Muscle Structure and Function Flashcards
muscle tissue
consist of muscle cells (fibres)
all muscle characteristics
excitability
contractibility
extensibility
elasticity
3 major muscle types
smooth
cardiac
skeletal
smooth muscle
has spindle-shaped non-striated uninucleated fibres
occurs in walls of internal organs
vessel, digestive tract
-is involuntary
Muscle types differentiated by
fibre shape
location of nuclei
appearance - striated, smooth
nature of control- voluntary or involuntary- hybrid
cardiac muscle
has striated, branched, uninucleated fibres
occurs in walls of heart
is voluntary
skeletal muscle
has striated, tubular, multinucleate fibres
is usually attached to skeleton
is voluntary
Epimysium
surrounds all the muscle fibre bundles (fasciculi) to form the entire muscle
Perimysium
surrounds several muscle fibres and forms bindles called fasciculi
Fassiculus
bundle of up to 150 muscle fibres
endomysium
wraps each muscle fibre
by weight, a single muscle fibre is made up of primarily
water
single muscle fibre (cell, weight consists of)
75% water
20% protein
5% other
-minerals (K+, Na+, CI-) fats, CHO, amino acids, enzymes, ATP, lactate ect.
Microstructure of muscle: sarcolemma
muscle cell membrane surrounding muscle fibre
Microstructure of muscle: satellite cells
located within the sarcolemma (between the plasma and basement and membrane)
-help regenerative cell growth (myogenic stem cells)
-play a role in hypertrophy
Microstructure of muscle: sarcoplasm
protoplasm (enzymes, fat, glycogen)
nuclei
sarcoplasmic reticulum (SR)
network of tubules and vesicles (triads)
located around myofibrils
provides structural integrity and spreads depolarization
role: stores, releases and reabsorbs Ca2+
each sarcomere contains ____ triads
two
triad system
2 large sacs (vesicles)
-terminal cistern of the SR
small central sac
-T tubule
Muscle microstructure
within the single muscle fibre there are myofibrils
-myofibrils =1/1000mm in diameter
up to 8000 myofibrils
myofibrils contain myofilaments
Myofilaments are _______ that make up sarcomere units
proteins
myofilaments
-functional unit of muscle fibre
-runs from z-line to z-line
order from whole muscle
-myofilament
-myofibril
-muscle fibre
-muscle fasiculi
whole muscle
muscle fasiculi
muscle fiber
myofibril
myofilament
at what level would we find a bundle of muscle fibres?
fascicle
Myofibril proteins (aka myofilaments) making up the sarcomere include:
myosin (thick filament)
actin (thin filament)
Actin and myosin are _______ proteins
contractile
within the actin filament
troponin (thin filament)
tropomyosin (thin filament)
Both troponin and tropomyosin are _______ proteins
regulatory
12-15 other proteins are present; however, myosin and actin make up _________
85% of myofibrillar complex
I band
light, actin only
A band
dark, actin and myosin overlap
sarcomere:
an arrangement of actins and myosins, bordered by z-discs
actin
a thin myofilament which is parallel to and slides past myosin, a thick, myofilament, resulting in muscle contraction
z discs
thick structures that are perpendicular to and anchor the actin
I-band: a _____ area that contains only ____
light, actin
A-band: a ______ area that contains _____
dark, myosin and actin
H-zone: a _____ area that contains only _____
light, myosin
which is considered a “light” zone
H zone and I band
Actin contains which contractile proteins
G-actin
F-actin
tropomyosin
troponin
3 subunits (I, C and T)
regulatory proteins: tropomyosin
lies along actin like a cord
-inhibits actin-myosin interaction
regulatory proteins: troponin
embedded at regular intervals along actin
-interacts with Ca2+
-removes inhibition
muscle contractile proteins
myosin
-cross bridges (actin and myosin overlap)
globular heads
-actin binding site
-ATP binding site
-Heavy and light chains
myosin has ____ heads
each head has ____ “heavy chain”
2, 1
ATPase activity will determine speed of contraction
Myosin is composed of _________
heavy chains and light chains
type of heavy chains determines the ATPase activity
3 predominant types of MHCs:
Type 1 MHC: slowest contracting
Type 2 MHC: moderately fast contracting
Type 3 MHC: fast contracting
Type IIB= very fast contracting
functions of skeletal muscle
-stabilize body
-moment of joints
-locomotion
- movement of limbs = improve circulation
-thermogenesis (shivering) capillirization
-body posture
venous return
skeletal muscle has a rich vascular network
-flow is rhythmic
-vessels compress during contraction phase
-vessels open during relaxation phase
muscle action contraction and relaxation: 2 components
mechanical: sliding filament model
chemical: energy - via ATP hydrolysis
mechanical component: sliding filament theory
-contraction occurs as myosin and actin slide past one another
-myosin pulls actin, actin slides past myosin
sliding filament model
-myosin bridges attach to actin filament
-cross bridges rotate
-cross bridges detach
repeat
-only about 50% of cross bridges attached at any one time
which shortens during a contraction
the sarcomere
rearrangement of actin and myosin at rest and surfing muscle ______
shortening
during contraction (concentric)
-the length if the thick and thin filament do not change
-the length of the sarcomere decreases as actin is pulled over myosin
which filament has moved as the sarcomere contracted ?
actin
chemical component of sliding filament theory
-main molecule used for energy in muscle contraction is from ATP hydrolysis
-adenosine triphosphate
ATP is broken down to ADP+Pi + energy
ADP= adenosine triphosphate
Pi= inorganic phosphate
sliding filament theory - chemical
ATP – ADP + Pi +energy
globular head of myosin contains (actin activated) myosin ATPase