Muscles
that the skeleton is the passive element of the motor system;
that the skeletal muscles are built from a striated muscle tissue.
to describe the functions of the muscle system;
to show the connection between the structure of the muscle and its functions;
to explain the antagonistic nature of how muscles function;
to describe how bones, joints, muscles and tendons work together in the motor system.
Skeletal muscles
Striated muscles of the skeleton are the active part of the motor systemmotor system. They are attached to bones and allow their movement in regard to each other (and at the same time the movement of the body), participate in maintaining the vertical posture and facilitate breathing. A human being to a greater degree controls the movements of his skeletal muscles, thanks to which they can be exercised.
Skeletal muscles have different sizes, shapes, placements and functions.
Some of them, like biceps brachii, called biceps, is a surface muscle and you can feel it and observe how it works. Other muscles are invisible, situated deep under the skin or very small. Facial muscles, also know as mimic muscles, have one side attached to the skull and the other to the skin of the face. They allow us to express various emotions.
The most important muscle when it comes to its movements is the diaphragm. It separates the abdominal cavity from the chest cavity. Its contraction causes us to inhale.
How the arm muscle is built
Skeletal muscles are mainly fusiform. The main muscle mass is the muscle bellymuscle belly which is composed of long fibres that can contract. At its ends there are tendonstendons, which attach muscles to the bones. Tendons are built of connective tissue which cannot contract, but it tenses during muscle contraction.The muscle belly at one end can be split and create muscle heads, just like in the case of a biceps, which has two heads.
You know that tendons appear on both sides of the muscle belly and are the point of connection to the bone. Decide in how many places the quadriceps is attached to the bones.
How skeletal muscles work
In order to cause movement, a muscle must contract. The contraction happens thanks to protein fibers that are present in muscle cells. Reacting to a signal that comes from the nervous system (neural impulse) they slip between each other thus making the entire muscle thicker and shorter. When it is attached to 2 bones (which are connected together by a joint), over the joint and under the jointjoint, it becomes shorter, bringing the bones closer to each other.
The majority of body movements is based on the work of pairs of muscles (single or working as a group) - when one of them contracts, the other loosens. Bones and muscles work closely together while moving, and together they act like levers. When we bend the forearm, the biceps contracts, its tendons are tense and bring the bones of the forearm closer to the arm. At the same time the antagonist of the biceps, the triceps, must be loosened. The triceps is responsible for extending the forearm in the elbow.
The biceps is situated in the front part of the arm, whereas the triceps is located in the back part of the arm. The muscle which contracts and brings the forearm closer is the flexor, and the one that is loosened at that time is the extensor. While the flexor contracts, the limb becomes bent in the elbow. The work of the biceps and triceps is antagonistic in nature.
On the illustration below there is the quadriceps femoris muscle. Decide, whether the statemets below regarding that muscle are true or false.
| True | False | |
| It is a flexor, as it contracts when we bend the lower leg. | □ | □ |
| It is a flexor, as it relaxes when we bend the lower leg in the knee. | □ | □ |
| It is the extensor, as it relaxes itself while we bend the lower leg. | □ | □ |
| It is the extensor, as it contracts when we extend the lower leg in the knee. | □ | □ |
Match the pairs: English words with Polish definition.
miejsce przyczepu mięśnia do kości zbudowane z niekurczliwej, ale elastycznej tkanki łącznej, środkowa część mięśnia zbudowana z kurczliwych włókien mięśniowych, część organizmu złożona ze szkieletu, połączeń kości i mięśni szkieletowych, odpowiedzialna za utrzymanie postawy ciała i ruch organizmu, ruchome połączenie kości składające się z powierzchni stawowych, jamy stawowej oraz torebki stawowej
| muscle belly | |
| joint | |
| tendon | |
| motor system |
Summary
Skeletal muscles are the active part of the motor system, whereas bones and their connections are the passive part.
Bones, muscles, joints and tendons work with each other to make our bodies move.
Muscle is composed of a muscle belly able to contract and of tendons.
Movement of the muscles is realized in an antagonistic way.
The motor system works closely with the cardiovascular system and the nervous system.
Keywords
joints, muscles, muscle head
Glossary
brzusiec – środkowa część mięśnia zbudowana z kurczliwych włókien mięśniowych
staw – ruchome połączenie kości składające się z powierzchni stawowych, jamy stawowej oraz torebki stawowej
ścięgno – miejsce przyczepu mięśnia do kości zbudowane z niekurczliwej, ale elastycznej tkanki łącznej
układ ruchu – część organizmu złożona ze szkieletu, połączeń kości i mięśni szkieletowych, odpowiedzialna za utrzymanie postawy ciała i ruch organizmu