Week 5 -muscle Flashcards
what type of protein is actin?
globular
what do myofibrils consist of?
bundled up myofilaments (actin and myosin)
they form the structural unit of a muscle fibre
contain sarcomeres
sarcomere? how are they formed?
contraction unit of the muscle
formed by the overlapping of actin and myosin
what are myofilaments?
actin (thin) and myosin (thick)
muscle fiber?
myofibrils form a muscle fiber
made through the fusion of many myoblasts to form a large cell
why do we have multiple nuclei in skeletal muscle?
the cells are very large due to the fusion of myoblasts (muscle precursor cells) in development. As a result of this the muscle cells are actually a combination of many cells together (which is why they tend to be referred to as fibres rather than cells) and so have multiple nuclei.
why are the nuclei located at the periphery in skeletal muscle?
and why is the muscle striated?
The nuclei are located at the periphery of the cell due to the large numbers of myofibrils inside the muscle cell. The myofibrils also give the muscle a striped look (striated appearance).
what is a fascicle?
muscle fibers bundled together
they are associated with CT
endomysium?
areolar CT
Surrounds the individual muscle fibre - Therefore the endomysium helps to connect the individual muscle cells together.
perimysium?
Surrounds and supports the fibres that form fascicles
epimysium?
dense irregular CT
Surrounds the whole muscle – is the third layer of CT.
sarcolemma?
the plasma membrane of the cell, has multiple nuclei
T tubules?
invagination of the sarcolemma
filled with interstitial fluid
Muscle action potentials travel along the sarcolemma and through the T tubules, quickly spreading throughout the muscle fiber.
sarcoplasm?
within the sarcolemma, the cytoplasm of a muscle cell
contains myoglobin and myofibrils
what is myoglobin?
protein that is found only in muscle, binds oxygen molecules that diffuse into muscle fibers from interstitial fluid.
• Releases oxygen when it is needed by the mitochondria for ATP production
what is the sarcoplasmic reticulum?
wraps around the myofibrils
In relaxed muscle, SR stores calcium ions, Release of Ca2 from the terminal cisterns of the sarcoplasmic reticulum triggers muscle contraction.
Z disc?
At either end of the sarcomere and are the attachment points for actin filaments.
separates one sarcomere from another
A band?
Appear dArk. The thick filament containing myosin extend the entire length of the A band
thin filaments over lap
I band?
Appear lIght. contains the remainder of the thin filaments but no thick filaments.
Z disc passes through each centre of the I band
H zone?
middle of the A band that contains thick filaments only
lighter region
M line?
centre of the H zone that contains proteins that hold thick filaments together at centre of sarcomere.
sliding filament model of contraction?
states that during contraction the thin filaments slide past the thick ones so that the actin and myosin filaments overlap to a greater degree:
When the nervous system stimulates muscle fibers, the myosin heads on the thick filaments latch onto myosin-binding sites on actin in the thin filaments, and the sliding begins.
what is a muscle contraction?
the shortening of a sarcomere
H zone disappears when they shorten
what are contractile proteins? and describe the 2 types.
generate force during contraction;
actin- on each actin molecule is a myosin-binding site, where a myosin head can attach. join to form actin filaments (thin filaments)
myosin- main component of thick filament and functions as motor protein
what are regulatory proteins? and describe the 2 types.
help switch the contraction process on and off
tropomyosin- component of thin filament, covers myosin binding sites on actin
troponin- component of thin filament. Ca ions bind and change shape which moves tropomyosin away from the binding site and muscle contraction begins
what are structural proteins?
name 5
which keep the thick and thin filaments in the proper alignment, give the myofibril elasticity and extensibility, and link the myofibrils to the sarcolemma and extracellular matrix.
titin, a-acticin, myomesin, nebulin, dystrophin
what is titin?
structural protein that connects Z disc to M line which stabilizes thick filament position
elasticity of myofibril
what is a-acticin?
structural protein of Z disc that attaches to actin molecules of thin filaments and to titin molecules
myomesin?
structural protein that forms M line, binds to titin molecule and connects adjacent thick filaments to one another
