MUSCLES

             Muscle is a tissue composed of cells or fibers, the contraction of which produces
movement in the body. There are three types of muscles:

1 - Smooth muscle - controlled by the autonomic nervous system; may either be generally inactive or then respond to neural stimulation or hormones or may be rhythmic.

2 - Cardiac muscle - found in the heart, acts like rhythmic smooth muscle, modulated by neural activity and hormones.

3 - Skeletal muscle - move us around and responsible for most of our behavior; most attached to bones at each end via tendons.

The muscle is composed of subunits called fascicles. Fascicles are bundles of individual muscle fibers. Each fiber is one elongated cell that may extend for the length of the muscle. Each muscle fiber cell has several nuclei (unlike most cells, which have only one), and is segmented into distinct sectional bands. Within each muscle cell are numerous myofibrils, which also extend for the length of the muscle cell. Sarcomeres are the basic contractile subunit of myofibrils.

Muscle growth is a specialized form of protein synthesis. As we saw above, a steroid hormone (testosterone) enters the muscle cell by diffusing directly across the cell membrane, combines with a receptor in the cell and then stimulates gene transcription and protein formation via the DNA -> mRNA -> tRNA -> protein pathway. Specific receptors and genes are involved.

Muscles In The Body

LIGHTNING

              Lightning is a brilliant electric spark discharge in the atmosphere, occurring within a thundercloud, between clouds, or between a cloud and the ground. This enormous electrical discharge is caused by an imbalance between positive and negative charges. During a storm, colliding particles of rain, ice, or snow increase this imbalance and often negatively charge the lower reaches of storm clouds. Objects on the ground, like steeples, trees, and the Earth itself, become positively charged—creating an imbalance that nature seeks to remedy by passing current between the two charges.
             Some scientists think that Lightening may have played a part in the evolution of living organisms. The immense heat and other energy given off during a stroke have been found to convert elements into compounds that are found in organisms.
             It's true that being inside a building when lightening strikes is your safest bet, but that doesn't mean you shouldn't take some precautions. If a building gets struck the electrical current will most likely travel through the wiring or plumbing before going into the ground. That's why you should stay off of corded phones (cellular and cordless are okay) and away from running water (so no showers or hand- or dish-washing). Don't use stoves, computers, or anything else that's connected to electricity

Lightning

WHAT MAKES US FEEL TIRED?

                            All day long our muscles are used as we do different types of work. The energy comes from A.T.P or Adenosine Triphosphate which gets converted into lactic acid. This must be removed constantly to allow the muscles to function. There are also other chemicals collectively called fatigue toxins which go round the body in the blood. So not only does your hand feel tired after you've been using it for a long while, your entire body including the brain experiences fatigue.
                             Rest is the best cure for fatigue. However a change in activity can also refresh you. You can rest by doing something different e.g. go for a walk, play a game, or sing. Activity increases the respiration, improves blood circulation and makes the glands more active and the toxins are removed faster from the tired parts of the body. However if you are extremely fatigued you will find yourself dropping off to sleep even if you try to do something else.

A Tired Person

                           

DO PLANTS SLEEP?

                Plants do not relax their muscles and close their eyes. Nor do they lie down and sleep as we do. However, since the food manufacturing activity in the plants depends on the sun, they do stop working at sunset. In some plants the "sleep" movements are quite obvious since their leaves fold up in the dark. At sunrise they begin their work again.

Example Of Sleeping Plants