Learning Objectives
By the end of this section, you will be able to:
- Identify the cellular continuum of function
- Differentiate between the positive and negative cellular feedback responses
- Discuss the types of inflammation and systemic response
- Identify causes of cellular injury
- Discuss the various causes for cellular injury
The body responds to stress at the cellular level, and the responses affect surrounding cells, tissues, organs, systems, and, eventually, the entire body. Understanding the body’s cellular response to stress will help the nurse recognize the physical effects and how pharmacological interventions can help.
Cellular Continuum of Function
The cellular stress response is a cascade of chemical and hormonal signals that activate cellular products needed to re-establish homeostasis. One example is the activation of a type of protein called heat-shock protein to respond to changes in temperature, low pH, or low oxygen level (Fulda, 2010). Cells can respond in adaptative ways to stress or even through apoptosis, which is cell destruction to eliminate a stressor to the system. The process by which a cell experiences stress by either dying or becoming more resilient depends on various factors, including toxicity of the stressor, cell strength, duration of the stress, and age of the cell, among others.
Each cell in the body is programmed to live a certain length of time and then die; this is known as programmed death (Fulda, 2010). Cells can die by programmed death such as apoptosis, necrosis, or autophagic cell death. The cell recycles select parts of itself, in a process called autophagy (self-eating), to maintain cellular balance. An example would be self-destruction of red blood cells after 120 days, when they pass through the spleen and the iron portion is recycled for the next generation of red blood cells. Without apoptosis and autophagy, the body would not be able to clean up degraded cells. The interplay of genetics and environmental factors can affect the timeline of life for the cell. Stress is a large factor in potential early destruction of a cell. Stress on a cell can also create positive outcomes or negative results. Stressing the muscle fiber cells can increase elasticity and strength or tear and break them down, depending on various external factors.
A cell will respond to an initial exposure to a stressor, just as in the Generalized Adaptation Syndrome, with an alarm stage of activation of pathways to survive. However, if resources such as nutrition, oxygen, or fluids are not adequate, the cell will not survive. Initial responses to cellular stress include production of needed proteins to repair damage from a stressor, as in the case of wound injury.
Control of the Steady State
The adaptive ability of a cell will determine its fate after experiencing stress. An example of the impact of various factors upon a cell to adapt is the effect of exercise on the telomeres within a cell. The distinct structures at the end of a strand of a chromosome within the cell are called telomeres. They have been likened to the plastic caps at the end of a shoelace. Telomeres have repeated sequences of DNA, and every time the cell divides, the telomeres shorten until they eventually become so short, the cells dies. This reveals one of the ways a cell is programmed to die. Studies show that exercise strengthens the telomeres, extending their lifespan, whereas poor nutrition and stress weaken them (Shammas, 2011). Research on cell death has been conducted regarding cancer and chronic degenerative conditions such as Parkinson’s disease and Alzheimer’s disease.
Each cell works to maintain homeostasis and balance throughout stress states by adjusting protein and enzyme production and adapting the functions that affect the tissue and the organ comprising the tissue. Control of the steady state is the quest. Biological homeostasis is achieved by establishing an internal stability for the cell and adapting to demands of the external environment. The body accomplishes balance through regulatory processes known as positive and negative feedback.
Positive Feedback
The method the body uses to enhance a desired outcome by amplifying chemical or hormonal messages to the organs of influence is called positive feedback. An example of positive feedback is seen during labor and delivery. The release of oxytocin from the posterior pituitary gland stimulates uterine contractions during labor, with the desired outcome of the delivery of the baby.
During cellular stress, positive feedback may promote cellular death to minimize oxygen and nutrition demands on the body, such as occurs with weight loss during times of scarcity. More commonly used throughout the body, however, is negative feedback.
Negative Feedback
The feedback loop of communication of hormones and chemicals in the body to decrease a desired output is called negative feedback. An example is when the body tries to reach a balance by releasing insulin when the glucose level in the blood is high. When blood glucose levels drop with the help of insulin secretion from the pancreas, then the signaling changes to stop releasing insulin so glucose levels do not fall too much. When glucose levels drop during fasting or sleep, the negative feedback loop then sends chemical messengers to the liver to break down glycogen, which is stored glucose, where it can then elevate blood sugar levels to the normal range. It is a constant balance and exchange of signals all with the goal of maintaining a stable internal environment.
Remarkably, the negative and positive feedback loops occur automatically. When body temperature rises, the negative feedback system in chemoreceptor sites of the thyroid and brain sense a higher-than-desired temperature, which triggers the action of sweating in the skin. Each body system works together to achieve balance in an ever-changing milieu.
Cellular Adaptation and Response
One powerful adaptation at the cellular level includes the inflammatory response, which is triggered by a stressor, pathogen, or antigen from inside or outside of the body. When a stressor is identified by chemicals and T cells in the blood, additional chemicals, called cytokines (e.g., histamine), are released to notify the surrounding area that an antigen is present. Mast cells release chemicals, which stimulate vasodilation and increase movement of white blood cells to the area. It is as if the immune system is alerting the body’s military troops about an invasion and, through this chemical communication, vasodilation allows more troops to enter the battlefield. This cellular adaptation is a remarkable and quite sophisticated way to respond to threats.
Generally, inflammation is a helpful response to allergens and pathogens, but it can cause problems when the body attacks itself in a process called autoimmune hypersensitivity. Hypersensitivity is when the body’s response is overreacting and causes additional and unwanted problems for the body such as autoimmune diseases like type 1 diabetes, lupus, multiple sclerosis, Hashimoto’s thyroiditis, and others.
Types of Inflammation
Inflammation is a large factor that is both a stressor and response to stress. It can be either acute or chronic. An acute response is appropriate against a pathogen or antigen but can become detrimental when it continues for days, weeks, and even years. Acute inflammation will occur when there is a break in the skin, or even during hay fever season, but when it is chronic, it can become a devastating stressor to the body when nutrients and energy become depleted. People with chronic allergies experience lasting symptoms of physical stress, such as constant itching eyes, runny nose, skin inflammation, and emotional stress. Medications such as antihistamines can stop the inflammatory response and clinical symptoms.
Link to Learning
View this video to learn about the inflammatory response from Alila Medical Media.
A topic of popular interest is irritable gut syndrome, also known as leaky gut. The hypothesis is that certain foods and environmental triggers weaken the immune system, which is largely housed in the gastrointestinal tract. Bloating, fungal growth, brain fog, fatigue, and lethargy result when the gut is unable to fight these allergens. People who experience celiac disease or have a gluten allergy are familiar with the gastrointestinal bloating and distress from eating a food they are allergic to. The body identifies the food as an antigen, which results in uncomfortable inflammation of the gut.
The term chronic inflammatory response syndrome (CIRS) refers to conditions of chronic stress caused by chronic inflammation in the body. Other chronic conditions are now also being linked to an inflammatory response gone awry, such as in Alzheimer’s disease or dementia due to inflammation in the brain (Kinney et. al., 2018).
Systemic Response to Inflammation
Inflammation is often local, due to a physical injury to the body’s protective skin, but it can also be systemic when the body attempts to protect itself inside. When the inflammatory response becomes systemic, the body can experience great stress as it struggles to restore stability. Systemic inflammation can occur with generalized infections in the blood or with trauma. Conditions that cause any type of shock, such as anaphylactic, neurogenic, sepsis, or cardiogenic shock, can result in massive circulatory vasodilation and cause hypotension that threatens adequate perfusion to tissues.
Massive vasodilation, hypotension, tachycardia, and tachypnea, in response to infection and autoimmune disorders or burns, is referred to as systemic inflammatory response syndrome (SIRS). It can be fatal if the body cannot overcome the extreme inflammatory response. What begins as the body’s attempt to protect itself becomes systemic and affects all body systems, which may not be able to accommodate the widespread reaction.
Link to Learning
This video discusses SIRS criteria and presents an example case for analysis.
Chemical Mediators
The inflammatory response is a complex process that involves many chemicals. The chemicals work in a cascading manner. Mediators of inflammation include leukotrienes, prostaglandins, vasoactive peptides known as kinins, phospholipids to activate clotting, and cytokines. Each chemical sends signals of stress in the development of the inflammatory response. The inflammatory response may be triggered by bacteria, pathogens, trauma, toxins, heat, or other noxious events. Histamine, bradykinin, and prostaglandins cause vasodilation, which allows fluids to flood the bloodstream, which cause swelling. The classic signs of inflammation are rubor (redness), pallor (blanching caused by swelling tissue), dolor (pain caused by inflamed tissue pressing against nerves), tumor (swelling), and calor (heat). Loss of function can also result when tissues swell, making mobility of the affected area unstable or painful, such as a swollen ankle after injury.
Pharmacological interventions target one or more of the signs of inflammation. Anti-inflammatories decrease swelling and block prostaglandins. Fever reducers act to decrease the fever within the tissues. Pain medications act to numb the pain receptors at the tissue site and block activation of nociceptors, which detect noxious stimuli. The inflammatory mediators of pain include prostaglandins, pro-inflammatory cytokines, and chemokines, which nonsteroidal inflammatory drugs and even some narcotics act upon.
Cellular Injury
The cascade of activating chemicals protects the body against further injury; however, depending on the severity of the stressor, this activity may exhaust the cell’s ability to respond to and repair injury. As seen in the General Adaptation Syndrome, cells respond first in the acute stage with alarm and the inflammatory response, but if cells cannot overcome the insult to the body, efforts to adapt may lead to exhaustion. Large injuries seen in trauma and burns that destroy high volumes of cellular tissues may cause permanent damage.
Laboratory tests are used to help monitor the body’s ability to respond, adapt, and overcome a physical stressor. Common laboratory tests for this purpose include measuring levels of lactate, blood urea nitrogen (BUN), and creatinine; a hemogram, which looks at red cells, white cells, and platelets; and end products of metabolism found in the urine, such as protein. When the body’s muscles break down due to a stressor in a trauma or even a rigorous athletic event, high levels of proteins such as creatine kinase or creatine phosphokinase in both the blood and urine can reveal rhabdomyolysis, or massive destruction of muscle and the resultant increase in byproducts of muscle breakdown in the blood.
Managing inflammation is one process nurses can help with by administering medications as ordered and promoting a decrease in tissue swelling by applying cold compresses and elevating the inflamed area, if possible. Decreasing cellular injury after a physical stressor can be managed with the actions abbreviated in the word PRICE: pain reduction, rest, ice, compression, and elevation. Additionally, nurses promote the patient’s nutrition to support the energy of cells toward recovery.
Nutritional Imbalance
All the efforts to respond to a physical stressor, including the inflammatory response, require energy from the cells. Supporting the cells with adequate oxygenation and nutrition can increase the cells’ ability to function and recover. Cells that are well hydrated and nourished have a better chance of being able to adapt to stress. Cells that are deprived of needed oxygen, fluids, and nutrition will not adapt well and may fail.
The core nutritional fuels for the body are carbohydrates, fats, and proteins. All are needed for cellular growth and recovery. Cells prefer carbohydrates as a fast-acting fuel to burn for adenosine triphosphate production but can use fats and proteins in the absence of carbohydrates or insulin, which allows glucose, as the simplest form of carbohydrate, to enter the cell. When the body uses fats or proteins as alternate energy sources, a negative byproduct is ketone bodies, which create an acidic environment for the cells. A balance of the macronutrients (carbohydrates, fats, and proteins) and micronutrients (vitamins and minerals) is needed for ideal cellular function. Hydration without added artificial flavorings, chemicals, excess calories, or caffeine is what cells need to function.
When cells have an imbalance of nutrients, cells die. Starvation at the cellular level is not conducive to good function or recovery from stress. Without adequate nutrients, red blood cells, white blood cells, chemical mediators, and platelets cannot be made, all of which are part of the inflammatory process. Without the inflammatory process, which includes the immune system’s response, the body cannot adequately protect itself.
Hypoxia
A major purpose of the inflammatory process is to deliver oxygen to the site of injury or invasion. Vasodilation enlarges the area where red blood cells can flood the tissue area, delivering needed oxygen. All cells need oxygen to complete their internal metabolic processes, including the production of proteins, enzymes, and chemicals. Some cells may function through anaerobic processes, yet oxygen is needed for ideal functioning in the majority of the body’s cells. The inflammatory process assists the body with the delivery of oxygen.
Physical Influences
There are many physical factors that influence the inflammatory response. These can include disruptions in the ability of the blood vessels to dilate or insufficient oxygen-carrying capacity of the red blood cells. If the body cannot deliver oxygen due to a blockage (ischemia); decrease in blood pressure, which pushes oxygen across cellular membranes (seen in shock or sepsis); or inadequate red blood cell count, seen in anemia or hemorrhage, cells will die.
An example of a physical influence that can affect the normal, well-intended inflammatory response is an injury to the brain, where normal swelling can cause increased cranial pressure. As the brain tissue swells, it has nowhere to expand in the hard, skull-encased area, and the swelling tissue pushes back on itself, possibly causing the brain to herniate through the spinal cord, which can cause death of the brain. Another example is when a bone is fractured with no break in the skin and then put in a closed cast before swelling has subsided. Again, because the inflammation has nowhere to expand, the tissue pushes back on itself, causing damage within, known as compartment syndrome. The medical remedy for these two examples is to surgically open the area to allow for tissue expansion. Casts are generally not placed until swelling has gone down; an open split is placed initially instead.
Temperature
The word inflammation is derived from the Latin word inflammare, which means to burn, and indicates the identification, even in ancient time, of a key feature of the inflammatory response to injury or infection. The body strives to keep the body in an ideal temperature range throughout the organs; this process is called thermoregulation. Using negative feedback, the body has a desired set point and senses variations in that temperature by chemoreceptors. If the body temperature elevates, sweating is elicited to decrease the core temperature. If the body temperature decreases below the set point, then muscles contract to shiver and stimulate heat production. All these adjustments are done autonomically.
During the inflammatory process, local temperature increases due to the increase in circulation to the body region affected. Elevating the temperature is also a chemical attack to create an unsuitable environment for the survival of pathogens. When the body experiences SIRS, the temperature of the entire body increases, which can be uncomfortable to the individual and, in a hospital setting, is managed by antipyretics. In other medical naturopathic traditions, such as Indian Ayurvedic medicine, American Indian medicine, and traditional Chinese medicine, the fever from inflammation or illness is actually promoted because its effects help destroy pathogens that may be causing the illness. In Western medicine, fever is usually addressed quickly to promote patient comfort and rest.
Radiation
Radiation is both a promoter of injury and remedy for many cancerous conditions. Radiation, which, ironically, is carcinogenic, or cancer causing, is also used as a treatment for cancer. The etiology of its use is found in the physiological effects of radiation at the cellular level. Radiation can cause mutations in chromosomes during mitosis, damaging cells and their byproducts. It has the power to change the expression of genes, which is why it is used in cancer tumors. Radiation can be used to destroy undesirable tumor cells because it disrupts normal tumor cell growth. Fast-growing cells are most affected by radiation; unfortunately, that means noncancerous cells are also destroyed, such as hair cells and gastrointestinal lining cells, causing hair loss and nausea and vomiting, respectively.
Radiation-damaged tissues result in inflammation similar to the response seen after an attack by a pathogen, which is why oncologists limit radiation exposure (Schaue et al., 2015). The damaged tissue recovers with time as the body’s regulatory mechanisms respond to remodel the skin and tissue for normal wound healing. Although radiation treatment has the goal to narrowly target the desired cancerous tissue area, the wide response of inflammation expands beyond the initial radiation border, and a wider range of tissue is negatively affected. A careful nursing assessment is needed to assess for peripheral tissue damage and intervene to promote comfort to aid the body’s inflammatory response.
Trauma
Trauma, just like pathogens or radiation, will trigger the inflammatory response for protection. Any physical, emotional, or sexual trauma causes stress to the body. Traumatic injury produces excessive release of proinflammatory mediators, which activate vasodilation, white blood cell attraction to the area, and chemical release of histamine, cytokines, and prostaglandins.
In addition to stabilizing injured body appendages or bones and working toward hemodynamic and respiratory stabilization from a trauma, medical interventions address the increase in tissue swelling, fever, and pain. Generally, in a trauma with a fracture, the bones can only be stabilized initially with an open splint, rather than a closed cast, to allow for the inflammation to subside. Pain control, rest, elevation, and compression are common approaches to help decrease the inflammation in the acute phase. For massive systemic trauma, the inflammatory response also reacts systemically, leading to massive vasodilation, hemodynamic instability, and SIRS, often causing death.
Chemical Influence
In addition to the chemicals released during the inflammatory response, such as histamine and cytokines, the sympathetic nervous system prompts release of epinephrine and norepinephrine during stress, which further creates a demand on the cardiovascular and respiratory systems. The main chemical mediators during inflammation include (1) vasodilator stimulators such as histamine and serotonin, (2) peptides such as bradykinin, and (3) eicosanoids such as thromboxanes, leukotrienes, and prostaglandins (Abdulkhaleq et al., 2018). Additional chemicals released from the kidneys or electrolytes in the blood affect the inflammatory response and stress response.
Macrophages, neutrophils, and lymphocytes are drawn to the site of an injury within minutes as chemicals released from mast cells lining the site of injury are broken open and released due to the injury. Histamine, prostaglandins, leukotrienes, free radicals, serotonin, and even oxygen continue to promote a chain of organized responses that have cellular and vascular effects, which contribute to the inflammatory process. The inflammatory response also includes pyrogens (which initiate fever); interferons; plasma proteins, such as complement; and kinins that produce clotting as needed. After basic neutrophils and leukocytes are attracted to the area of injury, white blood cells further differentiate bringing helper T cells to the area to target antigens. It is as if the helper T cells are paint ball players that tag the offending pathogen with a marker protein so the white blood cells can recognize the enemy and engulf and destroy them through phagocytosis.
In modern medicine, counter-attacking chemicals are used in pharmaceuticals to decrease the innate chemical reactions of the body, such as antihistamines, antipyretics, and antibiotics. External chemicals, however, can be noxious to the body and trigger an inflammatory response. Air pollutants like car exhaust and smoke, and synthetic chemicals in beauty and cleaning products can be stressful to the body and trigger the body’s allergic response. Sneezing, coughing, choking, wheezing, and runny eyes are results of the body’s attempt to get rid of the irritant. Even chemicals in food products can stimulate an allergic reaction, which is seen in those with food allergies including gluten and food dyes.
Infection or Infectious Influence
A common cause of stress that triggers the inflammatory response is entry of pathogens into the body, including viruses, bacteria, and fungi. The body recognizes these protein-enveloped entities and cells as foreign, which then triggers the immune and inflammatory responses. Depending on the location and volume of pathogen, the body may be triggered to a localized or a systemic inflammatory response. If a pathogen enters the skin from a scratch or small wound, the inflammatory response is localized and easy to treat. Localized redness, heat from the site, swelling, and pain may result. If, however, a pathogen enters through the respiratory system, such as a flu virus, or gastrointestinal system, then a systemic reaction will follow because the larger body system affected.
Treatment for an infectious agent is focused on medications to treat the offending pathogen and commonly includes antibiotics, antivirals, or antifungals. Additionally, systemic medications are given, such as antipyretics for the comfort of the patient. Choosing the correct antimicrobial medication is, of course, key to success because the medication must be able to effectively kill the pathogen. Nurses will respond to orders that require a culture of the tissue, blood, secretion, or urine to identify the organism and its responsiveness to the right medication. Then, nurses will administer the prescribed antimicrobial at the correct times to maximize therapeutic response. With the decline in the pathogen population as a result of the correct pharmacological treatment, the inflammatory response also decreases, and the alarm stage of physical stress can end.
Immune Response
The immune system is a brilliant, complicated, and impressive system that is often not given adequate recognition because it is not as tangible as the other systems of the body taught in an anatomy class. The immune system can be divided into the innate and adaptive divisions. The innate division includes the first physical barriers to prevent infection or assault on the body such as the skin, mucus membranes, and higher acid levels in the stomach and vagina. The physical barriers are the first wall against pathogens and include larger mast cells that line tissues and organs, such as the endothelial lining in the stomach, respiratory tract, gastrointestinal tract, vagina, mouth, eyes, and nose. As discussed, if an injury occurs that breaks the cellular barrier, the mast cells are broken open, releasing histamine, which serves as a megaphone to call the immune system’s attention to the area. Vasodilation and increased numbers of red blood cells, white blood cells, and platelets rush to the area.
The adaptive division of the immune system then takes over, using chemical mediators to mark the pathogens so immunoglobulins can identify the offending agents and destroy them. Memory T cells are formed to remember the unique protein structure of the pathogen to be ready for any future assault by creating an immunity to it. Young children who have not been exposed to common pathogens rely on the thymus gland in the center of the chest to create immunoglobulins, but after receiving vaccines and exposure experiences, their body becomes more mature and they can then rely on developed T cells and antibodies in the adaptive immune system.
Link to Learning
Watch this video about the immune system’s response to bacterial infection.
Genetic Influence
The age-old question of nurture versus nature continues to be asked about development of diseases. Both genetic and environmental factors influence an individual’s ability to respond to stress, injury, and infection effectively. It is true that some genetic factors result in a disadvantage in fighting stress and disease, such as in patients with congenital conditions like cerebral palsy and cystic fibrosis, but most individuals can strengthen or weaken their body’s resilience and adaptation by their life choices.
One analogy is that your genetics may be like a loaded gun, but your behaviors of nutrition, sleep, hydration, exercise, avoidance of toxins, and overall healthy behaviors, or lack of them, are what aim the trigger toward or away from disease. Stress can activate or mutate cells at the chromosome level. Chronic stress causes strain, and as has been discussed in this module on inflammation, causes additional potential problems for and demands on the body. Genetic mutations occur when there is damage to DNA; as cells containing damaged DNA replicate, so do the errors, furthering the incorrect or damaged coding for the cells, tissues, and body organs. Although nurses may not be involved in genetic counseling, they are involved in patient education about healthy lifestyles, which has a powerful impact at the genetic level.
Cellular Healing
When cells are damaged, the body automatically moves quickly into recovery and repair through the inflammatory response. Oxygen and nutrients are brought to the damaged tissues and cells to help with restoration. Variations in healing time and ability, again, are affects by genetics; available resources, including nutritional support; and the mental health of the individual. General wound healing takes 14–21 days, but individual cells may heal more quickly with sufficient support.
Nurses can aid healing at the cellular level by providing the patient nutrition, hydration, adequate sleep, and mental health support. Nurses can help teach their patients to honor their body and make decisions that demonstrate respect for their body. Florence Nightingale, known as the mother of modern nursing, emphasized the importance of environmental cleanliness, air, water, and support to help a person heal from injury, infection, or disease. Even before germ theory emerged, she understood the relationship between an external supportive environment and the internal environment of the body to heal.
Cellular Regeneration
Cellular regeneration is the ability of the body to restore damaged or destroyed cells, tissues, and organs to full function. All cells within the body replicate and regenerate based on the type of cell they are and tissues they create. Nerve cells have a slower rate of regeneration; however; in recent studies, nerve cells have been seen to regenerate in areas where this has not been seen before. Patients with spinal cord injury or stroke have had amazing recoveries. Unfortunately, there are so many complicated variables that not all patients experience recovery success.
Beginning with the inflammatory response, cells can begin to regenerate after injury or antigen exposure as blood delivers oxygen and nutrition to damaged cells and tissue. The ability to regenerate depends on the existing health of the cell and organism. Documented methods that stimulate cellular regeneration include intermittent fasting; caloric restriction; reduction in triglyceride levels; decreasing sugar and alcohol consumption; stem cell supplementation; vitamin C, vitamin E, beta-carotenes, and lutein consumption; and supporting healthy inflammatory pathways. Foods high in healing nutrients include cruciferous vegetables like cauliflower, broccoli, kale, cabbage, bok choy, and brussels sprouts. Nurses can help monitor these factors and offer patient education on healing methods.
Cellular Replacement
Cellular replacement is the process of replacing an aging cell with a newer, identical cell. The human body experiences cell growth and destruction every day. Each time a cell divides, the cell duplicates its genetic material; however, the telomeres in each cell become a little shorter until they are depleted, and the cell eventually dies. When the cells die, another generation of cells is formed to replace the old one. Cell death can be accelerated or delayed by health and behavior choices. Accidents, illness, and injury can speed up cell death, and positive supportive behaviors and choices can extend telomere length and life.
Each specific cell type in the body has an established cellular replacement time frame. For example, skin cells in the outer epidermis are constantly being replaced by younger cells developed in the lower basal area. When a person repeatedly sunburns, those immature cells may not be ready to replace the older cells on the epidermis. The body rushes to repair the exfoliated surface cells, but in the hurry, the basal area may produce immature cells, which are prone to DNA mutations, leading to skin cancer. It is as if a person becomes in a rush to make paper copies and the copy machine is forced to speed up, making errors more frequently.
Cells are replaced throughout the entire human body every 7–10 years. White blood cells replace themselves within 2–5 days, red blood cells every 120 days, and skin every several days. Studies show that cells stop dividing after 50 or so divisions, leading to aging and eventual death.
The quest for youth and eternal life still is an unsolved mystery; in the meantime, nurses can help patients improve the length of their life by practicing healthy behaviors and learning to manage their own stress more effectively.