Question

One amongst the following is not a property of cardiac muscle fibres

• A. Their T- tubules occur at the level of Z - discs
• B. They are innervated by branches from cranial and spinal nerves
• C. Striated in appearance
• D. Their refractory period is longest

Answer 1

The correct option is A Their T- tubules occur at the level of Z - discs

Cardiac muscle fibres are involuntary and striated in appearance, which is present in the heart. The main characteristic of this is they initiate their rhythmic impulses. Their refractory period is the longest. This type of muscle fibres is innervated by branches from cranial and spinal nerves. Skeletal muscle contains Z-discs to connect the one muscle fibre from another muscle fibres. But cardiac muscle fibres do not contain Z-disc

Thus, the correct answer is 'Their T- tubules occur at the level of Z - discs.'