Structure and Function

The nervous system is the information system for the body.  The nervous system has three primary functions: communication and control, survival, and mental processes. Communication and control includes identifying and interpreting sensations from inside and outside the body such as pain, smell, sight and hunger sensations. From these sensations, the nervous system then determines the response and control of the body. Survival is achieved by the nervous system’s reflex responses and autonomic centers. This allows rapid response without requiring conscious thought to carry out survival instincts. Examples of these independent abilities include breathing and slamming on the brakes while driving a car to avoid an accident or reacting to danger. The third function, mental processes, allows for our ability to think, rationalize, learn, feel emotion and reason.

The nervous system has two primary divisions: the central nervous system (CNS) and the peripheral nervous system (PNS). The CNS includes the brain and spinal cord. The skull and the spinal column provide bony protection for the brain and the spinal cord. The brain stem connects the brain to the spinal cord. The brain stem controls major body functions such as respiration, pulse, temperature and blood pressure. The brain allows for higher processes related to thinking, feeling, logic, artistic expression and learning. Many parts of the brain contain both a motor and a sensory component. When an area of the brain is damaged, there are often multiple symptoms such as weakness, paralysis, loss of the sense of smell or taste, emotional changes, or balance issues. Much of the brain is poorly understood. The spinal cord contains the reflex centers for the body, which allows the body to react very quickly in response to a stimulus without thinking. An example of this is jerking your hand away from a hot stove.

The PNS includes all nerve tissues throughout the body including the cranial nerves, spinal nerves and the autonomic nervous system. The cranial and spinal nerves are located throughout the body and allow communication between the body and the CNS.

Nerves either transmit information to the brain and spinal cord, or they send instructions to the body from the CNS to carry out directions.

The autonomic nervous system (ANS) carries out the body’s automatic functions such as breathing, digestion and heartbeat. The ANS has two divisions that work opposite of each other: the sympathetic nervous system and the parasympathetic nervous system. The sympathetic nervous system is the body’s fight or flight system, which prepares the body for an emergency. The sympathetic nervous system accelerates the heart rate, raises the blood pressure, enlarges the air passages, dilates the pupils of the eyes to allow better vision, and shuts down unnecessary areas of the body such as digestion and reproduction. The parasympathetic nervous system works antagonistic to the sympathetic nervous system. The parasympathetic nervous system assists the body to return to a calmer, more relaxed state. The parasympathetic nervous system slows the heart rate, lowers blood pressure, increases digestion and slows breathing.

Age-Related Changes

Gradual changes occur in the nervous system with age. In infancy, a baby relies on reflexes and instincts to survive. Throughout childhood the nervous system refines its function and develops the ability to respond rapidly and accurately. After approximately the age of 25, the nervous system gradually slows. Nerve impulses travel more slowly or are lost altogether, which can result in a resident having a slower gait and slower reaction times. Reflexes may slow, and a person’s ability to respond to stress may decrease. With age, there is a gradual loss of sensory perception over time including hearing loss, visual changes and other sensory alterations. Postural and gait changes also alter with age. The body may not acclimate as rapidly to position changes such as adjusting blood pressure when standing, which can result in dizziness and lightheadedness while the body attempts to compensate for the position change. Thermoregulation is also a concern with aging. With age, the body is less efficient at controlling body temperature. A fever in an older adult is a significant concern because it requires a higher response by the brain to whatever is causing the fever.

Dementia

Dementia is a gradual, progressive decrease in mental functioning. Dementia is characterized by language difficulties, memory impairment, difficulty recognizing familiar objects, and difficulty learning new things. Alzheimer’s disease is the largest group of dementias.

Alzheimer’s disease (AD) is a slow, progressive decline in mental function. It is the most common form of dementia in the United States. Changes occur in the nerve cells that control memory and cognitive function. As the disease progresses, it gradually affects more parts of the brain and the body functions controlled by those parts of the brain. After a person is diagnosed with AD, the average lifespan is eight to 10 years. Alzheimer’s is divided into stages that blend into each other. The following tables identify changes in stage one and stage two.

Alzheimer’s: Stage One In the first stage, the resident is often undiagnosed and living at home.Alzheimer’s: Stage Two A diagnosis is usually made in this stage. The person generally requires extensive supervision and assistance with basic needs.

Alzheimer’s: Stage Three The person in stage three requires total care with basic needs. Symptoms include severe memory loss, inability to comprehend, complete disorientation, minimal emotional reactions, and the inability to communicate verbally. As a person progresses through stage three, there is often increasing difficulty with eating, chewing and/or swallowing. This person must be evaluated carefully to determine how he or she is able to take medications.

Cerebrovascular Accident

A cerebrovascular accident (CVA) is a sudden impairment of blood flow to part of the brain, usually due to partial or total blockage. CVA is commonly called a stroke. Stroke is a major cause of death and disability in people 65 and older. If brain cells are deprived of oxygen for six minutes or more, cell destruction can occur, which leads to tissue death in the brain. Signs and symptoms vary according to the area of the brain involved. CVA can occur without warning. CVA symptoms may include weakness or paralysis on one side of the body, aphasia (inability to understand or communicate using written or spoken language), dysphagia (difficulty swallowing), limited visual field, changes in level of consciousness, and/or bowel or bladder dysfunction.

Drugs that Affect the Nervous System

1. Sedatives and hypnotics depress the central nervous system (CNS) by slowing nerve impulses. Based on the degree of CNS depression, drugs are classified as either sedatives or hypnotics. Some drugs can be either one, depending on the amount of the dose. Sedatives produce a slowed response to stimuli but do not result in sleep. Hypnotics tend to have a more depressant effect and cause the person taking them to sleep. Sedatives and hypnotics are used to treat insomnia, to produce sedation or anesthesia, or to prevent seizures. Side effects of sedatives and hypnotics may include drowsiness, dizziness, respiratory depression, skin rash, restlessness, confusion, nightmares and/or delirium.
2. Barbiturates are CNS depressants derived from barbituric acid. They are used for their hypnotic or sedative effect, or to control seizures. Phenobarbital is a barbiturate used as an anticonvulsant.
3. Alcohol is often thought of by society as a stimulant, but in reality it is a depressant of the central nervous system. It is sometimes used in moderate amounts as a sedative.
4. Alzheimer’s drugs are acetylcholinesterase inhibitors. These medications prevent the breakdown of the chemical acetylcholine and improve cognitive function. They do not treat the underlying disease. They may slow the progression but will not cure Alzheimer’s disease. Side effects may include nausea, vomiting and/or dizziness.
5. Antianxiety medications are useful for short-term treatment of anxiety disorders. Some are used as muscle relaxants, anticonvulsants, and/or to treat
6. Nausea and vomiting. Side effects may include drowsiness, lethargy, depression and confusion. These medications may be habit-forming.
7. Anticholinergic agents may be used to treat mild forms of Parkinson’s disease or to treat Parkinson’s symptoms related to drugs such as antipsychotics. Side effects may include dry mouth, dizziness, blurred vision, constipation, urinary retention, confusion and/or depression. This group is not recommended for older residents due to the side effects.
8. Anticoagulants prevent blood clots or are used to treat existing blood clots, which may block blood flow to vital areas of the body. Side effects may include bleeding, blood in urine or stool, nosebleeds, bruising, and/or bleeding gums. 
9. Anticonvulsants reduce the frequency and severity of seizures. Side effects may include sedation, dizziness, inflamed gums, nausea and vomiting, and/or visual disturbances.
10. Antidepressants treat various types of depression. There are several types of antidepressants including MAOIs, SSRIs and tricyclic antidepressants. Side effects may include nausea, weight changes, sleep pattern changes, dry mouth, nervousness and/or restlessness. Effects generally take two to four weeks before results may be seen.
11. Antihistamines provide symptom relief of an allergic response caused by histamine release. Side effects may include dry secretions, sedation, hypotension, urinary retention, insomnia and/or decreased coordination.
12. Antihypertensives treat hypertension. These medications do not cure hypertension; they only control it. There are multiple sub-classifications of antihypertensives. Side effects may include hypotension, slow heart rate, drowsiness, nausea and/ or vomiting.
13. Antimanic agents treat long-term bipolar disorder. Dosage is established by monitoring the person’s blood levels. Side effects may include nausea, tremors, polyuria and/or heart irregularities. Toxicity can occur, and therefore any resident taking these drugs must be monitored.
14. Antiparkinson medications are primarily dopamine agonists. This group is the drug of choice for longterm treatment of Parkinson’s disease. Side effects may include dyskinesia, nausea and vomiting, hypotension, dizziness, anxiety and/or agitation.
15. Antipsychotics relieve symptoms of psychosis including delusions, hallucinations, agitation and combativeness. Some are used for pain relief, and to treat nausea and vomiting. Side effects may include postural hypotension, insomnia, agitation, depression, dry mouth, constipation, urinary retention and/or EPS.
16. Cholesterol-lowering agents are also known as antilipemic agents. These drugs are used to treat high cholesterol. Side effects may include constipation, liver damage, muscle cramps, weakness, kidney damage and/or bleeding.
17. Diuretics increase urine excretion. They are divided into several categories according to their action. Side effects may include low potassium, muscle weakness, dehydration, postural hypotension, headaches and/or muscle cramps.
18. Mood stabilizers are also anticonvulsants and treat seizure disorders as well as rapid mood swings. Side effects may include sedation, dizziness, inflamed gums, nausea and vomiting, and/or visual disturbances.