What is the difference between the Parasympathetic Nervous System and the Sympathetic Nervous System?

The Nervous System can be split into three central pathways.The SNS and PNS are part of the Autonomic Nervous System, the autonomic nervous system is responsible for the involuntary actions of the human body, so these are things that we don’t consciously think about.
The sympathetic nervous system is known as the ‘flight or fight’ response and the parasympathetic nervous system is known as the ‘rest and digest’ response.
Both originate in the spinal cord and branch out from there.The sympathetic nervous system is the part of the autonomic nervous system that prepares the body to react to stresses such as threat or injury. It causes muscles to contract and heart rate to increase.The parasympathetic nervous system is the part of the autonomic nervous system that controls functions of the body at rest. It helps maintain homeostasis in the body. It causes muscles to relax and heart rate to decrease.
Putting these in context in the heart and lungs the sympathetic nervous system response: increases contraction of the heart and consequently increases heart rate, dilates the bronchial tube, hence increasing air flow to the lungs.
In the case of the parasympathetic nervous system response: decrease in Heart Rate due to decrease in contraction of the heart and the bronchial tubes constrict.