Medical Linguistics and Anatomy

HTH 2306, Medical Linguistics and Anatomy 1

Course Learning Outcomes for Unit V Upon completion of this unit, students should be able to:

6. Identify the major body cavities.

8. Examine the structure and function of the organs located within the skeletal, muscular, integumentary, cardiovascular, lymphatic and immune, nervous, sensory, endocrine, gastrointestinal, urinary, reproductive, and respiratory systems.

9. Identify the common signs, symptoms, and illnesses associated with the structure and functions of

the skeletal, muscular, integumentary, cardiovascular, lymphatic and immune, nervous, sensory, endocrine, gastrointestinal, urinary, and reproductive and respiratory systems.

Reading Assignment Chapter 9: The Nervous System: The Body’s Control Center Chapter 11: The Senses: The Sights and Sounds

Unit Lesson The Nervous System The nervous system is the portion of the human body that controls all body functions, maintains homeostasis, and allows the body to respond to various changes in the environment. The central nervous system (CNS) consists of the brain and the spinal cord, and the peripheral nervous system (PNS) consists of the peripheral nerves connecting the central nervous system to the remainder of the body. The structural and functional units of the nervous system are neurons, otherwise known as nerve cells (Jahangir, 2012). Through a series of electrochemical processes, impulses are transmitted by neurons to other neurons and to other cells outside of the nervous system. Although the transmission of these impulses is complex, they occur in the blink of an eye. For example, after touching a hot plate or pan, the pain receptors in your fingers almost instantaneously relay a message that results in you removing your hand to avoid further injury. Have you ever wondered why your heat races and your blood pressure rises when you are scared or afraid? When under stress, certain impulses prepare the body for a fight or flight response. These are all functions of your central nervous system. What We Know About the Structure and Function of the Brain The brain lies at the top of the spinal cord and fills the cranial cavity. The human brain consists of nearly 100 billion neurons. The surface of the brain is a series of folded and rippled areas that allows lots of surface area to fit into a tiny space (Colbert, Ankney, & Lee, 2013). The brain consists of various sections. Externally, the brain consists of the cerebrum, cerebellum, and the brainstem. The brainstem is of particular interest because it controls many of the body’s vital functions including breathing, swallowing, and vasomotor control. The death of neurons can occur as a result of anoxic brain injury (due to a lack of oxygen) or from lack of blood flow as a result of a cerebrovascular accident (CVA) or stroke. This can lead to disturbances in motor

UNIT V STUDY GUIDE

Nervous and Sensory Systems

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and sensory functions. However, the brain—with proper rehabilitation—can regenerate certain areas and re- learn how to carry out functions that were formerly impaired due to disease or injury. The Mysteries of the Brain: Persistent Vegetative State The term persistent vegetative state was coined by Jennett and Plum in 1972. This term describes someone who is awake but is not aware of his or her surroundings. For the public, the relatively recent court battle surrounding Terri Schiavo brought this condition to light. The brain stem receives sensory information and has the ability to control vital functions such as blood pressure, breathing, and heart rate. In essence, for individuals like Ms. Schiavo (those who have an intact brainstem), life can continue on as long as there is nutritional support to supplement the inability to consume food. The leading neurological authorities define a persistent or permanent vegetative state as “a clinical condition of complete unawareness of the self and the environment accompanied by sleep-wake cycles with either complete or partial preservation of hypothalamic and brainstem autonomic functions” (American Academy of Neurology, 1995, p. 1015). The clinical criterion for a persistent vegetative state is as follows:

1. no evidence of awareness of self or environment and an inability to interact with others; 2. no evidence of sustained, reproducible, purposeful, or voluntary behavioral responses to visual,

auditory, tactile, or noxious stimuli; 3. no evidence of language comprehension or expression; 4. intermittent wakefulness manifested by the presence of sleep-wake cycles; 5. sufficiently preserved hypothalamic and brainstem autonomic functions to permit survival with medical

and nursing care; 6. bowel and bladder incontinence; and 7. variably preserved cranial nerve (papillary, oculocephalic, corneal, vestibuloocular, gag) and spinal

reflexes. (American Academy of Neurology, 1995, p.1016) Ms. Schiavo’s unfortunate case raised a lot of questions about this condition. For example, can a patient like Terri Schiavo ever rebound from this situation? Is a patient in such a brain state aware of his or her surroundings? Can this type of patient perceive starvation or feel pain? Questions like these are difficult (if not impossible) to answer. Similar questions exist for nervous system disorders such as dementia. There is still a great deal of knowledge to be gained in regards to how the brain works. The BRAIN initiative Recently, the National Institutes of Health (NIH) announced the launch of a project known as the Brain Research through Advancing Innovative Neurotechnologies (BRAIN) Initiative (NIH, n.d.). This initiative is a part of a new focus on revolutionizing the current knowledge of the human brain. The NIH (n.d.) says the following about the BRAIN Initiative:

By accelerating the development and application of innovative technologies, researchers will be able to produce a revolutionary new dynamic picture of the brain that, for the first time, shows how individual cells and complex neural circuits interact in both time and space. (para. 1)

Implications for Health Professionals With nearly 100 billion neurons and 100 trillion connections, the human brain remains one of the greatest mysteries in science and one of the greatest challenges in medicine. Conditions such as dementia, Parkinson’s disease, autism, seizure disorder, traumatic brain injury, schizophrenia, and depression have a significant impact on our society. In spite of the advances in neuroscience in recent years, “the underlying causes of most neurological and psychiatric conditions remain largely unknown due to the vast complexity of the human brain” (NIH, n.d., para. 1). In recent years, scientists have made numerous discoveries that create the opportunity to unlock the mysteries of the brain. A well-known example is the mapping of the human genome. Discoveries in this area have produced opportunities for integration across fields and have created opportunities for advancement in prevention, diagnosis, and treatment of many conditions that currently have treatment limitations. As new research and technology emerges, it will be interesting to see what new mysteries are unlocked regarding the function and structure of the brain.

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The Sensory System General and special senses: The central nervous system processes and interprets nerve impulses from sensory receptors that detect environmental changes. Sensation is the conscious or subconscious awareness of changes in the external and internal environment. Feelings and sensations are the body’s responses to these nerve impulses. For a sensation to occur, there are four conditions that must be satisfied. First there must be a stimulus, or a change in the environment that activates the sensory neurons. Next, a sensory receptor must convert the stimulus to an electrical signal, which produces a nerve impulse. The nerve impulse is then conducted along a neural pathway from the sensory receptor to the brain. A region of the brain then receives and integrates the nerve impulses into a sensation (Tortora & Derrickson, 2012). Growing up, you may have learned about the five senses including vision, hearing, smell, taste, and touch. In actuality, sensory information is much more complex. General senses are spread throughout the body via muscle, joint, skin, and visceral receptors. The general senses include the sense of touch, pressure, temperature, and pain (Moini, 2013). We have the ability to feel hunger, taste different flavors, and experience hot and cold. These complex senses are known as special senses (Tortora & Derrickson, 2012) Types of Sensory Receptors Sensory receptors can be divided into five types.

 Chemoreceptors detect chemicals in the mouth, nose, and body fluids.

 Pain receptors respond to painful stimuli resulting from physical or chemical damage to tissue.

 Thermoreceptors detect temperature change.

 Mechanoreceptors are stimulated by pressure or movement changes.

 Photoreceptors detect light that strikes the retina of the eye. Sense of Hearing Imagine you are riding in a car with a friend who has a really powerful stereo system. Being a medical professional, you know that you are risking your hearing if you listen to music at the level your friend likes to play it. What do you do? Think about this: It is important to take preventive measures to preserve hearing and ear health. The ear is a very sensitive structure and can convert sound vibrations into electrical signals extremely fast. The ear has outer, middle, and inner parts. The outer ear is made up of the auricle, the external acoustic meatus, and the eardrum. Vibrations are transmitted through matter and produce sound. The ear’s auricle collects sound waves and directs them into the external acoustic meatus, and the waves end at the eardrum (Colbert et al., 2013). Many middle and high school students have some degree of hearing loss—mostly in higher pitches. Those who frequently attend concerts have an even higher rate of hearing loss. Tinnitus is associated with hearing damage. In cases of acute acoustic trauma (e.g., after attending a loud concert without earplugs), it may be temporary. However, in patients with progressive, permanent hearing loss, tinnitus is often chronic. This symptom is so significant that many people with hearing loss do not even notice the hearing loss; they come to the doctor complaining of the terrible ringing in their ears. Vision Legal blindness is defined as visual acuity with best correction of worse than or equal to 20/200. This means that at 20 feet away from the eye chart, the patient can only see as much detail as is seen at 200 feet away by a person with normal vision. The signs and symptoms of visual damage are sometimes so subtle and slow-developing that the patient cannot detect them. For instance, patients with chronic glaucoma generally develop tunnel vision so gradually that they are unaware of the change. This is why it is so important to have the pressure in your eyes checked regularly. It may be the only way to detect glaucoma early enough to prevent permanent vision loss. Some patients experience visual, auditory, or other stimuli with multiple senses. In this condition, called synesthesia, real sensory information from one sense generates perceived sensation in another sense. A

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patient may perceive colors when hearing certain sounds, hear sounds in response to smell, or feel something in response to sight. Pain What would happen if a person was unable to feel pain? What kind of injuries might that person be more susceptible to? How would it affect a child’s normal process of learning the difference between safe and unsafe activities? Patients with a rare genetic disorder called congenital insensitivity to pain with anhidrosis (CIPA) are completely unable to feel pain. Children with this disorder are prone to severe injury because they cannot tell when something is wrong with the body. They may even chew through their own lips or tongue without realizing anything is wrong. Effects of Aging As we age, many of our senses decline. For example, the senses of thirst and hunger diminish with age. It is likely that as we age, we will need assistance to improve our failing senses, particularly of sight and hearing. There are three serious visual disorders that frequently affect older people. These include cataracts, age- related macular degeneration, and glaucoma. Medical intervention may often be necessary to preserve function.

References American Academy of Neurology. (1995). Practice parameters: Assessment and management of patients in

the persistent vegetative state. Neurology, 45, 1015–1018. Colbert, B. J., Ankney, J., & Lee, K. T. (2013). Anatomy, physiology, & disease: An interactive journey for

health professionals (2nd ed.). Upper Saddle River, NJ: Pearson Education. Jahangir, M. (2012). Anatomy and physiology for health professionals. Burlington, MA: Jones & Bartlett. Moini, J. (2013). Anatomy and physiology for health professionals. Burlington, MA: Jones & Bartlett. National Institutes of Health. (n.d.). Why is the BRAIN initiative needed? Retrieved from

http://www.braininitiative.nih.gov/why.htm Tortora, G., & Derrickson, B. (2012). Introduction to the human body: The essentials of anatomy and

physiology (9th ed.). Hoboken, NJ: Wiley.

Learning Activities (Non-Graded) For a review of the Key Terms of the unit, click here to access the interactive Unit V Flashcards in PowerPoint form. (Click here to access a PDF version.) Non-graded Learning Activities are provided to aid students in their course of study. You do not have to submit them. If you have questions, contact your instructor for further guidance and information.