Muscular System

Question 1

how is movement accomplished?

Answer 1

1. by cilia/flagella on surface of some cells
2. force of gravity
3. muscle contraction

Question 2

types of muscle cells

Answer 2

1. skeletal
2. cardiac
3. smooth

Question 3

functions of skeletal muscles

Answer 3

1. movement: contractions of skeletal muscle
2. maintenance of posture: constant tone maintenance
3. respiration: contraction of skeletal muscles in the thoracic region + diaphragm
4. production of body heat: heat given off as by-product of contraction
5. communication
6. constriction of organs and vessels: peristalsis can occur
7. contraction of the heart: propels blood to other organs

Question 4

what are skeletal muscles?

Answer 4

muscles that are connected to bones; make up ~40% of body weight; have striations

Question 5

what do muscle cells consist of?

Answer 5

muscle fiber

Question 6

connective tissues surrounding the each skeletal muscle

Answer 6

1. epimysium
2. perimysium
3. endomysium
4. tendons
   * 1+2+3= 4

Question 7

what is epimysium?

Answer 7

outer layers of skeletal muscle; separates the muscle from other structures

Question 8

what is perimysium?

Answer 8

1. divides each muscle into fascicles (visible bundle of muscle fibers)
2. loose connective tissue serving as passageways for blood vessels and nerves to supply each fascicle

Question 9

what is an endomysium?

Answer 9

1. separates each individual muscle fiber in fascicle

2. serves as passageway for nerve fibers and blood vessels that supply each separate muscle fiber

Question 10

what do tendons help attach?

Answer 10

muscle to bone

Question 11

give a brief flow of what muscles consist of (biggest to smallest)

Answer 11

1. muscle
2. fascicles
3. muscle fiber
4. myofibrils
5. sarcomere (smallest functional unit)
6. myofilaments

Question 12

what is a sarcolemma?

Answer 12

plasma membrane of a muscle cell

Question 13

what protein filaments do myofibrils contain?

Answer 13

1. actin (thin)

2. myosin (thick)

Question 14

why do myofibrils contain actin and myosin filaments?

Answer 14

contraction of muscles can occur

Question 15

where are the nuclei of muscle fibers found?

Answer 15

just below the sarcolemma

Question 16

what do muscle fibers contain?

Answer 16

a single elongated muscle cell surrounded by plasma membrane (sarcolemma)

Question 17

what do sarcomeres do?

Answer 17

allow muscles to contract

Question 18

what is a sarcoplasmic reticulum?

Answer 18

highly specialized endoplasmic reticulum that stores calcium ions.

Question 19

why are calcium ions needed for contraction?

Answer 19

calcium ions will ensure the binding of myosin head with actin at attachment site

Question 20

what are myofibrils?

Answer 20

bundles of myofilaments/protein filaments

Question 21

what are the regions in a sarcomere?

Answer 21

1. I bands
2. A band
3. H zone

Question 22

what does the I band consist of?

Answer 22

one Z disk, extending to ends of myosin myofilaments; consists of only actin myofilaments and appears lighter staining.

Question 23

what does the A band consist of?

Answer 23

both actin and myosin myofilament + H band

Question 24

what does the H band consist of?

Answer 24

only myosin filament; appears darker staining + M line

Question 25

what is the M line?

Answer 25

delicate protein filament holds the myosin myofilaments in place

Question 26

what are Z disks?

Answer 26

stationary anchor for actin myofilaments

Question 27

what do actin myofilaments consist of?

Answer 27

1. tropomyosin

2. troponin

Question 28

what do actin myofilaments consist of?

Answer 28

1. tropomyosin

2. troponin

Question 29

what does tropomyosin do?

Answer 29

relaxed: covers attachment site of actin
contract: uncovers attachment site of actin

Question 30

what does troponin do?

Answer 30

subunit (a): anchors troponin to actin
subunit (b): prevents tropomyosin from uncovering attachment site in relaxed muscle state
subunit (c): binds calcium ions

Question 32

what do myosin heads do?

Answer 32

1. attach to rod portion by hinge region that bends and straightens during contraction
2. form cross-bridges to contract muscle (myosin heads attach to actin active sites)
3. myosin head break down ATP
4. ATP -> ADP + Pi

Question 32

what do myosin myofilaments consist of?

Answer 32

1. rod portion - parallel to myosin myofilament

2. myosin heads - extend laterally

Question 33

what is a skeletal muscle cell also known as?

Answer 33

skeletal muscle fiber

Question 34

isometric contraction

Answer 34

muscle contraction without movement

Question 35

isotonic contraction

Answer 35

muscle contraction with movement