Muscle Flashcards
3 types of muscle
Cardiac, smooth, skeletal
Voluntary muscle
Skeletal
Involuntary muscle
Cardiac, smooth
what are myofilaments made of?
actin, myosin
What is the epimysium
Connective tissue that surrounds the entire muscle
What is the perimysium
Connective tissue that surrounds the fasicle
What is the endomysium
Connective tissue that surrounds each muscle fiber (muscle cell)
What is a synctium?
A multinucleated cell that was created through the fusion of unicellular cells
Characteristics of skeletal muscle
Each cell has multiple, peripherally located nuclei
Striated
How vascularized is skeletal muscle?
Extensive capillary network due to high energy requirement
What is a sarcomere?
Single contraction unit (Z dsk to Z disk)
What are thin filaments of the sarcomere
Actin
What are thick filaments of the sarcomere
Myosin
What filament is most abundant in I band?
Actin, troponin, tropomyosin
What filament is most abunant in A band?
Myosin and Actin
What is the M line?
Where no actin filaments connect with myosin and two myosin filaments cross connect
Where are troponin and tropomyosin located?
I band
What filament is in the H band?
Myosin only
Which bands shorten during contraction?
I and H bands
How is troponin and tropomyosin configured?
Tropomyosin is wrapped around actin covering myosin binding sites
Troponin is attached to tropomyosin
Is troponin present in smooth muscle?
No
What is troponin C
Troponin C binds the calcium to activate movement of tropomyosin
How are myosin filaments arranged?
Two heavy chain tails are connected together with cross bridge heads
These heads move back during contraction
What 2 structures are important for calcium and muscle contraction?
Sarcoplasmic reticulum and T-tubules
What does the sarcoplasmic reticulum do?
Calcium storage
What do transverse tubules do?
Cell membrane invaginations that extend between the myofibrils and ensure high calcium inside every cell
What are terminal cisternae?
Expansions of sarcoplasmic reticulum
Located adjacent to T-tubules
What is a triad?
One T-tubule and its adjacent terminal cisternae
What happens at the neuromuscular junction?
ACh causes depolarization which spreads via T-tubules to triad junction to the dihydropyridine receptor activates the ryanodine receptor on the SR
What action does myosin have on ATP?
Hydrolyzes ATP
What are red muscle fibers?
Aerobic, endurance
Lots of mitochondria
High myoglobin
Slow twitch, sustained contraction
What are white muscle fibers
Sprint, anaerobic
Fast twitch
What are intermediate fibers?
Hybrid, mostly fast twitch
Where are muscle spindles located
Between endomysium and perimysium
What do muscle spindles do?
Determine position of body parts and extent of contraction
Characteristics of cardiac muscle
Striated
Involuntary
One centrally located nucleus
Intercalated discs
What is an intercalated disc?
Electron dense junctional complex with gap junctions, desmosomes, fascia adherens
What allows simultaneous contraction in cardiac muscle?
Intercellular junctions, anchors, sarcomeres
What is fascia adherens
Similar to Zonula Adherens but not the same (FA not belt-like)
How are contraction signals conducted in the heart?
Purkinje fibers and gap junctions
What are purkinje fibers?
Modified cardiac myocytes, assist in cardiac contraction
Characteristics of smooth muscle
Non-striated Involuntary Spindle-shaped cells One elongated nucleus Disorganized myofilaments
Does smooth muscle have connective tissue?
Yes, but there is little CT separating muscle cells (endomysium)
How does smooth muscle contract?
Myosin must be phosphorylated in order to bind to actin
Ca binds to calmodulin which activates light chain kinase
How is light chain kinase reglated?
Calmodulin Ca complex
An increase in cytosolic Ca induces calmodulin binding to myosin light chain kinase
How is skeletal muscle regenerated?
Satellite cells
Characteristics of satellite cells
Spindle-shaped cells with little cytoplasm
Located under the external lamina of muscle cell
Forms myoblasts which differentiate in to muscle fibers
What can inhibit muscle cell regeneration?
Damage to external lamina
How is muscle repar generally achieved?
Formation of connective scar tissue
What is the external lamina?
Surrounds sarcolemma of muscle cells
Secreted by muscle cells
Is there cell regeneration in cardiac muscle?
Very little
Transplantation of stem cells can initiate regeneration
How does smooth muscle regenerate?
Normal cell division
What is the pathological result of a cardiac infarction?
Muscle is replaced with connective scar tissue, not muscle so it loses contractability
