Muscle Lecture 1 Flashcards
Features of Skeletal muscle
single long cylindrical cells
Striated
Multiple peripheral nuclei
Voluntary control
Features of Cardiac muscle
branched
1-3 peripheral nuclei
involuntary
located in the heart
connected via intercalated discs
Features of Smooth muscle
uninucleic
located within gut and blood vessels
non voluntary
spindle shaped
how are muscles attached to bone
via tendon
how are skeletal muscle organized
highly organized contractile units
Function and location of M line
in the center of the sarcomere connects adjacent thick filaments
Location of the A band
runs the entire length of the thick filaments
location of the Z discs and function
connects to adjacent sarcomere. anchors thin filament
sheeted proteins
H region location
in the middle of the sarcomere (m line) where their is no filament overlapping
What are the elastic components within the sarcomere
titin
I band
between each z disc with the adjacent sarcomere only contains thin filaments
T tubulues structure location and function
Structure: continuation of the sarcolemma
deep invagination which circle each sarcomere
Located: between A and I band junction
function: allows action potential to be carried deep within the muscle cell
Sarcoplasmic reticulum
location,
function
location: above the M line
Function: stores/ releases calcium
Describe the Thick Myosin filament
structure
function
structure: 2 tails that are entwined to form a helix
2 globular heads that face away from the M line
heads: enzymatic which hydrolyses ATP
what are the regulatory proteins of the actin
Troponin- calcium binds to
tropomyosin- exposes the actin binding site
Which muscle is troponin and tropomyosin within
cardiac and skeletal muscle
describe the sliding filament theory during a contraction
z line gets pulled towards the m line
h area narrows
actin and myosin region overlap
what is needed in order for the cross bridge formation to occur
calcium must be bound to troponin therefore, tromyosin exposes binding sites of actin
what are the 4 cycles of the cross bridge cycle
- Cross bridge formation
- Powerstroke
- Detachment
- energization of the myosin head
describe cross bridge formation
occurs first
only occurs if tropinin has calcium and tromyosin has moved away from actin binding sit
ATP binds to myosin head causing to to attach to the exposed actin binding site
Powerstroke description
2nd process
ATp is hydrolysed to ADP and P and detaches from the myosin head
causing the myosin head to retract into its low energy position (45 degree angle)
causing the sarcomere to shorten
Detachment description
3rd process
Atp binds to the head of the myosin causing the myosin to lose attraction with the actin
therefore detachment occurs
Energization of the myosin head
ATP hydroylses into ADP and P causing the myosin head to retract into its high energy position (90 degrees)
Calcium importance
Allows the cross bridge cycle to occur
calcium levels must remain above critical threshold for CB cycle to occur
Describe the release of calcium
calcium is released from the SR into the cytoplasm
Describe the inactivation of the release of calcium
the active transport pump (ATPase) are constantly move the CA from the cytosol to the SR
Isometric contraction
tension variable
no shortening
length constant
isotonic contraction
tension constant
shortening
length variable
