Structure of myofibril, Biology

STRUCTURE OF A MYOFIBRIL -

  1. The dark bands of the myofibril are termed the A-bands (Anisotropic bands).
  2. Each A-band has at its middle a light zone called H-zone (Henson's line).
  3. The light bands are also called I-bands (Isotropic bands).
  4. Each I-band has at its centre a dark membrane termed the Krause's membrane or Dobie's line or Z disc or Z-line (Zwischenscheibe line).
  5. The sarcolemma is invaginated to form T -tubules (Transverse tubules).
  6. The T-tubules are present at the level of Z-line.
  7. The T-tubules form a simple mechanism of transportation of nuirients and carry the signals for contraction of the myofibrils from the sarcolemma to the interior.
  8. The part of the myofibril between two successive Z-lines is called sarcomere.
  9. Therefore, the sarcomere comprises A-band and half of each adjacent I-band.
  10. A sarcomere is about 2 to 3 mm long.
  11. The sarcomere is the functional unit of contractile system in muscle. In fact each sarcomere is a bundle of primary and secondary filaments.

204_structure of myofibril.png

(i)       Primary Filaments (= Myosin Filaments). The primary filaments are thicker and confined to the A-bands only.

They are free at both the ends. They are composed of myosin (protein) and bear minute projections called cross- bridges of the protein meromyosin.

(ii)      Secondary Filaments (= Actin Filaments). The secondary filaments are thinner and occur in I-bands, but extend for some distance into the A-bands between the primary filaments. This partial over lapping of the primary fila- ments by the secondary filaments gives dark appearance to the Abands. The secondary filaments are composed of the proteins actin, tropomysin and troponin. They are attached to the Z-lines by one end and are free at the other end. The secondary filaments are more numerous than the primary filaments. Six secondary filaments surround each primary filament. "

  1. The major component of muscle is water. Potassium is the most abundant mineral element in muscle.
  2. Other minerals such as sodium, calcium, phosphorus and magnesium are present only in traces.
  3. Muscles store glycogen. They have oxygen carrying pigment myoglobin or "muscle haemoglobin".
  4. Muscles also contain ATP, phosphocreatine, creatine, urea, etc.
Posted Date: 10/1/2012 3:52:54 AM | Location : United States







Related Discussions:- Structure of myofibril, Assignment Help, Ask Question on Structure of myofibril, Get Answer, Expert's Help, Structure of myofibril Discussions

Write discussion on Structure of myofibril
Your posts are moderated
Related Questions
what are the origin, morphology, active constituents, uses and market preparation of tanco beans

Q. What are biopolymers? Ans. Polymers are macromolecules made by the union of several smaller identical molecules, called monomers. Biopolymers are polymers present in th

Stages of Research Process: Planning Stage The planning stage of research process  includes a  series of  interdependent steps consisting of 1)  conceptualizatioq of  the r

Explain Assessment of Iron Status? In view of widespread iron deficiency, it is important to have reliable and sensitive measures of iron status. Iron status can be assessed by


Q. What is the kind of cell division that allows sexual reproduction? What is gametogenesis? Meiosis is the kind of cell division that permits sexual reproduction since it redu

A haploid cell contains: A.one half of a complete set of chromosomes B.several complete sets of chromosomes C.the correct number of chromosomes D.two complete sets of chromosomes E

Food Web - Ecosystem A plant may serve as a food source for many herbivores simultaneously, e.g. grass plants can support deer, cow, grasshopper or rabbit. Similarly a herbivo

How nutritional status influences the age? The nutritional status influences the age-related rate of functional decline in many organ systems in the body. Nutrition is also an

Pulmonary edema is life-threatening condition and therefore, treated as a medical emergency. As is the case with chronic stable heart failure, identification and correction of any