Muscular System Flashcards
1
Q
muscle tissue is divided into 3 muscles:
A
- Skeletal Muscle
- Cardiac Muscle
- Smooth Muscle
2
Q
____________ are attached to the skeletal system and allow us to move
A
Skeletal Muscle
3
Q
6 Functions of Skeletal Muscles:
A
- Produce skeletal movement
- Maintain body position and posture
- Support soft tissues
- Guard body openings (entrance/exit)
- Maintain body temperature
- Store Nutrient reserves
4
Q
Muscles have 3 layers of connective tissues:
A
- Epimysium
- Perimysium
- Endomysium
5
Q
Epimysium
A
- Exterior collagen layer.
- Connected to the deep fascia
- epi - outside; mysium - muscle
6
Q
Perimysium
A
- Surrounds muscle fiber bundles (fascicles).
- It contains blood vessels and nerve supply to fascicles
- peri - surround; mysium - muscle
7
Q
Endomysium
A
- Surrounds individual muscle cells (muscle fibers)
- Contains capillaries and nerve fibers contracting muscle cells
- Contains satellite cells (stem cells) that repair damage
- endo - internal/inside; mysium - muscle
8
Q
Skeletal muscle cells are called __________
A
Fibers
9
Q
Muscles have extensive vascular systems that:
A
- supply large amounts of oxygen
- supply nutrients
- carry away wastes
10
Q
Skeletal muscles are _________ muscles, controlled by ________ of the central nervous system
A
Voluntary
Nerves
11
Q
Skeletal Muscle Fibers
A
- Are very long
- Develop through fusion of mesodermal cells (myoblasts- embryonic cells))
- Become very large
- Contain hundreds of nuclei –multinucleate
- Unfused cells are satellite cells- assist in repair after injury
12
Q
The cell membrane of a muscle cell
A
Sarcolemma
13
Q
sarcoplasm
A
cytoplasm of muscle fiber
14
Q
- Transmit action potential – impulses through cell
- Allow entire muscle fiber to contract simultaneously
- Have same properties as sarcolemma
Filled with extracellular fluid
A
Transverse Tubules (T tubules)
15
Q
Myofibrils
A
1-2um in diameter
* Lengthwise subdivisions within muscle fiber
* Made up of bundles of protein filaments
16
Q
2 Types of Myofilaments:
A
- Thin filaments - made of the protein actin
- Thick filaments - made of the protein myosin
17
Q
__________ are responsible for muscle contraction
A
Myofilaments
18
Q
- A membranous structure surrounding each myofibril
- Helps transmit action potential to myofibril
- Similar in structure to smooth endoplasmic reticulum
- Forms chambers (terminal cisternae) attached to T tubules
A
Sarcoplasmic Reticulum (SR)
19
Q
________ is formed by 1 T tubule and 2 terminal cisterna
A
Triad
20
Q
Concentrate Ca2+ (via ion pumps)
A
Cisternae
21
Q
The contractile units of muscle
A
Sarcomeres
22
Q
the function of satellite cells
A
repair damage in the endomysium
23
Q
the function of tendons
A
a flexible tissue that connects the muscles to the bones
24
Q
the function of ligaments
A
fibrous connective tissue that attaches bone to bone
25
A striped or striated pattern within myofibrils: alternating dark, thick filaments (A bands) and light, thin filaments (I bands)
Muscle Striations
26
* the center of the A band
* at midline of sarcomere
M line
27
* the centers of the I bands
* at 2 ends of sarcomere
Z lines
28
The densest, darkest area on a light micrograph
Zone of Overlap
29
The area around the M line
H Zone
30
________ are strands of protein
Titin
31
_______ is caused by interactions of thick and thin filaments
Muscle Contraction
32
* is 2 twisted rows of globular G actin
* the active sites on G actin strands bind to myosin
F actin
33
holds F actin strands together
Nebulin
34
* is a double strand
* prevents actin-myosin interaction
Tropomyosin
35
a globular protein
Troponin
36
* Ca2+ binds to receptor on troponin molecule
* Troponin–tropomyosin complex changes
* Exposes active site of F actin
Initiating Contraction
37
* Contain twisted myosin subunits
* Contain titin strands that recoil after stretching
Thick Filament
38
The Mysosin Molecule
Tail:
binds to other myosin molecules
Head:
made of 2 globular protein subunits
reaches the nearest thin filament
39
During contraction, myosin heads:
* interact with actin filaments, forming cross-bridges
* pivot, producing motion
40
__________ is the location of neural stimulation
Neuromuscular Junction
41
* Releases neurotransmitter (acetylcholine or ACh)
* Into the synaptic cleft (gap between ______________ and motor end plate)
Synaptic Terminal
42
travels across the synaptic cleft
Acetylcholine or ACh
43
Generated by increase in sodium ions in sarcolemma
Action Potential
44
5 Steps of the Contraction Cycle
1. Exposure of active sites
2. Formation of cross-bridges
3. Pivoting of myosin heads
4. Detachment of cross-bridges
5. Reactivation of myosin
45
As sarcomeres shorten, muscle pulls together, producing tension
Fiber Shortening
46
Contraction Duration depends on:
* duration of neural stimulus
* number of free calcium ions in sarcoplasm
* availability of ATP
47
* Ca2+ concentrations fall
* Ca2+ detaches from troponin
* Active sites are recovered by tropomyosin
* Sarcomeres remain contracted
Relaxation
48
A fixed muscular contraction after death
Rigor Mortis
49
Skeletal muscle fibers _________ as thin filaments slide between thick filaments
shorten
50
____________ in the ____________ triggers contraction
Free Ca2+
sarcoplasm
51
it depends on:
the number of pivoting cross-bridges
the fiber’s resting length at the time of stimulation
the frequency of stimulation
Tension of a Single Muscle Fiber
52
Normal resting sarcomere length:
75% to 130% of optimal length
53
Number of pivoting cross-bridges depends on:
amount of overlap between thick and thin fibers
54
Optimum overlap produces greatest amount of tension:
too much or too little reduces efficiency
55
Length of twitch depends on type of muscle
Tension in a Twitch
56
skeletal muscles that help support your movement
Twitch muscles
57
A graph of twitch tension development
Myogram
58
3 Phases of Twitch
1. Latent period
2. Contraction phase
3. Relaxation phase
59
a phase of twitch in which the action potential moves through the sarcolemma
Latent period
60
a phase of twitch in which the calcium ions bind and tension builds to peak
Contraction phase
61
a phase of twitch in which the Ca2+ levels fall, active sites are covered, and the tension falls to resting levels
Relaxation phase
62
A stair-step increase in twitch tension
Treppe
63
Repeated stimulations immediately after relaxation phase:
stimulus frequency < 50/second
64
it refers to the addition of individual muscle fibers contraction to produce a combined wave of force
wave summation
65
incomplete tetanus
ex: cardiac muscle - to prevent the seizure of the heart
66
complete tetanus
ex. skeletal muscle
67
single motor neurons or?
efferent neurons
68
are the building blocks of muscle control allowing the precise coordination of movement
motor units
69
controled by a single motor neuron
motor units in skeletal muscle
70
fine control muscle
* small motor unit -
* eye muscle: 4 fibers per unit
ex. eyes, fingers
71
gross control muscle:
* large motor unit
* leg muscle: 2000 fibers per unit
ex. leg
72
smooth motion and increasing tension are produced by slowly increasing the size or number of motor units
recruitment (multiple motor unit summation)
73
* Achieved when all motor units reach tetanus
* it can be sustained only a very short time
Maximum Tension
74
* Less than maximum tension
* Allows motor units to rest in rotation
Sustained Tension
75
The normal tension and firmness of a muscle at rest
Muscle Tone
76
2 Types of Skeletal Muscle Tension
* Isotonic contraction
* Isometric contraction
77
normal tension and firmness of a muscle at rest
importance: crucial for generating our reflexes
muscle tone
78
increase flexibility, gives strength
ex: yoga, poliomyelitis
low tone
79
isotonic contraction
> resistance - (muscle shortens - concentric contraction
< resistance - (muscle lengthens - eccentric contraction
iso - equal
tonic - tension
80
* isometric contraction
iso: same/equal
metric: measure
- skeletal muscle develops tension but is prevented from changing length
81
concentric contraction
greater than (>) resistance, muscle shortens
82
eccentric contraction
less than (<) resistance, muscle lengthens
83
limit flexibility
high tone
84
After contraction, a muscle fiber returns to resting length by:
* elastic forces
* opposing muscle contractions
* gravity
85
The pull of elastic elements (tendons and ligaments)
Elastic Forces
86
Reverse the direction of the original motion
Opposing Muscle Contractions
87
Can take the place of opposing muscle contraction to return a muscle to its resting state
Gravity
88
the active energy molecule
Adenosine triphosphate (ATP)
89
the storage molecule for excess ATP energy in resting muscle
Creatine phosphate (CP)
90
Recharging ATP:
Energy recharges ADP to ATP by using the enzyme creatine phosphokinase (CPK)
91
Cells produce ATP in 2 ways:
1. aerobic metabolism
2. anaerobic glycolysis
92
__________ is the primary energy source of resting muscles
Aerobic Metabolism
93
_________ is the primary energy source for peak muscular activity
Anaerobic Glycolysis
94
Muscle Metabolism:
1. resting muscle
2. moderate activity
3. peak activity
95
When muscles can no longer perform a required activity
Muscle Fatigue
96
Results of Muscle Fatigue
1. Depletion of metabolic reserves
2. Damage to sarcolemma and sarcoplasmic reticulum
3. Low pH (lactic acid)
4. Muscle exhaustion and pain
97
The time required after exertion for muscles to return to normal
Recovery Period
98
The removal and recycling of lactic acid by the liver
Cori Cycle
99
Oxygen Debt
After exercise:
* the body needs more oxygen than usual to normalize metabolic activities
* resulting in heavy breathing
100
Skeletal muscles at rest metabolize _________ and store __________
fatty acids
glycogen
101
Hormones and Muscle Metabolism:
* Growth hormone
* Testosterone
* Thyroid hormones
* Epinephrine
102
the maximum amount of tension produced
Power
103
the amount of time an activity can be sustained
Endurance
104
Power and endurance depend on:
* the types of muscle fibers
* physical conditioning
105
3 Types of Skeletal Muscle Fibers:
1. Fast fibers - Contract very quickly
2. Slow fibers - Slow to contract, slow to fatigue
3. Intermediate fibers - Mid-sized
106
* Have large diameter, large glycogen reserves, few mitochondria
* Have strong contractions, fatigue quickly
Fast fibers
107
* Have small diameter, more mitochondria
* Have high oxygen supply
* Contain myoglobin (red pigment, binds oxygen)
Slow fibers
108
* Have low myoglobin
* Have more capillaries than fast fiber, slower to fatigue
Intermediate fibers
109
* mostly fast fibers
* pale (e.g., chicken breast)
White muscle
110
mostly slow fibers
dark (e.g., chicken legs)
Red muscle
111
Most human muscles:
* mixed fibers
* pink
112
Muscle growth from heavy training
Muscle Hypertrophy
113
Lack of muscle activity
Muscle Atrophy
114
What is the difference between aerobic and anaerobic endurance, and their effects on muscular performance?
* Physical Conditioning
* Improves both power and endurance
115
Anaerobic Endurance:
* Anaerobic activities (e.g., 50-meter dash, weightlifting):
- use fast fibers
- fatigue quickly with strenuous activity
Improved by:
- frequent, brief, intensive workouts
hypertrophy
116
Aerobic Endurance
* Aerobic activities (prolonged activity):
- supported by mitochondria
- require oxygen and nutrients
Improved by:
- repetitive training (neural responses)
- cardiovascular training
117
Cardiac muscle is ________, found only in the _________
striated
heart
118
7 Characteristics of Cardiocytes:
* are small
* have a single nucleus
* have short, wide T tubules
* have no triads
* have SR with no terminal cisternae
* are aerobic (high in myoglobin, and mitochondria)
*have intercalated discs
119
cardiac muscle cells
Cardiocytes
120
_________ are specialized contact points between cardiocytes
Intercalated Discs
121
4 Functions of Cardiac Tissue:
* Automaticity
* Variable contraction tension
* Extended contraction time
* Prevention of wave summation and tetanic contractions by cell membranes
122
Smooth Muscle
Nonstriated tissue
123
8 Characteristics of Smooth Muscle Cells:
1. Long, slender, and spindle shaped
2. Have a single, central nucleus
3. Have no T tubules, myofibrils, or sarcomeres
4. Have no tendons or aponeuroses
5. Have scattered myosin fibers
6. Myosin fibers have more heads per thick filament
7. Have thin filaments attached to dense bodies
8. Dense bodies transmit contractions from cell to cell
124
Functional Characteristics of Smooth Muscle:
1. Excitation–contraction coupling
2. Length–tension relationships
3. Control of contractions
4. Smooth muscle tone
