Structure of myofibril, Biology

Assignment Help:

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.

Related Discussions:- Structure of myofibril

State long-term benefits of exercise, State four long-term benefits of exer...

State four long-term benefits of exercise. The long-term advantages of exercise are: a) Enhance in size of the muscles used, b) Decrease of heart rate and c)  Enhance

Modern theory in biology, Modern Theory Naturalistic theory: Accordin...

Modern Theory Naturalistic theory: According to this theory Life originated upon our earth spontaneously from nonliving matter. But there are two significant points in this r

Venipuncture - blood collection, Venipuncture : patient shoul...

Venipuncture : patient should be seated or supine for at least 20 minutes before sampling. An arm with an inserted intravenous line should be avoided. The median cubi

What are the disadvantages of mucoperiosteal flap, What are the Disadvantag...

What are the Disadvantages of mucoperiosteal flap More traumatic - flap is raised  Sutures are required and the next procedure of impression is delayed till afterthe suture

Explain oedema - clinical signs of kwashiorkor, Explain Oedema - Clinical S...

Explain Oedema - Clinical Signs of Kwashiorkor? Oedema: Oedema refers to accumulation of fluid in the tissues and usually begins with a slight swelling in feet gradually spread

Importance of meiosis, Meiosis becomes significant for the following reason...

Meiosis becomes significant for the following reasons. Constant Number of Chromosomes: It brings about a reduction in the chromosome number from a diploid (2n) condition to

Explain rifamycins-rifampin, Explain Rifamycins-Rifampin Rifamycins - R...

Explain Rifamycins-Rifampin Rifamycins - Rifampin, like isoniazid, is potentially hepatotoxic, and gas- trointestinal disturbances, morbilliform rash and thrombocytopenic purpu

Explain about gastric ulcers, Q. Explain about Gastric ulcers? Gastric ...

Q. Explain about Gastric ulcers? Gastric ulcers occur in the lesser curvature of the antrum of stomach. A gastric ulcer appears to be caused by reflux of bile and factors that

What are the types of digestion, What are the types of digestion and of dig...

What are the types of digestion and of digestive system of platyhelminthes? Flatworms have incomplete digestive systems and they show intracellular and extracellular complement

Centimorgan (cm), Centimorgan (cM) is the unit of measure of a statistical...

Centimorgan (cM) is the unit of measure of a statistical probability recombination frequency between the alleles. One centimorgan is equal to the 1% chance that a marker at one ge

Write Your Message!

Captcha
Free Assignment Quote

Assured A++ Grade

Get guaranteed satisfaction & time on delivery in every assignment order you paid with us! We ensure premium quality solution document along with free turntin report!

All rights reserved! Copyrights ©2019-2020 ExpertsMind IT Educational Pvt Ltd