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An 8 year old was brought into ER w/ a broken radius. He has Duchenne…
An 8 year old was brought into ER w/ a broken radius. He has Duchenne muscular dystrophy.
Upstream causes
Duchenne muscular dystrophy
DMD gene mutates
Stops dystrophin from being made.
Dystrophin helps stabilize and protect muscle fibers.
When missing muscle fibers get damaged easy and inflammation can occur.
Fractured radius
Direct cause
He tripped and fell going down the strairs
Indirect cause
less active
Most likely due to DMD
Weaker
Background info
Physiology
Skeletal muscle fiber
T-tubules
Part of sarcolemma
(plasma membrane)
Folds into muscle fiber
Allows membrane potential to reach the rest of the cell.
Myofibrils
Contractile muscle fibers inside cell
Sarcoplasmic reticulum
Smooth ER that stores calcium in a resting muscle cell
Sarcomere
Thick myofilament
(myosin)
Thin myofilament
(actin)
2regulatory protein
Troponin
When calcium is released troponin changes shape and allows actin and myosin to interact and do muscle contraction
Tropomyosin
Protein buillding
RNA polymerase attaches to the DNA strand in the promoter region
An mRNA strand is made based on the DNA sequence
The mRNA strand leaves the nucleus
The mRNA strand attaches to the ribosome
tRNA moleecules bring amino acids to the ribosome
The complete amino acid chain is released from the ribosome & folds
Excitation-contraction coupling
A neuron releases aceylcholine
Chemically-gated sodium channels open
The membrane of a muscle fiber depolarizes
The volatge-gated calcium channels open
Calcium binds to troponin
Tropomyosin unblocks the myosin binding sites on actin
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Bone remodeling
Osteoblasts
Make new bone tissue
Osteoclasts
Breaks down old bone tissue
Anatomy
Skeletal muscle fiber
Myofibrils
Striations
Dark/light variations on myofibrils
T-tubules
Sarcoplasmic reticulum
Sarcomere
Thin myofilament
(actin)
2 regulatory proteins
Tropomyosin
Entire length of thin filament
Covers myosin binding site
Troponin
Interacts with calcium
Thick myofilament
(myosin)
Z-discs
Either side of sarcomere/zigzagging structure
M line
Found in middle of sarcomere
Anchors thick filaments together
H zone
Middle region where only thick filament is seen
A band
Dark bands
I-band
Only contains thin filament / lighter in bands
This is what causes the striations
Bone remodeling
Mature tissue is removed and new bone tissue is put in the place of
Muscular system
&
The skeletal system
Allows for movement and heat production
Three types of tissue
Cardiac muscle tissue
Striated
Smooth muscle tissue
Non-striated
Skeletal muscle tissue
Striated
Downstream effects
Muscular system
Decline in muscle strength between 6-11 years of age.
By age 13 most boys with DMD are using a wheel chair full time
Skeletal system
Scoliosis may occur
Respiratory system
Breathing problems due to weakness of the muscles of the diaphragm
Circulatory system
Progressive enlargement of the heart
Stops heart from pumping blood efficiently
Could be life threatening