Discuss the classifications of muscles according to their actions
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they are classified as voluntary and involuntary muscles.
Muscles can be classified into various categories based on their actions or functions. Let's explore the main classifications of muscles according to their actions:
1. Flexor Muscles: These muscles are responsible for flexing or decreasing the angle between two body parts. For example, the biceps brachii in the upper arm is a flexor muscle that allows you to bend your forearm at the elbow joint.
2. Extensor Muscles: In contrast to flexor muscles, extensor muscles increase the angle between two body parts, typically by straightening or extending a joint. The triceps brachii in the upper arm is an extensor muscle that enables you to straighten your arm at the elbow joint.
3. Abductor Muscles: Abductor muscles move a body part away from the midline of the body. An example is the deltoid muscle in the shoulder, which is responsible for abducting the arm away from the body.
4. Adductor Muscles: Adductor muscles perform the opposite action of abductor muscles by bringing a body part closer to the midline. The adductor muscles in the inner thigh help in bringing the legs together.
5. Rotator Muscles: These muscles are responsible for rotating a body part around its axis. The muscles involved in rotating the head, such as the sternocleidomastoid muscle, are an example of rotator muscles.
6. Pronator Muscles: Pronator muscles rotate the forearm and hand so that the palm faces posteriorly or downward. The pronator teres in the forearm is a pronator muscle responsible for rotating the forearm.
7. Supinator Muscles: Supinator muscles perform the opposite action of pronator muscles by rotating the forearm and hand so that the palm faces anteriorly or upward. The supinator muscle in the forearm is responsible for this movement.
8. Levator Muscles: Levator muscles raise or elevate a body part. An example is the levator scapulae muscle in the neck, which lifts the scapula or shoulder blade.
9. Depressor Muscles: Depressor muscles lower or depress a body part. The depressor anguli oris muscle in the face is responsible for lowering the corner of the mouth.
10. Sphincter Muscles: Sphincter muscles are ring-like muscles that function to close or constrict an opening. Examples include the external sphincter, which helps control bowel movements, and the orbicularis oris muscle that forms the lips.
Understanding the various classifications of muscles based on their actions is essential for studying anatomy and movement. Remember, these classifications often overlap, and many muscles can perform multiple actions depending on the joint involved and the directions of movement.