Differences between Sympathetic and parasympathetic systems

	Sympathetic system	Parasympathetic system
Origin of nerves	Thoracic and lumbar region of the spinal cord	Cranial and sacral regions of the spinal cord
Main neurotransmitter	Epinephrine and nor epinephrine	Acetylcholine
Innervated organs	Eye, GIT, Respiratory system,	Eye, GIT, Respiratory system,
Purpose	Responsible for  involuntary responses, such as “fight and flight”	Responsible for essential body functions, such as elimination, feeding, and resting functions.

Differences between Sympathetic and parasympathetic   systems:

        I.            Functions of Sympathetic nervous system :    

a.       Effects of stimulation of the sympathetic system: because several actions like increase heart rate, blood pressure, mobilize energy stores of the body, increase blood flow to skeletal muscles and cardiac muscle while decreasing blood flow to the skin and other internal organs.

b.      Fight or Flight response  :  sympathetic  work actively at emergencies cases like fight or flight    it act directly by activation of effectors organs and indirect by stimulating adrenal medulla to release epinephrine and little norepinepherine and these hormones enter the blood and activate effector  organs .

c.       Although sympathetic system is continually active to some degree like  maintaining the tone of vascular beds

      II.            Functions of Parasympathetic nervous system  :

                 

The parasympathetic system  responsible for maintaining essential body function  as digestive process and elimination of wastes. It oppose or balance  the actions of sympathetic system and generally it dominant over sympathetic system in rest and digest

 
 
Drugs stimulate sympathetic system called    sympathomimetics or adrenergics
Drugs stimulate parasympathetic system called  parasympathomimetic or cholinergic

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