REFLEXES
A reflex is an automatic or involuntary response to a stimulus; therefore, a reflex occurs without conscious thought. Reflexes are homeostatic; that is, they attempt to maintain homeostasis. They move the body from danger, keep the body from falling, and maintain a relatively constant blood pressure, pH, and level of water reabsorption. The different types of reflexes vary in complexity. Reflexes do not operate as isolated parts of the nervous system. Reflexes are integrated into the CNS as a reflex arc; therefore, the brain may inhibit or exaggerate a reflex when it receives a stimulus. For example, a person reflexively blinks the eyes when danger approaches, but after the brain realizes the danger, the person acts as a whole unit and moves the body away. Other examples of reflexes include constriction of the pupil of the eye when it is exposed to light, automatic increase in heart rate when the body senses a lowering of blood pressure, and the patellar (knee-jerk) reflex that occurs when an examiner taps the patellar tendon just below the kneecap. Deep-tendon reflexes are often tested as part of a clinical assessment to see if the nervous system is functioning properly. Figure 19-7 illustrates some simple reflexes. The nurse requires additional education to be competent in testing reflexes.
Special Considerations: LIFESPAN
Reflexes
Infants and small children also have slower reflexes owing to the immaturity of their nervous system. The myelin sheath is still forming during infancy; therefore, an infant’s response to stimuli is not as rapid as an older child’s or an adult’s. Some reflexes are present in infants and disappear by adulthood. These include the Moro, rooting, Babinski, and stepping reflexes.
NCLEX Alert The NCLEX requires knowledge of the nervous system and its ability to receive and send messages in the body An NCLEX clinical situation can describe an individual with paraplegia, quadriplegia, or hemiplegia. Depending on the described situation, the most appropriate response can relate to hazards of long-term paraplegia or basic functions of the nervous system.
EFFECTS OF AGING ONTHE SYSTEM
Intelligence, memory, the capacity to learn, and personality do not normally change as a person ages. Genetics, environmental conditions, physical changes resulting from disease processes, and psychological stressors are more likely than the aging process to influence such factors. A person’s ability to adapt is usually limited more by one’s physical body than by mental functioning. Table 19-4 outlines some effects of aging on the nervous system.
Generally, nerve cells cannot reproduce themselves. Damage to brain cells may result in permanent loss of some or all mental functions. Common causes of decreased mental function in older people include cerebrovascular accidents, such as stroke; conditions such as Alzheimer’s disease; and conditions related to atherosclerosis (“hardening of the arteries”). In addition, trauma, drugs, and degenerative disorders can cause irreversible organic brain damage in people of all ages.
TABLE 19-4. Effects of Aging on the Nervous System
|
FACTOR |
RESULT |
NURSING IMPLICATIONS |
|
Thought processes and ability to learn or reason should be retained. |
Losses in the thought process, reasoning, or l earning areas are not normal. |
Treat older adults as normal, intelligent people. Evaluate any changes in personality or thought processes. Encourage reading and learning new things; working puzzles. If underlying pathology exists, understand the disease and its progression. Adjust the environment to provide safety and security for the client. |
|
Sleep patterns may change; however, amount of sleep needed often is relatively unchanged. Less rapid eye movement (dream) sleep occurs. |
Person feels less rested; wakefulness periods at night are common. Older individuals may start using sleeping aids. |
Watch for behavioral changes caused by prescription and over-the-counter drugs. Caution against excess use of sleep aids. Be aware of client’s stressors; clinical depression secondary to cumulative losses is common. Encourage exercise during the day and eating a light meal in the evening. Reassure client that shorter periods of sleep are common. Treat frequent voiding and/or incontinence at night. |
|
Number of neurons decreases. |
Person exhibits decrease in voluntary movements. |
Allow for longer response time. |
|
Rate and spread of nerve transmission decrease. |
Persons may be startled more easily Reflexes may be slowed. Decision-making may be slower |
Prevent accidents. Teach safe driving and defensive driving techniques. |
|
Thermoregulation abilities often are reduced. |
Older adults are more susceptible to heat stroke or effects of cold. Skin may remain pink, even if client is cold (may not become pale or blue). |
Increase layers of clothing in all weather. Tell client foot protection is important because of decreased sensation and slowed circulation. |
|
Some short-term memory loss is normal. |
Person may be disoriented as to time and date. |
Reorient client as needed. |
|
Long-term memory usually is good. |
Initiate opportunities to reminisce because reminiscing is beneficial. |
|
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Motor skills are affected by physiologic changes in other systems. |
Person may lack dexterity. Falls may occur |
Encourage maintenance of abilities by daily exercise (walking is excellent). Encourage use of cane or walker for stability if needed. |
|
Remove obstacles, such as scatter rugs, to prevent falls. Provide adequate lighting. |
Safety and preventive measures are priorities for teaching when working with older adults. Loss of equilibrium and changes in proprioception can contribute to falling. Herpes zoster (shingles) is a painful inflammation of nerve endings that often affects older people.
Older adults who exhibit signs of confusion need to be evaluated to target the cause of confusion and determine if it is treatable. Sometimes electrolyte imbalances, hypoxia, small strokes (transient ischemic attacks, TIAs), drugs, pain, stress, infections, or anemia result in confusion. Confusion related to such factors is usually reversible. True dementia (e.g., as in Alzheimer’s disease) is irreversible, but may be managed.
Key Concept It is important to teach people to use helmets, infant car seats, seat belts, and other protective equipment to prevent traumatic brain injuries (TBI). In addition, some conditions, such as tetanus, encephalitis, and clostridium food poisoning, can permanently affect neurological functioning.
NCLEX Alert Two of the most common problems in older adults are hypertension and cardiovascular accidents (CVAs or strokes). The NCLEX may provide clinical situations that require you to respond with appropriate nursing interventions, use of medications, and long-term rehabilitation. Safety and preventive measures may be components of client/family teaching concepts.
KEY POINTS
• The primary functions of the nervous system are communication and control.
• The primary nerve cell is the neuron, supported by neuroglia.
• A neuron consists of a cell body, axon, and dendrites.
• The functions of the neuroglia are to protect and support the central nervous system (CNS) and peripheral nervous system (PNS).
• The central nervous system consists of the brain, spinal cord, and accessory structures.
• The four cerebral lobes—frontal, parietal, temporal, and occipital—are located in both hemispheres of the brain. The frontal lobe is responsible for higher mental processes. The parietal lobe is responsible for speech and some sensory input. The temporal lobe is responsible for smell, hearing, and some memory. The occipital lobe is responsible for vision.
• The hypothalamus regulates many body functions, such as temperature, thirst, hunger, urination, swallowing, and the sleep-wake cycle. It also secretes some hormones and influences release of hormones from the pituitary, thereby influencing the metabolism of nutrients and regulation of fluid balance and general homeostasis.
• The cerebellum is responsible for muscle control.
• The brainstem is made up of the midbrain, pons, and medulla. The midbrain functions as a reflex center. The pons contains nerve tracts and carries messages between the cerebrum and medulla and is also responsible for respiration. The medulla contains centers for vital body functions, such as heart rate, vasomotor tone, and respirations.
• The spinal cord conducts impulses to and from the brain and acts as a reflex center.
• The meninges cover the brain and spinal cord and include the dura mater, arachnoid, and pia mater.
• Twelve pairs of cranial nerves arise from the brain. Most of these convey impulses to and from the brain and the structures of the head.
• The spinal nerves are attached to the spinal cord. They are divided into 8 cervical pairs, 12 thoracic pairs, 5 lumbar pairs, 5 sacral pairs, and 1 coccygeal pair.
• The autonomic nervous system is divided into the sympathetic and parasympathetic divisions. The sympathetic system prepares individuals for emergencies. The parasympathetic system maintains body functions under normal conditions.
• The three types of neurons are sensory (afferent), motor (efferent), and interneurons (integrators). Sensory neurons carry information to the brain. Motor neurons carry information away from the brain. Interneurons integrate signals between the two.
