divided into two major parts: Somatic Nervous System The somatic nervous system consists of peripheral nerve fibers that send sensory information to the central nervous system AND motor nerve fibers that project to skeletal muscle.
The picture on the left shows the somatic motor system. The cell body is located in either the brain or spinal cord and projects directly to a skeletal muscle.
Autonomic Nervous System The autonomic nervous system is divided into three parts: The autonomic nervous system controls smooth muscle of the viscera internal organs and glands.
This picture shows the general organization of the autonomic nervous system.