Anatomy Week One

The first week in anatomy class we covered the nervous system.  We learned that there are two main divisions of the nervous systems, and these are the central nervous system and the peripheral nervous system.  The central nervous system consists of the brain and the spinal cord, and the peripheral nervous system includes all the nervous tissue outside the CNS.  In the peripheral nervous system the nerves are classified by their origin, for example the cranial nerves emerge from the base of the brain.  The nervous system is responsible for all of one's perceptions, behavior, memories, and movements.  The diverse actions of the nervous system can be divided into 3 main groups: the sensory function, the integrative function, and the motor function.  

The sensory function has sensory receptors that can detect internal stimuli.  Some examples of this are when the body can sense an increase in blood acidity and external stimuli such as a feeling a raindrop hitting your skin.  The sensory or afferent neurons carry these messages through cranial and spinal nerves into the brain and the spinal cord to be processed.

The Integrative function of the nervous system integrates or processes the sensory information received from afferent neurons by analyzing it, storing it, and making decisions for appropriate responses to that stimuli.  Interneurons are some of the many neurons involved in this process and these have axons that extend only for a short distance within the CNS and contact nearby neurons in the brain, spinal cord, or a ganglion.  The majority of the neurons in the body are the interneurons.  

The Motor function of the nervous system involves responding to to integration decisions that are made by the interneurons after being processed.  The Neurons that serve this function are called motor neurons or they can also be called efferent neurons.  These carry the information from the brain and the spinal cord through cranial and spinal nerves.  The cells and organs that are contacted by these neurons are called effectors.  Some examples of these are muscle fibers and glandular cells.  

Without even realizing it, our nervous system is constantly working, even in our sleep.  It is responsible for making sure that everything in our body is running smoothly.  It is the key factor in maintaining the bodies homeostatic balance.  It helps to make sure that things like our body temperature, blood acidity, heart rate, blood pressure, etc. are all in the ranges that they are supposed to be in.  If for some reason our body starts to go out of the normal ranges in maintaining homeostasis, it is responsible for detecting these changes, sending it to the integration centers in the brain, and then processing the proper course of action to correct the problem.  The nervous system is also responsible for processing external stimuli such as the rain drop falling onto one's skin, burning a finger, or falling down and scraping a knee.