[Biology Class Notes] on Muscles Pdf for Exam

In this article, students will learn about Muscles in our body, types, structure and functions of Muscles. Let’s first know what muscle is.

A muscle is a soft tissue found in both humans and animals. The word muscle is derived from the Latin word “musculus” meaning little mouse as some Muscles resemble the shape of a small mouse or the contraction of Muscles look like a moving mouse.

Muscles are made up of protein filaments of myosin and actin that slide past each other and produce expanding and contracting movements of Muscles. This kind of movement changes both the shape and length of the muscle cells. Muscles function in humans by producing motion and force and help in circulation of blood, changing and maintaining body pressure, movement of internal organs like the movement of food down the digestive tract, and also helps in locomotion.

The human muscular system comprises more than 600 Muscles and makes up about 40-50% of our overall body weight. Muscles are essentially attached to blood vessels, bones and other internal organs. Muscles are composed of special kinds of elastic tissue, tendons, nerves and tissues.

The functioning of Muscles helps in making movements of every kind in the body and internal organs by transferring substances from these organs throughout the body. Muscles function by using up energy by oxidation of carbohydrates and fats, especially from the stored energy molecules adenosine triphosphate (ATP).

Types

There are three types of Muscles found in the body:

• Cardiac Muscles 

• Smooth Muscles 

• Skeletal Muscles 

Out of these three types, cardiac Muscles are involuntary Muscles which means that the movement of cardiac Muscles cannot be controlled by us according to our will.

Skeletal Muscles

Skeletal Muscles are voluntary Muscles and are attached to the bones and involved in different body parts functioning. They come under the central nervous system control of the body. Skeletal Muscles are long and multinucleated. They are cylindrically shaped with branched cells which are attached to the bones by collagen fibres and tendons, which are composed of connective tissues.

The function of Skeletal muscle can be summed up briefly as follows:

Cardiac Muscles

Cardiac Muscles are found only in the heart and are involuntary like movement. They are made up of cylindrical-shaped cells. These are striated Muscles responsible for keeping the heart moving by circulating and pumping blood throughout the body. The interconnected Muscles provide flexibility and strength to the Cardiac muscle tissue and are involved in rhythmic relaxation and contraction of the heart Muscles . Cardiac Muscles are characterised by branched cylindrical fibres and a centrally located nucleus.

Cardiac Muscles are primarily found in humans and regulate rhythmic relaxation and contractions of the heart Muscles for pumping blood. The Cardiac Muscles have a specialised type of tissue called “pacemaker” cells that expand and contract by responding to electrical impulses of the central nervous system.

Smooth Muscles

Smooth Muscles are also involuntary Muscles that are non-striated and are present in major organs whose movements are not controlled by the will, such as the stomach, vessels, bladder, uterus, etc. They are spindle-shaped with a single nucleus. These Muscles are shorter than skeletal Muscles with a length ranging between 20 to 200 μm and thickness between 3-10 µm. These Muscles produce their connective tissue and lack actin, myosin and filaments.

Smooth Muscles perform various tasks in our body which can be given as follows: