Division Of Human Nervous System

Composition of nervous system

Nervous system composed of two main branches:
        I.            Central Nervous System  ( CNS )
      II.            Peripheral Nervous System  ( PNS )

1.       CNS composed of  :
a.       Brain: responsible for receiving and processing sensory informations, initiating responses, memories, generating thoughts and emotions.
b.      Spinal cord: responsible for conducting signals to and from the brain, and controls reflex activities.

2.       PNS  composed of :
a.       Afferent nerves:   responsible for carrying information from periphery to CNS.
b.      Efferent nerves:  responsible for carrying information from CNS to peripheral organs. It is divided into  :
                                                                                                                                                                                               I.                     Somatic Nervous System.
                                                                                                                                                                                             II.                     Autonomic Nervous System.


·         Somatic Nervous System responsible for controlling voluntary movements like contraction of skeletal muscles.
·         Autonomic Nervous system (ANS) also called involuntary nervous system, it is responsible for regulation of the functions of our internal organs (the viscera) such as the heart, respiratory system, stomach, intestines and exocrine glands.

• Drugs affeceting ANS  are useful in treatment of different conditions  including blood pressure disturbance , asthma , cardiac dysfunctions .nasal congestion ,skeletal muscle spasticity and nocturnal enuresis. While drugs affecting CNS provide sedation , relieve pain ,anxiety, suppress movements disorders , epilepsy and psychotic disorders.                                                                 
• ANS  divided into Sympathetic  and  parasympathetic systems                                                                                                                                                                                                                                                                                                                                                                                                                                                                      Next Lesson we will take about differences between sympathetic and parasympathetic systems