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123 terms

Muscle System

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Parallel Muscle
the fascicles are parallel to the long axis of the muscle
Most of the skeletal muscles in the body are
parallel muscles
flat bands with broad attachments at each end
aponeuroses
A skeletal muscle fiber can contract until it has shortened by roughly___%
30
convergent muscle
muscle fascicles extending over a broad area converge on a common attachment site
Ex. of convergent muscle
pectoralis muscle of the chest
Pennate muscle
fascicles form a common angle with the tendon
Unipennate
if all the muscle fibers are on the same side of the tendon
Bipennate
muscle fibers on both sides of the tendon ( more common)
multipennate
if the tendon branches within a pennate muscle
circular muscles or sphincter muscles
fascicles are concentrically arranged around an opening or a recess
guard entrances and exits of internal passageways such as the digestive and urinary tracts
circular muscles
lever
rigid structure that moves on a fixed point called a fulcrum
each bone is a
lever
each joint is a
fulcrum
levers can change
(1) the direction of an applied force (2) the distance and speed of movement produced by an applied force (3) the effective strength of an applied force
first class lever
fulcrum lies between the applied force and the resistance
second class lever
resistance lies between applied force and the fulcrum
Ex. first class lever
extension of the neck
Ex. second class lever
ankle extension by the calf muscles
Most common levers
third class
Third Class levers
applied force lies between resistance and the fulcrum
Ex. third class lever
biceps brachii muscle (flexes elbow)
origin
place where the fixed end attaches to a bone, cartilage, or connective tissue
insertion
site where the movable end attaches to another structure
flexion
when the joint angle is decreasing
extension
when the joint angle is increasing
adduction
motion that pulls part toward the midline of the body
abduction
motion that pulls part away from the midline of the body
agonist
a muscle whose contraction is chiefly responsible for producing a particular movement
antagonist
a muscle whose action opposes that of a particular agonist
synergist
provide additional pull near the insertion or may stabilize the point of origin
fixators
synergists that assist agonist by preventing movement at another joint and stabilizing the origin of the agonist
rectus
straight
rectus muscles are
parallel muscles
extrinsic
muscles whose position stabilize an organ
intrinsic
muscles located within an organ
axial muscles
position the head and spinal column and also move the rib cage
appendicular muscles
stabilize or move components of the appendicular skeleton
innervation
the distribution of nerves to a region or organ
action
movement produced when a muscle contracts
perineum
muscular sheet that closes the pelvic outlet
fibrosis
the formation of fibrous connective tissue; in muscles, the replacement of muscle tissue by fibrous connective tissue makes muscles weaker and less flexible
The strongest masticatory muscle is the
masseter
The muscle that rotates the eye medially is the
superior oblique muscle
The major extensor of the elbow is the
triceps brachii muscle
The powerful flexors of the hip are the
iliopsoas
all-or-none principle
states that a muscle fiber will contract to its fullest extent once stimulated
muscle tone increases when you are
anxious
muscle tone decreases when you are
asleep
deadweight
loss of all muscle tone
deadweight occurs when you are
unconscious
atrophy
decreasing in size and strength
hypertrophy
muscle enlargement
motor unit
a motor neuron plus all of the muscle fibers it innervates.
skeletal muscle (nuclei)
multi
skeletal muscle (filament organization)
In sacromeres along myofibrils
skeletal muscle (control mechanism)
neural, at single neuromuscular junction
skeletal muscle (function)
moves skeleton, creates heat, protects organs
cardiac muscle (nuclei)
one
cardiac muscle (filament organization)
In sarcomeres along myofibrils
cardiac muscle (control mechanism)
automaticity (SA node's pacemaker cells)
cardiac muscle (function)
circulate blood
smooth muscle (nuclei)
one
smooth muscle (filament organization)
scattered throughout sarcoplasm
smooth muscle (control mechanism)
automaticity (pacesetter cells), neural or hormonal
smooth muscle (function)
regulates blood vessels, moves urin, moves food
isometric exercises
contraction in which tension increases, but muscle length remains the same
isotonic exercises
tension in muscle builds until it exceeds resistance and the muscle shortens
diameter of slow fibers
small
diameter of intermediate fibers
intermediate
diameter of fast fibers
large
tension of slow fibers
low
tension of intermediate fibers
intermediate
tension of fast fibers
high
contraction speed of slow fibers
slow
contraction speed of intermediate fibers
fast
contraction speed of fast fibers
fast
fatigue resistance of slow fibers
high
fatigue resistance of intermediate fibers
intermediate
fatigue resistance of fast fibers
low
color of slow fibers
red
color of intermediate fibers
white
color of fast fibers
white
myoglobin content of slow fibers
high
myoglobin content of intermediate fibers
low
myoglobin content of fast fibers
low
capillary supply of slow fibers
dense
capillary supply of intermediate fibers
scarce
capillary supply of fast fibers
scarce
mitochondria of slow fibers
many
mitochondria of intermediate fibers
intermediate
mitochondria of fast fibers
few
sarcomere
functional unit of muscle
A band
contains both thick and thin filaments
I band
contains thin filaments only
H band
contains thick filaments only
M line
holds thick filaments together
Z line
thin filaments attach to this
striations (dark bands)
A bands
light bands
I bands
sarcolemma
cell membrane
sacroplasm
cytoplasm
sarcoplasmic reticulum
endoplasmic reticulum of muscle
multinucleated
several hundred nuclei
T-tubules
carry impulse into muscle cell interior
myofibrils
responsible for muscle fiber contraction
thin filaments
actin
thick filaments
myosin
satellite cells
assist in tissue repair
muscle fibers develop through the fusion of mesodermal cells called
myoblasts
What blocks the site of myosin cross bridge attachment?
tropomyosin
How many Ca++ ions bind to each troponin?
4
What happens after the Ca++ ions bind to troponin?
tropomyosin moves away from the binding site
Once energized, myosin binds to actin and
the head tilts and propels the thin filament
During relaxation, where are the calcium ions?
trapped within the SR
How does the action potential enter the cells interior?
T-tubules
3 proteins comprising the thin filaments
actin, tropomyosin, and troponin
In order for muscles to contract, the cross bridges must first do what?
attach to the actin filaments
Why do cross bridges not attach during relaxation?
because the sites for myosin attachment on the actin filaments are covered by tropomyosin attachment
What does troponin need to fulfill its purpose?
Ca++
What happens when Ca++ is absent?
The tropomyosin reverts back to its original position and blocks attachment
What controls relaxation and contraction?
movement of Ca++ from the SR to the cytoplasm and back