Muscle Cell | Definition, Anatomy, Types & Functions

By | October 16, 2019

Muscle Cell

Muscle Cell Definition:

A muscle cell is also known as Myocyte, which is a specialized animal cell that can shorten its length by using a series of motor proteins especially arranged in the cell. And several other associated proteins help, actin, and myosin form thin and thick filaments that slide past each other in order to contract small units of the muscle cell. These units are known as Sarcomeres, and many run end-to-end in larger fiber, known as Myofibril. The single muscle cell consists of many nuclei that are pressed against the cell membrane. A muscle cell is a long cell as compared to other kinds of cells, and many muscle cells connect with each other to create the long fibers present in muscle tissue

Muscle Cell Diagram

Muscle Cell

Types of Muscle Cell

Muscle cells are commonly called Myocytes. They are the specialized cells that makeup muscle tissue of the body. There are three types of muscle cells within the human body.

  1. Cardiac Muscles
  2. Skeletal Muscles
  3. Smooth Muscles

Muscle Cell

Cardiac Muscle Cell

Cardiac muscles composed of cardiomyocytes cells that are short and slender cells, and rectangular shape cells. They typically contain one nucleus, similar cell organelles as skeletal muscle cells, and plenty of acrosomes, which give the desired energy for contraction. Cardiomyocytes are structurally connected by intercalated discs that have gap junctions for diffusion and communication. They allow the transmission of contracted force between cells as electrical depolarization propagates from cell to cell, which facilitates a consistent contractile force. As these cardiac cells cannot divide, satellite cells are accountable for the replacement of the broken ones.

Muscle Cell

Skeletal Muscle Cell

Skeletal muscle cells are long, cylindrical, multi-nucleated and striated. Every nucleus regulates the metabolic needs of the sarcoplasm around it. Striated muscle cells have high energy needs, in order that they contain several mitochondria so as to generate adequate ATP. The sarcoplasm consists of myofibrils, that successively are created from thick and thin myofilaments. These cells create the muscle that we tend to use in movement and manufacture contraction because of the sliding of myosin heads over the actin filaments. This method is regulated by factors like ca, troponin, tropomyosin, and t-tubules.

Muscle Cell

Smooth Muscle Cell

Smooth muscle cells are elastic, not striated, spindle-shaped and contain one central nucleus. Smooth muscle cells are organized along in sheets and this organization means they will contract at the same time. They need poorly developed sarcoplasmic reticulum’s and don’t contain t-tubules, because of the restricted size of the cells. However, they contain different traditional cell organelles like acrosomes however in lower numbers. Smooth muscle cells are accountable for involuntary contractions and they additionally contain gap junctions for the diffusion of depolarization.

Muscle Cell

Structure of a Muscle Cell:

A muscle cell is composed of a compact bundle of many myofibrils. Each myofibril is composed of many sarcomeres bundled with each other and attached one end to another end. A special kind of endoplasmic reticulum is called Sarcoplasmic Reticulum, which extends in and around myofibril bundles. The sarcoplasmic reticulum concentrates a chemical that is necessary for the muscle cell to contract and it is activated by the signals which come from nerve cells.

The function of a Muscle Cell:

  • The brain sends an impulse down to the nerve in order to activate a muscle. The nerve impulse travels down the nerve cell to Neuromuscular Junction, from where a nerve cell meets with a muscle cell. Then the impulse travels to nerve cells and travels down special canals in Sarcolemma to reach toward the transverse tubules.
  • When troponin not present in Ca2, it will bind to tropomyosin and caused to cover up the myosin-binding sites on actin filaments. After introducing Ca2+ in Cytosol, troponin release tropomyosin. This act permits the myosin head to attach the actin filament.
  • Many heads and continues to use ATP to ensure a smooth contraction, while a small percentage of head attaches at one time. The myosin crawls until it reaches the Z plate. The sarcoplasmic reticulum is removing Ca+ from the cytoplasm continuously, and once concentration falls over specific level troponin rebinds to tropomyosin and muscle release.

Which of the following surrounds the individual muscle Cell?

Muscles are composed of connective tissue and contractile cells. The connective tissues surrounding the entire muscle is the epimysium. Bundles of muscle cells are called fascicles.  The connective tissues surrounding the fascicles are called perimysium. The fascicle is made of connective tissue which surrounds individual muscle cells. Its main functions are to electrically insulate muscle cells from one another. Three connective tissue layers of the muscle are endomysium, perimysium, and epimysium. They help to bind the muscle cells together, provide strength and support to the entire muscle. They are continuous with the tendons at the ends of the muscle.

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