Chapter 10: Muscle Tissue Flashcards
(135 cards)
1
Q
Functions of skeletal muscle
A
- move the body
- maintain posture
- protect and support
- regulate elimination of materials
- produce heat
2
Q
Characteristics of skeletal muscle
A
- excitability
- conductivity
- contractility
- extensibility
- elasticity
3
Q
Organ
A
two or more types of tissue that work together to perform a specific function
4
Q
Skeletal muscle
A
is an organ composed of muscle fibers, connective tissue layers, blood vessels, and nerves
5
Q
3 layers of connective tissue layers of wrapping of a skeletal muscle
A
1- epimysium
2- perimysium
3- endomysium
6
Q
Epimysium
A
dense irregular connective tissue wraps whole muscle
7
Q
Perimysium
A
dense irregular connective tissue wraps fascicle; many blood vessels/nerves
8
Q
Endomysium
A
areolar connective tissue wraps individual fiber; electrical insulation, capillary support, binding of neighboring cells
9
Q
Tendon
A
cordlike structure of dense regular connective tissue
10
Q
Aponeurosis
A
flattened sheet of dense irregular connective tissue
11
Q
Deep fascia
A
separates individual muscles
12
Q
Superficial fascia
A
separates muscles from skin
13
Q
Know the structural organization of skeletal muscle
A
14
Q
Is skeletal muscle vascularized?
A
yes, highly
15
Q
Is skeletal muscle innervated? If so, by what?
A
yes, by somatic motor neurons
16
Q
Somatic motor neurons
A
extend from the brain and spinal cord to skeletal muscle fibers
17
Q
Axon
A
nerve fiber
18
Q
Sarcoplasm
A
cytoplasm in skeletal muscle fibers
19
Q
Multinucleated
A
multiple nuclei
20
Q
Myoblasts
A
groups of embryonic muscle cells that fuse to form single skeletal muscle fibers during development
21
Q
Satellite cells
A
adult stem cells
22
Q
Know the development of skeletal muscle
A
23
Q
Structure and organization of a skeletal muscle fiber
A
24
Q
Sarcolemma
A
plasma membrane of a skeletal muscle fiber
25
T-tubules (transverse tubules)
deep invaginations within the sarcolemma that extend into the skeletal muscle fiber as a network of narrow, membranous tubules to the sarcoplasmic reticulum
26
Myofibrils
protein myofilaments surrounded by sarcoplasmic reticulum and extend the length of muscle fiber
27
Sarcoplasmic reticulum
an internal membrane complex that is similar to smooth ER in other cells; contains calcium pumps that release Ca2+ into the sarcoplasm
28
Terminal cisternae
enlarged calcium ion reservoirs
29
Triad
2 cisternae with a T-tubule in between
30
Myofilaments
contractile proteins within myofibrils;
2 types:
1- thick filaments
2- thin filaments
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Thick filaments
consist of bundles of ONLY myosin protein strands; each strand with a globular head and elongated tail
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Thin filaments
twisted strands of actin protein; F-actin (filamentous) composed of G-actin (globular); G-actin has a myosin binding site; tropomyosin and troponin placed along F-actin strand
33
Tropomyosin
short, thin, twisted filament that is a "stringlike" protein
34
Troponin
globular, or "ball-like", protein attached to tropomyosin; contains the binding site for Ca2+
35
Sarcomeres
myofilaments arranged in repeating units
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Z discs
composed of specialized proteins that are positioned perpendicular to the myofilaments and serve as anchors for the thin filaments
37
I bands
light-appearing regions that contain only thin filaments and Z disc; get smaller when muscle contracts (can disappear with maximal contraction)
38
A band
a dark-appearing region that contains thick filaments and overlapping thin filaments; contains H zone and M line; makes up general region of sarcomere
39
H zone
central portion of A band; only thick filaments; disappears with maximal muscle contraction
40
M line
middle of H zone and centermost region of A band; attachment site for thick filaments
41
Molecular structure of thick and thin filaments
42
Structure of a sarcomere
43
Striations
repeating light and dark bands of the overlapping myofilaments that form unique striped patterns within the skeletal muscle fiber
44
Connectin
stabilizes thick filaments from Z disc to M line; has spring like properties (passive tension)
45
Dystrophin
links internal myofilament proteins to external proteins; anchors some myofibrils to sarcolemma proteins; abnormalities of this protein cause muscular dystrophy
46
Myoglobin
within cells allow storage of oxygen used for aerobic ATP production; unique to muscle tissue; binds oxygen when muscle is at rest
47
Glycogen
stored for when fuel is needed quickly (storage form of glucose)
48
Creatinine phosphate
can quickly give up its phosphate group to help replenish ATP supply; unique to skeletal muscle tissue; anaerobic
49
Motor unit
a motor neuron and all the muscle fibers it controls
50
Neuromuscular junction
location where motor neuron innervates muscle; site of communication between motor neuron and motor end plate of muscle
51
Structure of a motor unit
52
Structure and organization of a neuromuscular junction
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Smaller motor units
have less than five muscle fibers and allow for precise control of smaller force output
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Large motor units
have thousands of muscle fibers and allow for production of large amounts of force but not precise control
54
Synaptic knob
houses synaptic vesicles with acetylcholine (ACh); calcium pumps establish calcium gradient, with more outside the neuron
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Motor end plate
specialized region of sarcolemma with numerous folds; has many ACh receptors which are opened by binding of ACh and allow Na+ entry and K+ exit
56
Synaptic cleft
separates the synaptic knob from the motor end plate; acetylcholinesterase (AChE) resides here and is an enzyme that breaks down ACh molecules
57
Muscle fibers exhibiting RMP
RMP inside the cell is -90mV compared to fluid outside the cell; threshold potential is -65mV
58
Skeletal muscle fiber at rest
59
End-plate potential (EPP)
the minimum voltage change (or threshold) in the motor end plate that can trigger opening of voltage-gated channels in the sarcolemma to initiate an action potential
60
Excitation of a skeletal muscle
1- binding of ACh at the motor end plate
2- excitation-contraction coupling
3- sarcomere: cross-bridge cycling
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Events in skeletal muscle contraction
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Neuromuscular junction: excitation of a skeletal muscle tissue
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Sarcolemma, t-tubules, and sarcoplasmic reticulum: excitation-contraction coupling
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Sarcomere: cross-bridge cycling
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Depolarization
the reversal in polarity at the sarcolemma (- to +)
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Repolarization
changes the membrane potential from positive to negative
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Refractory period
the muscle cannot be stimulated
68
Crossbridge cycling
multiple repetitions to attach, pull, release, and reset lead to fully contracted sarcomere
69
Power stroke
when the myosin head swivels
70
Tetanus
overstimulation of a muscle that leads to spastic paralysis
71
Botulism
muscular paralysis caused by a toxin that's ingested
72
Sarcomere shortening
73
3 ways to generate additional ATP in skeletal muscle
1- creatine phosphate
2- glycolysis
3- aerobic cellular respiration
74
Creatine phosphate
(Phosphagen System)
- unique to skeletal muscles
- high-energy bond found between creatine and phosphate
- phosphate can be transferred to ADP to form ATP
-catalyzed by creatine kinase
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Glycolysis (Anaerobic Cellular Respiration)
- occurs in cytosol
- does not require oxygen
- glucose is converted to 2 pyruvate molecules
- 2 ATP released per glucose molecule
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Aerobic Cellular Respiration
- makes the most ATP supply
- requires oxygen
- occurs within mitochondria
- pyruvate (from Glycolysis) broken down
- produces approximately 34 ATP
- triglycerides and amino acids can also be used as fuel to produce ATP
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Metabolic processes for generating ATP
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Lactate formation
pyruvate converted to lactate when O2 is low; lactate can be used as fuel by skeletal muscle fiber
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Utilization of energy sources
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Oxygen debt
amount of additional O2 needed after exercise to restore pre-exercise conditions
81
Additional oxygen required to
- replace O2 on hemoglobin and myoglobin
- replenish glycogen
- replenish ATP and creatine phosphate
- convert lactic acid back to glucose
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Skeletal muscle fibers classified based on:
- type of contraction generated
- means for supplying ATP
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Type of contraction generated
- power: related to the diameter of muscle fiber
- speed and duration
- fast-twitch fibers are more powerful and have quicker and briefer contractions than slow-twitch fibers
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Speed and duration related to
- type of myosin ATPase
- quickness of action potential propagation
- quickness of Ca2+ reuptake by sarcoplasmic reticulum
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Skeletal fibers classified based on means for supplying ATP
- oxidative fibers (fatigue resistant)
- glycolytic fibers (fatigable)
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Oxidative fibers
use aerobic cellular respiration; have extensive capillaries, many mitochondria, lots of myoglobin
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Glycolytic fibers
use anaerobic cellular respiration; have fewer capillaries, fewer mitochondria, fewer myoglobin, and large glycogen reserves
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3 types of skeletal muscle fibers
1- slow oxidative (SO) fibers (type I)
2- fast oxidative (FO) fibers (type IIa, intermediate)
3- fast glycolytic (FG) fibers (type IIx, fast anaerobic)
89
Slow oxidative (SO) fibers
- contractions= slower and less powerful
- high endurance since ATP supplied aerobically
- slender, red in color due to myoglobin
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Fast oxidative (FO) fibers
- contractions= fast and powerful
- primarily aerobic respiration
- intermediate size, light red color
91
Fast glycolytic (FG) fibers
- contractions= fast and powerful
- contractions are brief, as ATP production is primarily anaerobic
- thick, white in color due to lack of myoglobin
- most common type
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Hand muscles
have high percentage of fast glycolytic fibers for quickness
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Sprinters
have higher percentage of fast glycolytic fibers (fatigable)
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Back muscles
have high percentage of slow oxidative fibers to continually maintain postural support
95
Long-distance runners
have higher proportion of slow-oxidative fibers (endurance) in legs
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Muscle tension
force generated when a muscle is stimulated to contract (twitch)
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Muscle twitch
a single, brief contraction from a single stimulus
98
Threshold
the minimum voltage needed to stimulate the skeletal muscle to generate a twitch
99
Latent period
time after stimulus, but before contraction begins; no change in tension
100
Contraction period
time when tension is increasing; begins during power strokes as thick pulls thin filaments
101
Relaxation period
time when tension is decreasing; begins with release of cross-bridges; generally, lasts a little longer than a contraction period
102
Muscle twitch
103
Recruitment (Multiple Motor Unit Summation)
- muscle is stimulated repeatedly
- as voltage increases, more units are recruited to contract
- muscles can exhibit varying degrees of force
- above a certain voltage, all units are recruited and maximum contraction occurs
- a muscle relaxes completely before the next contraction
104
Treppe
increase in contraction strength
105
Wave summation
occurs when stimulations are delivered to a muscle fiber faster than it is able to completely relax
if stimulus frequency is set at about 20 per second,
- relaxation is not completed between twitches
- contractile forces add up to produce higher tensions
106
Incomplete tetany
if frequency is increased further; tension increases and twitches overlap
107
Tetany
if frequency is increased further still; tension is a smooth line, without relaxation; high frequency stimuli lead to fatigue
108
Fatigue
no tension production
109
Skeletal muscle response to change in stimulus intensity
110
Skeletal muscle response to change in stimulus frequency
111
Muscle tone
the amount of tension in muscle
112
Resting muscle tone
random contraction of small numbers of motor units causes the skeletal muscle to develop tension
113
Isometric contraction
although tension increases (force), it's still less than the resistance (weight); muscle length stays the same
114
Isotonic contraction
when skeletal muscle tension results in movement of the muscle; the tone of the muscle remains the same but the length changes
115
Isometric vs. Isotonic contraction
116
Fiber at shortened length (contracted) generates
weaker force; filament movement is limited (already close to Z disc)
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Fiber at resting length generates
maximum contractile force; optimal overlap of thick and thin filaments
118
Fiber at extended length (stretched) generates
weaker force; minimal thick and thin filaments overlap for cross-bridge formation
119
Concentric contraction
the shortening of muscle length
120
Eccentric contraction
lengthening of muscle
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Muscle length and tension relationship during muscle contraction
122
Length-tension curve
123
Maximizing force of contraction
124
Muscle fatigue
- reduced ability to produce muscle tension
- primarily caused by a decrease in glycogen stores during prolonged exercise
- insufficient Ca2+ to enter synaptic knob
- decreased number of synaptic vesicles
- altered ion concentrations impair action potential conduction and Ca2+ release from sarcoplasmic reticulum
- less Ca2+ available for troponin
125
Changes in muscle from a sustained exercise program
- endurance exercise leads to better ATP production
- resistance exercise leads to hypertrophy; limited amount of hyperplasia (increased number of fibers)
126
Changes in muscle from lack of exercise
atrophy= decrease in size due to lack of use
127
Fibrosis
muscle mass is often replaced by adipose connective tissue and dense regular connective tissue; decreased flexibility
128
Loss of muscle mass with age
- slow loss begins in a person's mid-30s due to a decrease in activity
- decreased size, power, and endurance of skeletal muscle
- loss in fiber number and diameter
decreased oxygen storage capacity
- decreased circulatory supply to muscles with exercise
129
Cardiac muscle tissue
- individual muscle cells arranged in thick bundles within the heart wall
- has one or two nuclei
- have large numbers of mitochondria and use aerobic respiration
- autorhythmic pacemaker that stimulates cardiac muscle cells
- branching cells
130
Intercalated discs
individual cells are joined to adjacent muscle cells at these specialized junctions
131
Smooth muscle tissue
found in organs of many body systems:
- cardiovascular system= blood vessels
- respiratory system= bronchioles
- digestive system= small & large intestine
- urinary system= ureters
- female reproductive system= uterus
- others= iris of the eye
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Smooth muscle cell shape
- fusiform
- central nucleus
- small
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Smooth muscle cell characteristics
- sarcolemma with various types of Ca2+ channels
- transverse tubules absent
- sarcoplasmic reticulum sparse
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Smooth muscle arrangement of anchoring proteins and contractile proteins
- dense bodies
- dense plaques
