Parasympathetic Nervous System quiz #1 Flashcards
Parasympathetic Nervous System quiz #1
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What are the primary physiological effects of the parasympathetic nervous system on the heart, lungs, gastrointestinal tract, bladder, and pupils?
The parasympathetic nervous system decreases heart rate, constricts bronchioles in the lungs, increases gastrointestinal activity (motility and secretion), promotes urination by contracting bladder smooth muscle and relaxing the sphincter, and constricts pupils to optimize close vision. Why is the parasympathetic nervous system referred to as the craniosacral division, and which nerve provides most of its innervation?
It is called the craniosacral division because its fibers arise from the brainstem (cranial region) and sacral region of the spinal cord. The vagus nerve (cranial nerve X) provides about 90% of parasympathetic innervation. Describe the arrangement and relative lengths of preganglionic and postganglionic fibers in the parasympathetic nervous system.
Preganglionic fibers in the parasympathetic nervous system are long and extend from the CNS to synapse within or very near the target organs (in terminal ganglia), while postganglionic fibers are short, allowing for quick responses in the target organs. What effect does the parasympathetic nervous system have on heart rate and bronchioles?
It decreases heart rate and constricts the bronchioles to conserve energy. How does the parasympathetic nervous system affect the gastrointestinal tract?
It increases movement and secretion in the gastrointestinal tract and relaxes sphincters to promote digestion. What changes does the parasympathetic nervous system cause in the bladder to promote urination?
It contracts the smooth muscle of the bladder and relaxes the sphincter, making urination easier. Why does the parasympathetic nervous system cause pupil constriction?
Pupil constriction optimizes close vision, which is useful in a relaxed state when scanning for danger is unnecessary. Why is the parasympathetic nervous system called the craniosacral division?
Because its fibers arise from the brainstem (cranial region) and the sacral region of the spinal cord. Which nerve provides the majority of parasympathetic innervation, and what percentage does it account for?
The vagus nerve (cranial nerve X) provides about 90% of parasympathetic innervation. Describe the relative lengths and synapse locations of preganglionic and postganglionic fibers in the parasympathetic nervous system.
Preganglionic fibers are long and synapse within or very near the target organs, while postganglionic fibers are short.
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