THE CENTRAL
NERVOUS SYSTEM The central nervous system (CNS) is like the body’s internal quarterback. This amazing and complicated mechanism simultaneously controls every aspect of our human systems. From respirations to digestion, the CNS is constantly watching and adjusting what your body needs. Best of all, it does this without the body even knowing about it.
By using nerve cells, the CNS works to send thousands of messages throughout the body—all telling a different part of the body what to do. There are more nerve cells in the brain than there are stars in the Milky Way! In fact, if they were lined up, it would form a 600-mile long line.
The right side of the brain controls the left side of the body, while the left side of the brain controls the right side of the body. As we age, our brain begins to deteriorate; losing up to a gram each year. The health of your brain is exceedingly important. Sodium and potassium are necessary nutrients to ensure proper function of the nervous system. Vitamin B is also beneficial for brain transmission.
VOLUNTARY & INVOLUNTARY
The central nervous system is separated into two specific systems: the voluntary and involuntary nervous systems. The voluntary nervous system controls things we consciously tell our bodies to do. Tasks such as walking, talking, eating or writing are all under our voluntary control.
The involuntary nervous system controls all of the things we don’t have to remind ourselves to do. These include breathing, heart rate, blood pressure and digestion. Imagine how busy you would be if you had to remember to take a breath every 5 seconds while telling your heart to beat once per second or so. There would be no time for anything else. You’d never get any sleep!!
SYMPATHETIC & PARASYMPATHETIC
The involuntary nervous system is made up of two separate divisions as well. These are called the sympathetic and parasympathetic nervous systems. Basically, the sympathetic division speeds things up while the parasympathetic slows things down.
When the body is in need of additional blood flow and oxygen, the sympathetic nervous system has the
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ability to tell the body to increase its heart rate and breathing to provide the necessary increases. It can accomplish much of this by a process called shunting, where the body is capable of moving blood to the areas where it is required. This becomes important in many medical emergencies.
The parasympathetic nervous system acts as the balance to the sympathetic. It acts to reduce heart rate, reduce blood pressure, slow respirations and bring your system back into balance. Life is a constant tug-of-war between the sympathetic speeding you up and the parasympathetic slowing you down.
A good example of these systems at work is during a near-miss car accident. Your initial reaction is an increase in heart rate, blood pressure and respiratory rate. A stress reaction! After a few minutes, you begin to calm down, your breathing and heart rate slow and your vital signs return to normal. Survival is all about the sympathetic and parasympathetic systems working together.
CIRCADIAN RHYTHMS
A circadian rhythm is a 24-hour cycle in biochemical, physiological and behavioral processes. Circadian rhythms have been widely observed in plants and animals, although they are present in many other species. Circadian rhythms are built-in and self- sustained within the body. These rhythms can be adjusted primarily by daylight and darkness, but can also be affected by factors such as time zones, fatigue and sleeplessness.
The circadian rhythm is linked to the light–dark cycle. Humans kept in total darkness for extended periods of time will eventually function with a free-running rhythm. The sleep–wake cycle will change without light.
The effects are amplified for crew members flying through multiple time zones and regions of sunlight/ darkness in one 24-hour period. Pilots and flight attendants may also spend many hours awake both day and night and are often unable to maintain normal sleep patterns. This situation can lead to fatigue and jet lag, which is a temporary disruption of the circadian rhythms brought on by passing through time zones.
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