MUSCULAR SYSTEM PART 1 IN ENGLISH

                                                    

                               MUSCULAR SYSTEM PART 1 IN ENGLISH

               watch my youtube video to understand this topic in easy way-

  https://www.youtube.com/watch?v=jX7ndhBuYbs

          MUSCULAR SYSTEM-

          MUSCLES-

          Muscles are contractile tissue. Muscles are responsible of all types of movements of our body. Muscles are also known as machines of our body. The scientific study of muscles is known as  myology

          FUNCTIONS OF MUSCLES-

          1. Movement- The muscular system’s main function is to perform movement. When muscles contract, they help in our movement such as  walking, running, swimming and even small movements such as speaking eating writing facial expressions etc.

          2. Posture- Skeletal muscles help keep the body in the correct position when someone is sitting or standing.

          3. Stability of joints- Muscle tendons stretch over joints and help in maintaining joint stability.

          4. Blood circulation- The heart consists of heart muscles that pumps blood throughout the body. Smooth muscle in the arteries and veins plays a further role in the circulation of blood around the body. Movement of muscles around big veins also help in return of blood towards heart.

          5. Respiration- Normal Respiration is assisted by muscular action of intercostal muscles and diaphragm. When someone wants to breath more deeply, it requires help from other muscles, including those in the abdomen, back, and neck.

          6. Digestion- the process of digestion starts in mouth and muscles of mastication help in making bolus tongue pushes it inside. Peristalsis movement is also carried out by muscles of GIT. From rectum, more muscles contract to pass the food out of the body as stool.

          7. Urination- smooth muscles of urinary bladder contract to push urine outside through urethra. 

          8. Childbirth- Muscle of uterus help in pushing the baby out. Pelvic flour muscles also help in the process of childbirth.

          9. Vision- Six skeletal muscles around the eye control its movements. These muscles work quickly and precisely, and allow the eye to: maintain a stable image, scan the surrounding area and track moving objects

          10. Temperature regulation- Almost 85 percent  of the heat a person generates in their body comes from contracting muscles.

CLASSIFICATION OF MUSCLES-

Ø  The Human body contains three types of muscle tissue:

Ø  Skeletal muscles ,

Ø  Smooth muscles and

Ø  Cardiac muscles.

SKELETAL MUSCLES-

Ø  Each of skeletal muscles is a separate organ composed of hundreds to thousands of cells, which are called muscle fibers because of their elongated shapes. This type of muscle is also called voluntary muscle because there is conscious control over it

Ø  A skeletal muscle consists of a large number of muscle fibres. The entire muscle is covered in a connective tissue sheath called the epimysium.

Ø  Within the muscle, the cells are collected into separate bundles called fascicles, and each fascicle is covered in its own connective tissue sheath called the perimysium. 

Ø  Within the fascicles are the individual muscle cells, each wrapped in a fine connective tissue layer called the endomysium.

Ø  The connective tissue coverings blend together at each end of the muscle to form the tendon, which connects the muscle to the bone.

Ø  Often the tendon is rope-like, but sometimes it takes the form of a broad sheet called an aponeurosis.

Ø  The most important components of a skeletal muscle are the muscle fibers themselves. The diameter of a mature skeletal muscle fiber ranges from 10 to 100 micrometer. The typical length of a mature skeletal muscle fiber is about 10 cm  although some are as long as 30 cm .

Ø  the muscle cells are  roughly cylindrical in shape, lying parallel to one another, with a distinctive banded appearance consisting of alternate dark and light stripes.

Ø  The multiple nuclei of a skeletal muscle fiber are located just beneath the sarcolemma , the plasma membrane of a muscle cell. Within the sarcolemma is the sarcoplasm, the cytoplasm of a muscle cell. The contractile elements of muscle fibers, the myofibrils, contain overlapping thick and thin filaments

Ø  Overall, there are two thin filaments for every thick filament in the regions of filament overlap. The two contractile proteins in muscle are myosin and actin, which are the main components of thick and thin filaments. One set of this system is known as sarcomere. A sarcomere extends from one Z disc to the next.

CONTRACTION OF SKELETAL MUSCLES-

Ø  The skeletal muscle cell contracts in response to stimulation from a nerve fibre. Muscle contraction occurs because myosin heads attach to and “walk” along the thin filaments at both ends of a sarcomere, pulling the thin filaments towards the M line.

Ø  As the thin filaments slide inward, the Z discs come closer together, and the sarcomere shortens. the lengths of the individual thick and thin filaments do not change. Shortening of the sarcomeres causes shortening of the whole muscle fiber, which in turn leads to shortening of the entire muscle.

SMOOTH MUSCLES-

Ø  Smooth muscles are not under conscious control, so these are also known as involuntary muscles. The muscle cells are small, have only one nucleus and are spindle shaped

Ø  Smooth muscle forms sheets in the walls of hollow organs and tubular structures to regulate diameter and propel substances through tracts. All internal organs contains smooth muscles Smooth muscles are normally innervated by branches of the autonomic nervous system and control the movement of these muscles. 

CARDIAC MUSCLES-

Ø  The myocardium is composed of specialised cardiac muscle found only in the heart. It is not under voluntary control but is striated, like skeletal muscle. Each fiber or cell  has a nucleus and one or more branches.

Ø  Cardiac muscle cells appear striated or striped under a microscope. These stripes occur due to alternating filaments that comprise myosin and actin proteins. Intercalated discs connect cardiac muscle cells. Gap junctions inside the intercalated discs relay electrical impulses from one cardiac muscle cell to another

Ø  Physiology of contraction of cardiac muscles is same as of skeletal muscles but these are not under voluntary control. They have self rhythmic power supported by heart pacemaker. Rhythm is also affected by autonomic nervous system (sympathetic and parasympathetic stimulation)