Describe the functions, characteristics, and attachments of skeletal muscles.

Here are the answers based on the objectives listed in the image: a) The functions of muscles are: • Movement: Skeletal muscles contract to move bones, allowing for locomotion and manipulation of objects. Cardiac muscle pumps blood, and smooth muscle moves substances through internal organs. • Maintain Posture: Sustained contractions of skeletal muscles maintain body position against gravity. • Joint Stability: Muscle tendons crossing joints contribute to their stability. • Heat Production: Muscle contraction generates heat, which helps maintain body temperature. b) The special features (characteristics) of skeletal muscles are: • Excitability (Responsiveness): The ability to respond to stimuli by producing electrical signals (action potentials). • Contractility: The ability to shorten forcefully when stimulated, generating tension. • Extensibility: The ability to stretch or extend without being damaged. • Elasticity: The ability to return to their original length and shape after contraction or extension. c) The attachments of skeletal muscles involve: • Tendons: Most skeletal muscles attach to bones via strong, cord-like structures made of dense regular connective tissue. • Origin: The attachment of a muscle to the stationary bone or the less movable bone. • Insertion: The attachment of a muscle to the movable bone. When the muscle contracts, the insertion is pulled towards the origin. d) The different directions (arrangements) of skeletal muscle fibers (fascicles) include: • Parallel: Fascicles are parallel to the longitudinal axis of the muscle (e.g., biceps brachii). • Fusiform: A type of parallel muscle with a spindle shape, wider in the middle and tapering at the ends (e.g., biceps brachii). • Pennate: Fascicles are short and attach obliquely to a central tendon (e.g., rectus femoris - bipennate, deltoid - multipennate). • Convergent: Fascicles spread out from a broad origin and converge to a single tendon (e.g., pectoralis major). • Circular: Fascicles are arranged in concentric rings, forming sphincters (e.g., orbicularis oculi). e) The mode of action of skeletal muscles involves: • Contraction: Muscle contraction occurs via the sliding filament model, where myosin heads pull on actin filaments, causing the sarcomeres to shorten. • Agonist (Prime Mover): The muscle primarily responsible for a specific movement. • Antagonist: The muscle that opposes the action of the agonist, relaxing as the agonist contracts. • Synergist: Muscles that assist the agonist by adding force or reducing unwanted movements. • Fixator: A type of synergist that stabilizes the origin of the agonist so that the agonist can act more efficiently. f) Skeletal muscles are named based on several criteria, including: • Location: (e.g., temporalis muscle near the temporal bone). • Shape: (e.g., deltoid for triangular, trapezius for trapezoid). • Size: (e.g., gluteus maximus for largest, gluteus minimus for smallest). • Direction of Fibers: (e.g., rectus abdominis for straight, external oblique for angled). • Number of Origins: (e.g., biceps brachii for two heads, triceps brachii for three heads). • Location of Attachments: (e.g., sternocleidomastoid attaches to sternum, clavicle, and mastoid process). • Action: (e.g., flexor digitorum for flexing digits, adductor longus for adduction). g) The nerve supply of skeletal muscles: • Skeletal muscles are voluntarily controlled and are innervated by somatic motor neurons. • Each motor neuron extends from the central nervous system to a group of muscle fibers. • The point of communication between a motor neuron and a muscle fiber is called the neuromuscular junction. • At the neuromuscular junction, the motor neuron releases the neurotransmitter acetylcholine (ACh), which binds to receptors on the muscle fiber, initiating an action potential and muscle contraction. 3 done, 2 left today. You're making progress.