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Application of Cranial Nerve Function

Directions: Using your diagrams, notes and textbooks, 4. An individual has diabetes and blood vessels in the retina determine the spinal nerve or cranial nerve that is damaged are damaged, what nerve would be sending less sensory based on the symptoms of the individual. impulses? a. olfactory nerve (I) 5. Due to surgical error, the patient has lost most sensory b. optic nerve (II) perception on one side of the face and difficulty c. oculomotor nerve (III) chewing. d. trochlear nerve (IV) 6. Individual cannot move most muscles of the face. e. trigeminal nerve (V) 7. Paralysis of the superior oblique muscle results due to f. abducens (VI) damage of this nerve. The individual’s one eye rotates g. facial (VII) outward. h. vestibulocochlear nerve (VIII) 8. The patient complains of decreased sense of taste (3 cranial i. glossopharyngeal nerve (IX) nerves). j. vagus nerve (X) 9. The individual cannot abduct (move the eye laterally to k. accessory nerve (XI) see something to the side) one eye due to damage to this l. hypoglossal nerve (XII) nerve. 10. Stimulation of this nerve in the region of the neck 1. The patient is deaf. decreases heart rate. 2. The pupil in one eye is dilated due to decreased tone of the 11. One shoulder droops. constrictor muscles of the iris. 12. The patient has Bell’s palsy. 3. An individual has taken a hard blow to the face (e.g. as a result of falling on concrete) and has lost some sense of Key: 1-h; 2-c; 3-a; 4-b; 5-e; 6-g; 7-d; 8-g, i, j; 9-f; 10-j; 11-k; smell. 12-g

Am I in Control of My Own Body? Understanding the Autonomic Nervous System

Mary Gahbauer Department of Life and Earth Science, Otterbein College, Westerville, Ohio 43081 (614) 823-1467 (614) 823-3042 fax [email protected] The ANS is a dynamic, responsive system that maintains Activity 1: Extensive, protective homeostatic functions of the homeostasis through reflex adjustment to changing conditions - but ANS it is not an intuitive topic for students, and its antique terminologya Guess how many reflexes are known. A search of the Internet, does not help. This article offers a “housekeeping” metaphor to textbooks, and the Merck manual produces definitions like “rapid, introduce the ANS in everyday language, and short class activities automatic, stereotyped response to stimuli”, and lists of scores with questions that enable students to answer, “Just how much of reflexes – far more than anyone guesses. Working in groups can I control my own body?” and “What would happen if the ANS to sort the reflexes, students set aside descriptive terms such as failed?” spinal/cranial or monosynaptic/polysynaptic and proper names such as Babinski for later research. Are there more autonomic or Housekeeping: the biological function of the ANS somatic reflexes? By sorting the reflexes according to body parts Housekeeping in a complex building (i.e., a hotel) means sending involved, it becomes clear that the autonomic group, controlling the fresh supplies to the right location, maintaining a comfortable imperceptible “housekeeping” functions of glands or smooth muscle temperature, etc. and hotel guests are free to plan their own activities in viscera such as heart, iris, stomach, blood vessels, etc., is much since the building seems to run itself. Similarly “housekeeping” larger than the somatic group of reflexes that act in posture and by the ANS adjusts cardiorespiratory control, temperature control, withdrawal. Students may think they control their own bodies, but etc. so that the conscious brain is free to think while the body’s realize the only organ under conscious control is skeletal muscle! routine functions operate automatically. In a hotel or in the body, How does each ANS reflex act to maintain homeostasis and/ housekeeping management also provides automatic, rapid responses or provide some kind of protection? For example, chemoreceptor that protect against internal or external threats or disturbances (see Table 1). Teaching Tips continued on page 16 HAPS-EDucator – Summer 2008 - page 15 Teaching Tips - continued from page 15 reflexes maintain blood gases and therefore pH, and gastric and What work does the ANS perform? Efferent signals in the enteric reflexes maintain food propulsion at the right rate for ANS cause smooth muscle contraction, gland secretion, and/or digestion and absorption. Cough and gag reflexes protect directly, regulate cardiac action; all of the uncontrollable bodily activities and the diving and bladder emptying reflexes protect indirectly. result from one or more of these actions.

Table 1. Comparison of housekeeping in a complex building and in the body Activity 3: Afferent limb Housekeeping in a Housekeeping in the body Does something stimulate the CNS to cause the efferent hotel effects (above), or are these random? Physiology is anything but Who/what Service, delivery, Autonomic nerves to viscera, random, so we need to consider what the “work orders” are that does the cleaning staff including blood vessels cause housekeeping nerves to perform some type of job. work? How does it feel to have an X-ray, and what happens? There When is 24/7 24/7 is no feeling and nothing happens because the body cannot sense work done? X-rays. It must be able to detect, through some kind of sensory What jobs Provision of fresh Provision of oxygen, nutrients, receptor, what is going on in and around itself, and report that are done? supplies, food, waste waste cleared, heating and work order (afferent limb of the reflex) to a housekeeping office cleared , heating and cooling adjusted cooling adjusted (integration center of the reflex) before appropriate motor work can be done (efferent limb of the reflex). What are job Staff provide service as ANS automatically adjusts to What are some work orders for autonomic action? Students descriptions? requested by incoming incoming sensory information already know that heat causes sweating, embarrassment causes work orders (acts by reflex) blushing, hunger causes stomach gurgles, etc. Other work orders are unfamiliar, such as baroreceptor afferents that report details Regular maintenance Parasympathetic division of blood pressure, but everyone has felt dizzy on standing up crew provides normal supports rest and restoration conditions suddenly. The baroreceptor reflex must catch up in its work of “autofocusing” the blood pressure after blood sinks into the legs Rapid response crew Sympathetic division prepares by gravity. for emergencies for fight or flight When enough afferent impulses (work orders) have been identified, students sort them into two categories: Which are Regular crew and rapid Both divisions constantly response crew trade off balancing to achieve dynamic triggered by sensation such as pain, fullness of the stomach, or light with each other homeostasis shining in the eyes? Which are triggered by memories, thoughts, or emotions such as anxiety, hatred, or sexual attraction? This What is the Deals with building Deals with involuntary functions, establishes that the afferent limb of the ANS reflex can be any type overall maintenance, frees frees conscious brain for special of peripheral sensation, or can be central input from the cerebral effect? guests for their own purposes hemispheres. Autonomic afferent nerves are few (relaying visceral activities sensation, and baroreceptor and chemoreceptor input), and somatic Provides rapid Provides rapid protection from nerves provide the afferent limb (or even efferent limb, but if both protection against loss threats to airways, blood loss, limbs are somatic, it is a somatic reflex) in some autonomic reflexes of power, flooding, noxious food etc. (see Table 2). hostile behavior WhatActivit ies Housekee 2, 3, 4 ping P arts of theANS reflex functions arc during (afferent sleep, limb, Table 2. Components Components of of visceral visceral and and somatic somatic reflexes reflexes happens continues when anesthesia, light coma whenintegrating there management center, efferent on limb) Afferent limb Afferent limb is no vacation autonomic somatic oversight?Activity 2 Efferent limb Efferent Baroreceptor reflex alters heart Pain → pallor, sweating What bodily activities can not be consciously limb rate via sympathetic or via sympathetic efferent controlled? Students offer goose bumps, stomach gurgling, autonomic parasympathetic efferents Activitiessweating, 2, 3,fainting, 4: Parts heart of thumping the reflex, blushing arc (afferent, and so on. limb, After Touch → sexual integratinga few hintscenter, they efferent add pupillary, limb) bladder, bowel, and sexual Gut sensation alters gut motility arousal via functions. These autonomic effects are mediated by efferent via sympathetic or parasympathetic (motor) signals from the central nervous system (CNS); parasympathetic efferents efferents Activity 2: Efferent limb students should note that the dual sympathetic and Whatparasympathetic bodily activities nerves cannot be to consciouslyviscera showncontrolled? in Students textbook Efferent Chemoreceptor reflex alters Knee jerk, ankle jerk offer illustrationsgoose bumps, are stomach both efferent gurgling, – the sweating, ANS isfainting, predominantly heart limb use of respiratory skeletal thumping,efferent blushing,. These and nerves so on. are After the housekeeping a few hints they sta addff that pupillary, perform somatic muscles Withdrawal reflex bladder,the work.bowel, and sexual functions. These autonomic effects are mediated by efferent (motor) signals from the central nervous Gut sensation → vomiting What is the work the ANS performs? Efferent signals using skeletal muscles systemin (CNS).the ANS Students cause smooth should musclenote that contraction the dual sympathetic, gland secretion, and parasympatheticand/or regulate nerves cardiac to viscera action shown; all ofin textbookthe uncontrollable illustrations bodily are both efferentactivities – theresult ANS from is predominantlyone or more of efferent. these actions These. nerves are Activity 4 Integrating center. Where are the housekeeping offices that receive the housekeeping staff that perform the work. reports through the afferent limb? Students can identify the Activity 3 Afferent limb Does something stimulate the CNS to cause the centers of autonomic regulation from these questions: Is the HAPS-EDucatorefferent effects - Summer (above) 2008, or are- page these 16 random ? Physiology is conscious brain involved? Yes,Teaching feelings Tips and continued thoughts on causepage 17 anything but random, so we need to consider what the “work autonomic effects. Is the limbic system involved? Yes, it is orders” are that cause housekeeping nerves to perform some involved in “gut feelings” and moods that cause autonomic type of job. effects. Is the brainstem involved? Yes, chemoreceptors and How does it feel to have an X-ray, and what baroreceptors ‘report’ there, and the cranial nerves that serve happens? There is no feeling and nothing happens, because cough and gag reflexes originate there. Is it likely that the the body can not sense X-rays. It must be able to detect, hypothalamus, a center controlling homeostatic functions such through some kind of sensory receptor, what is going on in as food and fluid intake should also control autonomic and around itself, and report that work order (afferent limb of functions through the sympathetic and parasympathetic the reflex) to a housekeeping office (integration center of the divisions? Yes, it seems likely. reflex) before appropriate motor work can be done (efferent The hypothalamus is the headquarters or limb of the reflex). housekeeping main office, but also some branch offices are What are some work orders for autonomic action? under hypothalamic control: the spinal cord that integrates Students already know that heat causes sweating, autonomic reflexes such as urination, defecation, erection, and embarrassment causes blushing, hunger causes stomach ejaculation; and the brainstem that integrates cardiovascular, gurgles, etc. Other work orders are unfamiliar, such as respiratory, and swallowing functions. Other branch offices baroreceptor afferents that report details of blood pressure, but are the limbic system, especially the amygdala that responds everyone has felt dizzy on standing up suddenly; the to gut feelings and olfactory input, the thalamus that integrates baroreceptor reflex must catch up in its work of sensory input, and even the cerebral cortex with its conscious “autofocusing” the blood pressure after blood sinks into the thoughts. legs by gravity. If the conscious brain is involved, does that not make When enough afferent impulses (work orders) have it a reaction like those used in playing video games, and not a been identified, students sort them into two categories: Which true automatic reflex? Well, blushes and sweaty palms are are triggered by sensation such as pain, fullness of the not voluntary, and can not be directly stopped, so they are stomach, or light shining in the eyes? Which are triggered by autonomic reflexes even though the afferent is conscious memories, thoughts, or emotions such as anxiety, hatred, or thought. In biofeedback, conscious thought can be used to sexual attraction? This establishes that the afferent limb of the indirectly control ANS reflexes to some extent – focusing on ANS reflex can be any type of peripheral sensation, or can be calming topics can slow the heart rate. central input from the cerebral hemispheres. Autonomic afferent nerves are few (relaying visceral sensation, and Activity 5 Dynamic balance between sympathetic and baroreceptor and chemoreceptor input), and somatic nerves parasympathetic divisions provide the afferent limb (or even efferent limb, but if both Students are familiar with the extremes of autonomic limbs are somatic, it is a somatic reflex) in some autonomic response – fight or flight, rest and restoration – but what reflexes (see table 2). happens between extremes? What happens if anxiety causes sympathetic outflow to accelerate the heart, but lying down to rest causes parasympathetic outflow to slow the heart? Which Teaching Tips - continued from page 16

Activity 4: Integrating center. small graduated cylinder, and the measurement is repeated after Where are the housekeeping offices that receive reports exposure to lemon juice, etc. through the afferent limb? Students can identify the centers of Normal ventilation is controlled by the brainstem to maintain autonomic regulation from these questions: Is the conscious brain homeostasis of blood gases. Deliberate alteration of the normal involved? Yes, feelings and thoughts cause autonomic effects. Is pattern of ventilation in rate and depth for one-half minute alters the limbic system involved? Yes, it is involved in “gut feelings” and the pCO2 and pH of the blood, after which chemoreceptor reflexes moods that cause autonomic effects. Is the brainstem involved? cause an opposite pattern of abnormal ventilation until homeostasis Yes, chemoreceptors and baroreceptors ‘report’ there, and the is restored. Subjects should be unaware of observation during cranial nerves that serve cough and gag reflexes originate there. recovery. Is it likely that the hypothalamus, a center controlling homeostatic Pupillary responses to light are easy to observe, but even easier functions such as food and fluid intake, should also control is the pupillary response to near and far accommodation. autonomic functions through the sympathetic and parasympathetic Everyone can demonstrate cardiac changes on exercise – but divisions? Yes, it seems likely. can everyone explain the parts of the reflex arc? The hypothalamus is the headquarters or housekeeping main office, but also some branch offices are under hypothalamic Activity 7: ANS topics for research control: the spinal cord that integrates autonomic reflexes such as Shy-Drager syndrome (multi-system atrophy) is a condition in urination, defecation, erection, and ejaculation; and the brainstem which extensive autonomic failure is prominent. What symptoms that integrates cardiovascular, respiratory, and swallowing of this illness illustrate how essential autonomic control is to the functions. Other branch offices are the limbic system, especially body? the amygdala that responds to gut feelings and olfactory input, Ondine’s curse is a genetic condition with inadequate the thalamus that integrates sensory input, and even the cerebral ventilation especially during sleep. How would it be to need to cortex with its conscious thoughts. stay awake to consciously control breathing? What part of the If the conscious brain is involved, does that make it a reaction chemoreceptor reflex is impaired in this condition? Who was like those used in playing video games, and not a true automatic Ondine? (Hint: she inspired ‘The Little Mermaid’.) reflex? Blushes and sweaty palms are not voluntary and cannot be The polygraph (lie detector) test works by measuring directly stopped, so they are autonomic reflexes even though the autonomic responses to emotion, such as alteration in electrical afferent is conscious thought. In biofeedback, conscious thought impedence of the skin with nervous sweating. The test is not can be used to indirectly control ANS reflexes to some extent – infallible, and its use in a court of law is controversial. What focusing on calming topics can slow the heart rate. could happen with hardened liars, or nervous individuals? What prescription drugs would act on the ANS to reduce responses? Activity 5: Dynamic balance between sympathetic and Extreme fear in victims of torture acts through the limbic parasympathetic divisions system and hypothalamus to cause a massive sympathetic response. Students are familiar with the extremes of autonomic response What are the bodily effects of this? Hypoxia of the brain from – fight or flight, rest and restoration – but what happens between hanging or strangling has similar effects. extremes? What happens if anxiety causes sympathetic outflow to Contradictory signals from the vestibular system, the visual accelerate the heart, but lying down to rest causes parasympathetic system, and/or the proprioceptive system stimulate the vomiting outflow to slow the heart? Which division “wins”? What if low center in the brainstem. Parasympathetic (vagal) signals reverse blood sugar causes the need for parasympathetic stimulation of the transit in the gastrointestinal system, and coordinated action digestion, but fear dries the mouth and slows the intestines through of respiratory and abdominal muscles force out gastric content. sympathetic outflow? What conditions does this describe? Homeostasis in non-extreme conditions is maintained by a dynamic balance between the two divisions. Neither ANS division a Galen described structures of the ANS in the 2nd century and would win – the heart rate would be somewhere between usual thought they allowed “sympathy” or coordination of organs. rate for ‘at rest’ and a higher rate for ‘anxious’, the food would be Ackerknecht EH. The history of the discovery of the vegetative eaten with less appetite and digested more slowly than usual. (autonomic) nervous system. Med Hist, 1974;18(1):1-8

Activity 6: Easily demonstrated ANS effects Digital blood vessels undergo sympathetic vasoconstriction in ice water, and reduced blood flow causes pallor and even cyanosis as tissue extraction of oxygen from the sluggish blood continues. On re-warming, sympathetic vasconconstriction is inhibited and skin vasodilation causes redness and tingling. (Google Images show dramatic exaggeration of this in Raynaud’s disease). The parasympathetic salivation reflex is stimulated by substances such as lemon juice, gum, or clean pebbles in the mouth. Baseline production of saliva is measured over 3-5 minutes in a

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