Anatomy of muscles Flashcards
What are 3 different types of muscles?
Skeletal
Cardiac
Smooth
what is skeletal muscle made of ?
Muscle fibres (MYOCYTE/ Muscle cell)
What are muscle fibres made of?
Myofibrils
What do myocytes have?
nuclei
What is Epimysium?
connective tissue layer around muscle
What is Perimysium?
layer of connective tissue around Fascicle
What is Fascicle ?
bundles of muscle fibres inside muscle
What is Endomysium?
layer of connective tissue around each muscle fibre
What are Satellite cells?
stem cells of muscle between basal lamina
what does connective tissue form?
supporting tissue so blood vessels/nerves can run in
are skeletal muscle fibres multinucleated?
YES
How are muscle fibres formed?
myoblasts fusing together
What are myofibril composed of?
Sarcomeres in series
Where does 1 sarcomere run from?
Z disk to adjacent Z disk
What is A Band?
distance between thick filament of same sarcomere
Does the Width of A band change?
NO
What is I band?
thin filaments , distance between ends of different sarcomeres
What is H band?
region between thin filament protrusions
What happens in sarcomere on contraction?
I and H band Shortens
What is Z line?
where thin filaments attach
What is M line?
middle region
What powers muscle contraction?
cross-bridges
What determines the amount of contraction force?
amount of overlap between myofibrils
What is a thick filament?
myosin with tail and 2 heads
What activity does myosin head have?
ATPase- hydrolyse ATP to ADP+Phosphate for Actin binding
When does Myosin bind to actin ?
Power stroke
When is Actin released from ?
Hydrolysis of ATP
When does recovery stroke occur?
when actin is released
what do 2 heavy chains in the tail form?
coiled coil
What is 2 globular head formed from?
2 light chains each
How many light chains in myosin?
4 light chains
How does head bind to actin?
2 motor domains
What are 2 types of light chain?
Regulatory and Essential
What is myosin arrangement?
anti parallel
What do myosin tails assemble into?
thick filaments
What is major protein in thin filament?
ACTIN
What other proteins in thin filaments?
Tropomyosin Troponin Nebulin Alpha Actinin Myosin
where are thin filaments anchored ?
Z Disc
What are barbed ends in Z disc cross linked by?
Alpha actinin
Where are pointed ends in M line capped by?
Tropomodulin protein
What is barbed end capped by ?
Capping protein T
What do capping proteins do?
regulate length of the precise filaments and ensures right polarity
What polarity does barbed end in Z disk match?
half of the thick filament
What do cross bridges on myosin filament do to actin?
pull thin filament into middle of sarcomere
What does force of contraction depend on?
sarcomere length
What is the plateau region in sarcomere shortening?
full overlap of thick and thin filaments
What is the structure of Tropomyosin?
alpha helical coiled coil
How many actin subunits for 1 tropomyosin?
7
What does Ca2+ bind to?
troponin and tropomyosin moves from myosin binding site
How many actin subunits for 1 troponin?
7
What happens at low Ca2+?
actin binding sites for myosin are blocked
What happens at high Ca2+?
contraction - binds to TnC of troponin and tropomyosin moves across actin
- myosin binding site on actin is exposed
What is Titin? (largest protein in body from Z to M line?
Carries tension from 1 sarcomere to another
What titin regulate?
thick filament length and restores overlap
What does Nebulin do?
bind across thin filament and regulate thin filament length
What does the Sarcolemma have?
T tubules
what are T tubules associated with?
Sarcoplasmic reticulum
When is Ca2+ released from Sarcoplasmic reticulum?
when muscle is depolarised
What does Ca2+ bind to?
troponin
What is Calsequesturin ?
Hold Ca2+ in Sarcoplasmic reticulum cisterna
Where does Action potential pass in depolarisation of muscle fibres?
t tubules to Ca2+ stores
How is action potential in nerve terminal transmitted to muscle ?
acetylcholine released and bind to receptors in membrane
What is DHPR (dihydropyridine) receptor?
on T tubules and Ca2+ channel
What does DHPR activate?
a RYR (ryanodine receptor) so release Ca2+ from SR
What is RYR?
Ca induced Ca release receptor so
How is Ca2+ removed from sarcoplasm after contraction?
ATP dependant Ca2+ pump and back into Sarcoplasmic reticulum
How does the muscle stay relaxed?
low Ca2+ by ATP pumps in Sarcoplasmic reticulum
What nervous system causes muscle contraction?
Sympathetic nervous system
What is released at neuromuscular junction?
Acetyl choline - binds to nicotinic cholinergic receptors so action potential within Sarcolemma
- AP down T tubules and activates DHPR and so RyR so Ca2+ spike
What does Ca2+ spike cause?
conformational change in Troponin Tm unit so myosin binding and sarcomere shortening
What happens when frequency of AP is increased?
stronger contraction since summation of tension
What happens if AP are too frequent?
Fused tension so muscle cant relax
Why does muscle twitch happen?
delay for contraction since time for Ca2+ to bind to troponin
What do large motor neurones innervate?
larger motor units
What are ATP sources?
Creatine Phosphate
Glycolysis
Oxidative Phosphorylation
What the type of Muscle Fibres?
Type 1 fibres - slow and anaerobic
Type 2 fibres- fast and anaerobic
What are the transmissions of forces?
longitudinal
Lateral
What is longitudinal trans. of force along fibre?
myosin crossbridges and titin carry tension from one sarcomere to the next
What is Lateral trans. of force along fibre?
Costamere link Z disk to sarcolemma
What do the Myofibrillar proteins have?
cytoskeleton so all sarcomeres connected