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Fall 2024 A&P > Skeletal Muscle pt 2 > Flashcards

Skeletal Muscle pt 2 Flashcards

Exam 3

1
Q

What are the 8 characteristics of skeletal muscles?

A

Largest contributor to body weight (non-obese)
Locomotion
Expression
Communication
Body temp
Storage of glycogen
“Effectors”/Targets of nerves
Large store of ions, fluids and proteins

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2
Q

What % of body weight do skeletal muscles contribute to (non-obese)

A

40%

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3
Q

Ligaments connect _____ to ______

A

bone to bone

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4
Q

Tendons connect ______ to _______

A

muscle to bone
- can be muscle-muscle via intermediate tendons

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5
Q

A single skeletal muscle cell is called a _______

A

muscle fiber

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6
Q

A single muscle fiber contains hundreds of _____

A

myofibril

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6
Q

What is the name of the cylinders that contain the actin and myosin

A

myofibril

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6
Q

What do we call a collection of one or more muscle fibers controlled by the same motor neuron?

A

Motor unit

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6
Q

Larger motor units are _________(easier/harder) to excite than smaller motor units

A

harder

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7
Q

What is the name of the functional/contractile unit of myofibril?

A

sarcomere - where myosin and actin overlap

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7
Q

Myosin filaments are also called _______ filaments

A

thick

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8
Q

Actin filaments are also called ______ filaments

A

thin

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8
Q

A group of muscle cells is a _________

A

fasciculous

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9
Q

many fasciculi = ______

A

muscle

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10
Q

skeletal muscles store energy as _____

A

glycogen

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11
Q

which two places is glycogen stored?

A

liver and skeletal muscles

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12
Q

The stronger the muscle cell, the more _______

A

myofibrils

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13
Q

how is myoglobin different from hemoglobin?

A

myoglobin has higher affinity for oxygen

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14
Q

Differentiate between type 1 and type 2 skeletal muscle classifications: speed

A

type 1 - slow
type 2 - fast

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15
Q

Differentiate between type 1 and type 2 skeletal muscle classifications: color

A

type 1 - red (more myoglobin)
type 2 - white

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16
Q

Differentiate between type 1 and type 2 skeletal muscle classifications: mitochondria

A

type 1 - a lot
type 2 - less

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17
Q

The _______ is the cell wall of the skeletal muscle cell

A

sarcolemna

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18
Q

_______ is the alternating color pattern of skeletal and cardiac muscle noted under a microscope

A

striations

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19
Q

The ____ extends from z disc to z disc

A

sarcomere

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20
Q

The area in which the thin filaments connect to each other is the _______

A

z disc

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21
Q

The area where there is only thin filaments is the _______

A

I band

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22
Q

The area where there is only thick filaments is the _______

A

H band

23
Q

______ is the elastic connective tissue that anchors actin and myosin

A

Titin

24
Q

A contracted myofibril pulls the two ______ closer together

A

z discs

25
Q

The _______ usually doesn’t change width during contraction

A

A band

26
Q

During contraction, the ______ shrink and the _____ disappear

A

I bands, H bands

27
Q

Differentiate between the repair mechanisms of motor neurons vs skeletal muscle

A

motor neurons - train track system to carry proteins from nucleus down neuron
skeletal muscle - multi-nucleated

28
Q

Myosin filaments are long strands of myosin molecules that are wrapped around at the ____

A

tail

29
Q

____ myosin molecules make up each filaments

A

200

30
Q

each myosin molecule has ___ chains that allow myosin molecules to attach

A

6 - 2 heavy and 4 light chains

31
Q

What are the two types of myosin light chains?

A

Essential LC (2) - ATPase
Regulatory LC (2) - determines activity level of head

32
Q

The myosin has an affinity for binding sites on the ______ filament called _____

A

actin - active sites (F-actin)

33
Q

________ prevents myosin head from binding to F-actin active sites

A

tropomyosin

34
Q

What are the 3 parts of the troponin complex?

A
  • Troponin I: Binds Actin
  • Troponin T: Binds Tropomyosin
  • Troponin C: Binds Calcium
35
Q

How does the troponin complex reveal the active sites?

A

When Ca++ binds to troponin C, the other two troponins (I and T) unravel strands and reveal active sites on actin filament

36
Q

Differentiate between the AP of the following muscles: ocular muscle, gastrocnemius, soleus

A

Ocular Muscles - don’t do a lot of heavy lifting just need to respond quickly; eyes are light weight → fast, short contractions
Gastrocnemius - in between muscle, next to soleus muscle; quicker acting than soleus
Soleus - calf muscles, lots of force for extended periods of time; takes longer to get going but lasts longer

37
Q

What is the mechanism of myofibril contraction?

A

“Sliding filament mechanism”

38
Q

Describe the 6 steps of cross-bridge cycling

A

Attached
1. ATP binds to myosin head, releasing it from actin molecule
Released
2. ATP → ADP + phosphate, creating tension within myosin molecule
Cocked
3. Ca++ combines with troponin C → unravels tropomyosin blocking active sites on actin → myosin can see active sites and bind
Weak cross-bridge
4. phosphate released and myosin binds to active site on actin
Strong cross-bridge
5. head uses tension to pull on active site → sarcomere shortened
Post powerstroke
6. ADP falls off → back to attached state

39
Q

What would happen in the cross-bridge cycle without ATP?

A
  • Myosin heads couldn’t reset, couldn’t produce force
  • Myosin head wouldn’t release from actin
40
Q

_______ is the lack of ATP in the skeletal muscles

A

rigor mortis - muscle stiffness

41
Q

If the sarcomere is over-stretched - not enough _______, wouldn’t be able to produce enough ______

A

surface area
force

42
Q

What is the ideal sarcomere surface area on the graph?

A

B or C, but C is more optimal - a little more room to shorten than B

43
Q

If the sarcomere is under-stretched - not enough _______, so won’t generate as much ______

A

room to shorten
force - start of the red line on the far left

44
Q

The sarcomeres of the heart ventricular wall are a little ______-stretched

A

under - would look like A on graph; augments pumping to return more blood to the heart

45
Q

After a tendon repair, the tendon is shorter and therefore the muscle is _____-stretched

A

over

46
Q

Frank-Starling mechanism

A

Force of contraction directly dependent on stretch of heart muscle

47
Q

Total tension =

A

passive + active tension

48
Q

Professional athletes need to stretch more because their skeletal muscle is _____-stretched

A

under

49
Q

Describe total, active, and passive tension on a graph

A
50
Q

________ tension is the outside force used to achieve stress

A

Passive

51
Q

______ tension is force generated by an AP

A

active - muscle contraction

52
Q

Load/Contraction Velocity Diagram:

A

Increased load = decreased muscle contraction speed
- important in heart muscle

53
Q

______ is skeletal muscle adaptation that occurs
from denervation/disuse of muscle

A

atrophy - loss of myofibrils 1st, then loss of skeletal muscles 2nd

54
Q

______ is skeletal muscle adaptation that occurs
from exercising

A

hypertrophy - increased myofibrils, cell size, and vascular bed growth - increased muscle size

55
Q

______ is skeletal muscle adaptation that occurs
from a lot of exercising (pro athletes), resulting in extra skeletal muscle cells

A

Hyperplasia

56
Q

Quantal regulation or summation

A

number of motor units activated/recruited
more muscle = more force

57
Q

Temporal (time) summation

A

force generation in comparison of rate stimulation (times per second)

58
Q

Tettany occurs when? At how many Hz?

A

Ca++ coming out of SR faster than it can be put back in
40 Hz

59
Q

temporal summation generates _____ force than quantal summation

A

more

60
Q

_____ is the peak force that a muscle can generate

A

tettany

Fall 2024 A&P (19 decks)

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