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adv. anatomy + physiology > m5 + 6 lect - muscular system > Flashcards

m5 + 6 lect - muscular system Flashcards

1
Q

what are the functions of skeletal muscle?

A

primary - movement
secondary - heat, stability, posture

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2
Q

what are muscle cells known as?

A

muscle fibers

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3
Q

what membrane wraps around a skeletal muscle fiber?

A

sarcolemma membrane
- contains T-tubules —> enhance depolarization throughout cell

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4
Q

what are the three parts of a muscle fiber?

A
  • sarcolemma membrane
  • sarcoplasmic reticulum (smooth ER)
  • myofibril
  • nmj = neuromuscular junction
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5
Q

what does the sarcoplasmic reticulum (smooth ER) do?

A

stores ionic calcium within cell

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6
Q

what is a sarcomere?

A

contractile unit of a cell

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7
Q

what is a myofibril?

A

cylindrical units of protein

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8
Q

what are the myofilaments?

A

actin - thin filament
myosin - thick filament

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9
Q

what are the 3 layers in actin filament?

A
  • globular actin (g-actin)
  • tropomyosin
  • troponin
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9
Q

what happens at the nmj?

A

connection of the nerve to the muscle cell
- acetylcholine is released = stimulates the action potential to occur

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10
Q

what is globular actin (g-actin)?

A

binding site for myosin

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11
Q

what is tropomyosin?

A
  • surrounds the g-actin
  • actively blocks actin and myosin from contracting
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12
Q

what is troponin?

A
  • connects tropomyosin and g-actin
  • attachment site for calcium
  • moves tropomyosin out of the way when Ca++ attaches
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13
Q

stimulation: happens in what nerve system? (voluntary innervation)

A

somatic nerve system

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14
Q

motor units:

A
  • are made of one neuron and the group of muscle fibers it innervates
  • varies from 4 to hundreds of fibers to produce gross or fine motor control
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15
Q

stimulation: what is a twitch?

A
  • a single stimulation and single contraction of a motor unit
  • had three phases: latent, contraction, relaxation
    can last from 30ms to 200ms depending on fast or slow twitch fibers
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16
Q

how many muscle fibers does one neuron have?

A

200 muscle fibers

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17
Q

what happens in the latent phase of a twitch stimulation?

A

depolarization/repolarization
last 3ms

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18
Q

what happens in the contraction phase of a twitch stimulation?

A
  • calcium is available
  • contraction lasts 30-200ms
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19
Q

what happens in the relaxation phase of a twitch stimulation?

A
  • calcium is reabsorbed
  • lasts 10-30ms
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20
Q

contraction: motor unit recruitment needs feedback from what receptor?

A

proprioceptors - receives stimuli from within the body, position/movement

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21
Q

contraction: what does motor unit contraction do?

A
  • the more motor units stimulated = the stronger the muscle contraction will be
  • produces coordination and strength
  • this activity takes place in the cerebellum and requires dopamine
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22
Q

what part of the cns produces fine muscle contraction?

A

the primary motor cortex - frontal lobe

23
Q

what neurotransmitters precipitates fine muscle contraction?

A

acetylcholine

24
Q

what link is between electrical and mechanical?

A

calcium

25
Q

what are the steps in the cross-bridge cycle?

A

step 1: cross bridging
step 2: power stroke (ADP + P)
step 3: detachment
step 4: reactivation

26
Q

what happens in cross-bridging (step 1 - cross bridge cycle)?

A
  • as calcium is released by the Sarcoplasmic Reticulum, it binds to the troponin complex
  • this will move the tropomyosin and allow cross-bridging to occur between the actin and the myosin
27
Q

what happens in the power stroke? (step 2 - cross bridge cycle)

A
  • with ATP (ADP + P) as fuel, the myosin ‘head’ will grab the G-actin and slide it to the middle
  • at the same time the myosin spins, allowing other ‘heads’ to reach and pull the actin closer
  • this shortens the sarcomere ( twists like a screw )
28
Q

what happens in the detachment? (step 3 - cross bridge cycle)

A
  • after ATP is consumed, another ATP binds to the myosin head and this triggers the release of myosin from actin
29
Q

what happens in the re-activation? (step 4 - cross bridge cycle)

A
  • ATP is oxidized, releasing energy and this moves the myosin into the ‘cocked’ or ready position
30
Q

what does rigor mortis mean?

A

occurs when there is no ATP left in a cell causing the filaments to fuse together

31
Q

changes in frequency of tension?

A
  • muscle fibers can be stimulated to maintain their contraction, if the frequency is increased
    —— the impulses sent in succession are called wave summation
  • as motor units are recruited and are stimulated the time between twitches becomes less and less until the muscle acts as if relaxation never occurs (up to 50 per second)
32
Q

the three types of tetanus?

A

1) unfused or incomplete tetanus
2) fused or complete tetanus
3) cramps

33
Q

what happens during unfused or incomplete tetanus?

A
  • if these twitches are rapid enough, the muscle begins to quiver (fasciculation - tremor) but still reflexes between twitches
  • caused by a lack of dopamine in the brain stem; Parkinson’s
34
Q

what happens during fused or complete tetanus?

A
  • occurs when the twitches are so close together that all the evidence the muscle relaxation is gone
  • generates by a very high frequency and a build up of calcium in the motor unit
    (completely normal)
35
Q

what happens during cramps?

A
  • painful tetanus caused by dehydration (release of aldosterone - save H2O) and to a loss of K+ in the cells
  • banana helps bc of potassium
36
Q

what is stronger stimuli generated by in a contraction?

A
  • generated by the weight of the resistance
37
Q

what happens during motor unit recruitment in a contraction?

A
  • as work is done, the cerebellum alternates the motor units that are stimulated
  • the heavier the weight, the increased the stimulus ; and the more motor units will be needed
  • stimulated through the use of proprioceptors
38
Q

what happens during the treppe effect in a contraction?

A
  • as a muscle is used, it becomes increasingly stronger to a maintained maximal stimulus
  • caused by an increased efficiency of the muscle to reabsorb and release calcium and breakdown ATP (enzymes)
39
Q

what is muscle tone?

A
  • this is the way we describe the health of a muscle and its ability to carry out work
  • it is firm and will be somewhat continually contracting at all times
    —— individual motor units will be activated in a random order to maintain contraction
    —— resting tone (burns energy even while at rest)
  • prevents injury
  • burns fat
40
Q

what is muscle growth?

A
  • caused by adding to the filaments (protein)
  • growth hormone, testosterone
41
Q

what kinds of contractions stimulate muscles in exercise?

A
  • isotonic
  • isometric
42
Q

what are isotonic contractions?

A
  • muscle contractions with the muscle changing length
    (concentric and eccentric types)
43
Q

what are isometric contractions?

A
  • muscle contractions in which the muscle length does not change
44
Q

what is muscle fatigue?

A
  • caused by oxygen debt and lack of ATP
    —– muscles need to replenish the O2
    —– removal of lactic acid caused by anaerobic respiration
  • ATP recovery happens quickly with the replenishment of O2 thru rest
  • lactic acid removal in anaerobic respiration requires movement and plenty of water
45
Q

what is produced as energy?

A

ATP
- energy needed for muscle contraction
- produced in the mitochondria
(red muscle cells have lots + will multiply with the body’s needs)

46
Q

in what three ways can ATP be produced?

A

1) direct phosphorylation (1)
2) aerobic respiration (36 - slow)
3) anaerobic respiration (2)

47
Q

what happens during direct phosphorylation? (1 ATP)

A
  • as ATP is ‘burned’, it loses a phosphate and becomes ADP
  • ADP then reacts with creatine phosphate in the cytoplasm, donating a P group, returning ADP to ATP
  • creatine is used very quickly (15 sec) (the used creatine will then be processed and excreted in the urine as creatinine)
48
Q

what happens during aerobic respiration? (32-36 ATP)

A

1) initiated by the oxidation of glucose
- glycolysis occurs in the cytoplasm
- producing 2 pyruvic acid, 2 ATP, 2 NADH
- now, pyruvic acid changes to acetyl coenzyme A gaining 2 more NADH, but losing 2 ATP

  • acetyl Co-A is then plugged in the mitochondria
    2) kreb’s cycle
  • 2 acetyl Co-A are run thru the cycle and produce 2 ATP and 6 NADH, and 2 FADH molecules

3) electron transport chain
- here, NADH and FADH are oxidized and 32 to 34 ATP are produced

49
Q

what happens in anaerobic respiration? (2 ATP)

A

this process undergoes glycolysis but stops at pyruvic acid
- lacking oxygen and will only produce 2 ATP per glucose
- because this process lacks oxygen, pyruvic acid will turn into lactic acid

  • only heart muscle, liver, and the kidneys can use lactic acid for energy
  • in skeletal muscle, it builds up and needs to be removed
50
Q

what are the types of muscle fibers?

A

slow oxidative - red - type 1 (aerobic)

fast oxidative - pink - hybred (produced by HIIT training)

fast glycolytic - white - type 2 (most force)

51
Q

what is smooth muscle?

A
  • found in the hollow organs, this muscle is involuntary with no visible striations

arrangement of myofilaments:
- fish net or candy cane arrangement
- dense bodies help anchor the actin filaments
- contract in a corkscrew like way

relies on extra cellular calcium (prolong contraction
- the connector is ralmodulin

52
Q

what is single unit smooth muscle?

A
  • visceral muscle found in hollow organs
  • innervated by varicosities => release Ach at effectors
  • contain gap junctions to allow wave-like contraction - peristalsis (functional syncytium) —- no NMJs
  • little innervation and stress relaxation response
  • muscle spontaneously contracts - contains varicosities
53
Q

what are varicosities?

A

nerve-endings

54
Q

what is multi-unit smooth muscle?

A

controlled by the SNS

richly innervated
- motor units produce control

  • acts more like skeletal muscle with NMJ
  • found in skin and blood vessels

adv. anatomy + physiology (24 decks)

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