Muscles & Movement: Muscles Flashcards
what are muscle cells called?
myocytes
what does it mean that muscle cells (myocetes) are contractile?
they are capable of producing muscle contractions
What forms of life have myocytes?
only animals
what are the 2 contractile elements of myocetes? what are their main functions?
thick and thin filaments
thick: produce contractile force in muscles
thin: acts as a framework to translate actinomyosin activity into force
What are thick filaments of myocetes made of?
~300 myosin II hexamers
What are thin filaments of myocetes made of?
polymers of alpha-actin (an isoform of actin) that have
ends capped by tropomodulin and Cap Z for stabilization
troponin and tropomyosin on surface
What proteins are compose myocyte thin filaments?
alpha-actin polymers
capping proteins: tropomodulin, CapZ
troponin, tropomyosin
Which myosin type is the muscle myosin?
myosin II
How are thick filaments organized?
~150 hexamers of myosin II on the left and ~150 hexamers myosin II on the right but connected by the tails
heads taaaaaaaaaails heads
where the heads are like bouquets
T or F: thick and thin filaments interact together
true
What are the 2 main muscle cell types?
striated
smooth
What determines whether myocetes are striated or smooth?
the arrangement of myosin and actin
What type of muscles are composed of striated muscle cells?
skeletal and cardiac muscles
How are actin and myosin arranged in striated muscle cells?
in parallel to produce a striped/striated appearance
What type of muscles are composed of smooth muscle cells?
ex. arterioles, iris, bronchioles, GI tract
How are actin and myosin arranged in smooth muscle cells?
there is no specific arrangement (not striated)
What are the stripes
How are thin filaments arranged?
arranged in a fixed array, that is 2 F-actin polymers are wrapped around each other in a helical shape
What surrounds both ends of each thick filament?
an array of thin filaments (6)
What is a sarcomere? which muscle cell type has sarcomeres?
the contractile unit of striated muscle which includes a single thick filament with 2 thin filaments on either end
striated muscles
How are sarcomeres arranged within a striated muscle cell? What does this create?
they repeat in parallel and in series = myofibril
What is a myofibril?
the structure that is composed of repeated, serial sarcomeres in striated muscles
How long are sarcomeres?
2 um long
What is the diameter of myocetes in striated muscles?
20 um