Muscle

Question 1

What makes up antagonistic pairs?

Answer 1

flexor and extensor

Question 2

What is isotonic muscle contraction?

Answer 2

muscle length changes and tension stays the same

Question 3

define concentric

Answer 3

shortening

Question 4

define eccentric

Answer 4

lengthening

Question 5

What is isometric contraction?

Answer 5

tension develops and muscle stays the same length

Question 6

What is the structure of myofibre?

Answer 6

large and cylindrical
multinucleated
packed with myofibrils

Question 7

Summarise the mechanism of excitation-contraction coupling for skeletal muscle

Answer 7

AP propagates along sarcolemma and into T-tubules
depolarisation activates dihydropiridine receptors sarcolemma which causes a conformational change
linked to ryanodine receptors on SR which open and cause calcium influx

Question 8

What are the z-lines?

Answer 8

defines the lateral boundaries of a sarcomere

Question 9

What is actin?

Answer 9

polymeric thin filament composed of 2 twisted alpha helices that displays polarity

Question 10

What is myosin?

Answer 10

thick filaments that contain numerous globular heads that interact with actin

Question 11

What is titin?

Answer 11

very large spring-like filament that anchors myosin to the z-line

Question 12

What is nebulin?

Answer 12

large filaments associated with actin

Question 13

What is tropomyosin

Answer 13

elongated protein bound to actin

Question 14

What is capZ?

Answer 14

associated with positive end of actin

Question 15

What is tropomodulin?

Answer 15

associated with negative end of actin

Question 16

Summarise the sliding filament theory

Answer 16

calcium presence causes troponin to move from the tropomyosin chain
this exposes a myosin binding site on actin surface and charged myosin heads bind
ADP released and myosin head pivots pulling actin filament
ATP binds to head and releases it from actin
ATP hydrolysed recharges the head

Question 17

How does isotonic contraction relate to the sliding filament theory?

Answer 17

muscle tension greater than load force so muscle contracts and fibres shorten

Question 18

How does isometric contraction relate to the sliding filament theory?

Answer 18

muscle tension = load forces so muscle doesn’t contract and myosin heads reattach to same point on actin

Question 19

Name the two pacemaker cells and describe their structure

Answer 19

SA - small, empty, spindle shaped

AV - spend shapes network

Question 20

Name the two conduction fibres

Answer 20

Bundle of His

Purkinje fibres

Question 21

What kind of muscle are cardiomyocytes

Answer 21

striated muscle

Question 22

What are intercalated disks?

Answer 22

specialised regions that connect individual cardiomyocytes

Question 23

What do intercalated disks contain?

Answer 23

numerous gap junctions so AP spreads rapidly cell to cell

Question 24

Summarise the mechanism of excitation-contraction coupling for cardiac muscle

Answer 24

AP propagates along sarcolemma and T-tubules
depolarisation opens vg-Ca2+ channels so calcium influx
calcium influx causes:
-calcium induced calcium release by binding to ryanodine receptor on SR
-initiates contraction binding to troponin
-further depolarisation

Question 25

Summarise the mechanism of excitation-contraction coupling for smooth muscle

Answer 25

depolarisation activates VG-ca2+ channel
Ca2+-CaM complex forms which activates myosin light chain kinase
MLCK phosphorylates myosin light chains which then forms cross bridges with actin

Question 26

How does smooth muscle differ from skeletal?

Answer 26

doesn’t contain regular arrangement of actin and myosin

Question 27

How do cardiac muscle and skeletal muscle differ?

Answer 27

cardiomyocytes aren’t multinucleated