Questions and Answers
What is the primary function of skeletal muscles?
Smooth muscle cells are striated.
False
What is the function of cardiac muscle contraction?
Heartbeat
What is the main symptom of Fibromyalgia?
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Skeletal muscles constantly maintain tone, which keeps us sitting or standing ____.
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What causes muscular hypertrophy?
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Match the muscle terms with their descriptions:
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Myasthenia gravis is a viral infection.
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Tendinitis implies an inflammation of ________ attachment point.
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Study Notes
Muscular System
- The muscular system is responsible for movement within the body, maintaining posture, facilitating respiration, producing body heat, and aiding in communication.
- There are three types of muscle tissue: skeletal, cardiac, and smooth.
Functions of the Muscular System
- Body movement: contraction of skeletal muscles is responsible for overall movements of the body.
- Maintenance of posture: skeletal muscles constantly maintain tone, keeping us sitting or standing erect.
- Respiration: muscles of the thorax are responsible for movements necessary for breathing.
- Production of body heat: heat is given off as a by-product when skeletal muscles contract.
- Communication: skeletal muscles are involved in all aspects of communication (e.g., speaking, writing, typing, gesturing, and facial expression).
- Constriction of organs and vessels: smooth muscle within internal organs and vessels causes constriction, helping to propel and mix food and water in the digestive tract, regulate blood flow, and more.
- Heartbeat: cardiac muscle causes the heart to beat, propelling blood to all parts of the body.
Characteristics of Skeletal Muscle
- Constitutes approximately 40% of body weight.
- Also called striated muscle due to transverse bands visible under a microscope.
- Properties:
- Contractility: ability to shorten with force.
- Excitability: ability to respond to stimuli.
- Extensibility: ability to stretch to normal resting length and beyond to a limited degree.
- Elasticity: ability to recoil to original resting length after stretching.
Structure of Skeletal Muscle
- Surrounded by connective tissue sheath (epimysium or fascia).
- Composed of numerous visible bundles (muscle fasciculi) surrounded by loose connective tissue (perimysium).
- Each muscle fiber is surrounded by loose connective tissue (endomysium) and contains:
- Sarcoplasm (cytoplasm of muscle fiber).
- Myofibrils (threadlike structures extending along muscle fiber).
- Sarcomeres (basic structural and functional units of skeletal muscle).
Smooth Muscle and Cardiac Muscle
- Smooth muscle cells:
- Small, spindle-shaped, and usually with one nucleus per cell.
- Contain less actin and myosin than skeletal muscle cells.
- Not striated due to lack of sarcomeres.
- Contract more slowly than skeletal muscle cells.
- Under involuntary control.
- Cardiac muscle cells:
- Long, striated, and branching, with usually only one nucleus per cell.
- Actin and myosin myofilaments organized into sarcomeres.
- Contraction rate between that of smooth and skeletal muscle.
- Auto-rhythmic contraction.
- Under involuntary control and influenced by hormones.
Skeletal Muscle Anatomy
- Most muscles extend from one bone to another and cross at least one joint.
- Contraction causes most body movements by pulling one of the bones toward the other across the movable joint.
- Attachment points: origin (most stationary end) and insertion (end attached to bone undergoing greatest movement).
- Muscles grouped to oppose each other's actions (agonist and antagonist).
Clinical Conditions of Muscular System
- Cramps: painful, spastic contractions of muscle due to irritation within a muscle.
- Fibromyalgia: chronic muscle pain syndrome with widespread muscle pain and no known cure.
- Hypertrophy: enlargement of a muscle due to an increase in myofibrils within muscle fibers, often resulting from exercise.
- Atrophy: decrease in muscle size due to a decrease in myofilaments within muscle fibers, often resulting from disuse or damage to the nervous system.
- Myotonic muscular dystrophy: inherited disorder characterized by failure of muscles to relax following forceful contraction and muscular weakness.
- Myasthenia gravis: chronic progressive autoimmune disease resulting from destruction of acetylcholine receptors in the neuromuscular junction.
- Tendinitis: inflammation of tendon attachment point, often resulting from overuse or trauma.
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Description
Learn about the functions of the muscular system, including body movement, maintenance of posture, and more. Explore the three types of muscle tissue: skeletal, cardiac, and smooth.
