Nervous System

• nervous system - is the most complex and highly organized body system. it receives information from the sensory organs through nerves, transmits the information through the spinal cord and processes it in the body.
• nervous system - directs our body's reaction to the world. it manages all these activities by sending lightning-quick signals of electrochemicals between cells
• nerve cell - basic unit of structure and function in the nervous system, also called a neuron
• neurons consists of a cell body and several nerve fibers called dendrites
• dendrites - receives signals from other cells
• nucleus - controls the entire neuron
• cell body - organizes and keeps the cell functional
• dendrites - branch-like extensions that receive impulsions and carry them toward cell body
• axon - single extension of the neuron that carries impulses away from cell body
• sensory neurons - carry impulses from inside and outside the body to brain and spinal cord
• interneurons - found within brain and spinal cord, process incoming impulses and pass them on to motor neurons
• motor neurons - carry impulses away from the brain to spinal cord
• when a nerve impulse comes to the end of an axon, it produces the chemical called neurotransmitter, to be released
• central nervous system - serves as the main processing center for the entire nervous system
• brain - an organ located within the skull that functions as organizer and distributor of information for the body. It has three main parts.
• cerebrum - the 4 lobes of the brain, which are the frontal, temporal, parietal and occipital lobes perform specialized functions.

  Performs higher functions like interpreting touch, vision and hearing, as well as speech, reasoning, emotions, learning and fine control of movements.
• cerebellum - Its function is to muscle movements, maintain posture and balance.
• brainstem - acts as a relay center connecting the cerebrum and cerebellum to the spinal cord. performs many automatic functions such as breathing, heart rate, body temperature, wake and sleep cycles, digestion, sneezing, coughing, vomiting, and swallowing.
• spinal cord - serves as a channel for signals between the brain and the rest of the body, and controls simple musculoskeletal reflexes without input
• peripheral nervous system - connects the central nervous system to the organs and limbs. It has two main divisions.
• somatic nervous sytem - associated with the voluntary control of body movements and has two main parts.
• spinal nerves - the nerves that carry motor and sensory signals between the spinal cord and the body.
• cranial nerves - the nerve fibers that carry information into and out of the brain stem
• autonomic nervous system - associated with the involuntary (you do not consciously control these) control of body movements such as blood flow, heartbeat, breathing and digestion, and has two subdivisions:
• sympathetic - it is activated when the body is in a dynamic role or stress. (e.g., increased heart rate and breathing, dilation of pupil, sweating, etc.). flight or fight response
• parasympathetic - it maintains body functions and restores the body to normal or relaxed mode.