P-Chapter 3: The Autonomic Nervous System Flashcards
(10 cards)
Which of the following is correct regarding the autonomic nervous system (ANS)?
A. Afferent neurons carry signals from the CNS to the effector organs.
B. The neurotransmitter at the parasympathetic ganglion is norepinephrine (NE).
C. The neurotransmitter at the sympathetic ganglion is acetylcholine (ACh).
D. Sympathetic neurons release ACh in the effector organs.
E. Parasympathetic neurons release NE in the effector organs.
C. The neurotransmitter at the sympathetic and parasympathetic ganglia is acetylcholine. Sympathetic neurons release NE and parasympathetic neurons release ACh in the effector cells. Afferent neurons carry signals from the periphery to the CNS
Which of the following is correct regarding somatic motor neurons?
A. The neurotransmitter at the somatic motor neuron ganglion is acetylcholine.
B. The neurotransmitter at the somatic motor neuron ganglion is norepinephrine. C. Somatic motor neurons innervate smooth muscles.
D. Somatic motor neurons do not have ganglia.
E. Responses in the somatic motor neurons are generally slower than in the autonomic nervous system.
D. Somatic motor neurons innervate skeletal muscles (not smooth muscle) and have no ganglia. Answers A and B are incorrect, since there are no ganglia. Also, the responses in the somatic motor nervous system are faster compared to the responses in the autonomic nervous system due to the lack of ganglia in the former.
Which of the following physiological changes could happen when a person is attacked by a grizzly bear?
A. Increase in heart rate.
B. Increase in lacrimation (tears).
C. Constriction of the pupil (miosis).
D. Increase in gastric motility.
A. When a person is in the “fight-or-flight” mode, as in the case of a bear attack, the sympathetic system will be activated. Activation of the sympathetic system causes an increase in heart rate and blood pressure and a decrease (not increase) in gastric motility. It also causes dilation (not constriction) of the pupil and inhibition of lacrimation.
Which of the following changes could theoretically happen in a person when the parasympathetic system is inhibited using a pharmacological agent?
A. Reduction in heart rate.
B. Constriction of the pupil (miosis).
C. Increase in gastric motility.
D. Dry mouth (xerostomia).
E. Contraction of detrusor muscle in the bladder.
D. Activation of the parasympathetic system causes a reduction in heart rate, constriction of the pupil, an increase in gastric motility and salivation, and contraction of the bladder muscle. Therefore, inhibition of the parasympathetic system causes an increase in heart rate, dilation of the pupil, a decrease in gastric motility, dry mouth, and relaxation of detrusor muscles.
Which of the following statements is correct regarding the sympathetic and parasympathetic systems?
A. Acetylcholine activates muscarinic receptors.
B. Acetylcholine activates adrenergic receptors.
C. Norepinephrine activates muscarinic receptors.
D. Activation of the sympathetic system causes a drop in blood pressure.
A. Acetylcholine is the neurotransmitter in the cholinergic system, and it activates both muscarinic and nicotinic cholinergic receptors, not adrenergic receptors. Norepinephrine activates adrenergic receptors, not muscarinic receptors. Activation of the sympathetic system causes an increase in blood pressure (not a drop in blood pressure) due to vasoconstriction and stimulation of the heart.
Which 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.
C. The parasympathetic nervous 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 the control of the sympathetic system.
Which of the following is correct regarding neurotransmitters and neurotransmission?
A. Neurotransmitters are released from the presynaptic nerve terminals.
B. Neurotransmitter release is triggered by the arrival of action potentials in the postsynaptic cell.
C. Intracellular calcium levels drop in the neuron before the neurotransmitter is released.
D. Serotonin and dopamine are the primary neurotransmitters in the ANS.
A. Neurotransmitters are released from presynaptic neurons, triggered by the arrival of an action potential in the presynaptic neuron (not in the postsynaptic cell). When an action potential arrives in the presynaptic neuron, calcium enters the presynaptic neuron and the calcium levels increase in the neuron before the neurotransmitter is released. The main neurotransmitters in the ANS are norepinephrine and acetylcholine.
An elderly man was brought to the emergency room after he ingested a large quantity of carvedilol tablets, a drug that blocks α1, β1, and β2 adrenergic receptors, which mainly mediate the cardiovascular effects of epinephrine and norepinephrine in the body. Which of the following symptoms would you expect in this patient?
A. Increased heart rate (tachycardia).
B. Reduced heart rate (bradycardia).
C. Dilation of the pupil (mydriasis).
D. Increased blood pressure.
B. Activation of α1 receptors causes mydriasis, vasoconstriction, and an increase in blood pressure. Activation of β1 receptors increases heart rate, contractility of the heart, and blood pressure. Activation of β2 receptors causes dilation of bronchioles and relaxation of skeletal muscle vessels. Thus, inhibition of these receptors will cause vasorelaxation (α1 blockade), reduction in heart rate (β1 blockade), reduction in contractility of the heart (β1 blockade), reduction in blood pressure, bronchoconstriction (β2 blockade), and constriction of blood vessels supplying skeletal muscles (β2 blockade).
All of the following statements regarding central control of autonomic functions are correct except:
A. Baroreceptors are pressure sensors located at various cardiovascular sites.
B. The parasympathetic system is activated by the CNS in response to a sudden drop in blood pressure.
C. The parasympathetic system is activated by the CNS in response to a sudden increase in blood pressure.
D. The sympathetic system is activated by the CNS in response to a sudden drop in blood pressure.
B. When there is a sudden drop in blood pressure, the baroreceptors send signals to the brain, and the brain activates the sympathetic system (not the parasympathetic system) to restore blood pressure to normal values.
Which of the following is correct regarding membrane receptors and signal transduction? A. ANS neurotransmitters bind to membrane receptors on the effector cells, which leads to intracellular events. B. Cholinergic muscarinic receptors are examples of ionotropic receptors. C. Cholinergic nicotinic receptors are examples of metabotropic receptors. D. Metabotropic receptors activate ion channels directly
A. Neurotransmitters generally bind to the membrane receptors on the postsynaptic effector cells and cause cellular effects. Acetylcholine (ACh) binds to cholinergic muscarinic receptors in the effector cells and activates the second messenger pathway in the effector cells, which in turn causes cellular events. These types of receptors that are coupled to second messenger systems are known as metabotropic receptors. Thus, metabotropic receptors do not directly activate ion channels. ACh also binds to cholinergic nicotinic receptors and activates ion channels on the effector cells directly. These types of receptors that activate ion channels directly are known as ionotropic receptors.
