Human Anatomy: Muscle Tissue Overview

Learning Objectives

• Students should identify the main characteristic of skeletal muscle.
• Students should explain the function of muscle tissue.
• Students should list the three types of muscle tissue.
• Students should differentiate between smooth, cardiac, and skeletal muscle.
• Students should explain the term used to name skeletal muscle.
• Students should explain the functions of smooth, cardiac, and skeletal muscle.

Muscle Tissue

• Bones cannot move on their own. Movements are caused by the contraction and relaxation of muscle cells.
• Muscles make up about 40-50% of total body weight and are composed of highly specialized cells.
• There are 650 muscles and 187 joints in the human body.

The Muscular System

• The muscular system is a complex network of muscles that enable various body movements.
• The presentation covered different types of muscles (e.g., facial muscles, back muscles, muscles of the abdomen, leg muscles, forearm muscles, and hand muscles).
• Diagrams illustrate the various muscles.

Functions of Muscular Tissue

• Produce body movements (e.g., lifting, peristalsis, heart beating, bladder contraction).
• Maintain body posture (muscles contract continuously)
• Store and move substances within the body by smooth muscle contraction and relaxation.
• Produce heat. Muscle contraction accounts for approximately 80% of body heat production.

Types of Muscle Tissues

• Cardiac muscle:

  • Involuntary.
  • Found only in the heart.
  • Cylindrical and striated.
  • Cells branch and interconnect to form a complex network.
  • Points where cells attach are called intercalated discs.
  • Has only one nucleus per cell.

• Smooth muscle:

  • Involuntary.
  • Non-striated.
  • Small cells with one nucleus.
  • Lines the walls of hollow organs.
  • Tubular structure for transporting substances through the tract
  • Moves in a wave-like contraction.

• Skeletal muscle:

  • Voluntary muscle.
  • Striated muscle.
  • Attached to bone by tendons.
  • Moves bones.
  • Muscle fibers are cylindrical in shape.
  • Movement is controlled.

Muscle Structure

• Skeletal muscle tissue is composed of muscle fibers (cells).
• Muscle tissues comprise of:
  • Endomysium - surrounds individual muscle fibers
  • Perimysium - surrounds bundles (fascicles) of muscle fibers,
  • Epimysium - surrounds the entire muscle.
  • Tendon - connects muscle to bone.
• Sarcolemma- specialized plasma membrane of muscle fiber.
• Myofibrils - long organelles within the muscle fiber, composed of sarcomeres.
• Sarcoplasm - the cytoplasm of the muscle cell.
• Sarcoplasmic reticulum - specialized smooth endoplasmic reticulum; stores calcium ions and releases them during muscle contraction.

Sarcomere

• The smallest functional unit of a myofibril.
• Contains thick and thin filaments arranged in compartments.
• Filaments overlap to create striations.
• These filaments (thick and thin filaments) and their interaction cause contraction

Myofilaments

• Thick Filaments (myosin):

  • Composed of myosin proteins that form a rod-like tail and globular heads.
  • Heads act as cross-bridges, binding to actin filaments during contraction.

• Thin Filaments (actin):

  • Composed of actin protein arranged in helixes.
  • Specific binding sites for myosin heads.
  • Regulated by tropomyosin and troponin.

• The organization of filaments within a sarcomere influences the muscle contraction process

Muscle Contraction

• Initiated by nerve impulses.
• Nerves release acetylcholine (ACh), a neurotransmitter at the neuromuscular junction.
• ACh binds to receptors on the sarcolemma and triggers an action potential.
• This leads to calcium ion release from the sarcoplasmic reticulum, exposing active sites on actin.
• Myosin heads bind to actin, and the sliding filament mechanism shortens the sarcomere and generates muscle contraction.
• Muscle contraction requires energy (ATP)
• Energy sources include: Creatine phosphate (CP), Glucose, and Glycolysis.

Nerve and Blood Supply to Skeletal Muscles

• Skeletal muscle fibers need an impulse from nerve cells to contract,
• Blood vessels deliver the necessary nutrients and oxygen to produce ATP,
• Blood vessels remove waste products produced by the muscles.

Muscular Dystrophy

• A group of inherited diseases that damage and weaken muscles over time.
• The damage and weakness is caused by a lack of a protein called dystrophin.
• Dystrophin supports the muscle fibers and helps them function normally. Without it, the muscles weaken and degenerate over time.
• Various types exist (e.g., Duchenne muscular dystrophy, Becker muscular dystrophy).

Contraction Deformity

• The result of stiffness or constriction in muscles, joints, tendons, ligaments, or skin.
• Limits normal movement.
• Develops when connective tissues become less flexible.

This quiz focuses on the characteristics and functions of muscle tissue in the human body. Students will explore the three types of muscle: skeletal, smooth, and cardiac, and will learn how these muscles work to facilitate movement. Prepare to differentiate between these muscle types and understand their specific roles in the muscular system.