Sacromere is the structure and functional unit of the skeletal muscle, it is also called the basic contractile unit of the muscle.

Each sarcomere extends between two (2) lines of myofibril. This each myofibril contains many sarcomeres arranged in series throughout its length. When the muscle is in relaxed state, the average length of each sacromere in 2-3  microns.

Sacromere consist of many thread like structure called myofilaments. Two types of myofilaments are;

  • Action filaments
  • Myosin filaments

Actin filaments with a diameter of 20A and a length Iµ. These filaments extend from either side of the ‘z’ lines, run across I band and enter into ‘A’ band up to ‘H’ zone.

Myosin filament are thick filament with a diameter of 115A0 and  length  of 1.5µ. These filaments are situated in A band. There are some lateral  process (projections) or cross bridges arising from myosin filaments. These bridges have enlarged structures called myosin heads at their tips.

The myosin heads attach themselves to actin filaments. These head pull the actin filaments during contraction of the muscle by means of a mechanism called sliding mechanism of ratchet mechanism.

During the contraction of the muscle, the action filaments glide down between the myosin filaments towards the centre of ‘H’ zone and approach the corresponding actin filaments from the next ‘z’ line (see the figure below). The ‘z’ lines also approach the ends of myosin filaments, so that, the ‘H’ zones and ‘I’ band are shortened during contraction of the muscle.

During the relaxation of the muscle the action filaments and ‘z’ lines come back to the original position.

Sacrcomere is resting muscle(A) and contracted muscle (B). During contraction Z lines come close, H zone and I band are reduced and no change in A band.


Protein energy malnutrition is a kind of malnutrition where by the protein, energy and nutrient is not sufficient for the body to make use of.

Protein-energy malnutrition can also be referred to as a form of malnutrition where there is inadequate calorie or protein intake.


  1. Kwashiorkor
  2. Marasmus

Kwashiorkor: This is caused by inadequate supply of protein   in the diet which can repair warm out tissue.

Marasmic Kwashiorkor mark protein deficiency and also calorie insufficiency signs present, sometimes referred to as the most severe form of malnutrition

Protein energy malnutrition may be secondary to other conditions such as chronic renal disease or cancer cachexia in which protein energy washing may occur.

Symptoms  of Kwashiorkor

  1. Low body weight
  2. Muscle waster
  3. Large belly or a stomach that sticks out
  4. Easy pulling of the hair
  5. It leads to Oedema (which has to with the enlargement of liver. It can be attributed to increase blood corlisol)

Causes of Kwashiokor

  1. Poverty
  2. Inadequate food supply

Marasmus is a severe form of malnutrition. This disease is generally seen in the infants. The disease occurs due to shortage of basic nutrients, protein, vitamins and calories to the body. This disease is generally seen in children.

 Symptoms  of Marasmus

The symptoms  of marasmus often depend upon the degree of malnutrition. Following are some symptoms.

  1. Chronic diarrhea 8.        Prolonged vomiting
  2. Dizziness 10.      Diarrhea
  3. Fatigue 12.      Delay in healing of wounds
  4. Sever weight loss 14.      Muscle atrophy
  5. Change in level of  Consciousness                6.        Paralysis of legs.
  6. Loss of bowel and bladder control              9.       Diarrhea
  7. Lethargy 13.     Hypotonia
  8. Growth retardation


  1. Poverty 2.        Inadequate food  supplies
  2. Contaminate water 4.        Poor and unbalanced diet
  3. Deficiency of vitamin A, E and K

Treatment of Marasmus

  1. Vitamin B5 treatment             2.        Treatment  for hypoglycemia
  2. Treatment for hypothermia             4.        Treatment for dehydration


What is Sacromere?

Sacromere is the basic component of cross striated myofibril that is located in the muscle. These are made up multiproteins and are made up of three various types of filament systems. The striated muscles where thesacromere  is located are the organs which help in rapid movement with a force in a particular direction.Sacromere is also called a beautiful protein macromolecular machine owing to its complex structure that is based on the polymers and protein molecule’s modular design.


What are the three properties of Sacromere?

These properties are better understood in context with the interaction between the proteins and the structural molecule of the Sacromere. Sacromere has three distinct properties that are very helpful for its functioning:

  • Ability to become short efficiently and rapidly
  • Capacity to switch on and off within a matterof milliseconds
  • Structural self regularity and precision self-assembly

What are the three main functional classes of sacromere?

Sacromere constitutes three vital functional classes:

  • Contractile:The example of contractile class is myosin and actin proteins which evolve into polymetric filaments and are responsible for the shortening and rapid reaction associated with sacromere.
  • Regulatory:The regulatory proteins of sacromere are troponin and tropomysosin which binds to actin and help in the regulation of actin-myosin interaction. This results in contraction due to shift in the concentration of Ca2+.
  • Structural:The structural proteins help in stabilizing, integrating and laying down the structure of sacromere during development.

What is the molecular composition of sacromere?

Sacromere is a complex structure constituting nearly 28 different types of proteins. The thick as well as the thin myofilaments are polymers of protein molecules associated covalently. When the myosin and actin are extracted the filaments disappear. Together actin (20%) and myosin (54%) constitute around 70% of myofibrilllar proteins. Along with myosin, the thick filament also contains certain nonprotein myosin. These are the myosin binding proteins- C,H and X which are present in the middle third of each thick filament. The thin filaments also constitute troponin and tropmyosin apart from actin.

What are the functions of Sacromere?

The two proteins- actin and myosin perform the function of conversion of chemical elements into physical elements when contraction occurs in the muscle. The actin-myosin protein complex is also thought to hydrolyze ATP and hence is connected in the process of energy contraction. The synthetic thread of actomyosin was also found to contract when added to ATP thereby linking chemical process with mechanical work.

 What are the diseases of Sacromere?

Mutations within the sacromeric proteins can lead to cardiac arrest. Familial hypertrophic cardiomyopathy is an autosomal disease which is a result of ventricular hypertrophy, myocyte hypertrophy and disarray.


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