Parasympathetic Nervous System
Mechanism of Accommodation: The accommodation reflex is controlled by the autonomic nervous system (ANS) and involves both sympathetic and parasympathetic pathways.Parasympathetic control: The parasympathetic nervous system plays the primary role in accommodation.
What our notes say
- Mechanism of Accommodation: The accommodation reflex is controlled by the autonomic nervous system (ANS) and involves both sympathetic and parasympathetic pathways.Parasympathetic control: The parasympathetic nervous system plays the primary role in accommodation. (MEDICAL PHYSIOLOGY II ESsays)
- This relaxation is mediated by the parasympathetic nervous system. (MEDICAL PHYSIOLOGY II ESsays)
- Food stimulates the parasympathetic nervous system to reduce HCO3- secretion into the saliva. (GIT Physiology Exam Questions)
- Food stimulates the parasympathetic nervous system to increase HCO3- secretion into the saliva. (GIT Physiology Exam Questions)
- Vagal Stimulation: The parasympathetic nervous system, via the vagus nerve, enhances mucus production through acetylcholine release. (Secretions of the Small Intestine and Their Control)
Study material on Parasympathetic Nervous System
Practice questions on Parasympathetic Nervous System
A feature of the sympathetic (not parasympathetic) nervous system:
- Ganglia in effector organs.
- Long preganglionic neurons.
- Preganglionic neurons release norepinephrine.
- Preganglionic neurons originate in thoracolumbar spinal cord. ✅ Answer: D. Preganglionic neurons originate in thoracolumbar spinal cord.
Answer: A. Preganglionic neurons originate in thoracolumbar spinal cord. is the physiologically correct answer per standard MBChB-level teaching on this topic. ---
Concerning the parasympathetic nervous system:
- Its postganglionic cell bodies are in the CNS.
- Its stimulation increases salivary secretion.
- Its stimulation inhibits intestinal motility.
- Its postganglionic cell bodies are located on skeletal muscles.
- Its stimulation causes bronchodilation. ✅ Answer: B
Answer: A. Parasympathetic stimulation generally increases the secretion of watery saliva from salivary glands.
Which of the following statements about the parasympathetic nervous system is correct?
- Preganglionic neurons release norepinephrine.
- Postganglionic neurons release acetylcholine at target organs.
- Receptors on target organs are always nicotinic.
- Ganglia are typically located far from target organs.
Answer: B. In the parasympathetic nervous system, preganglionic neurons release acetylcholine, which acts on nicotinic receptors on postganglionic neurons. Postganglionic neurons then release acetylcholine at the target organs, where it acts on muscarinic receptors. Therefore, statement B is correct. Preganglionic neurons (A) release acetylcholine, not norepinephrine. Receptors on target organs (C) are muscarinic, not nicotinic
The main neurotransmitter of the parasympathetic nervous system is:
- Norepinephrine
- Dopamine
- Acetylcholine
- Serotonin
Answer: C. Acetylcholine (ACh) is the neurotransmitter for both preganglionic and postganglionic parasympathetic neurons.
The primary neurotransmitter of the parasympathetic nervous system is:
- Norepinephrine
- Dopamine
- Acetylcholine
- Serotonin
Answer: C. Acetylcholine (ACh) is the neurotransmitter for all preganglionic fibers and postganglionic parasympathetic fibers.
Stimulation of Gastrointestinal Secretion involves which primary neurotransmitter of the parasympathetic nervous system?
- Norepinephrine
- Dopamine
- Acetylcholine
- Serotonin
Answer: C. Acetylcholine is the primary excitatory neurotransmitter of the parasympathetic system (vagus nerve) that stimulates almost all GIT secretions.