Biology Ch 11. The Musculoskeletal System Flashcards
Three main types of muscle
Skeletal, smooth, and cardiac
Skeletal muscle
Often support and movement, propulsion of blood in the Venus system, and thermal regulation, it appears striated, is under voluntary control (somatic nervous system), is multinucleated, can be derived into red fibers that curiosity to phosphorylation and white fibers that rely on anaerobic metabolism
Stiated
Striped, how skeletal and cardiac muscle appears under microscope, when actin and myosin fibers arranged into repeating units
Red fibers
aka slow twitch fibers - carry out oxidative phosphorylation, high myoglobin content, high levels of mitochondria, common in muscles that contract slowly, but can sustain activity (posture)
White fibers
aka fast twitch fibers - carry out anaerobic metabolism, lower myoglobin concentration, present in muscles that contract rapidly but fatigue quickly
Smooth muscle
Is in the respiratory, reproductive, cardiovascular, and digestive systems, it appears non-striated, is under a involuntary control, and is uninucleated, it can display myogenic activity
Myogenic activity
Contraction without neural input
Cardiac muscle
Comprises the contractile tissue of the heart, appear striated, is under involuntary control, is uninucleated or sometimes binucleated, can also display myogenic activity, cells connected with intercalated discs that contain gap junctions
Intercalated discs
Connects cells in cardiac muscle, contains many gap junctions
Gap junctions
In intercalated discs, connection between the cytoplasm of adjacent cells, site of electrical synapsing or the flow of ions directly between cells, allows for efficient depolarization and contraction
Sarcomere
The basic contractile unit of striated muscle, made of thick (myosin) and thin (actin) filaments
Myosin in muscle
Thick filaments in sarcomeres
Actin in muscle
Makes up, along with troponin and tropomyosin, the thin filaments in sarcomeres
Troponin
Found on the thin (actin) filament and regulate actin-myosin interactions
Tropomyosin
Found on the thin (actin) filament and regulate actin-myosin interactions
Z lines
Define boundaries of each sarcomere
M-line
Located in the middle of the sarcomere, right through myosin filaments
I band
Contains only thin filaments
H zone
Consists of only thick filaments
A band
Contains the thick filaments in their entirety, the only part of the sarcomere that maintains a constant size during contraction
Myofibrils
Created when sarcomeres attach end-to-end, surrounded by sarcoplasmic reticulum covering
Myocyte
A muscle cell or muscle fiber, contains many myofibrils arranged in parallel
Sarcoplasmic reticulum
Surrounds myofibrils, a calcium containing modified endoplasmic reticulum
Sarcolemma
Cell membrane of a myocyte, capable to propagating an action potential and distributing the action potential to all sarcomeres using transverse tubules
T-tubules
Transverse tubules - Connected to the sarcolemma and oriented perpendicular to the myofibrils, allowing the action potential to reach all parts of the muscle
Neuromuscular junction
Where muscle contraction begins, where the motor neuron releases acetylcholine binds to receptors on the sarcolemma, causing depolarization, signals from motor/efferent neurons
Muscle contraction
Motor neuron releases acetylcholine that binds to receptors on the sarcolemma at the neuromuscular junction, this depolarization spreads down the sarcolemma to the T tubules triggering the release of calcium ions, calcium binds to troponin causing a shift in tropomyosin and exposure of the myosin binding sites on the actin thin filament, myosin heads bind the expose sites on actin forming cross bridges and pulling the actin filament along the thick filament, resulting in contraction
Sliding filament model
Model of shortening of the sarcomere where myosin heads bind to the expose sites on actin, forming cross bridges and pulling the actin filament along the thick filament, this occurring in a repetitive manner results in contraction
Muscle relaxation
Acetylcholine is degraded by acetylcholinesterase, terminating the signal in allowing calcium to be brought into the sarcoplasmic reticulum, ATP binds to the myosin head allowing it to release from Acton
Simple twitch
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
A more prolonged and stronger contraction that occurs when simple twitches occurs so frequently as to not let the muscle relax at all
Oxygen debt
Difference between the amount of oxygen needed and the amount present, can be reduced by muscle cells that have additional energy reserves
Creatine phosphate
Transfers a phosphate group to ADP, forming ATP, created during periods of resting to get ATP quickly during periods of use
Myoglobin
A heme containing protein that is a muscular oxygen reserve
Tonus
A constant state of low-level contraction, seen in the blood vessels, smooth muscle is capable of it
Cardiac muscle myogenic activity
Starts at SA node –> AV node –> bundles of His –> purkinje fibers
Titin
Acts as a spring and anchors the actin and myosin filaments together, preventing excessive stretching of the muscle
Sarcoplasm
A modified cytoplasm located just outside the sarcoplasmic reticulum
Motor end plate
The nerve terminal in the neuromuscular junction
Motor unit
The nerve terminal and its myocytes
Myosin-binding sites
Locations on the actin thin filaments that are made accessible when Ca2+ binds to troponin causing a change in confirmation of tropomyosin
Muscle powerstroke
When myosin attaches to the myosin binding site on action, ADP and Pi dissociate from the mysosin, providing energy for a powerstroke
Acetylcholinesterase
Degrades acetylcholine in the synapse, terminating the signal
Latent period
Time between reaching threshold and the onset of contraction, action potential spreads along the muscle and allows for calcium to be released from the sarcoplasmic reticulum
Simple twitch periods
Latent period, contraction period, relaxation period
Endoskeletons
Internal skeletons (like in humans), are not able to protect the soft tissue structures as well as exoskeletons
Exoskeletons
External skeletal (like in anthropods), must shed and regrown to accommodate growth
Human skeletal system divisions
Axial and appendicular skeleton
Axial skeleton
Consists of striations in the midline such as the skull, vertebral column, ribcage, and hyoid bone
Appendicular skeleton
Consists of the bonds of the limbs, the pectoral girdle, and the pelvis
Bone
Derived form the embryonic mesoderm and includes both compact and spongy types
Compact bone
Provides strength, is very dense, forms outmost portions of the bone
Spongy bone
aka cancellous bone, has a lattice like structure consisting of trabeculae, cavities are filled with bone marrow, internal core of the bone
Trabeculae
Bony spicules/points in spongy bone
Diaphyses
Cylindrical shafts within long bones that flare to form metaphases
Epiphyses
Where long bones terminate, contain an epipihyseal or growth plate, use spongy cores for more effective dispersion of force and pressure at joints
Epipihyseal plate
aka growth plate, causes linear growth of the bone, close during puberty
Periosteum
Layer of connective tissue that surrounds bone, site for muscle attachment, some periosteal cells capable of differentiating into bone-forming cells
Tendons
Attach bones to muscles
Ligaments
Attaches bones to each other
Bone matrix
Contains both organic compounds such as collagen, glycoproteins, and peptides, and inorganic compounds like hydroxyapatite, provides strength to compact bone
Hydroxyapatite
Inorganic components (calcium, phosphate, and hydroxide ions) that harden together and form crystals
Lamellae
Concentric circles of bony matrix in compact bone
Bone organization
Lamellae around Haversian or Volkmannn’s canals
Osteon
aka Haversian system, structural unit of bone
Lacunae
Between lamellar rings, where osteocytes reside, are connected by canaliculi to allow for nutrient and waste transfer
Osteocytes
Mature bone cells
Canaliculi
Connected to lacunae, allow for nutrient and waste transfer between osteocytes and Haversian and Volksmanns canals
Osteoblasts
Build bone
Osteoclasts
Resorb bone
Parathyroid hormone
Peptide hormone released be parathyroid in response to low blood calcium, increases resorption of bone, increases calcium and phosphate concentrations in the blood
Vitamin D
Activated by parathyroid hormone, increases resorption of bone, leads to increased turnover and the production of stronger bone
Calcitonin
Peptide hormone released by parafollicular cells of the thyroid in response to high blood calcium, increases bone formation, decreases calcium concentration in the blood
Cartilage
Firm, elastic material secreted by chondrocytes, matrix is the chondrin, usually found in areas that require more flexibility or cushioning, avascular and not innervated
Chondrocytes
Secretes cartilage
Chondrin
Firm but elastic matrix of cartilage
Endochondral ossification
Process by which bones form from fetal cartilage
Intramembranous ossification
The process by which bones, especially those of the skull, form directly from undifferentiated tissue in fetal life
Mesenchyme
Undifferentiated tissue
Immovable joints
Fused together to form sutures or similar fibrous joints
Movable joints
Strengthened by ligaments and contain a synovial capsule, include hinge joints and ball and socket joints
Synovial capsule
Enclose the actual joint/articular cavity
Synovial fluid
Secreted by the synovium, aid in motion by lubricating the joint
Synovium
Layer of soft tissue that secretes synovial fluid
Articular cartilage
What each bone in a joint is coated in to aid in movement and provide cushioning
Antagonistic pairs
Pairs of muscles that serve opposite functions, when one muscle contracts, another lengthens
Red marrow
Filled with hematopoietic stem cells, responsible for the generation of all the cells in our body
Yellow marrow
Composed of primarily fat, is relatively inactive
Bone marrow
Fills cavities between trabeculae in spongy bone, can be either red or yellow
Long bones
Common the appendicular skeleton, characterized by diaphyses that swell into metaphases and terminate in epiphyses
Haversian canals
Longitudinal canals (axis parallel to the bone), contain blood vessels, nerve fibers, lymph vessels
Volkmanns canals
Transverse canals (axis perpendicular to the bone), contain blood vessels, nerve fibers, lymph vessels
Sutures
Bones that are fused together in immovable joints
Origin
The end of the muscle with a larger attachment to bone, usually the proximal connection
Insertion
The end of the muscle with the smaller attachment to bone, usually the distal connection
Synergistic muscles
Muscles that work together to accomplish the same function
Flexor
A muscle that decreases the angle across a joint
Extensor
A muscle that increases the angle across a joint
Abductor
A muscle that moves a part of the body away from the midline
Adductor
A muscle that moves a part of the body toward the midline
Medial rotation
Rotates the axis of the limb toward the midline
Material rotation
Rotates the axis of the limb away from the midline
