Parasympathetic Nervous System. Answers & Explanations/Rationale.

Which one of the following statements concerning the parasympathetic nervous system is correct? (A)The parasympathetic system uses norepinephrine as a neurotransmitter (B) The parasympathetic system often discharges as a single, functional system (C) The parasympathetic division is involved in accommodation of near vision, movement of food, and urination (D)The postganglionic fibers of the parasympathetic division are long compared to those of the sympathetic nervous system (E) The parasympathetic system controls the secretion of the adrenal medulla Answer: C. The parasympathetic system maintains essential bodily functions, such as vision, movement of food, and urination. It uses acetylcholine, not norepinephrine, as a neurotransmitter, and it discharges as discrete fibers that are activated separately. The postganglionic fibers of the parasympathetic system are short compared to those of the sympathetic division. The adrenal medulla is under control of the sympathetic system. 2. Which one of the following is characteristic of parasympathetic stimulation? (A)Decrease in intestinal motility (B) Inhibition of bronchial secretion (C) Contraction of sphincter muscle in the iris of the eye (miosis) (D)Contraction of sphincter of urinary bladder (E) Increase in heart rate Answer: C. All other choices are examples of sympathetic (or anti-parasympathetic) activities. 3. Which of the following are features of the parasympathetic nervous system? (A)The preganglionic neurons release ACh as a transmitter (B) The postganglionic neuron is short and the pre ganglionic neuron is long (C) The preganglionic neurons exit from T1 to L5 spinal segments (D)The receptors on the postganglionic neuron include both nicotinic and muscarinic (E) ACh is the only transmitter released by the preganglionic neurons Answer: A, B, (and D). Choice C is for sympathetic, while parasympathetic preganglionic neurons exit from craniosacral region. Other neuroactive peptides are co-released by the preganglionic neurons. Muscarinic receptors on the postganglionic neuron act as auto-receptors to regulate ACh release. 4. Parasympathetic nervous system is different from sympathetic nervous system in majority of cases. Which of below is NOT one? (A)Length of preganglionic neurons (B) Length of postganglionic neurons (C) Major transmitters released by postganglionic fibers (D)Types of receptors at ganglions (E) Types of receptors at neuroaffector junctional (F) All of the above (G)None of the above Answer: D. In PSNS, preganglionic neurons are longer, and postganglionic neurons are shorter than in SNS. In PSNS, the major neurotransmitter at postganglionic neurons’ ends are Ach, while in SNS, they are NE. Types of receptors at NAJ are muscarinic in PSNS, and adrenergic in SNS. However, both PSNS and SNS use nicotinic receptors mainly at ganglions. 5. Which of the following is a feature of the sympathetic, but not the parasympathetic nervous system? (A)Ganglia located in the effector organs (B) Long preganglionic neurons (C) Preganglionic neurons release norepinephrine (D)Preganglionic neurons release ACh (E) Preganglionic neurons originate in the thoracolumbar spinal cord (F) Postganglionic neurons release epinephrine (G)Postganglionic neurons release ACh Answer: E. Sympathetic preganglionic neurons originated in spinal cord segments T1-L3, thoracolumbar region. Preganglionic neurons are short, and ganglia located in the paravertebral chain. Postganglionic neurons release norepinephrine. Both sympathetic and parasympathetic preganglionic neurons release ACh. 6. Which of the following are features of the sympathetic nervous system? (A)Both epinephrine and norepinephrine are released from the postganglionic fibers (B) Cranial nerve III contains some parasympathetic fibers emanating from the Edinger Westphal nucleus (C) Preganglionic fibers synapse very close to the effector organ innervated by the postganglionic neuron (D)Preganglionic sympathetic neurons release norepinephrine as the transmitter (E) The cell bodies of the postganglionic neurons have alpha 2 receptors on them Answer: B. The Edinger-Westphal nucleus is the accessory parasympathetic cranial nerve nucleus of the oculomotor nerve (cranial nerve III), supplying the constricting muscles of the iris. Epinephrine is released by adrenal glands. Sympathetic preganglionic fibers synapse very close to the spinal ganglions, and release ACh. The postganglionic nerve terminals have alpha 2