Page 118 - 84 human physiolofy part-1

Chapter 6

Medical Mysteries

Sleep Twitches

The twitching phenomenon that happens in the early stage of sleep is called a hypnagogic massive
jerk, or simply a hypnic jerk. It has also been referred to as a sleep start. There has been little research
on this topic, but there have been some theories put forth. When the body drifts off into sleep, it
undergoes physiological changes related to body temperature, breathing rate and muscular tone. Hypnic
jerks may be the result of muscle changes. Another theory suggests that the transition from the waking
to the sleeping state signals the body to relax. But the brain may interpret the relaxation as a sign of
falling and then signal the arms and legs to wake up. Electroencephalogram studies have shown sleep
starts affect almost 10 percent of the population regularly, 80 percent occasionally, and another 10
percent rarely.

Muscle movement or twitching also may take place during the Rapid Eye Movement, or REM,
phase of sleep. This also is the time when dreams occur. During the REM phase, all voluntary muscular
activity stops with a drop in muscle tone, but some individuals may experience slight eyelid or ear
twitching or slight jerks. Some people with REM behavioral disorder, or RBD, may experience more
violent muscular twitching and full-fledged activity during sleep. This is because they do not achieve
muscle paralysis, and as a result, act out their dreams. Researchers think that people with RBD lack
neurological barriers that define the different stages of sleep. New research done by the Mayo Clinic
and published in the July 2003 issue of Sleep Medicine shows that melatonin can help lessen RBD
symptoms.

Resources:

Sleep twitches, or myoclonic jerks, as they are sometimes called, are explained in easily
understood language on this website.
Learn more about REM Behavior Disorder, or RBD, and treatment for sufferers.
View information about various sleep disorders such as insomnia, apnea, and narcolepsy.

Microbiology

Clostridium tetani
Tetanus
Normally a nerve impulse initiates contraction of a muscle. At the same time, an opposing muscle
receives the signal to relax so as not to oppose the contraction. Tetanus toxin blocks the
relaxation, so both sets of muscle contract. The usual cause of tetany is lack of calcium, but
excess of phosphate (high phosphate-to-calcium ratio) can also trigger the spasms.

Clostridium botulinum
Infant botulism (floppy baby syndrome) the most common form of botulism in the U.S. of the
four forms of botulism.
If ingested, the toxin is absorbed in the intestine, goes to the blood, and on to the nervous system.
It acts on the peripheral nervous system by blocking the impulse that is normally passes along to
the nervous system. By clocking the impulse that is normally passed along to motor end plates so
the muscle contraction can be released, resulting in paralysis.

118 | Human Physiology