Category: Biology Second Paper Lecture Sheet

Muscles that stretch or spread a limb are called extensor muscles. The process of extending or spreading a part of an extensor muscle is called extension. For example, the triceps muscle extends the forearm.

Muscles that contract or bend a limb are called flexor muscles. The process of bending or contracting a part of a flexor muscle is called flexion. For example, the biceps muscle bends the elbows or fingers

Not only the muscles but also the role of the skeletal system is very important in human movement. Muscles and bones work together to aid in movement. The role of muscles in locomotion is mentioned below.
1. Flexor Muscles: Muscles that contract or bend a limb are called flexor muscles. The process of bending or contracting a part of a flexor muscle is called flexion. For example, the biceps muscle bends the elbows or fingers
2. Extensor Muscles: Muscles that stretch or spread a limb are called extensor muscles. The process of extending or spreading a part of an extensor muscle is called extension. For example, the triceps muscle extends the forearm.
3. Adductor muscle: The muscle that pulls any part of the body closer is called adductor muscle. The process of pulling an adductor muscle to a limb is called adduction. For example, the latissimus muscle pulls an organ closer.
4. Abductor muscle: The muscle that moves a part of the body away is called abductor muscle. Abduction is the movement of a part of the abductor muscle away. For example, the deltoid muscle moves an organ away.
5. Depressor muscle: The muscle that lowers any part of the body is called depressor muscle. The process by which a depressor muscle moves down a limb is called depression. For example, the mandibula muscle lowers the jaw.
6. Levator muscle: The muscle that raises any part of the body is called levator muscle. The process of raising a limb of the levator muscle is called levitation. For example, the masseter muscle raises the jaw. Gastrocnemius muscle of knee, soleus muscle of foot etc.
7. Rotator Muscle: The muscle that rotates any part of the body around or right-left is called rotator muscle. Rotation is the process of turning a part of the rotator cuff around or left and right. For example, the pronator muscle causes lateral rotation and the supinator muscle causes lateral rotation. The piriformis muscle helps rotate the femur.
8. Protractor Muscle: The muscle that extends a part of the body forward is called a protractor muscle.
9. Retractor Muscles: Muscles that extend a body part backwards are called retractor muscles.

Glucose is produced by breaking down glycogen stored in cells. Glucose is used in all respiration and produces ATP. ATP provides energy for muscle contraction.

Movement of any part of the body requires the combined effect of two muscles. The two muscles work in opposite ways. One of the muscles is called antagonistic muscle of the other. These are called antagonistic muscle pairs.

This muscle contracts and expands the heart to maintain normal blood flow. Cardiac muscle contains functional syncytium. That is, when one cell shrinks, other cells shrink.

This muscle is found only in the wall of the heart. The muscle of the heart is called the myocardium. Myocardium has two layers. Epicardium and Endocardium. The outer layer is called epicardium and the inner layer is called endocardium.

Cardiac cells appear long, cylindrical and branched. Its length is 0.8 mm and diameter is 12-15 micrometers.
1. Sarcolemma: It is covered by a membrane called sarcolemma.
2. Sarcoplasm: Cytoplasm of muscle is called sarcoplasm. It contains mitochondria.
3. Nucleus: In the center of every cell is a nucleus. It performs biological functions of cells.
4. Myofibrils: Myofibril fibers run along the length of the cell. Myofibrils have striated spots.
5. Intercalated disc: Two adjacent sarcolemmas fuse to form a disc. One is called an intercalated disc. It is one of the identifying features of heart muscle.

The muscle that forms the wall of the heart is called cardiac muscle. It is a type of involuntary muscle. Between the heart muscles are the connective tissue of the areola. It never gets bored.

1. The contraction-expansion capacity of this muscle is slow and long-lasting.
2. It regulates the rhythmic activity of the organs.
3. It controls the movement of food material in the process of peristalsis.
4. Controls the contraction and expansion of blood vessels, airways, excretory canals etc.