The single-unit smooth muscles are:

'Oxygen debt' is the amount of oxygen required for

The sheath covering the bundle of muscle fibres is

Assertion: Fatigue is the inability of a muscle to relax.
Reason: It is due to lactic acid accumulation by repeated contractions.

The major protein in the thick filament of skeletal muscle fibre is

Analogy type questions:
$(1)$ Red muscle fibers / White muscle fibers have fewer mitochondria but more sarcoplasmic reticulum.
$(2)$ When nerve impulses reach the neuromuscular junction,acetic acid / acetylcholine neurotransmitter is released.