Cardiovascular system:
The sympathetic supply to heart, when stimulated, increases the force and rate of contraction of heart and causes vasocontraction. The ovarall effect is increased blood pressure. The parasympathetic system is essentially opposite to that. It causes decreases rate of contraction of heart and causes the blood vessels to dilate. The overall effect is decreased blood pressure.
Respiratory system:
The sympathetic nervous system causes dilation of the airways and thus increases the rate of respiration. The parasympathetic system is opposite to that, causing contraction of airways and thus decreasing the rate of respiration.
Note:
If you find it hard to remember the effects of sympathetic and parasypathetic nervous system of various organs, just keep the following two points in mind:
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Sympathetic nervous system prepares the body for emergency, so every thing that happens in emergency (such as increased heart rate, increased rate of respiration, dilation of pupils etc) is caused by sympathetic stimulation.
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Parasympathetic nervous system is activated when the body is in resting condition. So every thing that happens during resting phase (such as slow rate of respiration, low blood pressure, increased mobility of the Gastrointestinal tract, etc) is caused by the parasympathetic nervous system.
