Ch. 11: The Musculoskeletal System Flashcards
what are muscle subtypes
- skeletal
- smooth
- cardiac
what does skeletal muscle do
- voluntary movements
- somatic nervous system
- multi nucleated
what kind of muscle is striated
skeletal muscle
cardiac muscle
d/t repeating units of sarcomeres
what are red fibers/slow twitch fibers
- high myoglobin content
- aerobic energy
- high levels in muscles that contract slowly and sustain activity (posture)
what does myoglobin do
oxygen carrier that uses iron (in a heme group) to bind to oxygen
what are white/fast twitch fibers
- low myoglobin content
- high levels in muscles that contract rapidly and fatigue quickly
what does smooth muscle do
- involuntary action
- autonomic nervous system
- mono-nucleated
what occurs during myogenic activity
smooth or cardiac muscle contractions in response to stretch/stimuli without nervous system input
what does cardiac muscle do
- cardiac muscle contractions
- autonomic nervous system
- mono AND dinucleated
how do cardiac muscle cells communicate
intercalated disks and gap junctions
allow for free flow of ions between cells and rapid, coordinated depolarization
what muscle types exhibit myogenic activity
smooth and cardiac muscle
what is a sarcomere
basic contractile unit of muscle
- made of thick (myosin) filaments and thin (actin, troponin, tropomyosin) filaments
what are thick filaments made of
myosin
what are thin filaments made of
actin, troponin, tropomyosin
what does titan do
anchors actin and myosin together, preventing excessive stretching
where is the z-band located
the boundary of the sarcomere
where is the m-line located
down the center of the sarcomere
what does the I band contain
exclusively thin filaments
what does the H zone contain
exclusively thick filaments
what does the A-band contain
ALL thick filaments, with occasional overlap with thin filaments
what are myofibrils formed of
sarcomeres attached end to end
what is the sarcoplasmic reticulum
- covering that surrounds the myofibrils
- modified endoplasmic reticulum
- high Ca2+ ion content
what is the sarcoplasm
modified cytoplasm, located just outside the sarcoplasmic reticulum
what is the sarcolemma
- the cell membrane of a myocyte
- can propagate action potential to all sarcomeres in a muscle using transverse tubules
what is the function of the transverse tubules
oriented perpendicularly to myofibrils and allow sarcolemmas to propagate action potentials to all sarcomeres in a muscle
how is a myocyte defined
- contains many myofibrils arranged in parallel
- also called a muscle fiber
flow of signal for muscle contraction
efferent neurons propagate signal –> nerve terminal/motor end plate –> acetylcholine released into synapse –> acetylcholine binds to sarcolemma receptors –> depolarization –> action potential travels through t-tubules –> action potential travels into sarcoplasmic reticulum –> Ca2+ released
what does a motor unit consist of
nerve terminal + myocytes
what occurs at the neuromuscular junction
nervous system communicates with muscles
where are myosin-binding sites and how are they exposed
actin/ thin filament
Ca2+ binds to troponin which changes conformation of the tropomyosin its bound to which exposes the sites on actin
how is the sarcomere shortened
exposed actin myosin-binding sites form bridges with myosin (thick filament), pull on each other, and draw the thin filaments toward the M line
which regions on a sarcomere change during contraction and which stay the same
H-zone and I-bands shorten while A-band is unchanged
what is responsible for the powerstroke
dissociation of ADP + Pi
how is myosin released from the actin filament
ATP binds to myosin
how does relaxation occur
acetylcholine is degraded by acetylcholinesterase –> signal terminates –> sarcolemma depolarizes –> SR takes up Ca2+
what kind of response to muscle cells exhibit
all-or-nothing
just like the neurons that control them
what kind of response is a simple twitch
single muscle fiber response to a brief stimulus
what occurs during the latent period
after reaching threshold, action potential spreads along the muscle and allows for Ca2+ to be released before the onset of contraction
what occurs during the phenomenon of frequency summation
after frequent and prolonged stimulation, contractions combine to become stronger and more prolonged
what qualifies as tetanus
frequent stimulation –> frequent contractions –> unable to relax –> muscle fatigue
both d/t disease and normal conditions
how is creatinine phosphate produced
a phosphate group is transferred from ATP to creatine in order to produce ADP during times of anaerobic muscle contraction
what value does oxygen debt represent
the difference between the amount of oxygen needed by the muscles and the actual amount present
what organisms have exoskeletons
typically arthropods (crustaceans and insects)
whole organism is encased, better protection of soft tissue, must be shed for growth
what organisms have endoskeletons
vertebrates
skeleton is inside the soft tissue, better for growth, less soft tissue protection
what comprises the axial skeleton
central framework
skull, vertebral column, ribcage, hyoid bone
what comprises the appendicular skeleton
limbs, pectoral girdle, and pelvis
what are the major components of the skeleton
bone and cartilage
what embryonic layer is bone derived from
the mesoderm
what types of bone tissue are there
compact bone and spongy bone
what kind of bone marrow are hematopoietic stem cells located in
red bone marrow
what comprises yellow bone marrow
fat; relatively inactive
where is compact bone located in a bone
the outermost portions of bone
where is spongy bone located
the internal core
where are diaphyses located
cylindrical shafts of bones
where and how are metaphases formed
produced at the ends of bone shafts/diaphyses as the diaphyses swell
where are epiphyses located
the terminal ends of bones, spongy core
what is the function of the periosteum
fibrous sheath that surrounds the bones and allows for muscle attachment
what do tendons attach
muscle to bone
what to ligaments attach
bones to other bones at joints
what do osteoblasts do
build bone
what do osteoclasts do
reabsorb bones as macrophages
“chew bone”
what is cartilage made of
chondrin that is secreted by chondrocytes
what occurs during endochondral ossification
cartilage hardens into bones
where are immoveable joints located
primarily in the skull
bones are fused together to form sutures
what is located in the synovial capsule
the joint cavity and synovium (soft tissue layer) which secretes synovial fluid for lubrication
what is the purpose of articular cartilage
covers the articular surfaces of the bone to cushion impact on the bones
