Structure of skeletal muscle

Question 1

What are parallel muscles best at

Answer 1

Can shorten the most

Question 2

What are convergent muscles best at

Answer 2

like a fan, can go various directions

Question 3

what are pennate muscles best at

Answer 3

can produce most tension

Question 4

what are circular muscles best at

Answer 4

open and close things

Question 5

What is the epimysium continuous with

Answer 5

tendon and periosteum

Question 6

what is the perimysium continuous with

Answer 6

epimysium

Question 7

What is the endomysium continuous with

Answer 7

the perimysium

Question 8

what is the sarcolemma

Answer 8

the cell membrane

Question 9

what is the sarcoplasmic reticulum

Answer 9

ER with calcium pumps

Question 10

what is a myofibril

Answer 10

actin and myosin packed and organized into bundles, responsible for contraction and relaxation

Question 11

what is a sarcomere

Answer 11

1 contractile unit (Z disc to Z disc)

Question 12

what are titin proteins

Answer 12

elastic, connect thick filaments to Z disc.

Question 13

What happens to the H zone during contraction

Answer 13

Thin filaments slide into Hzone decreasing it.

Question 14

1000s of sarcomeres end to end

Answer 14

myofibril

Question 15

Striation

Answer 15

100s of myofibrils lined up together

Question 16

What are the factors affecting strength of muscle contraction

Answer 16

1) frequency of stimulation
2) number of muscle fibres contracting
3) Type of muscle fiber

Question 17

Explain frequency of stimulation

Answer 17

single AP = weak muscle twitch (not useful)
many consecutive= tetanus
- more Calcium released than can be pumped in, enough musc tension to pull on tendon

Question 18

Explain number of muscle fibres contracting

Answer 18

-1 motor unit = motor neuron plus all the muscle fibres it innervates.
Small unit - percise
large unit- powerful
-Number of motor units recruited, only a few = weak
many = strong, asynchronous recruitment

Question 19

What is asynchronous recruitment

Answer 19

shifts of motor units to avoid fatigue

happens during sub maximal contraction

Question 20

Explain the 2 Types of sources of energy

Answer 20

-ATP stores only last 2 seconds, so body needs other sources

there is intermediate and sustained

Question 21

What are intermediate sources

Answer 21

Lasts about 1 min, 1 step transfer of energy and phosphate from creatine phosphate

Question 22

What are sustained sources

Answer 22

There is aerobic and aerobic

Question 23

What are aerobic sources of energy

Answer 23

They require oxygen. The make many ATP but are slow.

Question 24

what are anaerobic energy sources

Answer 24

No oxy. But less ATP, fewer steps, create lactic acid.

Question 25

What are the 3 types of muscle fibres

Answer 25

1) Slow oxidative
2) Intermediate fibers
3) Fast-glycolytic fibers

Question 26

What are slow oxidative fibres

Answer 26

• slow to contract, slow to fatigue
• marathon, or posture
• Use aerobic respiration (need oxygen)
• Red, many mitochondria, many capillaries,

Question 27

What are intermediate fibres

Answer 27

• Medium resistance to fatigue
• Aerobic resp.
• some mitochondria, some capillaries, low myoglobin, pink

Question 28

What are fast-glycolytic fibres

Answer 28

-fast to contract, fast to fatigue
sprinter, power lifter 
-Glycolysis (anaerobic) produces lactic acid 
-more myosin & actin = larger 
-white

Question 29

What causes muscle fatigue (4)

Answer 29

1) Decreased energy reserve 2) damage 3) decreased ph. which causes decreased calcium binding 4) central fatigue which is mental, decreases muscle recruitment

Question 30

What is oxygen debt

Answer 30

After exercise, elevated O2 consumption continues until the debt is repaid.
It is the amount of O2 required to restore ATP, creatine, phosphate and glycogen
remove lactic acid and power sweat glands