ANS Physiology-Critical thinking

1. When a person is startled or sees a “pleasurable” object, the pupils of the eyes may dilate. What division of the ANS is involved in this reaction? Describe the nerve pathway involved.

2. Reduced secretion from salivary and lacrimal glands can indicate damage to what nerve?

3. Patients with diabetes mellitus can develop autonomic neuropathy, which is damage to parts of the autonomic nerves. Given the following parts of the ANS—vagus nerve, oculomotor nerve, splanchnic nerve, pelvic splanchnic nerve, outflow of gray ramus—match the part with the symptom it would produce if the part were damaged:

a. impotence

b. subnormal sweat production

c. relaxed stomach muscles and delayed emptying of the stomach

d. diminished pupil reaction (constriction) to light e. bladder paralysis with urinary retention.

4. A patient has been exposed to the organophosphate pesticide malathion, which inactivates acetylcholinesterase. Which of the following symptoms would you predict: blurring of vision, excess tear formation, frequent or involuntary urination, pallor (pale skin), muscle twitching, or cramps? Would atropine be an effective drug to treat the symptoms? Explain.

5. Epinephrine is routinely mixed with local anesthetic solutions. Why?

6. A drug blocks the sympathetic division’s effect on the heart. Careful investigation reveals that, after administration of the drug, normal action potentials are produced in the sympathetic preganglionic and postganglionic neurons. Also, injection of norepinephrine produces a normal response in the heart. Explain, in as many ways as you can, the mode of action of the unknown drug.

7. A drug is known to decrease heart rate. After cutting the white rami of T1–T4, the drug still causes the heart rate to decline. After cutting the vagus nerves, the drug no longer affects heart rate. Which division of the ANS does the drug affect? Does the drug affect the synapse between preganglionic and postganglionic neurons, the synapse between postganglionic neurons and effectors, or the CNS? Is the drug’s effect excitatory or inhibitory?

8. Make a list of the responses controlled by the ANS in (a) a person who is extremely angry and (b) a person who has just finished eating and is relaxing.

9. Shock is the medical condition that results when body tissues do not receive enough oxygen-carrying blood. It is characterized by low blood flow to the brain, leading to decreased levels of consciousness. Why would a patient with a cervical spinal cord injury be at risk of going into shock?

10. Imagine yourself at the starting block of the 100-meter dash of the Olympics. The gun is about to go off in the biggest race of your life. What is the autonomic nervous system doing at this point? How are your organs responding?

11.  A person in shock may have pale, cold, and clammy skin and a rapid and weak pulse. What is the role of the autonomic nervous system in producing these symptoms? Discuss how drugs that influence autonomic activity might be used to treat someone in shock.

12.  Some patients with hypertension (high blood pressure) are given beta blocking drugs to lower their blood pressure. How does this effect occur? Explain why these drugs are not administered to patients with a history of asthma. Why might drinking coffee help asthma?

13. Why do many cold medications contain an alpha-adrenergic agonist and atropine (belladonna)? Why is there a label warning for people with hypertension? Why would a person with gastritis be given a prescription for atropine? Explain how this drug might affect the ability to digest and absorb food.

14. Cathy stayed up through the night studying for a big examination. She felt very on edge and found that she frequently had to use the inhaler to treat her asthma. In the physiology lab that afternoon, she found that her pulse rate and blood pressure were higher than usual. In the physiology lab exercise the following week, Cathy handled a number of drugs (epinephrine, atropine, and others) that she administered to a frog heart. Later that day, she developed a severe headache and had a very dry mouth. When she looked at her face in the mirror, she noticed that her pupils were dilated. What may have been responsible for Cathy’s fast pulse and high blood pressure the day of her exam, and for her headache and other symptoms the day of the frog lab?

Remember that Cathy had a rapid pulse and higher than usual blood pressure after staying up studying for an exam and taking her asthma inhaler.

Why did Cathy have a rapid pulse and higher blood pressure than usual?

Was there more than one factor that contributed to these symptoms?

Remember that Cathy developed a headache, dry mouth, and dilated pupils following the use of various drugs in the frog heart lab.

Which drug likely produced these effects in Cathy?

How did the drug have these effects?

15. Does the autonomic nervous system have a sensory limb?

16. What is the significance of having dual control through sympathetic and parasympathetic innervation?

17. Explain the following observations: a. Adrenaline usually produces a rise in blood pressure. But if ergot is injected before adrenaline, adrenaline produces a fall in blood pressure. b. Acetylcholine usually produces a fall in blood pressure. But if atropine is injected before acetylcholine, a high dose of acetylcholine gives a rise in blood pressure. c. If a cat is exposed to a barking dog, its heart rate increases. The increase is less marked after denervation of the heart. A small increase in heart rate persists even after inactivation of adrenals.

18. Give the site of action of curare, atropine and hexamethonium.

19. You’ve been to the “all-you-can-eat” buffet and have consumed large amounts of food. After returning home, you recline on the couch to watch television. Which division of the nervous system will be handling your body’s after-dinner activities? List several organs involved, the major nerve supply to each organ, and the effects of the nervous system on their functions.

20. Mrs. Young is experiencing a bout of diarrhea that is keeping her house-bound. She would like to attend a birthday party for her brother but is afraid to attend because of her diarrhea. What type of drug, related to the autonomic nervous system function, could she take to help relieve her diarrhea?

21. Ciara is driving home from school, listening to her favorite music, when a dog darts into the street in front of her car. She manages to swerve to avoid hitting the dog. As she continues on her way, she notices her heart is racing, she has “goose-bumps,” and her hands are sweaty. Why is she experiencing these effects?