7 Common Myths about the Human Body

1. Reading in the dark will hurt your eyes. 
When reading in dim light your eye muscles receive mixed signals: Relax to collect the most light and at the same time, contract to maintain a focused image.  Your eye muscles are working harder which may result in strain. This can cause headaches, back and neck aches, blurred vision, or sore eyeballs. So although you may strain your eyes you will not weaken them.

2. Knuckle Cracking Causes Arthritis
As a rule, painless cracking of joints is not harmful. The “cracking” sound that you hear is usually from negative pressure pulling gas temporarily into the joint.  If you feel pain from cracking your knuckles there could be an underlying abnormality of the joint structure, such as an injured ligament or loose cartilage.  You should consult your Doctor if you have pain while cracking your knuckles.

3. You will catch a cold if you go out in the freezing weather with wet hair
“You cannot catch a cold from being cold; you catch a cold from germs and being cold has nothing to do with it. Plenty of tests have been conducted proving this.” – Bill Nye
Where did this common refrain come from? Many think that French chemist Louis Pasteur is partly to blame. In 1878, he noticed that chickens where immune to anthrax and postulated that it was because of their high body temperature. He began his experiment by exposing chickens to anthrax and then dipping their feet into icy cold water to see if this affected their odds of catching the disease. All of the chickens developed anthrax and died. He then repeated his experiment, but this time he wrapped the exposed chickens in a warm blanket. All the chickens survived.  Amazingly, this experiment and others are what led Louis Pasteur to discover vaccines.

4. You Only Have Five Senses
Researchers at Harvard Medicine believe there are at least 9 senses and most researchers believe there are at least 21 senses! 

• Pressure
• Itching
• Time
• Thirst 
• Hunger
• Thermoception:  Ability to sense heat and cold.  
• Proprioception:  This sense gives you the ability to tell where your body parts are, relative to other body parts. 
• Tension Sensors:  Allow the brain the ability to monitor muscle tension.
• Nociception:  Pain receptors.
• Equilibrioception:   The sense that allows you to keep your balance and sense body movement in terms of acceleration and directional changes. 
• Stretch Receptors:  These are found in such places as the lungs, bladder, stomach, and the gastrointestinal tract.  
• Chemoreceptors:  Involved in detecting blood born hormones and drugs.  It also is involved in the vomiting reflex.
• Magentoception:  This is the ability to detect magnetic fields.

5. Eating carrots improves your vision
One of my favorite WWII myths! This myth was developed as a cover story for the new British Radar system.  Not wanting to alert the Nazi’s to their new technology, they released various pieces of propaganda.  They stated that the new detection method was a result of pilots eating more carrots and being able see better and more clearly in the dark.  Their propaganda campaign was so successful that many British people grew and ate more vegetables at this time. 
This isn't a complete myth; carrots contain Vitamin A, which is very important for eye health.

6. Urinating on a Jellyfish Sting will Soothe the Pain
Urine and freshwater are not recommended to soothe a jellyfish sting.  Any change in the salts of the cnidocyte can cause the nematocysts to release more venom, causing more pain.  It is recommend to wash the area with saltwater which will deactivate the nematocysts.

7. You Can Cure a Snake Bite by Sucking Out the Poison
This does not work and can actually cause more harm to the affected area. In recent studies, suction did not remove a significant quantity of poison and caused necrosis (death of cells) in the suctioned area.  You can also cause further poisoning in the mouth’s mucous tissue if you use your mouth to suction. You can also introduce new bacteria from the mouth to the wound, further complicating the problem.
        What to do instead:

• Keep the person calm. Stress increases the blood flow which has the effect of moving the poison through their system faster.
• Keep the bitten limb below the person's heart level to minimize blood moving through the body.
• Keep the person as still as possible and remove items which may constrict swelling limbs.
• Call for help.

---