Question

Indicate whether (a) skeletal (b) cardiac (c) smooth muscle has the following characteristics. A characteristic may apply to more than one muscle type.

_______ contraction usually voluntary

_______ contraction usually involuntary

_______ regulated mostly by somatic nerves

_______ regulated mostly by autonomic nerves

_______ striated

_______ non-striated

_______ able to stretch

_______ elastic

Answer 1

The skeletal muscle fiber is voluntary and striated. It consists of numerous small and cylindrical myofibrils with 1µm in diameter. The myofibrils contain two types of myofilaments composed of proteins myosin and actin. The thick myofilaments are called myosin filaments and thinn filaments are the actin filaments. Each skeletal muscle consists of numerousmuscle fibers that lie parallel to one another and enclosed by a connective tissue. The muscles are striated like skeletal and cardiac muscles or unstriated like smooth muscle. The muscles are categorized into voluntary muscle (skeletal muscle) or involuntary muscle (cardiac or smooth muscle) depending on the innervations of somatic nervous system. The cardiac muscle is satiated and involuntary containing short and stumpy cells called cardio or myocytes. Smooth muscles are also involuntary and do not have striations. The smooth muscles cells are called myocytes and they are fusiform in shape. The smooth muscles have flexibility and able to stretch because they are supported by elastic connective tissue.

(a) contraction usually voluntary

(b) and (c) contraction usually involuntary

(a) regulated mostly by somatic nerves

(b) and (c) regulated mostly by autonomic nerves

(a) and (b) striated

(c) non-striated

(c) able to stretch

(c) elastic