Muscle Tissue Overview Quiz

Muscle Tissue Overview

• Muscle tissue is found in various locations throughout the human body, and it is responsible for movement, posture maintenance, joint stabilization, and heat generation.
• Muscles are classified based on their structure and appearance of contractile cells. There are three main types: skeletal, smooth, and cardiac.

Types of Muscle Tissue

• Skeletal muscle:
  • Attached to bones, responsible for body movement.
  • Responsible for maintaining body position and posture.
  • Precise eye movement is handled by extraocular muscles.
  • Plays critical roles in speech, breathing, and swallowing.
  • Found throughout the body's skeletal system.
• Smooth muscle:
  • Found in the walls of hollow organs like the stomach, intestines, uterus.
  • Regulates blood vessel diameter and other functions.
  • Responsible for involuntary movements like peristalsis.
  • Plays a role in processes like churning food and movement of urine.
• Cardiac muscle:
  • Found in the heart.
  • Responsible for the heart's involuntary rhythmic pumping action.
  • Crucial to blood circulation.

Skeletal Muscle Structure

• Skeletal muscles are composed of
  • large bundles of muscle fibers
  • layers of connective tissues
  • muscle fibers, including:
    • sarcolemma (cell membrane).
    • sarcoplasm(cytoplasm).
    • myofibrils (cytoplasmic rod-like structures).
    • sarcoplasmic reticulum (ER for muscle cells).
• Muscle fibers consists of myofibrils.
• Myofibrils composed of repeating units called sarcomeres.

Skeletal Muscle Physiology

• Mechanism of contraction: Muscle contraction is triggered by Ca2+ ions released by sarcoplasmic reticulum.
  • Ca2+ stimulates myosin heads to form cross-bridges with actin, and use energy from ATP.
• Innervation: Skeletal muscles are innervated by the somatic nervous system, making them voluntary.
• Motor end-plate: Axons of motor neurons form the synaptic cleft, and release neurotransmitter at the motor end-plate-acetylcholine

Types of Muscle Fibers

• Red muscle fibers:
  • Rich in myoglobin and mitochondria.
  • Blood supply is high.
  • Slow, sustained contractions.
  • Involved in posture maintenance.
• White muscle fibers:
  • Low in myoglobin and mitochondria.
  • Blood supply is low.
  • Fast, powerful contractions.
  • Involved in rapid movements.
• Intermediate muscle fibers: Characteristics fall between red and white.

Cardiac Muscle Structure

• Cardiac muscle cells are branched, cylindrical and connect end-to-end.
• They are interconnected by intercalated disks, containing gap junctions (for communication) and desmosomes (strong attachments)

Cardiac Muscle Physiology

• Specialized conducting cells: These form a specialized conducting system that regulates the heart's rhythmical, involuntary beating
• Pacemaker cells: Regulate the heart rate, initiating the contractions
• Modified nodal cells: Generate the rhythm of heart contraction and can be modulated by the autonomic nervous system.

Smooth Muscle Structure

• Smooth muscle cells are spindle-shaped.
• They lack striations.
• Connected by gap junctions.
• Organized in sheets within an organ's wall.
  • longitudinal, circular, or oblique layers.
• Dense bodies: analogous to Z lines, which anchor the thin filaments.

Smooth Muscle Physiology

• Mechanism of contraction: Ca2+ triggered contraction involves interaction between myosin and actin thin filaments
• Regulation: Smooth muscle contraction is often regulated by hormones, nerves, and other factors.
• Functions: Smooth muscles are involved in the involuntary control of hollow organs (e.g., stomach, intestines) and blood vessels.