The Musculoskeletal System Flashcards
What is skeletal muscle?
responsible for voluntary movement and innervated by the somatic nervous system
What are sarcomeres?
the functional contractile unit of striated muscle; repeating units of actin and myosin; thick and thin filaments
What are slow-twitch fibers?
aka “red fibers”; have high myoglobin content and primarily derive their energy aerobically
What is myoglobin?
an oxygen carrier that uses iron in a heme group to bind oxygen, imparting a red color
What is fast-twitch fibers?
aka “white fibers”; contain much less myoglobin
Muscles that contract rapidly but fatigue quickly, contain mostly _____ fibers?
white
Muscles that contract slowly but can sustain activity contain mostly ______ fibers?
red
What is smooth muscle?
responsible for involuntary action and innervated by autonomic nervous system
Which types of muscle are multinucleated?
skeletal, cardiac (sometimes)
What is tonus?
a constant state of low-level contraction, as may be seen in blood vessels; more sustained contractions
What is myogenic activity?
smooth muscle can actually contract without nervous system input and responses directly to stretch or other stimuli
What is cardiac muscle?
contraction is involuntary and innervated by the autonomic nervous system; looks striated; also exhibits myogenic activity
What are intercalated discs?
connect cardiac cells and contain gap junctions
What are gap junctions?
connections between the cytoplasm of adjacent cells allowing for the flow of ions directly between the cells
What are thick filaments?
organized bundles of myosin
What are thin filaments?
made of actin, troponin and tropomyosin
What is titin?
a protein that acts as a spring and anchors the actin and myosin filaments together; preventing excessive stretching of the muscle
What are myofibrils?
sarcomeres attached end to end
What is the sarcoplasmic reticulum (SR)?
a modified endoplasmic reticulum that contains a high concentration of Ca2+ ions and covers myofibrils
What is the sarcoplasm?
modified cytoplasm located just outside the SR
What is the sarcolemma?
the cell membrane of a myocyte; capable of propagating an action potential and can distribute the action potential to all sarcomeres in the muscle
What are transverse tubules (T-tubules)?
tubules that are oriented perpendicular to the myofibrils through which the action potentials can be transmitted
What is another word for a muscle cell?
myocyte
What is a muscle fiber?
a bunch of myofibrils arrange in parallel; aka a myocyte
Pathway of the muscle contration
Neuromuscular junction —> motor neurons —> nerve terminal —> acetylcholine to receptors —> depolarization
What is the neuromuscular junction?
where the nervous system communicates with muscles via motor neurons
What is the motor end plate?
nerve terminal or synaptic bouton
What is a motor unit?
the nerve terminal and its myocytes
What are the events that initiate muscle contraction starting with the lease of neurotransmitter?
Release of acetylcholine from motor neuron —> activation of acetylcholine receptors in sarcolemma —> depolarization of sarcolemma —> spreading of signal using T-tubules —-> release calcium from sarcoplasmic reticulum (SR) —> binding of calcium to troponin –> conformational shift in tropomyosin —> exposure of myosin-binding sites —> myosin binds to actin
What is tetanus?
when muscles contractions become so frequent that the muscle is unable to relax at all; results in muscle fatigue
What is creatine phosphate?
created by transferring a phosphate group from ATP to creatine during times of rest to be uses for muscles contraction
What are the two supplemental energy reserves in muscle?
creatine phosphate and myoglobin
What are exoskeletons?
encase whole organisms and are usually found in arthropods; must be shed though
What are endoskeletons?
internal but are not able to protect soft tissue as well; like humans but better able to accommodate growth
What is the axial skeleton?
skull, vertebral column, ribcage and hyoid bone
What is the appendicular skeleton?
bones of the limbs
What are the two bone types?
compact and spongy/cancellous
What are trabeculae?
bony spicules/points in spongy bone; spaces between are filled with bone marrow
What are the types of bone marrow?
Red - hematopoietic stem cells - generation of all cells in blood
Yellow - made of fat and inactive
What are long bones?
characterized by cylindrical shafts called diaphyses and swell at each end to form metaphyses and terminate in epiphyses
What is the epiphyseal (growth) plate?
a cartilaginous structure and the site of longitudinal growth
What is the periosteum?
a fibrous sheath that surrounds the long bone to protect it as well as serve as site for muscle attachment; necessary for bone growth and repair
What are tendons?
attach muscle to bone
What are ligaments?
hold bones together at joints
What is the bone matrix?
strength of compact bones and made up of organic and inorganic materials
What is osteans/Haversian systems?
the structural units of the bony matrix
What is lamellae?
concentric circles of bony matrix that surround channels of the Haversian system
What are Haversian canals?
longitudinal canals (axis parallel to the bone) as part of the Haversian system; contain blood vessels, nerve fibers and lymph vessels
What are Volkmann’s canals?
transverse canals (axis perpendicular to the bone) as part of the Haversian system; contain blood vessels, nerve fibers and lymph vessels
What are lacunae?
small spaces between the lamellar rings that house mature bone cells (osteocytes)
What are canaliculi?
tiny channels that connect the lacunae and allow for exchange of nutrients and waste between osteocytes and the canals
What are the two types of cells responsible for bones?
osteoblasts and osteoclasts
What are osteoblasts?
build bone
What are osteoclasts?
polynucleated resident macrophages of bone the resorb it
What does parathyroid hormone do?
promotes resorption of calcium and phosphate from the bone into the blood in response to low calcium in the blood
What does Vitamin D do?
promotes resorption of the bone and in response the bone overcompensates with new, stronger bone growth
What does calcitonin do?
promotes bone formation and lowers blood calcium levels
What is cartilage?
softer and more flexible than bone; contains firm but elastic matrix called chondrin; avascular and not innervated
What is endochondral ossification?
the hardening of cartilage into bone and is responsible for most long bones
What is intramembranous ossification?
undifferentiated embryonic connective tissue is transformed into and replaced by bone
What are immovable joints?
consist of bones that are fused together to form sutures or similar fibrous joints; found primarily in the head
What are movable joints?
permit bones to shift relative to one another and strengthened by ligaments that connect the bones
What is a synovial capsule?
it covers the joint cavity
What is the synovium?
a layer of soft tissue that secretes synovial fluid which lubricates the movement of structures
What is articular cartilage?
contributes to the joint by coating the articular surfaces of the bones so that impact is restricted to the lubricated joint cartilage rather than to the bones
Which muscle end is the origin?
the end of the muscle with a larger attachment to the bone (usually proximal)
Which muscle end is the insertion?
the end of the muscle with the smaller attachment to the bone (usually distal)
What is a flexor muscle?
decreases the angle across a joint
What is an extensor muscle?
increases or straightens this angle
What is an abductor muscle?
moves a part of the body away from the midline
What is medial rotation?
moving the axis of the limb towards the midline
What is lateral rotation?
moving the axis of the limb away from the midline
