Muscular and Skeletal Systems Flashcards
Skeletal system
Endoskeleton serves as the framework
Provides protection by surrounding delicate internal organs
Cartilage
Connective tissue that is softer and more flexible than bone
Retained in places where firmness and flexibility are needed
Chrondrocytes
Cells that synthesize cartilage
Bone
Specialized mineralized connective tissue that withstands physical stress
Hard and strong while somewhat elastic and lightweight
Compact and spongy
Compact bone
Dense bone that does not appear to have any cavities when observed with the naked eye
Matrix deposited in osteons
Osteons
Haversian systems
Structural units of boney matrix
Consists of central microscopic Haversian canal surrounded by concentric circles of bony matrix (calcium phosphate) lamellae
Spongy bone
Less dense
Interconnecting lattice of bony spicules (trabeculae)
Cavities between spicules are filled with yellow or red bone marrow
Yellow marrow
Inactive
Infiltrated by adipose tissue
Red marrow
Involved in blood cell formation
Osteoblasts
Synthesize and secrete organic constituents of the bone matrix
Once surrounded by their matrix, they mature into osteocytes
Osteoclasts
Large, multinucleated cells involved in bone reabsorption where bone is broken down and minerals are released into the blood
Endochondral ossification
Existing cartilage is replaced by bone
Intramembranous ossification
Mesenchymal (embryonic or undifferentiated) connective tissue is transformed into and replaced by bone
Bone formation
Endochondral
Intramembranous
Axial skeleton
The basic framework of the body
Skull, vertebral column, rib cage
Appendicular skeleton
The bones of the appendage and the pectoral and pelvic girdles
Ligaments
Attach bone to bone
Tendons
Attach skeletal muscle to bones
Origin
The point of attachment of a muscle to a stationary bone
Proximal end in limb muscles
Insertion
The point of attachment of a muscle to a bone that moves
Distal end in limb muscles
Extension
The straightening of a joint
Flexion
The bending of a joint
Muscle tissue
Bundles of specialized contractile fibers held together by connective tissue
Skeletal, smooth, and cardiac
Pyramidal system
Provide rapid commands to the skeletal muscles and organs
Nervous control involving the axons of the pyramidal cells of the motor cortex, descending from the brain to synapse on lower motor neurons in the brain stem and spina cord
Extrapyramidal system
Red nucleus in the mesencephalon is primarily control of skeletal muscle tone
Issue somatic motor command at the unconscious, involuntary level
Skeleton muscle
Responsible for voluntary movements
Innervated by the somatic nervous system
Fibers of multinucleated cells created by the fusion of several mononucleated embryonic cells
Myofibril
Filaments embedded in skeleton muscle fibers
Divided into sacromeres
Sacroplasmic reticulum
Envelopes myofibrils by a modified endoplasmic reticulum that stores calcium ions
Sarcolemma
The cell membrane of muscle fibers
Capable of propagating an action potential
Connected to a T system oriented perpendicularly to the myofibrils
T system
Transverse tubules
Provide channels for ion flow throughout the muscle fiber
Can propagate an action potential
Perpendicular to myofibrils
Striated muscle
Striations of light and dark bands
Sacromere
Contractile units composed of thin (actin) and thick (myosin) filaments
Z line
Define the boundaries of a single sarcomere
Anchor the thin filaments
Move toward each other during contraction
M line
Runs down the center of the sarcomete
I band
The region containing only thin filaments
H zone
The region containing only thick filaments
A band
Spans the entire length of the thick filaments and any overlapping thin filaments
Contraction
Stimulated by message from the somatic nervous system sent via a motor neuron
Receptors stimulated on the sarcolemma to generate an action potential. Conducted along the sarcolemma and T system and into the interior of the muscle fiber
Sarcoplasmic reticulum releases calcium ions into the sarcoplasm which binds tropinin C on actin filaments
Allosteric changes allow myosin heads to bind these site on actin
ATP allows power stroke to pull Z bands closer together causing actin and myosin to slide past each other
Types of muscle contractions
Isotonic Dynamic Concentric Eccentric Isometric
Isotonic contraction
When a muscle shortens against a fixed load while the tension on that muscle remains constant
Dynamic contraction
Concentric and eccentric
Results in a change in length of the muscle with a corresponding change in tension on that muscle
Concentric contraction
The muscle fibers shorten and the tension on the muscle increases
Eccentric contraction
The muscle fiber lengthens and the tension on the muscle increases
Isometric contraction
When both ends of the muscle are fixed and no change in length occurs but the tension increases
Simple twitch
The response of a single muscle fiber to a brief stimulus at or above the threshold stimulus
Consists of a latent period, contraction period, and relaxation period
Latent period
The time between stimulation and the onset of contraction
The action potential spreads along the sarcolemma and Ca2+ ions are released
Relaxation period
The muscle is unresponsive to a stimulus
Absolute refractory period
Temporal stimulation
When muscle fibers are exposed to very frequent stimuli and cannot fully relax
Contractions combine, becoming stronger and more prolonged
Tetanus
Tonus
Muscles never completely relax and maintain partially contracted state at all times
Cori cycle
During periods of strenuous activity, convert lactic acid in the liver to glucose for discharge into the bloodstream for energy or rebuild glycogen reserves
Smooth muscle
Responsible for involuntary actions
Innervated by the autonomic nervous system
Smooth, continuous contractions
Found in the digestive tract, bladder, uterus, and blood vessel walls
Central nucleus and not striated
Cardiac muscle
Characteristics of skeletal and smooth muscle
Strong, forceful contractions
Actin and myosin filaments arranged in sarcomeres giving striated appearance
Only one or two central nuclei
Creatine phosphate
Temporary store of high-energy compound
Myoglobin
Haemoglobin-like protein found in muscle tissue
High oxygen affinity to maintain oxygen supply in muscles
