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Flashcards in Muscle Physiology Deck (47):
1

Events at the NEUROMUSCULAR JUCTION: Part one - In the SYNANPTIC KNOB of SOMATIC MOTOR NEURON

-AP opens voltage-gated Ca2+ channels
- Ca2+ influx triggers exocytosis of SYNAPTIC VESICLES
- Ach diffuses across SYNAPTIC CLEFT

2

Events at the NEUROMUSCULAR JUNCTION: Part two - At the motor end plate of SKELETAL MUSCLE FIBER

- Ach binds ligand-gated channels
- Na+ influx depol. MUSCLE FIBER to threshold
- AP generated along SARCOLEMMA
- AchE removes Ach and stops signal

3

What does the "E" is AchE stand for?

AcetylcholinESTERASE

4

After travelling along the SARCOLEMMA, where does AP go?

Down the TRANSVERSE TUBULES

5

What kind of channels does AP open in the TERMINAL CISTERNAE of SR?

Voltage-gated Ca2+ channels

6

Where is Ca2+ released into?

The CYTOSOL

7

What does Ca2+ bind to?

TROPONIN

8

When TROPONIN changes shape, what effect does it have on TROPOMYOSIN?

It moves TROPOMYOSIN to expose the MYOSIN binding sites on ACTIN

9

How does Ca2+ get back into the SR?

A PUMP

10

What would happen if Ca2+ pumps stop working?

Ca2+ will build up and the MUSCLE will stay contracted, no relaxation

11

What is it called when MYOSIN HEADS bind to ACTIN?

The CROSS BRIDGE

12

What happens during a POWERSTROKE?

MYOSIN pulls ACTIN, shortening the SARCOMERE and causing CONTRACTION

13

What releases MYOSIN from ACTIN?

ATP

14

What provides energy for the MYOSIN HEAD to re-cock for another POWERSTROKE?

ATP splitting

15

How many times does the CROSS BRIDGE CYCLE repeat?

Many times

16

ISOTONIC, CONCENTRIC CONTRACTION = ?

Muscle shortens e.g. lift object

17

ISOTONIC, ECCENTRIC CONTRACTION = ?

MUSCLE lengthens e.g put down object

18

ISOMETRIC CONTRACTION = ?

MUSCLE stays the same length e.g. holding object, maintaining body position

19

CONTRACTION of many SACROMERES leads to

CONTRACTION of many MYOFIBRILS

20

CONTRACTION of many MYOFIBRILS leads to

CONTRACTION of MUSCLE FIBERS + pull on ENDOMYSIUM

21

CONTRACTION of MUSCLE FIBERS leads to

CONTRACTION of MUSCLE FASCICLE + pull on PERIMYSIUM

22

CONTRACTION of MUSCLE FASCICLE leads to

CONTRACTION of whole MUSCLE + pull on EPIMYSIUM

23

CONTRACTION of whole MUSCLE pulls on TENDON which pulls on

PERIOSTEUM/BONE

24

T or F: Do MUSCLES push

F, they pull

25

How many MUSCLE groups are required for action?

At least 2

26

What are the 4 functional MUSCLE groups?

1) PRIME MOVERS
2) ANTAGONISTS
3) SYNERGISTS
4) FIXATORS

27

PRIME MOVER =

a force for specific movement, aka AGONIST e.g. BRACHIALIS for arm FLEXION

28

ANTAGONIST =

Reverse, slow, stop movement e.g. TRICEPS BRACHII for arm FLEXION

29

SYNERGISTS =

Stabilize joints, aids PRIME MOVER movement e.g. BICEPS BRACHII

30

FIXATORS =

Holds BONES in place e.g. rotator cuff MUSCLES

31

How long does AP last?

1-2 msec

32

How long does CONTRACTION last?

7-100 msec

33

What leads to TETANUS

Many consecutive APs

34

1 MOTOR UNIT =

1 MOTOR NEURON + all MUSCLE FIBERS it innervates

35

What factors effect CONTRACTION?

1) Freq. of STIM.
2) Number of MUSCLE FIBERS contracting
3) Type of MUSCLE FIBER

36

How many MUSCLE FIBERS/MOTOR UNITS for precise movement?

About 10

37

How many MUSCLE FIBERS/MOTOR UNITS for powerful movement?

About 1000

38

What is the benefit of MOTOR UNITS recruited in shifts?

Allows sustained CONTRACTION without fatigue

39

An immediate source of energy:

One step transfer of E and PHOSPHATE from CREATINE PHOSPHATE (CREATINE PHOSPHATE + ADP = CREATINE + ATP)

40

Sustained E sources:

AEROBIC and ANAEROBIC RESPIRATION

41

AEROBIC RESP. =

Requires O2, makes 32 ATP/GLUCOSE, many steps = slooow

42

ANAEROBIC RESP. =

No O2, makes 2 ATP/GLUCOSE, few steps, makes LACTIC ACID = changes pH

43

Slow-oxidative fibers =

Slow to contract/fatigue, uses AEROBIC, mitochondria, many caps, hi myoglobin, appear red
e.g. MUSCLES of leg, back, marathon, endurance

44

Intermediate fibers =

intermediate resistance to fatigue, AEROBIC, some mitochondria, some caps, lo myoglobin, appears pink

45

Fast-glycolytic =

fast to contract/fatigue, fast/powerful, but not for long, ANAEROBIC, more MYOSIN, ACTIN = larger diameter fibers, appears white

46

MUSCLE fatigue is caused by

1) Dec. E reserves
2) Damage to MUSCLE FIBER
3) Dec. pH leading to dec. Ca2+ binding to TROPONIN
4) Central fatigue: mental, pain, dec. motor recruitment

47

O2 debt =

Amount of O2 required to restore levels of ATP, CREATINE PHOSPHATE, GLYCOGEN, remove lactic acid, power sweat gland activity