Ch. 11: The Musculoskeletal System Flashcards
3 main types of muscle
Skeletal, smooth, cardiac
Skeletal muscle
Involved in support and movement, propulsion of blood in the venous sys, and thermoregulation. Appears striated, is under voluntary (somatic) control, is polynucleated, and can be divided into red (slow-twitch) fibers that carry out oxidative phosphorylation and white (fast-twitch) fibers that rely on anaerobic metabolism
Smooth Muscle
In the respiratory, reproductive, cardiovascular and digestive systems. It appears nonstriated, is under involuntary (autonomic) control, and is uninucleated. It can display myogenic activity or contraction without neural input
Cardiac muscle
Comprises the contractile tissue of the heart. It appears striated, is under involuntary (autonomic) control, and is uninucleated (sometimes binucleated). It can also display myogenic activity. Cells are connected w intercalated discs that contain gap junctions
Sarcomere
Basic contractile unit of striated muscle. Made of thick myosin and thin actin filaments
Troponin and Tropomyosin
Found on the thin filament and regulate actin-myosin interactions
Sarcomere can be divided into
Different lines, zones, and bands
Z-lines
Boundaries of each sarcomere are defined by Z-lines
M-line
Located in the middle of the sarcomere
I-band
Contains only thin filaments
H-zone
Consists of only thick filaments
A-band
Contains the thick filaments in their entirety. It is the only part of the sarcomere that maintains a constant size during contraction
Myofibrils
Sarcomeres attached end-to-end
Myocyte
Muscle cell or muscle fiber, contains many myofibrils
Sarcoplasmic Reticulum
Surrounds myofibrils, calcium containing modified endoplasmic reticulum
Sarcolemma
Surrounds myofibrils the cell membrane of a myocyte
T-tubules
A system of T-tubules is connected to the sarcolemma and oriented perpendicularly to the myofibrils, allowing the incoming signal to reach all parts of the muscle
Neuromuscular Junction:
Muscle contraction begins at the neuromuscular junction, where the motor neuron releases acetylcholine that binds to receptors on the sarcolemma, causing depolarization
Depolarization
Spreads down the sarcolemma to the T-tubules, triggering the release of calcium ions
Calcium
Binds to troponin, causing a shit in tropomyosin and exposure of the myosin binding sites on the actin thin filament
Sliding filament model
Shortening of the sarcomere occurs as myosin heads bind to the exposed sites on actin, forming cross bridges and pulling the actin filament along the the thick filament, resulting in contraction
Muscle Relaxation
Acetylcholine is degraded by acetylcholinesterase, terminating the signal and allowing calcium to be brought back into the SR. ATP binds to the myosin head, allowing it to release from actin
Simple twitch
An all or nothing response exhibited by muscle cells
Frequency Summation
Addition of multiple simple twitches before the muscle has an opportunity to fully relax
Tetanus
Simple twitches that occur so frequently as to not let the muscle relax at all can lead to tetanus, a more prolonged and stronger contraction
Oxygen Debt:
Muscle cells have additional energy reserves to reduce oxygen debt (the diff between the amt of oxygen needed and the amt present) and forestall fatigue
Creatine Phosphate
Can transfer a phosphate group to ADP forming ATP
Myoglobin
Heme containing protein that is a muscular oxygen reserve
Endoskeleton
Internal skeletons (like those in humans)
Exoskeletons
External skeletons (like those in arthropods)
human skeletal system divisions
Axial and appendicular skeletons
Axial skeleton
Consists of structures in the midline such as the skull, vertebral column, ribcage, and hyoid bone
Appendicular skeleton
Consists of the bones of the limbs, the pectoral girdle and the pelvis
Bone is derived from
Embryonic mesoderm and includes both compact and spongy (cancellous) types
Compact Bone
Provides strength and is dense
Spongy or cancellous bone
Has a lattice-like structure consisting of bony spicules known as trabeculae. The cavities are filled w bone marrow
Long bones contain
Shafts called diaphyses that flare to form metaphyses and that terminated in epiphyses
Epiphysis
Contain an epiphyseal (growth) plate that causes linear growth of the bone
Periosteum
Bone is surrounded by a layer of connective tissue called periosteum
Tendons
Bones to muscle
Ligaments
Bones to bones
Bone matrix
Has both organic components, like collagen, glycoproteins, and other peptides, and inorganic components, like hydroxyapatite
Lamellae
Concentric rings that bone is organized into
Haversian or Volkmann’s canal
Center of the concentric rings
Osteon or Haversian system
Structural unit of lamellae and Volkmann’s canal
Lacunae
Between lamellar rings, where osteocyte reside, which are connected with canaliculi to allow for nutrient and waste transfer
Bone remodeling
Carried out by osteoblasts (build bone) and osteoclasts (resorb bone)
Parathyroid Hormone
Increases resorption of bone, increasing calcium and phosphate concentrations in the blood
Vitamin D
Also increases resorption of bone, leading to increased turnover and, subsequently, the production of stronger bone
Calcitonin
Increases bone formation, decreasing calcium concentrations in the blood
Cartilage
Firm, elastic material secreted by chondrocytes. Its matrix is called chondrin. Usually found in areas that require more flexibility or cushioning. Avascular and not innervated
Endochondral ossification
In fetal life, bone forms from cartilage through endochondral ossification.
Intramembranous ossification
Some bones, esp those of the skill, form directly from undifferentiated tissue (mesenchyme)
Classification of joints
Immovable or movable
Immovable joints
Fused together to form sutures or similar fibrous joints
Movable joints
Usually strengthened by ligaments and contain a synovial capsule
Synovial fluid
Secreted by the synovium, aids in motion by lubricating the joint
Articular Cartilage
Each bone in the joint is coated with articular cartilage to aid in movement and provide cushioning
Antagonistic Pairs
Muscles that serve opposite functions come in antagonistic pairs; when one muscle contracts the other lengthens
