Muscles Flashcards
1
Q
What percent body mass does muscle tissue make up?
A
30 - 40%
2
Q
What is myology?
A
Study of the muscles
3
Q
What are the 3 types of muscle?
A
- Skeletal
- Cardiac
- Smooth
4
Q
What kind of muscle attaches to the bone or skin?
A
Skeletal muscle
5
Q
What kind of muscle constitutes the bulk of the heart wall?
A
Cardiac muscle
6
Q
What kind of muscle is found in the walls of hollow organs?
A
Smooth muscle
7
Q
What are the longest muscle cells called?
A
Fibers
8
Q
What type of muscle? • Attached to bones • Longest muscle cells : FIBERS • Striated • Voluntary : consciously controlled • Multi-nucleated: multiple nuclei/fiber
A
Skeletal muscles
9
Q
What kind of muscle? • Only found in the heart walls • Striated • Involuntary: you can NOT control your heartbeat consciously • Uni-nucleated and branched • Intercalated discs join cardiac cells together (gap junctions)
A
Cardiac muscle
10
Q
What kind of muscle? • Found lining walls of hollow organs • Elongated fusiform cells : FIBERS • Involuntary: you can NOT control smooth muscle consciously • Non-striated • Uni-nucleated
A
Smooth muscle
11
Q
What are the four functions of muscle?
A
- Producing movement
- Maintaining posture
- Storing and moving substances within the body
- Generating heat
12
Q
What are the four properties of muscle?
A
- Electrical excitability
- Contractility
- Extensibility
- Elasticity
13
Q
Which property of muscle?
• Ability to receive and respond to a stimulus
• Causes changes in resting membrane potential in the muscle cell
• Respond via an electrical impulse (action potential) passing along the muscle cell
A
Electrical excitability
14
Q
Which property of muscle?
• Ability to shorten/contract forcibly when stimulated by an action potential to generate tension/force pulling
A
Contractility
15
Q
Which property of muscle?
• Ability to stretch without being damaged
• Smooth muscle has the most extensibility
A
Extensibility
16
Q
Which property of muscle?
• Ability to recoil and resume its normal resting length after stretching
A
Elasticity
17
Q
What surround fibers and whole muscles?
A
Connective tissues
18
Q
Connective tissue that surrounds
muscles, groups of muscles, blood vessels, nerves, organs
A
Fascia
19
Q
composed of loose connective tissue (areolar and adipose) which separates the muscles from the skin.
• Serves as a passageway for nerves and vasculature
A
Superficial Fascia
20
Q
dense connective tissue that groups muscles together into compartments and also surrounds individual muscles
A
Deep (investing) fascia
21
Q
What is endomysium?
A
areolar CT around fibers
22
Q
What is perimysium?
A
Dense irregular CT around fascicles
23
Q
What is epimysium?
A
Dense irregular CT around entire muscle
24
Q
An artery vein and nerve
• Enter and exit same spot
A
Neuromuscular bundle
25
Each nerve contains both what?
Motor neurons and Sensory neurons
26
Somatic motor neurons travel from _____ to _______ _______
CNS, motor fibers
27
Axon terminals form the what?
Neuromuscular junctions
28
What is a motor unit?
neuron and all the fibers it supplies
29
What is a muscle direct attachment?
muscle directly attaches to bone via the CT layer that is extremely short
30
What is a muscle indirect attachment?
Muscle CT extends as either a tendon (ropelike) or an aponeurosis (sheet-like) that attaches to bone
31
Where do muscles originate and insert?
* Usually a bone
* Tendon/ligament
* Skin
32
What is a fixed immoveable point of
| attachment?
Origin
33
What is an insertion?
Moveable bone
34
What happens when muscles contract?
The insertion moves towards the origin allowing for specific actions to occur.
35
What determines power production and range of motion of the muscle?
Fascicle arrangement
36
Which arrangement is two long axis, tendon at each end?
Parallel
37
Which arrangement is fat in the middle, tapered ends into tendons?
Fusiform
38
Which arrangement is concentric rings?
Circular
39
Which arrangement radiates out from a single tendon to broad attachment?
Triangular
40
Which arrangement is feather like, fibers insert obliquely on the tendon
Pennate
41
What are the 3 types of pennate arrangement?
* Unipennate: obliquely from 1 side of the tendon
* Bipennate: obliquely on both sides of a central tendon
* Multipennate: obliquely between multiple tendons
42
Which of the following is not a
function of muscle?
a. Produce movement
b. Maintain body posture
c. Store and move substances throughout the body
d. Generate heat
e. All of the above are functions of muscle
e. All of the above are functions of muscle
43
Extensibility is:
a. Ability to receive and respond to a stimulus
b. Ability to shorten/contract forcibly when stimulated by an action
potential
c. Ability to stretch without being damaged
d. Ability to recoil and resume its normal resting length after
stretching
c. Ability to stretch without being damaged
44
```
Which of the following is a loose
connective tissue that surrounds
muscle fibers?
a. Epimysium
b. Perimysium
c. Endomysium
```
c. Endomysium
45
Myoblasts in the embryo fuse
| together to form the ______
Myocyte
46
Growth after birth occurs through
| _______ of the muscle fiber
hypertrophy
47
What is the sarcolemma of muscle fibers?
The plasma membrane
48
What is the cytoplasm of the muscle fibers?
Sarcoplasm
49
What are transverse tubules?
Invaginations of sarcolemma; fast even conduction of APs?
50
What is sarcoplasmic reticulum?
Smooth ER
51
What are myofibrils?
Contractile elements of the fibers
52
• Conduct impulses that travel from a
nerve to the sarcolemma towards the
muscle fibers
• Ensures that each myofibril contracts at the same time
Transverse tubules
53
What is the sarcoplasmic reticulum?
Membranous fluid filled sacs similar to
| smooth ER that encircles each myofibril
54
• Stores calcium (Ca2+) ions
• releases on demand when muscle is
stimulated to contract
• 1 T-tubule + 2 terminal cisternae = TRIAD
Sarcoplasmic reticulum
55
• Rod-like contractile elements
running parallel to the length of
the fiber
Myofibrils
56
```
• Contain sarcomeres
• Contractile structural and
functional unit of fiber
• Made up of myofilaments
• Thick and thin filaments
```
Myofibrils
57
Each myoFIBRIL is composed of
| smaller contractile proteins called?
myoFILAMENTS
58
What are the two types of myofilaments?
* Thin (actin) filaments
| * Thick (myosin) filaments
59
From Filaments to muscle put in order.
Myofilaments < Myofibrils < Muscle Fibers (myocyte) < Fascicles < Muscles
60
* Double stranded fibrous protein
* G-actin – globular heads contain binding sites for myosin; polymerise to form Factin
* F-actin – Double stranded fibrous protein
Thin Actin Filament
61
```
• ~300 proteins/filament
• Each protein contains:
• 1 tail
• 2 heads
• Bind to G actin to form cross
bridges during contraction
• Contain ATP binding sites –
contraction cannot occur without
ATP
```
Thick Myosin Filaments
62
What structural protein anchors thick filaments to the Z disc and M line
• Spring-like that aids in muscle recoil
• Stabilizes thick filaments
Titin (connectin)
63
What structural protein forms the M line
| • Binds adjacent thick filaments
Myomesin
64
What structural protein links myofilament proteins to proteins of the sarcolemma?
Dystrophin
65
What structural protein helps maintain alignment of the thin filaments in the sarcomere?
Nebulin
66
What structural protein binds actin to titin?
Alpha-actinin
67
What genetic disorder is characterized by progressive muscle degeneration and weakness?
Muscular Dystrophy
68
What is one of the most common forms of muscular dystrophy and is caused by recessive mutations in the dystrophin gene on X chromosome?
Duchenne Muscular Dystrophy (DMD)
69
What is caused by mutations in the dystrophin gene?
| • Individuals with BMD share similar signs and symptoms but with later onset and more varied time course
• Becker Muscular Dystrophy (BMD)
70
What regulatory protein covers myosin binding site in relaxed muscle and moves out of the way for contraction?
Tropomyosin
71
```
What regulatory protein keeps tropomyosin covering myosin
binding site?
• Calcium causes a conformational change
• Moves tropomyosin
• Myosin binding site exposed
```
Troponin
72
What are sarcomeres?
Smallest functional contractile units.
73
What is the area between 2 Z-discs
Sarcomere
74
What are A bands?
Thick filaments
75
What are I bands?
Thin filaments
76
What are Z discs?
Where thin filaments are anchored
77
What are H zones?
Center of A band only thick
78
What is the M line?
Center of H where thick filaments
| join.
79
What is the Sliding Filament Theory?
When muscle contract thick and thin
filaments slide past one another
causing sarcomere to shorten.
80
What happens in the Sliding Filament Theory?
* The width of A band does not change
* The H zone disappears
* The I bands shorten
* The Z discs move closer together
* The sarcomere shortens
* HI goes bye
81
Keep Ca⁺⁺ from getting out until needed
Voltage-gated Ca⁺⁺ channels
82
* On terminal cistern
| * Dump Ca⁺⁺ into sarcoplasm from cistern
Ca⁺⁺ release channels
83
Pump Ca⁺⁺ into terminal cistern from
| sarcoplasm
Ca⁺⁺ ATPase pumps
84
```
Which of the following stores
calcium?
a. T-tubules
b. Terminal cisternae
c. Calmodulin
d. Troponin C
e. Sarcolemma
```
d. Troponin C
85
```
During sarcomere shortening, which
of the following would get smaller?
a. Z disc
b. A band
c. M line
d. I band
e. Actin
```
d. I band
86
Which protein is spring-like to help with muscle recoil and is anchored to the Z disc and M line?
a. Titin
b. Myomesin
c. Dystrophin
d. Nebulin
e. Alpha-actinin
a. Titin
87
What are neurons that travel from
| the CNS to the muscle fibers?
Somatic motor neurons
88
Where do neuron cell bodies reside?
In the brain OR spinal cord (ventral horn)
89
What do Axons do?
* Axons travel via the motor nerve to the muscle they serve
* Axon divides as it enters the muscle
* Each axon gives off axon terminals that form the Neuromuscular Junction
90
What are small motor units?
* fine motor control
| * Muscles of fingers
91
What are large motor units?
* less precise (gross) motor control
| * Biceps brachii
92
Junctions between axons and muscle fibers are called?
Neuromuscular Junctions
93
What neuromuscular junctions contain vesicles?
Pre-synaptic
94
What neuromuscular junctions contain receptors?
Post-synaptic
95
What does the synaptic cleft contain?
Contains acetylcholinesterase that breaks down ACh.
96
```
• Contains synaptic vesicles
(exocytosis)
• Contain neurotransmitter
Acetlycholine (Ach)
• Excitatory chemical that stimulates
the post-synaptic cell to change
membrane potential
```
Presynaptic Neuron Terminal
97
• Contains folds in the sarcolemma to
increase surface area where it meets a
synaptic end bulb = motor end plate
• Contains ACh receptors
Post-Synaptic Muscle Fiber
98
What is contraction?
The generation of force
99
• Shortening of the muscle fibers
• Occurs when the tension of the crossbridge between the thin and thick
filaments overcomes the force
opposing contraction
Muscle contraction
100
Cross-bridges release and the
thin/thick filaments return to normal
length
Muscle Relaxation
101
Propagation of action
| potential along sarcolemma
Excitation
102
Excitation-Contraction Coupling
* Nerve impulse triggers ACh release from pre-synaptic cell into synaptic cleft
* ACh binds receptors on sarcolemma
* Muscle fiber gets excited
* Action potential travels along sarcolemma (transverse tubules)
* Reaches voltage-gated Ca++ channels causing conformational change
* Allows Ca++ release channels to open
* Ca++ floods the sarcoplasm
* Conformational change in troponin
* Moves tropomyosin, exposing myosin binding sites
* Contraction cycle begins
103
Excitation-Contraction Coupling
* Continues if ATP and Ca⁺⁺ levels sufficient
* Z discs drawn closer
* Sarcomere shortens
* Pulls adjacent sarcomeres in myofibril
* Myofibrils shorten myocyte
* Myocyte pulls on endomysium
* Fascicles pull on perimysium
* Muscles pull on endomysium
* Tendons pull on bone (skin)
* Movement
104
Excitation-Contraction Coupling
* Excitation ends/action potential no longer propagating
* Ca++ voltage-gated channels plug Ca++ release channels
* Ca++ ATPase pumps pump Ca++ into cisterns
* Calsequrestrin binds to Ca++ to increase storage
* Ca++ in sarcoplasm rapidly decreases
* Troponin changes
* Tropomyosin to cover myosin binding sites
* Muscle relaxation
105
Contraction Overview
• An action potential travels down a motor neuron and stimulates….
• ACh release from the pre-synaptic terminal
• ACh binding to ACh receptors on muscle causing influx of Na+ ions
• Action potential generated and propagated down the sarcolemma to the TRIAD
• Sacroplasmic reticulum releases Ca2+ ions
• Ca2+ and ATP together cause the cross-bridge cycle:
• Myosin heads attach to actin, bend and release actin several times shortening
the sarcomere..
• Sarcomeres shorten
• Muscle fibers shorten
• Whole muscle shortens
106
When someone dies, the body becomes “stiff”
Rigor Mortis
107
* Produces botulinum toxin
* Blocks release of acetylcholine
* No acetylcholine
* No action potential in myocyte
* No contraction
* Paralysis
* Most cases of botulism occur from improper canning
* Honey in infants
* Used cosmetically for prevention of wrinkles
* Used clinically for spasticity
Clostridium Botulinum
108
Results in overstimulation and
| excessive muscle contraction.
Clostridium Tetani
109
```
• Spastic paralysis caused by toxin
produced by Clostridium tetanus
• Prevents release of inhibitory
neurotransmitters GABA and
glycine in spinal cord
```
Clostridium Tetani
110
Acetycholine is released from the:
a. Pre-synaptic terminal
b. Post-synaptic terminal
c. Terminal cisternae
d. Synaptic cleft
e. Dendrite
b. Pre-synaptic terminal
111
Which of the following best
describes a motor unit?
a. A muscle and all the neurons that supply it
b. A muscle fiber and all the neurons that supply it
c. A motor neuron and the single muscle fiber it supplies
d. A motor neuron and all the muscle fibers it supplies
e. A motor neuron and the blood vessels that supply a muscle
d. A motor neuron and all the muscle fibers it supplies
112
Which of the following is the correct sequence of events for muscle contractions?
a. Muscle cell action potential, neurotransmitter release, ATP-driven power stroke, calcium ion release from SR, sliding of myofilaments
b. Neurotransmitter release, muscle cell action potential, motor neuron
action potential, release of calcium ions from SR, sliding of myofilaments,
ATP-driven power stroke
c. Motor neuron action potential, neurotransmitter release, muscle cell
action potential, release of calcium ions from SR, ATP-driven power
stroke, sliding of myofilaments
d. Neurotransmitter release, motor neuron action potential, muscle cell
action potential, release of calcium ions from SR, ATP-driven power stroke
?
113
What is required for contraction, pumping Ca⁺⁺ out of sarcoplasm and
into cisterns?
ATP
114
What are the 3 ways of producing ATP?
1. Creatine phosphate – storage for excess ATP
2. Anaerobic glycolysis – Insufficient O2 levels
3. Aerobic respiration – Sufficient O2 levels
115
* At rest myocyte produce excess ATP
* Creatine kinase moves 1 phosphate from excess ATP to creatine
* Creatine phosphate (storage at rest)
* During contraction creatine kinase removes phosphate from creatine phosphate
* ADP ATP
* Faster than making ATP
* Short lived storage (15s)
* Sprinting, explosive movements, etc
Creatine Phosphate
116
```
• Glucose catabolism
• Does not require O2
• Utilize glycogen or glucose
• Occurs in sarcoplasm
• Breaks 1 glucose into 2 pyruvic acid
and 2 ATP
• If sufficient O2 – pyruvic acid enters
mitochondria for aerobic respiration
• If insufficient O2 – pyruvic acid goes
through anaeorobic respiration
```
Glycolysis
117
```
• O2 is present
• Pyruvic acid is sent to mitochondria
• Goes through Krebs cycle/electron
transport chain
• Makes 30 to 32 ATP
• Provides long term energy source
• 2 minutes to hours
```
Aerobic Respiration
118
```
• If insufficient O₂: pyruvic acid
converted into lactic acid
• Lactic acid converted into glucose in
liver / used by heart
• If rate of lactic acid production
exceeds rate of conversion → build
up of lactic acid
• Increasing acidity of blood / muscle
• 2 minutes of activity
```
Anaerobic Respiration
119
```
What type of contraction?
• A contracting muscle does not shorten
• Ex. if muscle load > muscle tension
• OR if load is not moved
• Ex. trying to pick up a car
```
Isometric Contractions
120
What type of contraction?
* Muscle tension > muscle load
* Load is moved
* Ex. picking up a textbook
121
What gives the muscles tone?
Small number of motor units involutarily activated for small degree of contraction to give muscle tone.
122
What is hypotonia?
Decrease in muscle tone
123
What is flaccid paralysis?
Loss of muscle tone, atrophy of muscles.
124
What is hypertonia?
Increased muscle tone leading
| to excessive muscle contraction or rigidity.
125
What is muscle atrophy?
Wasting of muscles
126
What are two types of atrophy?
1. Disuse
| 2. Denervation
127
What type of atrophy occurs when muscles are not used?
Disuse
128
What type of atrophy occurs when nerve supply to a muscle/s is cut?
Denervation
129
Growth of muscle fibers due to increased myofibrils
Hypertrophy
130
Occurs due to an increase in
myofibrils with increased
myofilaments NOT FIBERS
Hypertrophy
131
```
• Myoblasts that do not fuse to
form single muscle fiber
• ________ ______ remain with
skeletal muscle tissue and assist
in repair of muscles
```
Satellite cells
132
What does an agonist muscle do?
Produces a specific movement
133
What does an antagonist muscle do?
Opposes a movement
134
What is a synergist?
Helps with a movement
135
What stabilizes a joint?
Fixators
136
* Drugs that mimic the effects of testosterone
| * Taken to increase protein production, especially in the muscles
Anabolic Steroids
137
What are some adverse side effects of steroids?
* Left ventricular hypertrophy
* Liver damage
* Gynecomastia
* Testicular atrophy
* Increased body hair
* Acne
* “Roid rage”
138
```
The antagonist muscle for the
quadriceps femoris would be:
a. Triceps brachii
b. Hamstrings
c. Sartorius
d. Iliopsoas
```
b. Hamstrings
139
Which of the following molecules found in skeletal muscle cells binds oxygen that can later be used during aerobic metabolism to help generate ATP?
a. Creatine
b. Creatine phosphate
c. Myoglobin
d. Titin
e. Glycogen
c. Myoglobin
140
When oxygen is plentiful inside a skeletal muscle cell, what happens to the pyruvic acid that is formed during glycolysis?
a. It is converted into lactic acid
b. It diffuses into mitochondria to be broken down to generate ATP
c. It diffuses out of the cell and into the bloodstream
d. It is used to convert creatine into creatine phosphate
e. It is converted into glycogen
a. It is converted into lactic acid
141
Muscle growth comes from what?
a. Increased division and production of myofibers
b. Increased production of myofibrils
c. Hypertrophy of actin filaments
d. Hypertrophy of myosin filaments
b. Increased production of myofibrils
142
* Individual muscle cells arranged in thick bundles in the heart wall
* Branched
* Shorter and thicker than skeletal muscle fibers
Cardiac Muscle
143
What is cardiac muscle joined by?
Intercalated discs
144
```
• Uni-nucleated fusiform shaped cell
• Diffuse junctions instead of NMJ
• Controlled by the autonomic nervous system
(instead of a motor neuron) - involuntary;
• NO SARCOMERES
• Have actin and myosin
• Dense bodies act as z-discs
• Calmodulin replaces troponin
```
Smooth muscle
145
Innervating nerve fibers have
| numerous bulb-like swellings called?
varicosities
146
What are the 2 smooth muscle layers?
```
1. Longitudinal Layer
• Parallel direction to the length of the
organ
2. Circular Layer
• Perpendicular direction to the length
of the organ
```
147
Explain smooth muscle contractions.
* Exhibit slow synchronized contractions
* Resistant to fatigue
* Smooth muscle contraction is similar to skeletal muscle:
* Rise in intracellular Ca2+ triggers contraction (extracellular)
* Actin and myosin interact
* Requires ATP (much less than skeletal)
148
```
Which of the following is false
regarding smooth muscle?
a. It is uninucleated
b. It is not-striated
c. It is involuntary
d. It is made of long cylindrical muscle fibers
e. None of the above
```
d. It is made of long cylindrical muscle fibers
149
This structure is unique to cardiac muscle and allows individual cells to be firmly attached to each other and allow the action potential to spread rapidly through the muscle, so contractions are smooth and coordinated.
a. Desmosomes
b. Gap junctions
c. Intercalated discs
d. Z discs
e. Sarcomeres
c. Intercalated discs
