Question

Name four effector organs that are dually innervated by the sympathetic and parasympathetic nervous systems. How does each system effect the effector organs listed?

Answer 1

Answer

The four effector organs that are dually innervated by the sympathetic and parasympathetic nervous systems are :

1. Heart
2. Pupil of eye
3. Bronchi
4. Urinary bladder
   

1) Heart

• Sympathetic stimulation increases the generation of action potentials by SA node in the heart leading to increased heart rate. It also increases contractility of cardiac muscle leading to increased stroke volume.
• Upon parasympathetic stimulation, the action potential firing from SA node as well as force of contraction both decreases. It causes decreased heart rate and decreased stroke volume.

2) Pupil of eye

• Sympathetic system causes contraction of dilator pupillae muscle surrounding the pupil that leads to pupillary dilation.
• Parasympathetic system causes contraction of sphincter pupillae muscle surrounding the pupil that leads to pupillary constriction.

3) Bronchi

• Sympathetic system causes relaxation of the bronchial smooth muscles leading to bronchodilation.
• Parasympathetic system causes contraction of the bronchial smooth muscles leading to bronchoconstriction.

4) Urinary bladder

• Sympathetic system helps the detrusor muscle to remain in relaxed state. The urine is accomodated in the bladder without rise in the pressure. Urination is inhibited.
• Parasympathetic system causes contraction of detrusor muscle and urination is promoted.