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Locomotor System > Physiology: Muscular Work > Flashcards

Physiology: Muscular Work Flashcards

1
Q

What does the amount of movement that a muscle can produce depend on?

A

the original length of its fibers

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2
Q

What happens to muscle fibers during movement?

A

Muscle fibers reduce in length.

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3
Q

What is the most familiar characteristic of muscle work?

A

muscle strength

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4
Q

What force does a muscle produce when it shortens?

A

a tensile force

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5
Q

What does muscle force produce?

A

the tendancy to rotate

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6
Q

What two factors are used to describe a muscle strength?

A

1) the ability to generate a tensile force (the force a muscle creates when it shortens)
2) the ability to create a rotation

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7
Q

How is the assessment of muscle strength in vivo typically performed?

A

by the determination of the amount of weight a subject can lift.

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8
Q

What device is used to determine the amount of weight a subject can lift?

A

isokinetic dynamometer

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9
Q

What does the force of muscle contractions depend on?

A
  • length-tension relationship
  • size of the muscle
  • number of motor units
  • the frequency of stimulation
  • the angle of the joint
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10
Q

When is the maximal force generated in the LENGTH-TENSION RELATIONSHIP?

A

When the muscle is stretched to a length approximately 20% grater than its resting length.

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11
Q

When is the maximal force generated in the SIZE OF MUSCLE?

A

Large muscles have more muscle fibers, and therefore generate more force tha smaller muscles.

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12
Q

When is the maximal force generated in the NUMBER OF MOTOR UNITS RECRUITED?

A

The smooth and stready increase in muscular tension is produced by increasing the number of active motor units.

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13
Q

When is the maximal force generated in the FREQUENCY OF STIMULATION?

A
  • single twitch
  • summation of twitches (second contraction is larger than the first)
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14
Q

When is the maximal force generated in the ANGLE OF THE JOINT?

A

each joint has an optimum angle of force application.

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15
Q

What does the joint’s optimum angle of force application depend on?

A

The relative positions of:
- the tendinous insertions on the bone,
- the load being moved.

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16
Q

What does the tension produced by a sarcomere depend on?

A

the number of actin-myosin cross-bridges it forms.

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17
Q

How do muscles create force?

A

by cycling myosin cross-bridges

18
Q

State the equation of cross bridge formation.

A

A + M + ATP –> A + M + ADP + Pi + force

A- actin
M- myosin

19
Q

What does the number of cross-sections depend on?

A

the length of the sarcomere.
(It determines the amount of overlap there is between myosin and actin)

20
Q

What is the most important factor determining the tensile force generated by a muscle’s contraction?

A

muscle size

21
Q

Is the overall size of a muscle a good indicator for the number of fibers contained in the muscle?

A

No, it is a poor indicator.

22
Q

Explain the relationship between muscle size and force of contraction.

A

complicated

23
Q

What do the properties of the whole muscle depend on?

A
  • the properties of fibers
  • organization of the fibers
24
Q

How are muscle fibers arranged in relation to the muscle’s line of action?

A

oblique to the muscle’s line of action (rarely run the whole length).

25
Q

What is the peak force production? What is it related to?

A
  • related to the physiological cross sectional area (PCSA)
26
Q

What is the PCSA? What does it estimate?

A

PCSA- physiological cross sectional area
- estimates the sum of the cross sectional area of all the fibers
- standard measure

27
Q

What is the PCSA approximately equal to?

A

The anatomical cross sectional area in parallel fiber muscle.

28
Q

How does the PCSA compare to the anatomical crossection in pennate muscle?

A

PCSA&raquo_space; anatomical cross sectional area

29
Q

Compare the contraction force of pennate muscle and muscle with parallel fibers.

A
  • PCSA is much larger in pennate muscle
  • anatomical crossections are very similar
  • all other factors are equal
  • pennate muscle is capable of generating more contraction force
30
Q

When exposed to stimuli from the nervous system, how is the response of muscles categorised?

A
  • “all or none” law
  • if enough individual fibers contract at one time then the entire muscle will contract.
31
Q

What happens as workload on a muscle increases?

A

the muscle will reach a point at which it will be no longer able to contract (no matter how much electrical stimulation it recieves).
This point is called the “point of muscle overload”.

32
Q

What is the point of muscle overload?

A

The point at which the muscle workload is so large that the muscle cannot contract any longer, no matter how much stimulation is given.

33
Q

How can muscular work be considered?

A
  • strength (power)
  • endurance
34
Q

What is strength?

A

The maximum amount of tension produced by a particular muscle or muscle group.

35
Q

What is endurance?

A

The amount of time for which an individual can perform a particular activity.

36
Q

What factors determine the muscular work capabilities of any skeletal muscle?

A

1) types of muscle fibers
2) physical conditioning/training

37
Q

How is muscular work classified? State both names.

A

1) STATIC- isometric ‘same length’
2) DYNAMIC- isotonic ‘same tension’

38
Q

Explain static work. State its other name. How is static work achieved? What does it lead to?

A
  • a muscle remains contracted for a period of time, but there is no movement.
  • isometric
  • heavily contracted muscles squeeze blood vesseks restricting blood flow.
  • no oxygen delivery, no removal of lactic acid (waste product)
  • RESULT: muscular aches and pain
39
Q

Explain dynamic work. State its other name. How is static work achieved? What does it lead to?

A
  • rythmical contraction and relaxation of a muscle, reulting in movement.
  • isotonic
  • contractions and relaxations act as pumps for blood flow
  • muscle is supplied with more blood, oxygen,
  • lactic acid is removed from muscle at a greater pace
40
Q

How is the work output calculated? Equation.

A

WP (gmm) = WL (g) x LH (mm)
WP- work performed by the isolated muscle
WL- weight which the muscle can lift
LH- weight lifing height

41
Q

How is the work output calculated? In words.

A

The work output is estimated by multiplying the weight that the muscle can lift by the height of lifing.

Locomotor System (19 decks)

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