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Chapter 14: Muscle Tissue Back To Chapter

14.1: Overview of Muscle Tissues

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Anatomy and Physiology

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Overview of Muscle Tissues

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14.2: Gross Anatomy of Skeletal Muscles

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Muscle tissue is one of the four main tissue types in the human body. It comprises cells with the remarkable ability to contract to perform various physiological functions.

Muscles are of three types — skeletal, cardiac, and smooth muscles.

Skeletal muscles are striated and are indirectly attached to bones. They can be voluntarily controlled to move body parts, such as the arms or legs.

These muscles also help maintain body posture. For instance, the neck muscles aid in holding the head upright.

Cardiac muscles are found exclusively in the heart. Although striated, they function involuntarily and are autorhythmic — meaning they are not entirely dependent on neural signals for contractions.

This rhythmic contraction functions to pump blood through the cardiovascular system.

The third type, smooth muscles, are found lining the hollow visceral organs and blood vessels.

They are non-striated, involuntary muscles that control the passage of substances through the body, for instance, the movement of food through the esophagus.

Additionally, all muscles, especially skeletal muscles, contribute significantly to maintaining normal body temperature by generating heat during contractions.

14.1: Overview of Muscle Tissues

The human body has three types of muscle tissue: skeletal, smooth, and cardiac. Each class has unique properties that enable them to perform specific functions. However, all muscle tissues share certain properties, including elasticity, contractility, and excitability.

Elasticity
Elasticity is the ability of muscles to stretch and return to their original shape. This property is partly due to elastic fibers — macromolecules that run through the muscles. These fibers are firm and resilient, giving muscles support, flexibility, and the ability to stretch and recoil without breaking or tearing. Elastic fibers also help absorb energy from physical activity, leading to less fatigue and improved performance.

Contractility
Contractility refers to the ability of muscle cells to shorten when stimulated. They can contract and relax upon stimulus, causing the muscle to shorten or lengthen. Contractile proteins, such as myosin and actin, are responsible for muscle cells' contracting and shortening motion without damaging the cell structure.

Excitability
Excitability is the ability of muscle cells to contract upon stimulation by electric signals. Electrically excitable cells, such as neurons and muscle cells, use the membrane potential or difference in the electrical charge distribution across the cell membrane to transmit signals between different cellular regions. These signals are generated by the opening or closing of ion channels at specific locations in the membrane, resulting in localized changes in the membrane potential. The muscle cells change their electric charge in response to neurotransmitters released by the neurons, which leads to contraction or relaxation.

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