Human Physiology - Locomotion and Movement (Skeletal System, Joints, Muscle Contraction)
Review the key concepts, formulae, and examples before starting your quiz.
🔑Concepts
The skeletal muscle is composed of muscle bundles (fascicles) held together by a connective tissue layer called fascia. Each fascicle contains many muscle fibres, which are syncytium (containing multiple nuclei).
The functional unit of contraction is the Sarcomere, the portion of a myofibril between two successive -lines.
Myofibrils contain two primary contractile proteins: Actin (thin filament) and Myosin (thick filament). Actin consists of -actin, tropomyosin, and troponin.
The Sliding Filament Theory: Muscle contraction occurs by the sliding of thin filaments over thick filaments. This is initiated by a neural signal reaching the neuromuscular junction, releasing Acetylcholine ().
Role of Calcium: Action potential causes the release of from the sarcoplasmic reticulum. binds to the subunit of troponin, uncovering the active sites on actin for myosin.
The Axial Skeleton ( bones) comprises the skull, vertebral column, sternum, and ribs. The Appendicular Skeleton ( bones) comprises the bones of the limbs and the girdles.
The Human Vertebral Formula is , representing Cervical, Thoracic, Lumbar, Sacral (fused), and Coccygeal (fused) vertebrae.
Joints are classified into: Fibrous (immovable, e.g., skull sutures), Cartilaginous (limited movement, e.g., between vertebrae), and Synovial (freely movable, e.g., Ball and Socket, Hinge).
📐Formulae
💡Examples
Problem 1:
Explain the changes in the -zone, -band, and -band during muscle contraction.
Solution:
During contraction: The -zone shortens or disappears, the -band reduces in length, but the -band retains its length.
Explanation:
As actin filaments slide towards the center of the sarcomere, the gap between them (-zone) closes. The distance between -lines decreases, shortening the -band, while the length of the myosin filaments (-band) remains constant.
Problem 2:
Identify the type of joint present between the Atlas and the Axis vertebrae.
Solution:
Pivot Joint.
Explanation:
The pivot joint allows for rotational movement, such as turning the head from side to side. It is a type of synovial joint where the odontoid process of the axis fits into a ring formed by the atlas.
Problem 3:
A person is suffering from an autoimmune disorder where the neuromuscular junction is affected, leading to fatigue and paralysis of skeletal muscles. Identify the condition.
Solution:
Myasthenia gravis.
Explanation:
Myasthenia gravis is an autoimmune disorder that affects the acetylcholine receptors at the neuromuscular junction, preventing effective muscle release and contraction.