Question

Where are mitochondria located in a relaxed muscle fiber?

	A.	In the t-tubules
	B.	In the sarcoplasmic reticulum
	C.	in the sarcoplasm
	D.	In the sarcolemma

Answer 1

Answer ---- ( C ) sarcoplasm

Sacroplasm is the cytoplasm of the muscle fiber or cell which contains the mitochondria and nuclei.

We will see the description of all the terms mentioned in options.

First the structure of the sarcomere which is the repeated unit of muscle fiber enclosed within two Z BANDS.

Sarcomere is the unit of the muscle fiber which repeated again and again between the two Z lines.

Z lines makes the boundaries of the sarcomere on each side and the area between the two z line is sarcomere which holds the thin filament called actin together.

Actin are binded to the z line which forms the boundary of the sarcomere.

There are two proteins called as the actin and myosin in which actin is the thin filament and the myosin is the thick filament.

Myosin is attached to the ATP which is the energy source for the muscles.

If the binding site of actin protein are exposed by the calcium ions then the myosin use to bind with them.

There are some band which are seen in sacromere.

Z line is the line which makes the boundary of the sarcomere and actin filaments are found attachment on them on both side and they firm's a repeating unit and area between two z line is sarcomere.

Just near the z line there is a I band also called isotropic band which is the area of the actin protein and no myosin are found here.

Following this there i another band called A band which is anisotropic band and this covers the full length of the thick filament and it has both type of filament.

After this there is a H zone which is the zone of myosin protein and no actin protein is found here.

And then there is M line which is the center line of the sarcomere.

Skeletal muscles are made from the tubular muscles cells that are called as myofibers and these myofibers have many myofibrils which are made from repeated unit of sarcomere. Whuch have these bands.

T- tubules are called as the transverse tubules which are the extensions in the plasma membrane of the skeletal and cardiac muscles and present in center of them.

They helps in conducting the better action potentials in these muscles and membranes and they also helps in regulating the calcium concentration in these muscles.

These tubules also make the heart contracts more forcefully when required.

These tubules are also formed from the phospholipid layer and they are directly attached to the sarcolemma of the skeletal muscles and at one end and there second end is in the tubular network form and use to several functions for the help.

Help in action potential and regulations of the calcium in cell.

These t- tubulins are present in both artrial and ventricular of the cardiac muscles and they are between 40 to 250 in nanometer and they are present in the area of the Z lines where the actin filaments are dominantly present.

They are also related to the calcium storage in the cells as the sarcoplasmic reticulum

Sarcoplasmic reticulum is the membrane bound structure present in the muscles cells , it is mainly involed in the storagr of the calcium ion and involved in the muscke contractions.

This cytoplasm of the muscle fiber is called as the sarcoplasm and the membrane of the muscles fiber is called as the sarcolemma and it has sarcoplasm. Sarcoplasm contains the nuclei and the mitochondria.

Sarcoplamsic has mainly a storage of the calcium ion in it.

Sarcoplamsic reticulum maitains the concentration of the inside the cell and outside for the relaxation and excitation coupling the Ca + is very important and helps cardiac muscle for work better and maintains the calcium concentration.

Cell membrane of the muscle fiber is known as the sacrolemma that have enclosed the sarcoplasm which is the cytoplasm of the mucsle fibers which having fibrils and repeating unit of the sarcomere.

It provides the muscles the structure and the important coment to perform several functions it is very large in the size.

So conclusively the cytoplasm of the muscle fiber also called as the sarcoplasm contains the mitochondria which provides energy to the muscle cells or fiber.

Answer is C , rest all options are wrong as i have mentioned description of all.

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