Muscles

Question 1

What are the functions of muscles mentioned in class?

Answer 1

Generating heat= thermogenesis
Movement
Balance
Stopping movement (sphincters= a ring constricting muscle that relaxes to open body cavities)

Question 2

What is a sphincter muscle?

Answer 2

A ring constricting muscle that relaxes to open body cavities. Located on both sides of the stomach, bladder, anus

Question 3

What is a myofibril and what is its relationship to a muscle fiber? To a sarcomere?

Answer 3

Muscle fibers are made up of myofibrils, and myofibrils are made up of sarcomeres.

Question 4

What is a fascicles and what is its relationship to a muscle? To muscle fibers?

Answer 4

Muscles are made up of fascicles, and fascicles are made up of muscle fibers.

Question 5

What is the individual unit that contracts in a muscle in a sarcomere?

Answer 5

The actin?

Question 6

What is the sarcolemma?

Answer 6

The plasma membrane around muscle fiber

Question 7

What are t-tubules?

Answer 7

The transverse invaginations of sarcolemma.

Question 8

What is the sacroplasmic reticulum?

Answer 8

looks like smooth ER, but function is to store Ca2+

• -SR surrounds myofibrils
• -meets w/T-tubules

Question 9

What is sarcoplasm?

Answer 9

Like cytoplasm but in the muscle?

Question 10

What are the thick and thin filaments made from?

Answer 10

Thick= myosin
Thin= actin

Question 11

How do troponin and tropmyosin fit in with the think and thin filaments?

Answer 11

The tropnin and the tropomyosin slide off the actin binding sites

Question 12

What is the role of ACh (acetylcholine) and AChE (acetylcholine esterase) in contraction of a sarcomere?

Answer 12

• ACh binds to receptors on muscle fiber
• binding starts action potential along sarcolemma
• Acetylcholine esterase (AChE) destroys ACh

Question 13

What is the role of t-tubules in contraction of a sarcomere?

Answer 13

action potential runs to T-tubules, causes SR to release Ca2+

Question 14

What is the role of the SR in sarcomere contraction?

Answer 14

The SR releases calcium.

Question 15

What is the role of Ca2+ in sarcomere contraction?

Answer 15

Ca binds to troponin,
–causing shape change
that slides troponin/ tropomyosin strand along actin (thin f.)

Question 16

How do troponin, tropomyosin, actin, and myosin interact in sarcomere contraction?

Answer 16

When the troponin/tropomyosin reacts with the Ca2+, then it slides off the myosin binding sites on the actin, the sites then bind with the swivel heads on the myosin creating a contraction.

Question 17

What is the role of ATP in sarcomere contraction?

Answer 17

-myosin grabs ATP and detaches from actin
• ATP hydrolyzes to ADP & P, re-cocking myosin for next
crossbridge

Question 18

What is a myosin binding site and where do you find it? And what is its purpose?

Answer 18

A myosin binding site is like a little ridge covered in troponin on the actin. When the troponin is removed, the myosin binding sites bond to the myosin making the heads in the myosin swivel until they are inside the sites. Then a contraction is created.

Question 19

What is happening to a muscle when it atrophies? When it hypertorphies?

Answer 19

-increase in muscle size, HYPERTROPHY, is increase in fiber diameter. Caused by packing in more myofibrils, mitochondria, SR, etc.
• same parts can disappear = ATROPHY

Question 20

What molecule makes red meat red and what is the job of that molecule?

Answer 20

High amounts of myoglobin/oxygen

Question 21

What do muscles store to use as energy?

Answer 21

Glycogen, oxygen, and phosphate?

Question 22

What are the origin and insertion of muscles?

Answer 22

Origin – “anchor point” for muscle

Insertion – what the muscle moves

Question 23

What is a motor unit?

Answer 23

A motor unit is motor neurons that are densely branched, which enables on such axon to connect to many muscle fibers.

Question 24

What is a twitch?

Answer 24

The contractile response of a single muscle fiber to a single impulse