Muscle Tissue, Case study 5 Flashcards
duchenne’s muscular dystrophy
caused by a genetic mutation, resulting in the absence or insufficient amounts of the dystrophin protein to be present in the sarcomere
- X chromosome linked bc more common in males (ie if they have the gene, they have DMD bc they can’t pass it on unless they have it)
lordosis
excessive convex curvature of the lumbar vertebrae
kyphosis
excessive concave curvature in spine of cervical, thoracic and sacral regions
dystrophin
a protein that attaches onto actin filaments and connects them to the sarcolemma
how does muscular dystrophy cause muscle weakness?
- tears in muscles from poor structure, then always trying to repair muscles and so they are weak when used bc not enough myosin and actin are present
OR - muscle fibers are not connected all the way to the CT surrounding structures (tendons, bone) and so when H band shortens, there is no pull on surrounding tissues
skeletal muscles system functions
heat production body movement posture maintenance communication respiration
mnemonic for remembering functions of skeletal muscle
holy == heat prod. billy's === body movement puppy == posture can === communication run == respiration
properties of skeletal muscle
contractility
excitability
extensibility
elasticity
contractility
muscles can contract, generating force or tension
excitability
muscles can respond to a stimulus by producing action potentials
- they are electrically excitable
extensibility
muscle can be stretched beyond its resting length and still be able to contract bc of overlapping proteins
elasticity
muscles can recoil to their original resting length after it’s been stretched
skeletal muscle cells are (one word)
fibers
skeletal muscle cells
- highly organized structure
- long (run length of muscle)
- multinucleated bc they come from myoblasts merged together during embryology
- nuclei loc just below plasma membrane
order of layers of CT surrounding muscle tissue
fascia - muscle groups
epimysium - around whole muscle
perimysium - surrounds fascicle
endomysium - loose areolar/reticular CT b/w cells in a fascicle
tendon
dense regular CT
- layers of periosteum (dense irregular) become dense regular
fascia
surrounds groups of muscle
- dense irregular CT
epimysium
dense irregular CT
- surrounds whole muscle
fascicle
multiple muscle fibers grouped together
surrounded by perimysium
perimysium
surrounds fascicle
endomysium
loose areolar/reticular CT b/w muscle fibers
myofibril
proteins bundled inside muscle fiber/cell
- run length of muscle fiber and create striped appearance of muscle
sarcolemma
muscle cell membrane
sarcoplasm
cytoplasm of muscle cell
myofilaments
muscle filaments: protein strands inside myofibril
each muscle fiber has its own _ and _.
- capillary beds
- branch of a somatic motor neuron
how are mitochondria dispersed around a muscle fiber?
they are everywhere bc they are where ATP is being generated
- can acquire more mitochondria through more endurance training
myofibrils are surrounded by what
triad
consists of 1 T-tubule with a terminal cistern on either side
T-tubule
transverse tubule
- evaginations in the sarcolemma that run around each myofibril
- how AP get to each part of muscle cell
- 2 wrap around each sarcomere
sarcoplasmic reticulum
smooth endoplasmic reticulum, wrap around myofibrils to be kind of network like
- store calcium
terminal cisterns
one found on either side of T-tubules, makes up a part of the triad
z-disk
runs across proteins and helps hold myofibrils together
- forms contractile unit called a sarcomere
dystrophin
connects actin filaments on “free” side of z-disk to sarcomere and can also extend to endomysium
myoglobin
makes muscles red
- picks up and carries oxygen
titin
large coiled protein, gives skeletal muscle its elastic ability
attaches z-disk to m-line
what are the types of proteins present in an actin myofilament
actin proteins
tropomyosin
troponin
actin protein
ball shaped
lined up and twisted on 2 strands of tropomyosin to make a helix shape
tropomyosin
2 long strands of protein that wrap around and cover all myosin-binding sites
troponin
3 parts:
- 1 attaches to actin
- 1 attaches to tropomyosin
- 1 binds to calcium when avail from SR; when binds causes troponin to change shape and tropomyosin moves away from binding sites
myosin myofilament
myosin protein is composed of 2 protein strands twisted together
- a filament is composed of 300 molecules all stuck together, held at the m-line
myosin ATPase
located on myosin head
- ATP allows head to bend upward, grab actin and pull towards m-line
