Muscles - Anatomy

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Muscles - Anatomy
Muscles - Anatomy

Video: Muscles - Anatomy

Video: Muscles - Anatomy
Video: THE MUSCLES SONG (Learn in 3 Minutes!) 2024, March
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The muscles

The human body is made up of over 650 muscles. The smallest movement can only take place with the help of muscles. This happens consciously on the one hand, but also covertly, such as with the heartbeat or digestion…

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The muscles are divided into three groups:

  • Skeletal muscles: These muscles are also called striated muscles. It can be controlled arbitrarily, that is, consciously activated. Most of the striated muscles are attached to the skeleton and are responsible for active movements.
  • Organ muscles: These muscles are also called smooth muscles. In contrast to the skeletal muscles, it does not appear striped, but smooth. It is found in organ systems such as the stomach, intestines, bladder, blood vessels etc. It is involuntarily controlled by the nervous system and cannot be consciously influenced.
  • Heart muscles: The heart is also a muscle, it is a special striated musculature.

Building the muscles

The striated muscles responsible for the musculoskeletal system have a special structure that is connected to the brain. At the beginning of every movement there is a nerve stimulus that is transmitted from the brain to the muscles via the spinal cord. This is followed by a cascade of reactions that ultimately leads to tension in the muscle (muscle contraction).

A muscle consists of individual, hierarchically arranged structural elements. The smallest unit is the so-called myofibril. Many myofibrils form a muscle fiber that is up to 15 cm long and up to 100 µm wide. Many muscle fibers are combined to form muscle fiber bundles. The union of several muscle fiber bundles forms the actual muscle. The muscle itself is embedded in a connective tissue sac (fascia) that merges into tendons. The muscle is attached to the bone by tendons.

At each muscle fiber are so-called motor end plates, which emanating from the brain nerve stimulus over the muscle nerve (motor neuron received). This nerve delivers the decisive electrical impulse that excites the muscle and causes it to work actively - it provides the initial spark, so to speak. A muscle nerve can supply up to 1,000 muscle fibers at the same time. The more motor units a muscle has, the finer its movement can be.

A myofibril consists of two different protein building blocks that do the actual work of the muscle, actin and myosin. Actin filaments appear light under the microscope, myosin filaments are thicker and darker. Together this gives the picture of the horizontal stripes.

The muscle contraction

If a nerve stimulus reaches the motor end plate of the muscle, the transmitter acetylcholine is released. This mediates between nerve and muscle, creating an action potential. As a result, the calcium concentration in the muscle fiber increases. Actin and myosin filaments slide into each other again and again, the actual contraction of the muscle.

In order for the muscles to be able to work actively, they are dependent on a special "energy currency", the adenosine triphosphate (ATP). In the body, it is primarily obtained from glucose and fatty acids using oxygen (aerobic energy metabolism). Under very high stress, ATP can also be produced without oxygen (anaerobic energy metabolism).

For more information, see Exercise and Energy Metabolism.

Tendons

Sights are white, shiny, fibrous connections between muscles and bones. They consist of connective tissue and effect the transmission of force from the muscle to the bone. Without tendons, no movement would be possible, so to speak. The tendons also contain blood vessels and nerves that merge into the muscle.

Tendon sheaths and bursa

Tendon sheaths and bursa reduce possible friction points under the influence of movement. You thus prevent damage to tendons. Certain tendons are enclosed by a tendon sheath (vagina tendinis) like a sliding tube. This is filled with a viscous liquid so that a tendon can slide in such a cavity. Tendon sheaths are found in the body mainly on the hands and feet, as the frictional resistance is very high here when moving.

For more information on exercise and its positive effects on health, see Live Healthy: Exercise