In a skeletal muscle fiber,what is the $H$-zone?

The backward bending of the shank is worked out by

$\text{ATP}$ase is located in $:-$

Total number of muscles in the human body is:

Choose the correct statements regarding muscle contraction. $A$. $A$ motor neuron carries a signal sent by the Central Nervous System $(CNS)$ to the sarcolemma of the muscle fibre. $B$. The neural signal generates an action potential which causes the release of $Ca^{++}$ into sarcoplasm. $C$. Increase in $Ca^{++}$ inactivates the actin for breaking cross bridges. $D$. Actin binds to the myosin head to form a cross bridge. $E$. Shortening of sarcomere takes place, by pulling actin filaments towards the centre of '$A$' band. Choose the correct answer from the options given below:

Provide the full names for the following structures found in muscle fibers:
$(1)$ $Z-$ disc
$(2)$ $H-$ zone