Skeletal muscle Structure Function and Physiology

About more than 300 muscles are consist in muscular system. Movement of body parts are brought by muscle contraction.

Each of skeletal muscle is attached to bone at least two places-

Origin Non-movable part of skeleton. Origin of muscle remains stationary when muscle contracts.

Insertion Freely movable part of skeleton. When muscle is contract, that part of skeleton can freely moved.
   

Structure of skeletal muscle

Skeletal muscle composed with large number of muscles fiber. Each muscle fiber has a nerve supply. Every muscle fiber is long and cylindrical in shape. Each muscle fiber has multiple nuclei which lie in the peripheri. 

The cytoplasm of muscle cell called carcoplasm.
The membrane of muscle fiber called carsolemma.

Function of skeletal muscle

1. They help in body movement.
2. Glycogen and protein are stored in muscles.
3. They provide the shape body.
4. Muscles are elastic in nature, they return to their original position after extension and contraction.
5. Muscle is contracted after receives stimuli, short and thick to do work. 
6. Muscle is generates force and heat.
7. Muscle is maintains body posture.

Physiology of muscles

A nerve action potential (nerve impulse) elicits muscle action potential in the following way :

Release of acetylcholine

Action potential comes to nerve terminal, that potential open the voltage gated calcium channels at nerve terminal. The movement of calcium ion inside the cell. Vesicles filled with acetylcholine present at nerve terminal. Calcium evoked vesicle of Ach. Ach vesicles are ruptured and release Ach.

Activation of Ach receptors

Two molecules of Ach Ach binding  to Ach receptor on the motor end plate. Voltage gated sodium channels are open and influx of sodium ion in muscle fibers.

Production of muscle action potential

Numbers of sodium ion inside muscle fiber are increase and generate action potential that potential cause muscle contraction.

Physiology-Flow-Chart

Muscle Name and Origin

Muscle Name	Origin	Insertion (End)	Action (Function)
Frontal belly	Epicrainal aponeurosis	Skin superior to supraorbital margin	Raises eyebrows, wrinkles, move skin of forehead
Occipital belly	Occipital bone	Epicrainal aponeurosis	Draw scalp posterior
Orbicularis coris	Muscles fibers surrounding opening of mouth	Skin at corner of mouth	Movement of lips during speech
Superior rectus	Attached to orbic around optic foramen	Superior and central part of eye balls	Move eyeballs superiorly and rotate them
Inferior rectus	Attached to orbic around optic foramen	inferior and central part of eye balls	Move eyeballs inferiorly and rotate them
Subclavis	First rib	Clavicle	Movement of collar bone and stabilze pectoral girdle

Functions of skeletal system

The skeletal system of human perform several basic functions :

Protection: the skeletal bones are protect most important internal organ from damage or injury.  For example : rib cage protect the heart and lungs, skull bone protect the brain.

Support: the skeleton system gives structural frame for body. It support tissues and also provide the attachment point for the most of skeletal muscles.

Mineral storage and release: bone stores many minerals, especially calcium and phosphors (contribute to the strength of bone). Bone tissue stores 99% of calcium. On requirement, bone release minerals into blood and also distribute the mineral to the other body parts.

Help in movement: bones help to move body. Many skeletal muscles attach to bones, when muscles are contract, they pull on bone to produce movement.

Blood cell formation: certain bone called red bone marrow, they produce red blood cells (RBC), white blood cells (WBC) and platelets, this process called hemopoiesis. Red bone marrow is present in several bones such as pelvic (hip) bones, sternum (chest bone), skull, vertebrae (backbone), humerus (arm) bone and femur (thigh) bone.

Triglyceride storage: especially adipose tissue consist the yellow bone marrow which store triglycerides.