BSC2085C Exam Study Guide - Skeletal and Muscular Systems
Study Guide for BSC2085C Exam
Skeletal System
Functions of the Skeletal System
Provides structure and support to the body.
Protects vital organs (e.g., brain, organs in thoracic cavity).
Aids in movement by serving as levers for muscles.
Produces blood cells in the bone marrow (hematopoiesis).
Stores minerals (e.g., calcium, phosphorus) and fat.
Red vs. Yellow Marrow
Red marrow: Responsible for hematopoiesis; found in flat bones and the ends of long bones.
Yellow marrow: Fat storage tissue; primarily found in the medullary cavity of long bones.
Types of Tissues in the Skeletal System
Bone tissue: Composed of mineralized matrix; provides strength and structure.
Cartilage: Flexible tissue that cushions joints; present in areas like the nose, ears, and joints.
Ligaments: Connects bone to bone; provides stability to joints.
Tendons: Connects muscle to bone.
Structure & Components of a Long Bone
Diaphysis: Long shaft; comprised of compact bone.
Epiphysis: Ends of the bone; contains spongy bone and is covered by articular cartilage.
Metaphysis: Area between diaphysis and epiphysis; contains the growth plate (epiphyseal plate).
Medullary cavity: Hollow center of the diaphysis containing yellow marrow.
Spongy vs. Compact Bone
Compact bone: Dense, organized structure; makes up the outer layer of the bone.
Spongy bone: Lighter, porous structure inside the bone; contains trabecular spaces filled with bone marrow.
Osteons & Canaliculi vs. Trabeculae
Osteons: Basic structural unit of compact bone; consists of concentric lamellae surrounding a central canal (Haversian canal).
Canaliculi: Small channels that connect lacunae, allowing for nutrient and waste exchange between osteocytes.
Trabeculae: Rod-like structures forming the network of spongy bone.
Matrix of Bone
Composed of organic components (collagen fibers) and inorganic components (hydroxyapatite, which is a mineral form of calcium phosphate).
Provides tensile strength (collagen) and compressional strength (mineral content).
Osteoblast Function and Development
Osteoblasts: Cells responsible for bone formation.
Secrete bone matrix and facilitate mineralization.
Osteoclast Function and Development
Osteoclasts: Cells responsible for bone resorption; break down bone tissue to release minerals back into the bloodstream.
Differences between Intramembranous and Endochondral Bone Formation
Intramembranous ossification: Bone develops from mesenchymal tissue; occurs in flat bones (e.g., skull).
Endochondral ossification: Bone formed from a hyaline cartilage model; occurs for most bones in the body.
What is an Epiphyseal Plate? Function?
The epiphyseal plate (growth plate) is a hyaline cartilage structure at the junction of the epiphysis and metaphysis.
Function: Site of longitudinal growth in long bones; cartilage is replaced by bone as the individual matures.
How and Where Does Bone Growth Occur?
Bone growth occurs at the epiphyseal plate through proliferation and ossification.
Cartilage cells in the plate divide and increase in number, while older cartilage mineralizes and is replaced by bone cells, increasing the length of the bone.
Bone Maintenance and Hormones Involved
Thyroid hormones: Regulate metabolism and influence bone growth and remodeling.
Parathyroid hormone (PTH): Increases blood calcium levels by stimulating osteoclasts and releasing calcium from bone.
Steps of Bone Repair
Hematoma formation (blood clot).
Fibrocartilaginous callus formation (soft callus).
Bony callus formation (hard callus).
Bone remodeling (compact bone replaces spongy bone).
Joints
Three Types of Joints
Fibrous Joints: No movement (e.g., sutures in the skull).
Cartilaginous Joints: Limited movement (e.g., intervertebral discs).
Synovial Joints: Freely movable joints (e.g., knee, elbow).
Roles & Locations in the Body
Fibrous: Stability; locations such as skull and teeth.
Cartilaginous: Shock absorption; found in the spine and ribcage.
Synovial: Wide range of motion; found in limbs.
Structure of a Synovial Joint and Functions of Its Components
Articular cartilage: Covers the surfaces of bones, reducing friction.
Joint cavity: Contains synovial fluid, which lubricates and nourishes cartilage.
Articular capsule: A fibrous envelope surrounding the joint; offers stability.
Ligaments: Connect bones and maintain stability.
Six Types of Synovial Joints and Locations in the Body
Hinge joints: Allow movement in one plane (e.g., elbow).
Ball-and-socket joints: Allows circular movement (e.g., shoulder).
Pivot joints: Allow rotation (e.g., neck).
Saddle joints: Allows movement in two planes (e.g., thumb).
Condylomus joints: Allow movement but limited rotation (e.g., wrist).
Plane joints: Allow gliding movements (e.g., carpals in the wrist).
Muscular System
Functions of the Muscular System
Produces movement by contracting and relaxing.
Maintains posture and body position.
Stabilizes joints and generates heat during muscle activity.
Byproducts of Muscle Contraction
Heat is generated as a byproduct of energy use during contraction. Lactic acid can accumulate during anaerobic respiration.
Features Common to All Muscles
Contractility: Ability to shorten and generate force.
Excitability: Ability to respond to stimuli.
Extensibility: Ability to be stretched.
Elasticity: Ability to return to original length after stretching.
Types of Tissues in the Muscular System
Skeletal Muscle Tissue: Voluntary movement; striated appearance.
Cardiac Muscle Tissue: Involuntary; found only in the heart; striated.
Smooth Muscle Tissue: Involuntary; non-striated; found in walls of hollow organs.
Differences Between Three Muscle Types
Skeletal muscle: Multi-nucleated; voluntary; striated.
Cardiac muscle: Single nucleus; involuntary; striated; intercalated discs present.
Smooth muscle: Single nucleus; involuntary; non-striated; spindle-shaped.
Anatomy of a Muscle Cell and Components
Composed of muscle fibers (cells) that contain myofibrils, which are further composed of sarcomeres.
Sarcomere: Basic functional unit of muscle contraction.
Anatomy of a Skeletal Muscle
Composed of bundles (fascicles) surrounded by connective tissue layers: epimysium, perimysium, and endomysium.
Smooth Muscle Structure
Composed of sheets of non-striated cells; controlled by autonomic nervous system.
Peristalsis
Wave-like contraction of smooth muscle that moves substances through hollow organs (e.g., digestive tract).
What is a Tendon?
Tendons are fibrous connective tissue that attaches muscle to bone, aiding in movement.
What is an Aponeurosis?
A broad, flat layer of fibrous tissue that connects muscles to the parts they move.
Connective Tissue Layers of Skeletal Muscles
Epimysium: Outermost layer surrounding the entire muscle.
Perimysium: Surrounds individual fascicles (bundles of muscle fibers).
Endomysium: Surrounds individual muscle fibers (cells).
Muscle vs. Fascicle vs. Muscle Fiber
Muscle: Composed of many fascicles.
Fascicle: Bundles of muscle fibers.
Muscle Fiber: Single muscle cell.
Myofibril vs. Sarcomere
Myofibril: Long, thread-like structure within muscle fibers; composed of many sarcomeres.
Sarcomere: Functional unit of muscle contraction, comprised of actin and myosin filaments.
Structure of a Sarcomere
Contains thin (actin) and thick (myosin) filaments; organized into I bands and A bands.
I band: Light band (only actin).
A band: Dark band (contains both actin and myosin).
M-line: Middle line of the sarcomere; anchors myosin.
Z-line: End boundary of the sarcomere; anchors actin filaments.
Roles of Tropomyosin and Troponin
Tropomyosin: A protein that covers binding sites on actin filaments in a relaxed muscle.
Troponin: A complex of proteins that binds calcium and causes tropomyosin to shift, exposing binding sites for myosin.
Steps of Muscle Excitation
Action potential travels down a motor neuron.
Acetylcholine is released into the neuromuscular junction (NMJ).
Binding of acetylcholine to receptors on the muscle cell membrane.
Depolarization of the muscle cell membrane, leading to action potential generation.
Role of Acetylcholine
Neurotransmitter that initiates muscle contraction by transmitting signals from the nerve to the muscle.
Role of T-Tubule
Transmits action potential into the muscle fiber, triggering calcium release from the sarcoplasmic reticulum.
Role of Sarcoplasmic Reticulum
Specialized endoplasmic reticulum in muscle cells; stores and releases calcium ions during muscle contraction.
Troponin vs. Tropomyosin
Troponin: Protein complex sensitive to calcium; facilitates muscle contraction.
Tropomyosin: Protein that regulates access to actin binding sites for myosin.
Steps of Muscle Contraction/Sliding Filament Mechanism
Calcium binds to troponin, causing tropomyosin to shift and expose actin binding sites.
Myosin heads attach to actin forming cross-bridges.
Myosin heads pull actin toward the center of the sarcomere (power stroke).
ATP binds to myosin heads, causing them to detach from actin.
Cycle repeats as long as calcium and ATP are available.
Role of Creatine Phosphate & How It is Made (Phosphate Transfer)
Creatine phosphate provides a rapid source of energy by donating a phosphate group to ADP to regenerate ATP during short bursts of activity.
Synthesized from creatine and ATP in muscle cells.
Roles of Hemoglobin and Myoglobin
Hemoglobin: Protein in red blood cells that transports oxygen.
Myoglobin: Oxygen-binding protein in muscle cells; stores oxygen for muscle contraction.
Different quantities present in fast-twitch vs. slow-twitch fibers: slow-twitch fibers contain more myoglobin.
Glycolysis vs. Aerobic Respiration in Muscles
Glycolysis: Anaerobic process that produces ATP from glucose without oxygen; results in lactic acid buildup.
Aerobic respiration: Efficient production of ATP with oxygen; occurs in mitochondria.
Fermentation and Lactic Acid Buildup
Occurs when oxygen is low; pyruvate from glycolysis is converted to lactic acid. This leads to muscle fatigue and soreness.
Factors Affecting Oxygen Availability
Altitude, pulmonary diseases, and other conditions that influence respiratory efficiency.
Factors Affecting Oxygen Demand
Exercise intensity, duration, and muscle groups involved; higher intensity increases oxygen demand.
What is Fatigue and How Does it Occur?
Fatigue is a temporary decrease in muscle ability to perform work; caused by metabolic changes, lack of glycogen, accumulation of lactic acid, etc.
What is a Motor Unit?
A motor unit consists of a motor neuron and the muscle fibers it innervates; responsible for muscle contraction.
Tonic vs. Twitch Fibers
Tonic fibers: Slow, sustained contractions; found in postural muscles.
Twitch fibers: Fast contractions; responsible for quick, powerful movements.
Traits of Slow Twitch Fibers (Type I)
Endurance-oriented; highly vascularized; high myoglobin content; resistant to fatigue.
Traits of Fast Twitch Oxidative Fibers (Type IIa)
Intermediate; capable of both anaerobic and aerobic metabolism; moderate resistance to fatigue.
Traits of Fast Twitch Glycolytic Fibers (Type IIx)
Primarily anaerobic metabolism; generate quick, powerful bursts of energy; fatigue quickly.
Distribution of Each Fiber Type
Varies by muscle group and function; e.g., endurance athletes tend to have more Type I fibers.
Switch from Type IIa to IIx
In response to high-intensity training, Type II fibers may convert from Type IIa (oxidative) to Type IIx (glycolytic) for quick bursts of energy.
Effect of Aerobic Training on Muscle Fibers
Increases the proportion of Type I (slow-twitch) fibers, enhancing endurance and aerobic capacity.
Hypertrophy and Atrophy
Hypertrophy: Increase in muscle size due to increased myofibril proteins; occurs with strength training.
Atrophy: Decrease in muscle size and strength due to disuse or inactivity.