Muscle Contraction 1

Question 1

what are the 3 types of muscle tissue?

Answer 1

-skeletal muscle: voluntary, connects skeleton

-smooth muscle: involuntary, mostly in hollow organs

-cardiac muscle: involuntary, heart

Question 2

Myofibrils

Answer 2

muscle->fascicle->muscle fiber->myofibril

-built from sarcomeres

Question 3

Sarcomeres:

Answer 3

-highly ordered and repeating units
-attach end to end to form myofibril
-basic contractile element of skeletal muscle
-composed of myofilaments

Question 4

Myofilaments:

Answer 4

-Actin (thin filaments)
-myosin (thick filaments)
-elastic filaments

interaction creates muscle contraction

Question 5

Actin (thin filaments):

Answer 5

-actually composed of three proteins
1.Actin: contains myosin binding site
2. tropomyosin: covers active side at rest
3. troponin: moves tropomyosin

-anchored at Z-disc

Question 6

Myosin (thick filaments):

Answer 6

-two intertwined filaments with globular heads

Globular heads:
-protrude 360o from thick filament axis
-will interact with actin filaments for contraction

Question 7

Elastic filaments:

Answer 7

-run through core of thick filament + anchor it to the Z disc
-stabilize and position thick filament

Question 8

Sarcomere regions:

Answer 8

-Z disc: boundary structure of sarcomere. Threadlike network of protein and is attachment for actin and elastic myofilaments
-I bands: Z discs to ends of thick filaments
-A bands: length of thick filaments
-H zone: region in A band where actin and myosin do not overlap
-M line: middle of H zone, delicate filaments holding myosin in place

Question 9

Actin-myosin interactions:

Answer 9

-myosin heads can bind to active sites on the actin molecules to form cross-bridges
-the myosin head flexes pulling the actin filament along with it
-using power from ATP, myosin head unbinds and flexes back, the binds to a new actin active site
-the process repeats, pulling the actin filament along each time

Question 10

Sliding filament theory:
Relaxed and contracted states

Answer 10

-process of actin-myosin interaction

Relaxed state:
-no actin-myosin interaction at binding site, myofilaments overlap a little

Contracted state:
-myosin head pulls actin toward sarcomere center (power stroke)
-filaments slide past each other (do not change length)
-sarcomeres, myofibrils, muscle fiber all shorten

Question 11

Muscle fibers

Answer 11

=muscle cells

Sarcolemma: cell membrane, conducts action potential

Sarcoplasm: cytoplasm of muscle cell, glycogen stored in glycosomes (energy source), myoglobin transports and stores oxygen (needed to make energy)

Transverse tubules (T-tubules):
-lateral extensions of sarcolemma
-carry action potential deep into muscle fiber
-communication and transport

Sarcoplasmic reticulum (SR):
-smooth ER that forms network around each myofibril
-Ca2+ storage