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Human physiology > Lecture 5: Skeletal muscle contraction > Flashcards

Lecture 5: Skeletal muscle contraction Flashcards

1
Q

Epimysium

A

Connective tissue surrounding entire muscle

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2
Q

Muscle

A

Made up of multiple fascicles

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3
Q

Perimysium

A

Connective tissue surrounding each fascicle

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4
Q

Fascicle

A

A bundle of myofibers

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5
Q

Endomysium

A

Delicate connective tissue surrounding each myofiber

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6
Q

Sarcolemma

A

Cell membrane of muscle fiber

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7
Q

Myofiber

A

Individual multinucleated muscle cell

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8
Q

Myofibril

A

A chain of sarcomeres within a myofiber

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9
Q

Myofilament

A

Actin and myosin filaments that make up a sarcomere

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10
Q

T-tubule

A

Invagination of sarcolemma that lie close to cisternae of the sarcoplasmic reticulum
Form triads with cisternae
Two per sarcomere

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11
Q

Z-discs (Z-lines)

A

Anchor actin filaments

Located at each end of sarcomere

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12
Q

I -bands

A

Composed entirely of actin

Width changes during contraction

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13
Q

A-bands

A

Composed of Actin and myosin

Width does not change during contraction

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14
Q

H-bands

A

Composed entirely of Myosin

Width changes during contraction

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15
Q

During contraction, Actin filaments:

A

Form the I-bands which become narrower in width

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16
Q

During contraction, A-bands:

A

Are equivalent to the length of the myosin filaments and do not change width

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17
Q

During contraction, H-bands:

A

Are the part of the A band that is not overlapped by actin filaments and becomes narrower

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18
Q

DHP receptors

A

Voltage-sensitive calcium channels located on sarcolemma T-tubules
Causes conformation change in ryanodine receptors
Minute amount of calcium flows into cytosol via these channels

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19
Q

Ryanodine receptors

A

Located on cisternae of sarcoplasmic reticulum
Open in response to DHP conformation change
Allow calcium into cytosol from SR

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20
Q

SERCA

A

Sarcoplasmic reticulum calcium ATPase

Uses ATP to pump calcium back into the SR

21
Q

Calsequestrin

A

In the SR, it maintains an optimum calcium concentration gradient to facilitate the return of calcium to SR

22
Q

Preload

A

Load on a muscle in the relaxed state (prior to contraction)

23
Q

Preload results

A

Stretches the muscle which stretches the sarcomere
Preload generate passive tension in the muscle
Muscle resists the tension applied to it
Force of resistance is measured as passive tension
The greater the preload, the greater the passive tension

24
Q

Afterload

A

The load the muscle works against

25
Q

Isotonic contraction occurs when

A

The muscle generates more force than the afterload

26
Q

Isometric contraction occurs when

A

The muscle generates less force than the afterload

27
Q

Cross-bridge cycling starts when

A

When free calcium is available and binds to troponin

28
Q

Continuous cycling of cross-bridges is

A

Contraction

29
Q

ATP role in cross-bridging

A

ATP is required to break the link with actin

30
Q

Cross-bridge cycling continues until

A

Withdrawal of calcium ion

ATP is depleted

31
Q

Sarcomere 3.5um

A

0 tension

32
Q

Sarcomere 2.2um

A

100% tension

33
Q

Sarcomere 1.65um

A

100% tension

34
Q

Sarcomere <1.65um

A

Tension drops towards 0

35
Q

Where is ATP required for muscle contraction

A

Most is used for sliding filament mechanism
Pumping calcium back into the SR (using SERCA)
Pumping sodium/potassium ions through the sarcolemma to re-establish resting potential

36
Q

Phosphocreatine

A

Releases energy rapidly
Reconstitutes ATP
ATP+phosphocreatine allows energy for 5-8 seconds contraction

37
Q

Glycolysis

A

Lactic acid buildup

Can sustain contraction for 1 minute

38
Q

Oxidative phosphorylation

A

Provides more than 95% of all ATP needed for long term contraction

39
Q

Characteristics of fast fibers

A 
Light/white fibers
Fewer mitochondria
Primarily use glycolysis or anaerobic respiration resulting in buildup of pyruvic and lactic acid
Little myoglobin
Larger concentration of ATPase
40
Q

Characteristics of slow fibers

A 
Dark/red fibers
More mitochondria
Primarily use aerobic respiration
More myoglobin
Smaller concentration of ATPase
41
Q

T or F: The numbers of myofibers can be increased after brith

A

False. Only the number of myofibrils can be increased, which increases mass of myofibers

42
Q

Motor unit

A

A neuron and the myofibers it innervates

All-or-none system

43
Q

A nerve cell may innervate how many myofibers

A

Anywhere from a few to several hundred

44
Q

Summation

A

An additional spike can occur before previous calcium ions have been returned to the SR
This increases the total amount of calcium ion in the cytosol and increases the rate of cross-bridge cycling
This increases muscle tension

45
Q

Tetany

A

If the frequency of spikes is fast enough, there is no time for relaxation between spikes.
The muscle remains at maximum contraction

46
Q

First class lever system

A

Fulcrum is in the middle

i.e., raising chin using sternocleidomastoid

47
Q

Second class

A

Resistance (out-force) is in the middle

i.e., raising the body on the ball of the foot

48
Q

Third class

A

Effort (in-force) is in the middle
i.e., Both in and out forces are on the same side of the fulcrum
Both forces move in same direction

Human physiology (16 decks)

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