Question

How many of the given features belong to red muscle fibers?
[Fast contraction, Well developed sarcoplasmic reticulum, plenty of mitochondria, quickly acquire fatigueness]
A) None
B) One
C) Two
D) Three

Answer 1

Hint: Red muscle fibres are present in the skeletal muscles that perform several functions in the body. The red muscles are rich in capillaries and are rich myoglobin due to which the muscles appear red. These muscle fibres perform aerobic oxidation.

Complete answer:
Muscle tissues are made up of muscle fibres. These fibres contain a single type of cell. These fibres help in controlling the movement in our body. There are two types of muscle fibres in our body.
- White muscle fibres- example muscles of the eye.
- Red muscle fibres. Example extensor muscles.

Let us discuss the characters of red muscle fibres.
i) Red muscles are rich in capillaries and myoglobin due to which these muscles appear red.
ii) These muscles have a less developed sarcoplasmic reticulum.
iii) These muscles bring about aerobic respiration. So, they have a large number of mitochondria.
iv) Due to less accumulation of lactic acid (product of anaerobic respiration), they do not get fatigued easily.
v) The contraction of these muscles occurs for longer periods. Hence the contraction rate is slower in the red muscle fibres.

The figure below shows the structure of muscle fibre.

Therefore the correct answer is option ‘B’ i.e, plenty of mitochondria.

Note: In the case of white tissue fibres, the mitochondria are less and do not contain myoglobin. Hence, they appear white. They have developed sarcoplasmic reticulum. The SR are the store of calcium. They regulate the extension and contraction of muscles.