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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
The area in which the thin filaments connect to each other is the _______
z disc
21
The area where there is only thin filaments is the _______
I band
22
The area where there is only thick filaments is the _______
H band
23
______ is the elastic connective tissue that anchors actin and myosin
Titin
24
A contracted myofibril pulls the two ______ closer together
z discs
25
The _______ usually doesn’t change width during contraction
A band
26
During contraction, the ______ shrink and the _____ disappear
I bands, H bands
27
Differentiate between the repair mechanisms of motor neurons vs skeletal muscle
motor neurons - train track system to carry proteins from nucleus down neuron skeletal muscle - multi-nucleated
28
Myosin filaments are long strands of myosin molecules that are wrapped around at the ____
tail
29
____ myosin molecules make up each filaments
200
30
each myosin molecule has ___ chains that allow myosin molecules to attach
6 - 2 heavy and 4 light chains
31
What are the two types of myosin light chains?
Essential LC (2) - ATPase Regulatory LC (2) - determines activity level of head
32
The myosin has an affinity for binding sites on the ______ filament called _____
actin - active sites (F-actin)
33
________ prevents myosin head from binding to F-actin active sites
tropomyosin
34
What are the 3 parts of the troponin complex?
- Troponin I: Binds Actin - Troponin T: Binds Tropomyosin - Troponin C: Binds Calcium
35
How does the troponin complex reveal the active sites?
When Ca++ binds to troponin C, the other two troponins (I and T) unravel strands and reveal active sites on actin filament
36
Differentiate between the AP of the following muscles: ocular muscle, gastrocnemius, soleus
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
What is the mechanism of myofibril contraction?
“Sliding filament mechanism”
38
Describe the 6 steps of cross-bridge cycling
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
What would happen in the cross-bridge cycle without ATP?
- Myosin heads couldn't reset, couldn't produce force - Myosin head wouldn't release from actin
40
_______ is the lack of ATP in the skeletal muscles
rigor mortis - muscle stiffness
41
If the sarcomere is over-stretched - not enough _______, wouldn't be able to produce enough ______
surface area force
42
What is the ideal sarcomere surface area on the graph?
B or C, but C is more optimal - a little more room to shorten than B
43
If the sarcomere is under-stretched - not enough _______, so won't generate as much ______
room to shorten force - start of the red line on the far left
44
The sarcomeres of the heart ventricular wall are a little ______-stretched
under - would look like A on graph; augments pumping to return more blood to the heart
45
After a tendon repair, the tendon is shorter and therefore the muscle is _____-stretched
over
46
Frank-Starling mechanism
Force of contraction directly dependent on stretch of heart muscle
47
Total tension =
passive + active tension
48
Professional athletes need to stretch more because their skeletal muscle is _____-stretched
under
49
Describe total, active, and passive tension on a graph
50
________ tension is the outside force used to achieve stress
Passive
51
______ tension is force generated by an AP
active - muscle contraction
52
Load/Contraction Velocity Diagram:
Increased load = decreased muscle contraction speed - important in heart muscle
53
______ is skeletal muscle adaptation that occurs from denervation/disuse of muscle
atrophy - loss of myofibrils 1st, then loss of skeletal muscles 2nd
54
______ is skeletal muscle adaptation that occurs from exercising
hypertrophy - increased myofibrils, cell size, and vascular bed growth - increased muscle size
55
______ is skeletal muscle adaptation that occurs from a lot of exercising (pro athletes), resulting in extra skeletal muscle cells
Hyperplasia
56
Quantal regulation or summation
number of motor units activated/recruited more muscle = more force
57
Temporal (time) summation
force generation in comparison of rate stimulation (times per second)
58
Tettany occurs when? At how many Hz?
Ca++ coming out of SR faster than it can be put back in 40 Hz
59
temporal summation generates _____ force than quantal summation
more
60
_____ is the peak force that a muscle can generate
tettany

Fall 2024 A&P (19 decks)

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