The Muscular System

Question 1

What are the functions of the skeletal muscles

Answer 1

movement, support, communication, posture

Question 2

What are the characteristics of skeletal muscle

Answer 2

contractility, extensibility, elasticity, conductivity

Question 3

What are myofibrils rich in

Answer 3

blood vessels and nerves

Question 4

What type of cell are myofibrils

Answer 4

multi-nucleate - syncytium

Question 5

What formed myofibrils

Answer 5

fusion of myoblasts

Question 6

What are t tubules

Answer 6

invaginations of muscle fibre membrane in the cytoplasm

Question 7

What do t tubules allow

Answer 7

electric depolarisation of membrane - propagation

Question 8

What does the myofibril cytoplasm contain

Answer 8

bundles of protein and mitochondria

Question 9

What are sacromeres

Answer 9

repeated units in myofibrils

Question 10

What are sarcomeres responsible for

Answer 10

contraction of muscle

Question 11

What does the dark A band of myofibrils contain

Answer 11

myosin filaments

Question 12

Which band is dense in myofibrils?

Answer 12

dark A band

Question 13

What is the I band in myofibrils composed of

Answer 13

actin - thin filament

Question 14

What does the I band in myofibrils span across

Answer 14

sarcomere

Question 15

How is actin made stable in myofibrils

Answer 15

plus ends anchored into the Z line

Question 16

What does anchoring of actin into the Z line prevent

Answer 16

polymerisation at the plus end

Question 17

What is nebulin

Answer 17

large protein

Question 18

What is nebulin made of

Answer 18

repeating actin binding domains

Question 19

What is the process of muscle contraction driven by

Answer 19

myosin heads

Question 20

What is contraction

Answer 20

thick filament of actin moves towards thin filament

Question 21

What does contraction obtain

Answer 21

shortening of sarcomere without changing length of filaments

Question 22

What is the myosin head normally attached to

Answer 22

specific binding site on actin filament

Question 23

What happens when the actin filament binds ATP

Answer 23

change in conformation, myosin head slides along actin filament

Question 24

What happens when the myosin head attaches to new binding site

Answer 24

phosphate is released - change in head conformation - power stroke

Question 25

What does the power stroke allow

Answer 25

actin filament to slide against myosin filament

Question 26

What does contraction require

Answer 26

energy - ATP

Question 27

How is contraction initiated

Answer 27

membrane depolarisation allows entry of calcium

Question 28

What is the starting point of contraction

Answer 28

calcium

Question 29

What has the ability to bind calcium

Answer 29

troponin

Question 30

What does the binding of calcium allow

Answer 30

conformational change - releases tropomyosin

Question 31

What is the function of calcium in contraction initiation

Answer 31

unmasks myosin binding sites on thin filament

Question 32

What is the function of releasing tropomyosin

Answer 32

unmasks binding site for myosin head

Question 33

What happens when a nerve impulse reaches the nerve terminal

Answer 33

Ca2+ released - causes release of ACh by exocytosis

Question 34

When does muscle contraction stop

Answer 34

when nerve impulses stop

Question 35

What can toxins cause

Answer 35

muscle paralysis

Question 36

What can botulinum toxin cause

Answer 36

muscle weakness, paralysis, death

Question 37

What can BOTOX be used for?

Answer 37

cosmetically, medically for cross eyedness

Question 38

What does botulinum toxin degrade

Answer 38

SNAP25

Question 39

What does botulinum toxin prevent formation of

Answer 39

complex needed for fusion of excitatory vesicles with membrane

Question 40

What is the function of SNAP25

Answer 40

promotes fusion of excitatory vesicles with membrane

Question 41

What does BOTOX cause to be retained inside the cell

Answer 41

ACh

Question 42

What happens if ACh is retained inside the cell

Answer 42

X muscle contraction

Question 43

What muscles are fatigue resistant

Answer 43

oxidative muscles

Question 44

What is the difference between slow and fast fibres

Answer 44

slow fibres - sustain contract for longer periods of time, fast fibres - contract rapidly

Question 45

Which muscle fibres are anaerobic

Answer 45

glycolytic

Question 46

Which muscle type has the highest concentration of mitochondria

Answer 46

slow oxidative

Question 47

How do cells generate ATP

Answer 47

aerobic metabolism in mitochondria

Question 48

What does aerobic muscle metabolism typically stimulate

Answer 48

slow fibres

Question 49

What muscle metabolism is anaerobic

Answer 49

glycolytic

Question 50

What does anaerobic muscle metabolism rely on

Answer 50

degradation of glycogen

Question 51

What does anaerobic muscle metabolism produce

Answer 51

lactic acid

Question 52

What is the NET production of anaerobic muscle metabolism

Answer 52

2ATP

Question 53

What does anaerobic muscle metabolism stimulate

Answer 53

fast fibres

Question 54

What does phosphocreatine allow production of

Answer 54

phosphate and ATP

Question 55

What do fast muscle fibres use heavily

Answer 55

phosphocreatine

Question 56

What happens to creatine in mitochondria

Answer 56

recycled into P-creatine at rest

Question 57

What metabolism do slow fibres use

Answer 57

aerobic

Question 58

What metabolism do fast fibres use

Answer 58

anaerobic

Question 59

What happens in the muscles during fatigue

Answer 59

lactic acid, pH decreases