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PHGY 209 > Muscle - Lecture 3 > Flashcards

Muscle - Lecture 3 Flashcards

1
Q

What happens when calcium leaves the sarcoplasmic reticulum (SR)

A

Binds to troponin (bound on thin filaments - actin). Troponin part of calcium binding familiy of protein and becomes active.

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2
Q

What happens after troponin becomes active (has bound calcium)

A

Change in conformation releases tropomyosin that was wrapped around the actin

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3
Q

What the release of tropomyosin from actin filaments allows

A

Liberates the actin molecule’s binding site for myosin head groups

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4
Q

How muscle comes back to a relaxed state after release of calcium from the SR

A

Calcium is pumped back into the SR so troponin and tropomyosin back in place

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5
Q

What is a twitch

A

A contraction of a muscle fiber in response to a single AP

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6
Q

Why a twitch lags (little gap before AP and contraction)

A

Because of the series of events that must happen between AP and muscle contraction

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7
Q

What is reflected by the duration of contraction (from a single AP)

A

The time that it takes for calcium concentration to return to baseline

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8
Q

Name of the force generated by a muscle and the two things that control it

A

Tension.

Is controlled by Recruitment and Summation

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9
Q

Skeletal muscle what it is adapted for (how much force and how large its functional range is)

A

Adapted for large force generation over a narrow operating range

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10
Q

Recruitment def.

A

Varying the number of muscle fibers involved in a contraction

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11
Q

By what mechanism do muscles vary the force of their actions

A

By recruitment

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12
Q

Motor units can be _____ or ______ but recruitment would involve putting more _______ to work and not _________ them

A

small or large. (more or less muscle fibers for a single motor neuron).
Recruitment : Put more motor units (so motor neurons) to work and not more muscle fibers per motor unit

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13
Q

Summation def. + what it applies to

A

Additive effects of several closely spaced twitches. APPLIES TO ONE MUSCLE FIBER

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14
Q

The closest the twitches, the higher the ___________

A

relative muscle tension

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15
Q

What is called the sustained contraction of a muscle fiber and what is necessary to get to it

A

Fused tetanus. Need close enough APs

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16
Q

What is the converse of a fused tetanus and when does it happen

A

Unfused tetanus : Happens when close twitches but not close enough. APs fired a little more frequently than the duration of the twitch

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17
Q

In an active muscle, individual fibers can either be ______ or _______

A

relaxed or contracted

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18
Q

Fused tetanus tension how much greater than twitch tension

A

3x greater

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19
Q

How ATP rate in muscle fiber changes over multiple twitches and why

A

Stays the same because rate of use = rate of production

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20
Q

What molecule changes ADP back to ATP and what it happens to it after this change

A

Creatine phosphate. Is a Pi storage molecule. After putting a phosphate on ADP to make it ATP, becomes creatine

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21
Q

Which enzyme is involved in creatine phosphate -> creatine / ADP –> ATP

A

Creatine kinase

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22
Q

How long creatine phosphate can sustain ATP formation in the cell and why

A

only a couple seconds because of the amount of creatine phosphate in the cell.

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23
Q

What does the creatine phosphate mechanism lasting a couple seconds serve for

A

Provides time for a more standard metabolic system to take over and produce ATP

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24
Q

Which molecule does the muscle fiber use for a sustained source of energy

A

Glucose

25
Q

Where does the muscle fiber take its glucose from (2)

A

From glycogen that it stores and when runs out of it, from the glucose in the blood

26
Q

2 processes that use glucose to produce ATP in the muscle fiber

A

Glycolysis and oxidative phosphorylation

27
Q

Glycolysis where and what + O2 or not

A

Cytoplasm. Uses glucose to convert ADP + Pi into ATP. NO O2 REQUIRED

28
Q

Oxidative phosphorylation where and what + O2 or not + waste

A

Mitochondria. Uses glucose to convert ADP + Pi into ATP. Waste : Lactic acid. Uses O2 !!

29
Q

What other substance oxidative phosphorylation can use to convert ADP + Pi to ATP and where does it take it

A

Fatty acids. From blood

30
Q

Types of SKELETAL muscle fibers (3)

A

Fast glycolytic fibers.
Slow oxidative fibers
Fast oxidative fibers

31
Q

Slow oxidative fibers : Duration and relative tension + why

A

Low levels of force over long time. Myosin with low ATPase activity

32
Q

Special molecule found in slow oxidative fibers + what it does

A

Myoglobin : Facilitates OXYGEN transport from blood to muscle fiber. Is an oxygen-binding molecule

33
Q

Colour of slow oxidative fibers and why

A

Red because of myoglobin

34
Q

Fast glycolytic fibers : Force/Time of tension + why called fast

A

Large forces over short periods of time. Fast because myosin with high ATP activity

35
Q

What fast glycolytic fibers use (which mechanism and which resource)

A

Use only glycogen from the muscle fiber (no glucose from blood) and use only glycolysis

36
Q

Consequence of fast glycolytic fibers using only glycolysis + colour and why

A

Lot of lactic acid produced.

Have a white colour because no myoglobin is used

37
Q

Fast oxidative fibers what they use/why this name

A

Intermediate properties. Fast myosin (high ATPase activity myosin) and oxidative metabolism

38
Q

Muscle fibers are generally a _______ of different types of _________ but there is usually _______ that is/are higher in proportion

A

mixture. skeletal muscle fibers. Usually one in higher proportion

39
Q

Muscle fatigue : Why and what DOES NOT cause it.

A

To protect muscle from damage. Not caused by depletion of ATP because that would cause rigor mortis

40
Q

Possible explanations (2) for fatigue in high intensity short duration activity

A

1) Change in ion gradients (increase in extracellular potassium)
2) Reduction of pH due to lactic acid build up

41
Q

Possible explanation for fatigue in low intensity long duration activity

A

Depletion of glycogen

42
Q

Other possible explanation for muscle fatigue

A

Central command fatigue. Failure of command signals from CNS

43
Q

Change in muscle physiology after high-intensity short duration exercise + which type of skel. fiber used

A

Fibers make more myofibrils : muscle fatter abd stronger. Fast glycolytic fibers are the ones used

44
Q

Change in muscle physiology after low-intensity long duration exercise + which type of skel. fiber used

A

Development of the structures like myoglobin/mitochondria that increase the efficiency of ATP extraction from oxidative metabolism. Slow oxidative fibers used

45
Q

Smooth muscle diff. with skeletal muscle

A

No stripes cause not highly ordered arrangement of actin/myosin, no sarcomere. Not as much force as rapidly as skel.

46
Q

Smooth muscle similarity with skel. muscle

A

Still uses actin and myosin (just not organized)

47
Q

Smooth muscle : Cell shape + Actin/myosin organization

A

Look like normal cells. Not elongated like muscle fiber

Actin stretched on cell length and myosin walks along thin filaments to pull cell shorter

48
Q

What ANS does and 2 types of muscle it controls

A

Controls internal organs. Controls cardiac muscle and smooth muscle

49
Q

ANS is intimately connected to the process of __________. It is a ___________ system because it has a ____________ component (BP, Temp, etc.)

A

homeostasis. sensory motor system. monitoring component

50
Q

3 major divisons of ANS

A

sympathetic system, parasympathetic system, enteric system

51
Q

What sympathetic system does (think about stress)

A

Fight or flight : Increased heart beat, sweaty palms, fast breathing, dilated pupils

52
Q

What parasympathetic system does

A

Rest and digest : Contractions of gut, slow breathing/heart rate

53
Q

Symp. and parasymp. when each works

A

Both are always active and work in contrast. Balance of both allows ANS to regulate internal milieu (homeostasis)

54
Q

What enteric system is / does

A

Complex network of neurons that line the digestive tract. Peristaltic contractions.

55
Q

Something particular about the enteric system (why is not simply an extension of the ANS)

A

Can operate by itself, independently

56
Q

2 kinds of peristaltic contractions

A

1) Mixing contraction

2) Movement contraction

57
Q

What are mixing contractions in the digestive tract

A

Intestines getting longer and shorter

58
Q

What are movement contractions in the digestive tract

A

Waves that occur all the way down through the digestive tract -> move the content down

59
Q

how symp./parasymp. and enteric systems linked together + consequence

A

Sympathetic and parasympathetic send inputs to the enteric system so they do not directly interact with the intestine

PHGY 209 (17 decks)

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