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A/P Lecture > Ch.9 part II > Flashcards

Ch.9 part II Flashcards

1
Q

Excitation-contraction coupling

A
  • mechanism by which an action potential causes contraction of a muscle fiber
  • involves sarcolemma, T tubules, sarcoplasmic reticulum, Ca 2+ and troponin
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2
Q

T tubules

A

-action potential enters into cell here, which triggers Ca 2+ gated channels to open

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3
Q

Sarcoplasmic reticulum

A

-enlarges due to the lumen of the t tubule being filled with extracellular fluid to form terminal cisternae

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4
Q

Terminal cisternae

A

-enlarged portion of sarcoplasmic reticulum

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5
Q

Triad

A

-t tubule and two adjacent terminal cisternae

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6
Q

Cross bridge cycling

A
  • the process by which each myosin molecule undergoes the cycle of cross bridge formation, movement, release, and return to original position
  • requires ATP
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7
Q

Power stroke

A
  • myosin heads move actin with every ATP that is added

- several power strokes happen with every action potential

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8
Q

Recovery stroke

A

-happens when myosin head returns to resting place and awaits for next ATP to start another power stroke

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9
Q

Muscle twitch phase

A
  • a single, brief contraction and relaxation cycle in a muscle fiber
  • consists of a lag phase, contraction phase, and relaxation phase
  • does not last long enough or generate enough tension to perform any work
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10
Q

Lag phase

A

-time between action potential coming from nerve and the Ca 2+ actually bindin with troponin

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11
Q

Contraction phase

A

-maximum contraction happens when actin molecules meet within a sacromere

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12
Q

Relaxation phase

A

-Ca 2+ pops off of troponin, tropomyosin covers active sites which makes myosin release from actin, titin pushes actin apart to equilibrium, complete contraction back to resting place

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13
Q

Motor unit

A
  • one nerve coming in will have a set of muscle fibers
  • not all fibers are signalled at once (axons only innervate a few fibers)
  • the finer the movement, the fewer fibers that are innervated
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14
Q

Motot unit response

A

-treppe, multiple motor unit summation, multiple wave summation, tetanus

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15
Q

Summation

A

-involves increasing the force of contraction of the muscle fibers within the muscle

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16
Q

Recruitment

A

-involves increasing the number of muscle fibers contracting

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17
Q

Treppe

A
  • when a rested muscle is stimulated repeatedly with maximal stimuli at a low frequency (which allows complete relaxation between stimuli)
  • second contraction produces a slightly greater tension and the third contraction produces even greater tension until equilibrium is reached
  • stimulus is maximal but delivered at low frequency
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18
Q

Multiple motor unit summation

A

-the relationship between increased stimulus strength and an increased number of contracting motor units

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19
Q

Multiple wave summation

A
  • in incomplete tetnus, muscle fibers produce action potentials so rapidly that no relaxation occurs
  • as the frequency of contraction increases, these are produced due to increased tension
20
Q

Tetanus

A
  • sacromeres don’t have time to reset
  • Ca 2+ never leaves and the power stroke never stops
  • muscle is locked into maximum contraction
  • stimulus is at threshold but delivered at high frequency
21
Q

Muscle contractions

A

-can be isometric or isotonic

22
Q

Isometric

A
  • length of the muscle does not change, but tension increases during contraction
  • “posture”
23
Q

Isotonic

A
  • amount of tension during contraction is constant but the length of the muscle changes
  • include concentric and eccentric
24
Q

Concentric contraction

A
  • the tension in the muscle is great enough to overcome the opposing resistance
  • increasing tension, muscle shortening
  • “starbucks curl”
25
Q

Eccentric contraction

A
  • tension is maintained but the opposing resistance is great enough to cause the muscle to increase in length
  • slowly letting muscles stretch out under control
26
Q

Energy sources for muscle contraction

A

-creating phosphate, anaerobic respiration, aerobic respiration

27
Q

Creatine phosphate

A
  • stockpiled in muscle fibers; requires use of creatine kinase
  • instant source of unlimited ATP for a very short period of time (8-10 secs)
  • only releases 1 ATP
28
Q

Anaerobic respiration

A
  • generates ATP rapidly after creatine phosphate is used up

- releases 2 ATP

29
Q

Aerobic respiration

A
  • happens all of the time; very efficient
  • releases 36 ATP
  • includes the use of glycogen and pyruvate
  • -glucose goes through glycolosis forming 2 pyruvate (2 ATP) which then goes through krebs cycle (34 ATP)
30
Q

Oxygen debt

A
  • caused by creatine/anaerobic mess
  • the process of reseting molecules burned through
  • insufficient oxygen consumption relative to increased activity
31
Q

Oxygen recovery

A

-repays oxygen debt which is time consuming

32
Q

Muscle fiber types

A

-type I, type IIa, type IIb

33
Q

Type I (slow twitch)

A
  • adaptive for long haul
  • very efficient
  • postural muscles
34
Q

Type IIa (fast twitch oxidative)

A
  • combo of slow twitch and fast twitch glycolytic)
  • efficient and instantaneous
  • lower limbs
35
Q

Type IIb (fast twitch glycolytic)

A
  • adapted for instantaneous response
  • polar opposite of slow twitch
  • upper limbs
36
Q

Myoglobin

A
  • has high affinity for oxygen

- inside of mitochondria and suck oxygen away from hemoglobin (slow twitch)

37
Q

Smooth muscle

A
  • neurally or hormonally controlled

- contain dense bodies, dense areas, intermediate filaments, caveolae, myosin kinase, calmodulin, myosin phophatase

38
Q

Dense bodies

A

-inside sarcoplasm

39
Q

Dense areas

A

-on the surface, attached to the sarcolemma

40
Q

Intermediate filaments

A
  • mesh around sarcolemma

- attached to dense bodies which form the intracellular cytoskeleton

41
Q

Caveolae

A
  • shallow, invaginated areas along the surface of the sarcolemma
  • comparable to t tubules
42
Q

Calmodulin

A

-protein in which Ca 2+ bind with in smooth muscle

43
Q

Myosin kinase

A

-enzyme that transfers phosphate group from ATP to myosin molecules in smooth muscle

44
Q

Myosin phosphatase

A
  • removes the phosphate group from the myosin molecules allowing the relaxation of smooth muscle
  • timing of this enzyme is important because it can cause relaxation or contraction for long periods of time
45
Q

Latch state

A

-period of sustained tensions due to the timing of myosin phosphatase

A/P Lecture (6 decks)

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