the nervous system carries out a complex array of tasks it allows us to sense smell produce speech control body movements regulate internal organs and remember past events these diverse activities can be grouped into three basic functions to collect and transmit sensory input integrate or process that information and then produce a motor output so the sensory function of the nervous system involves sensory receptors which detect internal stimuli such as the increase in blood pressure or external stimuli such as a raindrop landing on your arm this sensory information is then carried into the brain and spinal cord through our cranial and spinal nerves the integrative function processes sensory information by analyzing it and making decisions for an appropriate response or non-response and once the sensory information is integrated the nervous system May elicit an appropriate motor response by activating affectors which can be muscles or glands stimulation of an affector causes an output such as a muscle Contracting to produce movement or the secretion of a gland so giving you an example to provide a bit of context for those functions and let's say you've been out and about in the middle of summer it's quite hot and you've become dehydrated osmo receptors which are the receptors that detect osmolarity or the water content of your blood will detect that you were dehydrated this sensory information will then be transmitted into the spinal cord and brain from those receptors along a sensory path way upon reaching the brain and specifically the hypothalamus of the brain in this scenario and this sensory information will be integrated with other relevant sensory information such as the environmental conditions or the context and an appropriate outcome will be decided in this situation in an environment where a person has access to a glass of water the appropriate outcome would be to pick that glass up and have a drink in this scenario the relevant muscles required to pick that glass up would be stimulated this motor information will be transmitted from the brain down a motor Pathway to our fector the outcome will be that this person will then contract their muscles pick up that glass and have a drink so moving on from what the nervous system does to what the nervous system is made up of and how it's organized and the human nervous system consists of billions of neurons and even more neurog Gia or supporting cells this complex and intricate network of cells can be order uh organized sorry into two main subdivisions the central nervous system or CNS consists of the brain and the spinal cord the brain is a part of the central nervous system that sits within the skull the spinal cord is attached to the brain and sits down the middle of our vertebral column the central nervous system processes many different kinds of incoming sensory information it's a source of our thoughts emotions and memories and most of the signals to stimulate muscles to contract or glands to secrete also originate from our central nervous system the peripheral nervous system is then all of the nervous tissue outside of the central nervous system components of the peripheral nervous system consist of our cranial and our spinal nerves which are the nerves that exit the brain and then the spinal cord respectively the ganglia which are these small swellings of nervous tissue here which are made up mostly of neuronal cell bodies inic plexuses which are networks of neurons located in the walls of the organs in our gastrointestinal tract and then also various sensory receptors which are the structures that monitor those internal and external changes in the environment and include things like touch receptors in the skin photo receptors in the eye and alaor receptors in the nose all of the nervous tissue of the peripheral nervous system is then div divided further into a sematic nervous system an autonomic nervous system and an anic nervous system the sematic nervous system consists of sensory neurons that convey information to the central nervous system from a sematic receptors in the head body and Limbs and then also re receptors from our special Senses so Vision hearing taste and smell and then also consists of motor neurons which transmit information from the central nervous system to our sceletal muscles only so these are the muscles of the body that attach to Bone and can be voluntarily controlled the autonomic nervous system then consists of sensory receptors which convey information to the central nervous system from our autonomic sensory receptors so these are located primarily in viseral or soft organs of the body such as our stomach or the lungs and then motor neurons that transmit information from the central nervous system to our smooth muscle our cardiac muscle and our glands which are all affectors that are under involuntary control so we can't consciously control these organs and they just work automatically the motor portion of our autonomic nervous system is then further divided into two branches or two divisions we have the sympathetic division of the nervous system and then the parasympathetic division these divisions will focus on uh entirely in a future module however typically affectors receive input from both sympathetic and parasympathetic divisions of the autonomic nervous system with the two divisions having opposing effects for example the sympathetic nervous system which is also referred to as a division of the nervous system responsible for fight or flight will increase heart rate whereas the parasympathetic nervous system which is the division which is responsible for rest and digest will typically reduce heart rate the inic nervous system which is sometimes also just called the brain of the gut is a division of the nervous system which is also involuntary it was actually once considered part of of the autonomic nervous system but it's over 1 million neurons in inic plexuses that extend the length of the gastrointestinal tract so Sensory neurons within the inic uh nervous system monitor chemical changes within the gastrointestinal tract as well as stretching of organs like the stomach and the intestinal walls inic prot to neurons will govern the contractions of smooth muscle in the stomach and the intestines to propel food forward as well as the secretion of various digestive acids and hormones now some of these activities can take place without the involvement of the central nervous system which is why it is often separate to our autonomic nervous system so putting all of that together in one slide for you which is something that you might like to do on your own as part of your own revision and the nervous system is divided globally into the central nervous system and the peripheral nervous system the central nervous system is made up of the brain which sits inside the skull and the spinal cord which extends down from the brain and is found within the vertebral column the peripheral nervous system then consists of all of the nervous tissue sitting outside side of the central nervous system this includes the cranial and spinal nerves that exit the brain the brain stem and the spinal cord the ganglia or the clusters of cell bodies the anic plexuses in the gut and then all of the various receptors the peripheral nervous system is then further divided into three sections the sematic nervous system which includes sematic and special sens receptors these transmit sensory information to the central nervous system and then motor neurons which transmit motor information from the central nervous system to our scal muscles the autonomic nervous system contains receptors in the visceral or soft organs like the heart the lungs the liver they transmit sensory information bya Sensory neurons to the central nervous system then we have motor neurons which transmit motor information from the central nervous system to our cardiac muscle our smooth muscle and our glands which are all the effectors that we can't consciously control the motor division of the autonomic nervous system is also then further divided into our sympathetic and our parasympathetic divisions the effectors that are in inovated by the sympathetic division produce fight or flight responses so increasing heart rate increasing your respiratory rate or how fast you breathe increasing blood flow to the brain and muscles the effectors that are innovated by the parasympathetic division produce rest and digest activities such as increasing the rate of digestion slowing heart rate and increasing the filtration of blood the third division of the peripheral nervous system is the enteric nervous system this system consists of receptors and sensory neurons that monitor chemical changes and the degree of stretch in the organs of the gastrointestinal tract so the stomach and the intestines and then the motor division which is responsible for the contraction of smooth muscle which moves our food forward through our gastointestinal tract and the secretion of glands and Endocrine cells which produce acids and hormones that aid in digestion although the functions of the motor division of the anic nervous system are under involuntary control it does not always require input from the central nervous system and that's why it gets its own division and is not just part of the autonomic nervous system