Lecture Exam 3 SLOs

Question 1

Describe the relationships of the structure and function of a tendon

Answer 1

~ extends from thick muscle and tapers into connective tissue attaching the muscle to the bone

Question 2

Describe the relationship between the structure and function of the muscle body

Answer 2

~ bulk of muscle; thick for lots of muscle fibers and high contractility for force

Question 3

Describe the relationship between the structure and function of the epimysium

Answer 3

~ surrounds the entire muscle; large thin sheet of CT protecting enclosed muscle

Question 4

Describe the relationship between the structure and function of the fascicle

Answer 4

~ bundle of muscle fibers/cells; encloses muscle fibers, group multiple muscle fibers together for high contractility

Question 5

Describe the relationship between the structure and function of the perimysium

Answer 5

~ CT surrounding the fascicle; ct is strong and endures stretching and shortening, fascicles contain muscle fibers with contractile organelles inside

Question 6

Describe the relationship between the structure and function of the individual muscle fiber/cell.

Answer 6

~ elongated and cylindrical in shape, multinucleated to allow for transmission of signals along the entire length of the muscle

Question 7

Describe the relationship between the structure and function of the endomysium

Answer 7

~ CT surrounding individual muscle fibers

Question 8

Describe the relationship between the structure and function of the myofibrils

Answer 8

~ inside individual muscle fiber which is surrounded by endomysium, LOTS of them throughout the muscle body, run the entire length of the muscle to allow for unison contraction and shortening of the muscle upon pulling of myosin filaments on actin filaments

Question 9

Where are the nuclei located in the muscle fibers?

Answer 9

~ get pushed to the periphery of the myocyte due to abundance of myofibrils within myofibers

Question 10

Describe the importance of the sarcoplasmic reticulum

Answer 10

~ endoplasmic reticulum of muscle tissue; surrounds myofibrils like the foam netting surrounding delicate fruits, contains terminal cisternae (enlarged regions at the ends of the SR that make contact with T tubules, store Ca)

Question 11

What is a triad?

Answer 11

~ terminal cisternae, T tubule (invagination of sarcolemma), terminal cisternae

Question 12

Define sarcomere

Answer 12

~ functional unit of organization of myofibril and its overlapping arrangement of actin and myosin, hence the striated appearance of skeletal muscle
-from z line to z line

Question 13

What is the A band? What does it do during muscle contraction?

Answer 13

~ entire length of myosin regardless of overlap with actin
~ remains the same

Question 14

What is the I band? What does it do during muscle contraction?

Answer 14

~ length of only the thin actin filament, NO overlap with thick
~ shortens during contraction

Question 15

What is the H zone? What do during muscle contraction?

Answer 15

~ length of only the thick myosin filament, NO overlap with thin filaments
~ shortens during muscle contraction

Question 16

Why is the I band the lightest portion of the electro micrograph? Why is the A band the darkest? Why is the H zone darker than the I band?

Answer 16

~ thin filaments with no overlap with thick, more light can pass through them
~ A band is overlapping with thick and thin filaments, less light passes through
~ H zone is only thick filament, but thicker than I band so appears darker, less light passes

Question 17

Contraction is also known as? Muscles always push or pull?

Answer 17

~shortening
~ PULL toward M line

Question 18

Describe the formation of actin

Answer 18

~ G actin with myosin binding sites form F actin, then double helical actin strands (2 actin strands in double helix)

Question 19

Describe the functions of troponin and tropomyosin

Answer 19

~ regulatory proteins; do not directly participate in muscle contraction
~ tropomyosin covers myosin binding sites on actin blocking contraction, troponin is attached to tropomyosin, Ca from SR binds to troponin, troponin undergoes a conformational change, causing tropomyosin to roll off myosin binding sites on actin so myosin can grab on and muscle contraction can proceed

Question 20

Describe the relationship between the structure and function of myosin

Answer 20

~globular and fibrous portions
~ globular heads have actin binding sites and ATPase for the breakdown of ATP during muscle contraction
~ hundreds of myosin proteins, larger than actin
~ heads are staggered along the myosin allowing for continual force production
~ bare zone~ middle portion without any heads, typically associated with the H zone

Question 21

Describe the function of titin fibers

Answer 21

~ anchors myosin, extends from z line (like a spring allows uncoil and recoil during contraction)

Question 21

Describe the sequence of events that occurs in the cross-bridge cycle and relate this
sequence to the sliding filament model of muscle contraction

Answer 21

~ myosin heads grab onto myosin binding sites of actin and pull continually down the actin filament as the musxle fibers shorten
~ A band stays the same, H zone shortens, I band shortens
~ size of the protein doesn’t change but the overlap does, hence A band doesn’t change bc length of myosin regardless of overlap, but thin filaments get pulled closer to the M line, boundaries of sarcomere shorten