Muscular System Flashcards
long, cylindrical multinucleated cells
voluntary control
skeletal muscle
found in heart
involuntary control
striated
cardiac muscle
involuntary control
found in hollow viscera, skin, and iris
smooth muscle
all muscles develop from ______
except ____ which is from ________
mesoderm
iris, neuroectoderm
trunk muscles develop from
myotome region of somites; mesenchyme differentiates to myoblasts
limb muscles develop from
myogenic precursor cells in developing limb buds differentiate to myoblasts
define myogenesis
elongation of nuclei and cell bodies into myoblasts
contractile elements of the muscle fiber
myofilaments
in skeletal muscle development, primordial muscle cells fuse end to end to form _____
myotubes
mature myoblasts that are long and multinucleated
myocytes or myofibers
in skeletal muscle development, the myotome divides into (2)
epaxial division (dorsal)
hypaxial division (ventral)
epaxial division of myotome contains (2)
segmental muscles of body axis
extensor muscles of neck and vertebral column
hypaxial division of myotome contains (4)
cervical muscles
thoracic muscles
lumbar muscles
limbs, intercostal, and abdominals
in skeletal muscle development, myoblasts divide into (3)
pharyngeal arch muscles (facial expression)
tongue muscles
ocular muscles
somite myotomes become segmented, then
myoblasts of each segment give rise to different adult muscles
what are satellite cells
muscle stem cells
all fibrous CT investments in muscle are interconnected and form _______ and________
tendons and aponeuroses
Basal lamina surrounds _______
Endomysium surrounds _______
perimysium surrounds _______
Epimysium surrounds _______
a single myocyte
a singly myocyte
a fascicle of myocytes
a named muscle
what makes up a motor unit
1 motor neuron + all innervated muscle fibers
oxygen-transporting protein in myocytes
myoglobin
type of muscle fiber with more myoglobin, more mitochondria, aerobic, uses fat
endurance
Type 1 (red)
type of muscle fiber with less myoglobin, fewer mitochondria, anaerobic, uses glycogen
stronger but less endurance
Type 2A (white)
where can satellite cells be found?
adjacent to myocytes, inside basal lamina
myocyte plasma membrane
sarcolemma
invagination of sarcolemma specialized for depolarization
T-tubules
ER of muscle fibers
sarcoplasmic reticulum
what does the SR do?
stores Ca+, forms terminal cisternae (triad with T-tubule), regulates muscle contraction through controlled release and sequestering of Ca+
myocyte cytoplasm
extends from Z disk to Z disk
sarcoplasm
basic contractile unit of the the myocyte; composed of myofilaments
sarcomere
two types of myofilaments found in a sarcomere, and where they’re anchored
Myosin II (thick)
- anchored at M line
Actin (thin)
- anchored at Z disk
How are actin filaments Ca regulated?
they are decorated with troponin and tropomyosin
linear string of sarcomeres that runs the length of the myocyte
myofibril
what’s the A band
where the muscle contracts to (on each side)
what is found at the myoneural junction?
axon terminals
motor end plate
specialized section of sarcolemma with Ach receptors
motor end plate
what do the sensory nerves that innervate skeletal muscle do? (2)
provide feedback for spinal reflexes and regulation of contraction/relaxation
specialized group of myocytes associated with sensory nerves to monitor stretching
muscle spindles
group of collagen fibers associated with sensory nerves to monitor force of contraction
Golgi tendon organs
cardiac muscle forms from ______ _______ mesoderm, aka _________
lateral splanchnic
myoepicardial mantle
how are intercalated discs formed
myoblasts fuse together, but cell membranes don’t regress
half of cell volume of cardiac muscle is (2)
mitochondria and myoglobin
smooth muscle is regulated by
ANS
Describe the role of dense bodies in contraction of smooth muscle
dense bodies form unions of intermediate filaments and thin filaments
in interconnecting branching network that extends throughout cytoplasm
contraction all filaments to twist and shorten cell along it’s longitudinal axis
sternocleidomastoid injured at birth, so muscle is shortened on one side
congenital torticollis
when do limb buds appear?
end of 4th week
in limb formation, mesenchyme proliferates near posterior margin of limb bud and forms ___________
zone of polarizing activity (ZPA)
ectoderm near limb bud apex forms ________
apical ectodermal ridge (AER)
AER activates ZPA to express _________
sonic hedgehog gene
Five key steps in limb formation
limb bud
hand plate
digital rays
finger/toe buds
apoptosis of webbing
in week 7, upper limbs rotate ______ 90 degrees
lower limbs rotate _______ 90 degress
laterally
medially
area of skin supplied by a spinal nerve
dermatome
