Muscle Anatomy Quiz

Study Notes

Muscle Types

Skeletal Muscle: Voluntary, striated, attached to bones, responsible for movement by contracting and pulling on bones.
Cardiac Muscle: Involuntary, striated, only found in the heart, responsible for pumping blood throughout the body.
Smooth Muscle: Involuntary, non-striated, found in hollow organs like the intestines, bladder, and blood vessels, responsible for moving substances through these organs.

Muscle Shapes

Parallel Muscles: Fibers run parallel to the length of the muscle, resulting in long, large movements. Example: Sartorius muscle.
Fusiform Muscles: Spindle-shaped, with a wider muscle belly, allowing for powerful contractions. Example: Biceps brachii.
Pennate Muscles: Fibers attach obliquely to a central tendon, increasing the number of muscle fibers per unit of muscle volume for greater force.
- Unipennate: Fibers on one side of the tendon. Example: Extensor digitorum longus.
- Bipennate: Fibers on both sides of the tendon. Example: Rectus femoris.
- Multipennate: Multiple rows of diagonal fibers with a branching central tendon. Example: Deltoid muscle.
Convergent Muscles: Broad origin, fibers converge to a single tendon, resulting in a triangular shape. Example: Pectoralis major.
Circular Muscles: Arranged in concentric rings, surrounding openings, closing by contraction. Example: Orbicularis oris.

Muscle Naming

Deltoid: Triangular shape, located on the shoulder, named after the Greek letter delta.
Trapezius: Trapezoid shape, located in the upper back and neck, moves shoulder blades and extends the neck.
Serratus Anterior: Saw-toothed shape, located on the side of the chest, moves the scapula.
Rhomboid Major: Rhomboid shape (parallelogram), located in the upper back, retracts the scapula.
Latissimus Dorsi: Wide and flat, covers a large part of the back, involved in arm adduction and extension.
Orbicularis Oris: Circular muscle surrounding the mouth, puckers lips.
Biceps Brachii: Fusiform shape, two-headed structure, flexes the elbow.

Sarcomere and Muscle Contraction

Sarcomere: Basic contractile unit of striated muscle, made up of actin (thin filaments) and myosin (thick filaments) sliding past each other.
Sliding Filament Model: Myosin heads bind to actin, pull actin toward the center of the sarcomere, effectively shortening the sarcomere and causing muscle contraction.

Role of Calcium in Muscle Contraction

Calcium Release: Nerve signal triggers release of calcium ions from the sarcoplasmic reticulum, a storage organelle in muscle cells.
Troponin Binding: Calcium binds to troponin, a protein attached to actin, causing a conformational change in troponin and tropomyosin.
Exposure of Binding Sites: Tropomyosin shifts away from the myosin-binding sites on actin, exposing these sites for interaction with myosin heads.
Cross-Bridge Formation: Myosin heads attach to actin, forming cross-bridges, facilitating muscle contraction.
Relaxation: Calcium is pumped back into the sarcoplasmic reticulum, tropomyosin covers the binding sites, muscle relaxes.

Role of Tropomyosin in Muscle Contraction

Blocking Binding Sites: In a resting muscle, tropomyosin covers the myosin-binding sites on actin, preventing myosin from attaching and causing spontaneous contraction.
Calcium-Troponin Regulation: Calcium binding to troponin causes tropomyosin to shift, exposing the binding sites on actin.
Facilitating Cross-Bridge Formation: This exposure allows myosin to attach to actin, leading to contraction.
Return to Resting State: Calcium removal causes tropomyosin to cover the binding sites again, preventing further contraction.

Description

Test your knowledge on the different types and shapes of muscles in the human body. Learn about skeletal, cardiac, and smooth muscles, as well as various muscle shapes such as parallel, fusiform, and pennate. Dive into their functions and characteristics to enhance your understanding of human anatomy.