Intro/Skeletal Muscle Structure Flashcards
1
Q
Muscle makes up ___ in men
A
42-47% of body mass.
2
Q
Muscle makes up ___ in women
A
30-35%
3
Q
Types of muscle
A
Skeletal
Smooth
Cardiacs
4
Q
Each skeletal muscle is an organ. True or false?
A
True
5
Q
Properties of the cells of the skeletal muscle
A
- Long and cylindrical, in bundles
- Multinucleate
- Obvious Striations
6
Q
Which muscle type carries our voluntary actions?
A
Skeletal
7
Q
What are the skeletal muscle’s connective tissue components?
A
- Endomysium
- Perimysium
- Epimysium
8
Q
Skeletal muscles are found…
A
…attached to bones in the skeletal system
9
Q
Endomysium is found…
A
…between fibers
10
Q
Perimysium is found…
A
…surrounding bundles
11
Q
Epimysium is found…
A
…surrounding whole muscle
12
Q
Which tissue component of skeletal muscle covers the entire muscle?
A
Epimysium
13
Q
Smooth muscle is found…
A
…in the walls of hollow organs like blood vessels and the GIT
14
Q
Properties of the cells of smooth muscle
A
- Uninucleate
- No striations
15
Q
The movements of smooth muscle are voluntary. True or false?
A
False
16
Q
Which muscle type possesses two layers of opposite orientation?
A
Smooth muscle
17
Q
Muscle layers of smooth muscle
A
Circular
Longitudinal
18
Q
Components of connective tissue in smooth muscle
A
Endomysium
19
Q
Endomysium smooth muscle tissue
A
It surrounds cells
20
Q
Properties of cells of cardiac muscle
A
- Branching, chains of cells
- Single Nucleated
- Striations
21
Q
Cardiac muscle cells are connected by…
A
…intercalated discs
22
Q
Cardiac muscle movement - Involuntary or not?
A
Involuntary
23
Q
The heart muscle is called…
A
Myocardium
24
Q
Connective tissue component of cardiac muscle
A
Endomysium; it surrounds cells
25
A skeletal muscle fiber is an individual muscle cell. True or false?
True
26
Shape of muscle fibres
They are long and narrow in shape
27
Sarcolemma is...
...the plasma membrane of the muscle cell. It surrounds the sarcoplasm and has many nuclei (multi-nucleated)
28
The nuclei of the muscle cell are located...
...in the periphery of the muscle cell just beneath the sarcolemma
29
The organelle must abundant in skeletal muscle fibres is...
Mitochondria
30
Cellular levels of structures in the skeletal muscle fiber from 1 to 5 are...
```
Sarcolemma
Sarcoplasm with organelles and proteins
Myofibrils and myofilaments
SR
T tubules
```
31
Why are there abundant mitochondria in skeletal muscle fibres?
High demand for energy (ATP) required for muscle contraction
32
What is myoglobin?
A protein with a high affinity for oxygen, just like haemoglobin
33
Function of myoglobin
It transfers oxygen from the blood to the mitochondria of the muscle cell
34
What are myofibirils?
A cylindrical bundle of contractile proteins, which are called myofilaments, within a muscle fiber
35
What are myofilaments? Where are they found?
They are contractile protein filaments that make up the Myofibrils, located in the sarcoplasm of the muscle cell
36
What are the names of the myofilaments of striated muscle cells?
–Actin – thin filament
| –Myosin – thick filament
37
What is the Sarcoplasmic reticulum (SR)?
•Located where the SR ends, which is near the area where actin and myosin overlap
–The SR tubules and terminal cisternae store high concentrations of calcium, which is important in the process of skeletal muscle contraction
A saclike membranous network of tubules that are actually an elaborate form of smooth endoplasmic reticulum
38
SR surrounds ____ and contains ___
myofibril, terminal cisternae
39
Location of terminal cisternae on muscle fibre cells
They are located where the SR ends, which is near the area where actin and myosin overlap
40
Functions of SR
The SR tubules and terminal cisternae store high concentrations of calcium, which is important in the process of skeletal muscle contraction
41
Where are the transverse tubules (T-tubules) of skeletal muscle cells found?
They are invaginations found closely associated with SR and connected to the sarcolemma but penetrate the sarcolemma into the interior of the muscle cell
42
Functions of T-tubules
They bring extracellular materials into close proximity of the deeper parts of the muscle fiber
43
SR and T-tubules Function
–Activate skeletal muscle contraction when the muscle cell is stimulated by a nerve impulse
–Transmit nerve impulses from the sarcolemma to the myofibrils
44
The sarcomere is...
An arrangement of myofilaments with alternating bands of light and dark areas due to the organization of the actin and myosin, resulting in a striated appearance
45
What is smallest contractile unit of the muscle fiber?
Sarcomere
46
The components of the sarcomere are...
```
Z-lines
M-lines
A-bands
I-bands
Proteins
```
47
Z line properties
-
48
Actin is anchored by...
Z lines
49
Thick myofilaments (myosin) are anchored by...
M lines
50
Which two lines run perpendicular along the muscle fibres?
Z and M lines
51
Thin actin filaments project in either direction off of a Z disc and cross the entire length of the sarcomere. True or false?
Not entirely true. It projects off but doesn’t cross the entire length.
52
What is the H-Zone?
The lighter area within the A-Band that contains only myosin and contains the M line.
53
The A-band spans the length of the myosin filament. True or false?
True
54
There is no actin in the M band. True or false?
True
55
The I band is...
... a light area composed of actin only. It contains the Z line, which is the border of the sarcomere
56
Which is darker - A band or I band?
A-band
57
The basic component of each actin myofilament is...
G-actin (globular actin)
58
The actin myofilament consists of...
...two strands of G-actin molecules and myosin binding sites
59
The two strands of G-actin molecules in actin are twisted together with...
...two regulatory proteins:
–tropomyosin
–troponin
60
The sarcomere is broken up into three bands. True or false? What are they?
True. A band, two I bands
61
Structure of Tropomyosin
- Rod-shaped
- Occupies the groove between the twisted strand of actin molecules
- Blocks the myosin binding sites on the G-actin molecules
62
Troponin structure
A complex of three globular proteins:
•One is attached to the actin molecule
•One is attached to tropomyosin
•One contains a binding site for calcium
63
What are myosin cross bridges?
The myosin heads are known as cross-bridges because they can bind to and move along actin in the thin filament.
64
Myosin is composed of...
...a rod-like tail and two globular heads
65
What form the central portion of the myosin myofilament?
The tails
66
Orientation of the two globular heads of the myosin molecule
They face outward and in opposite directions
67
When does myosin interact with actin?
During contraction
68
Binding sites on myosin
There are binding sites for both actin and ATP
69
The ATP binding site for myosin contains...
The enzyme ATP-ase for the hydrolysis of ATP
70
What is Titin?
It connects myosin to the Z-lines in the sarcomere
71
Properties of Titin
–It is very elastic, able to stretch up to 3 times its resting length
–Important molecule because it is responsible for muscle flexibility
72
Not all muscle fibers are the same physiologically. True or false?
True
73
Criteria for muscle variation
–The predominant pathway utilized to synthesize ATP
–The amount of myoglobin
–Efficiency of ATPase
74
Classification of muscle fibres based on ATP synthesis pathway
* Oxidative fibers
| * Glycolytic fibers
75
Oxidative fibers properties
- Predominantly aerobic pathways
– Oxidative phosphorylation in the mitochondria
– Fatigue-resistant fibers
76
Glycolytic fibers properties
- Predominantly anaerobic pathways
–Glycolysis in the sarcoplasm
–Fatigable fibers
77
Classification of muscle fibres based on the amount of myoglobin present
* Red fibers - high amounts of myoglobin
| * White fibers - small amounts of myoglobin
78
Classification of muscle fibres based on the efficiency of ATPase
* Fast twitch fibers - decompose ATP rapidly
| * Slow twitch fibers - decompose ATP slowly
79
Slow-twitch, fatigue-resistant fibers properties
–Slow oxidative fibers, or red muscle fibers.
–Contain abundant myoglobin giving them their red color.
–Slow acting ATPase enzymes
–Abundant mitochondria
–Endurance type muscles
•Able to deliver strong, prolonged contractions.
80
Slow-twitch, fatigue-resistant fibers properties depend upon aerobic pathways for production of ATP. True or false?
True
81
Examples of slow-twitch, fatigue-resistant muscles
–Postural muscles - spinal extensors
| –Anti-gravity muscles - calf muscle
82
Gastrocnemius is not a slow-twitch, fatigue-resistant muscles. True or false?
False; it is.
83
Fast-twitch fatigable fibers properties
```
–Fast glycolytic fibers, or white muscle fibers.
–Contain small amounts of myoglobin
–Fast acting ATPase enzymes
–Few mitochondria
–Plenty of glycogen
–Extensive sarcoplasmic reticulum
```
84
Fast-twitch fatigable fibres contract slowly. True or false?
False
85
Fast-twitch fatigable fibres contract for limited periods of time. True or false?
True
86
Which type of muscle fibres depends on anaerobic metabolism?
Fast twitch anaerobic metabolism
87
Which muscle fibres are best suited for short duration, high intensity contractions?
Fast-twitch, fatigable fibres
88
Fast twitch fatigable fibres rapidly releases and stores calcium ions contributing to rapid contractions. True or false?
True
89
What are intermediate fibres?
Intermediate Fibers are fast-twitch fatigue-resistant fibers, fast and glycolytic fibers that lie between the red and white fibers
90
What determines the muscle cell type?
The motor nerve that innervates the muscle cell
91
A motor unit is...
A motor neuron and all of the muscle fibers it innervates
92
All of the muscle cells in a single motor unit are of the same type. True or false?
True
93
Which muscle fibre types are recruited first? Why?
Slow twitch fibers are recruited first because they are found in small motor units while fast twitch fibers are recruited last because they are found in large motor units
94
People are genetically predisposed to have relatively more of one fiber type than another. True or false?
True
95
Difference between marathon runners and sprinters
People who excel at marathon running have higher percentages of slow twitch fatigue resistant muscle fibers while people who excel at sprinting have higher percentages of fast twitch fatigable fibers
