How Does Aging Affect the Nervous System?
Sometimes it’s hard to separate the nervous system, an organ system like any other in the body, from your sense of self. While your brain is indeed a collection of cells, just like the liver and the heart, the fact that it controls memory, personality, and feelings, not to mention movement and sensation, makes it feel like the nervous system should be elevated to a level above the other organ systems.
The nervous system, made up of the brain, spinal cord, and a network of nerve cells that traverse the body, is fallible and susceptible to disease. And, like other cells in the body, cells in the nervous system change throughout your lifespan. As a result, they are susceptible to damage, but they are also responsive to healthy lifestyle changes that protect them from free radicals and damaging toxins.
The nervous system can be divided into the central and peripheral nervous systems:
- The central nervous system (CNS) comprises the brain and spinal cord.
- Sensory areas: receive sensory information from the skin and special senses.
- Motor areas: control movement.
- Integration: areas of the brain that integrate information from multiple sources, such as positional information from the eyes and ears.
- The peripheral nervous system (PNS) includes all the nerve cells entering and leaving the brain and spinal cord.
- Afferent: nerve cells carrying nerve impulses towards the CNS
- Sensory nerve cells carry information from the skin and special senses to the CNS.
- Efferent: nerve cells carrying nerve impulses away from the CNS
- Motor nerve cells carry information from the CNS to muscles and the visceral organs.
- Afferent: nerve cells carrying nerve impulses towards the CNS
Over time, the brain and spinal cord will atrophy or lose cells. Researchers found that 90-year-old brains were about 11% lighter than 50-year-old brains. Waste products from cellular metabolism may begin to build up in the brain. Protein may accumulate in nerve cells. Pigments such as lipofuscin and neuromelanin accumulate in the brain. Slight changes in the genetic code may accumulate over time, making it hard for cells to produce the needed proteins and break down the ones they no longer use. These cellular changes can cause memory impairment and a decrease in cognitive health.
Antioxidants are vitamins, such as vitamin C, and nutrients, such as coenzyme Q, NAD, and glutathione, that help neutralize the free radicals that damage cells. These vitamins and nutrients can keep free radicals from damaging DNA and cellular structures.
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Sensation involves receiving input from the skin, visceral organs, and special senses. For example, sensory information can tell you that there is a change in your environment, such as a runaway golf ball headed for your face, or a change in your internal environment, such as an overstretched stomach after indulging in a four-course meal. However, with aging, your senses may not provide as much detailed information.
Light passes through the cornea, which is the transparent covering over the pupil, the entrance to the eye, and the iris, the colored band of muscles that control the size of the pupil. After entering the eye through the pupil, light rays are bent by the lens to focus them on the neural layer lining the inside of the eye, called the retina. The retina converts the light energy into a nerve impulse that is carried to the brain. The brain interprets information and integrates it with information coming from the other senses.
Each of the structures in the eye may change with aging:
- The cornea becomes less sensitive and more prone to injury from dryness.
- The pupil decreases in size and becomes less reactive to changes in light levels.
- The lens becomes less flexible and may become cloudy (cataract).
- The eye dehydrates slightly. Fat pads surrounding the eye decrease in size. Both changes allow the eye to sink more into the socket.
- When the lens becomes less flexible, you may notice that it is difficult to see close-up and requires reading glasses or bifocals.
- Reduced peripheral vision and haziness from bright light can make it more difficult to see at night.
- Lutein and Zeaxanthin
- Vitamins A, E, and C
- Omega-3 Fatty Acids
- Vitamin B complex and vitamin B12
Taste And Smell
Odorant molecules are dissolved in saliva or mucus to stimulate taste and smell receptors. With age, you may produce less saliva, which can affect your sense of taste. In addition, nasal congestion or medications that cause sinus dryness can affect your sense of smell. Smoking and pollution exposure can hasten the process of losing taste and smell sensitivity.
The ear can be divided into three sections:
- Outer ear: This includes the external part of the ear and the ear canal. The external ear directs sound waves into the ear.
- Middle ear: The eardrum divides the outer and middle ear. It contains the inner ear bones, which amplify sound, and the eustachian tube, which equalizes pressure.
- Inner ear: Contains the vestibule, the cochlea, which is the organ of hearing, and the semicircular canals, which control balance.
Over time, damage to the small hair cells lining the cochlea can cause hearing loss, especially the ability to hear high-frequency sounds. If your hearing declines, you may notice more difficulty hearing conversations in a noisy room.
You may also notice a ringing sound in your ears that may interfere with your hearing. This is called tinnitus. Impacted ear wax, medications, and mild hearing loss can all contribute to tinnitus.
Check with your doctor to see if you are taking any medications that may negatively affect your hearing. Wear noise-canceling headphones when you are exposed to loud noises. Have your hearing checked regularly, especially if you notice any changes.
Decreased blood flow to nerve endings can cause abnormal or decreased sensations. Diabetes is a common cause of small blood vessel damage, which then causes nerve damage. Losing excess weight and choosing a diet that helps maintain your blood sugar within a normal range can help prevent type 2 diabetes. Even if the number on the scale doesn’t move, you’re changing your body composition by exercising regularly. Increasing muscle mass and reducing abdominal fat can improve blood glucose levels. Maintaining normal blood sugar levels protects the inner lining of small blood vessels and reduces the risk of nerve damage.
Muscle movement is controlled by areas in the frontal cortex of the brain. The right motor cortex controls the left side of the body, and the left motor cortex controls the right side of the body.
Growth hormones and androgens, such as testosterone, are hormones that stimulate muscle growth and bone density. Unfortunately, hormonal aging also occurs, causing changes in body composition such as reduced muscle mass, decreased bone density, and decreased strength. To slow the changes associated with aging, some people use supplements, such as Sermorelin, that increase growth hormone release from the pituitary gland in the brain.
Reflexes are automatic movements that typically protect the body or help maintain balance. For example, when your hand jerks away from a hot stove without thinking about it, that is a reflex. If you had to consciously think about pulling your hand back, your hand would be burned. You can modify reflexes with conscious thought, but it takes a few milliseconds to react.
Reaction time slows with aging because of loss of nerve cells and slower nerve transmission. Increased physical activity increases muscle strength and balance and slows the age-related decline in reflexive movements. Increased physical activity can boost energy levels, improve cardiovascular fitness, and help maintain a healthy weight.
Balance and coordination are also affected by changes in the nervous system. These changes can increase your risk of falling. Coordination, reflexes, and strength are all tied together. Increasing muscle strength and participating in activities that challenge your ability to maintain your balance can improve coordination and decrease your risk of falling.
Try these movements to improve balance and coordination:
- Stand on one foot.
- Walk heel to toe along a line.
- Stand on a foam cushion.
- Take a few steps with your eyes closed.
When working on your balance and coordination, work with a spotter. A friend or family member can stand close by to ensure that you don’t fall or run into something. Check your environment to verify there are no nearby hazards, as well.
Muscle fibers fill muscle cells. While the number of muscle fibers in a muscle cell is genetically determined, hormones and stress on a muscle can increase the number of myofibrils in the muscle. An increase in myofibrils increases muscle bulk and strength. Conversely, when a muscle is not used, the number of myofibrils decreases, and the muscle atrophies.
Sarcopenia is a loss of muscle mass and strength associated with aging. Muscle is lost at a rate of 0.5% to 1.0% per year after age 70. Strength decreases by 10% to 15% per decade up to the age of 70, after which it declines by 20% to 40% per decade.
Factors that may contribute to decreased muscle mass and strength include:
- Decreasing metabolic rate
- Increasing body fat
- Increasing insulin resistance
- Decreasing physical activity
- Lower testosterone and growth hormone release
- Nutritional and vitamin deficits
- Chronic inflammation
- Changes in the ability to produce metabolic energy
Muscle is plastic, which means that it can adapt to its environment. With training, older adults can experience:
- 20% to 30% increase in aerobic fitness.
- 5% per day in strength gains using a structured resistance training program.
- improved cardiovascular health.
Losing excess pounds, improving insulin sensitivity, stimulating growth hormone release, and supplementing with the vitamins and nutrients your muscles need to produce more myofibrils in response to resistance and aerobic training are ways to increase muscle strength and performance (besides overall better health!).
Aging awareness is the ability to reflect on and interpret the changes in your body associated with aging. Are you only “as old as you feel?” There are many ways to measure your awareness of aging:
- Subjective age: the age you feel.
- Age identity: preferred or ideal age?
- Self-perception of aging: unconscious feelings about aging.
- Attitudes towards aging: attitudes, behaviors, thoughts, and stereotypes about aging.
You may have drawn conclusions about how you will age based on your perception of the aging process. There are aging differences based on sex and gender. For example, many women expect menopause as a time of weight gain, fatigue, sleeping problems, hot flashes, and postmenopausal brain fog.
While many, or even all, of these things may occur, your awareness of the process and preconceived ideas about how menopause will affect you can make a difference. For example, several studies have shown that decreased activity after menopause, not necessarily just hormone changes, causes postmenopausal weight gain.
How old do you feel? If your answer is older than your chronological age. Your first step is to see your healthcare provider for a physical exam. If you get a clean bill of health, do an overall assessment of your physical health, sexual health, and cognitive health. Then, start taking steps to improve how you look and feel.
Decreased processing power in the brain can cause slower information processing. As a result, older adults may find that it is harder to focus attention on multiple tasks at the same time. Like muscles, brain tissue is also plastic, which means that you can strengthen your attention skills. You can also increase blood flow to the brain by engaging in aerobic exercise. Increased blood flow improves metabolic processes in brain cells. How this occurs is not known.
Driving is one skill that requires the ability to switch attention frequently. Strengthening your ability to focus your attention on multiple tasks at once or on unfamiliar tasks may help you retain your driving skills much longer in life.
Changes in working memory can occur with aging. However, how and why these changes occur is not well understood. Brain scans show that older adults may use different parts of their brains for working memory than younger adults.
Long-term memory is the ability to retrieve information that has been stored in the brain at some point. Episodic memories are memories that you have personally experienced. They occur in a setting at a certain point in time. People may have difficulty storing new episodic memories, encoding them in the brain, or retrieving them with age.
Semantic memory is the factual knowledge you have stored. Semantic knowledge does not seem to be as affected by the aging process. Older adults typically have a richer semantic knowledge of the world than younger adults.
Autobiographical memories are episodic and semantic memories about your past. Autobiographical memory is largely preserved with age. Events that occurred between the ages of 15 and 25 are most easily recalled, perhaps due to the emotionality attached to some of these events.
Procedural knowledge is understanding how to do something. Since learning new skills requires extensive practice, procedural knowledge is hard to attain but typically persists throughout your lifespan.
While processing speed may decrease with age, many brain functions remain stable or even improve. Like with muscles, the best way to improve, or at least maintain cognitive function, is to challenge your brain regularly.
Learning new skills, forming new memories, and improving vocabulary and language skills are all ways to exercise your brain. Older adults may find that it takes a little longer to learn something new, and they may need to work a little harder to encode recent memories. But, it is worth the effort. You have accumulated a lifetime of knowledge and experience, and keeping your cognitive function healthy allows you to enjoy the ability to access these memories and thoughts throughout your lifespan. Making healthy lifestyle changes helps protect you from age-related changes in your nervous system.
Start a cognitive health treatment plan today!