Muscles (1, 2, 3) Flashcards
(105 cards)
1
Q
Types of Muscles (3) - Where are they located? What are their characteristics? (voluntary? Nucleus? Striated?)
A
- Skeletal- with bones, are voluntary, multi-nucleated and striated»_space; make up large amount of body weight
- Cardiac - with heart, are involuntary, one nucleus and striated
- Smooth - with internal structures, are involuntary, one nucleus, and not striated.
- cardiac and smooth muscles make ip 10% of body weight together
2
Q
What are the 4 functions of muscles?
A
Produces movement, stabilizes body posture, stores and moves substances (sphincters) and generate heat`
3
Q
Name the properties of muscles (4)
A
- Electrical excitability
- Contractility
- Extensibility
- Elasticity
4
Q
Define Electrical excitability
A
= the ability to respond to stimuli by producing AP’s
>for muscle cells > 2 types of AP triggering stimuli
1. Autorhythmic electrical signals (within)
2. Chemical stimuli (NT’s and hormones)
The AP travels down the muscle and elicits a contraction
5
Q
Define Contractility
A
= the ability of muscle to contract when stimulated by an AP
> when a skeletal muscle contracts > generates tension while pulling on its attachment point
- can shorten (lifting a book) or can stay the same length (holding a book)
6
Q
Define Extensibility
A
= the ability for a muscle to stretch without being damaged
7
Q
Define Elasticity
A
= the ability for tissue to return to its original state after contraction or extension
8
Q
Skeletal muscle contains? (4)
A
Muscle fibers
connective tissue
blood vessels
nerves
9
Q
Connective tissue (3) components
A
= surrounds and protects muscular tissue
- subcutaneous layer
- adipose tissue
- deep fascia
10
Q
Define Subcutaneous Layer
A
separates muscles from skin, is composed of:
- adipose tissue
- areolar connective tissue
& provides a pathway for nerves, blood vessels and lymph vessels to enter/exit muscles
11
Q
Define Adipose Tissue
A
Provides insulation, stores trigylcerides
12
Q
Define Deep Fascia
A
(deep to subcutaneous layer)
Sheet of fibrous band, holds muscle tissue together and surrounds outer and individual muscles with in,
- holds muscles of “similar functions” together
- allows for free movement
- carries vessels
- fills space
13
Q
Define Tendon
A
attaches muscles to bone (periosteum)
e.g. achilles tendon
14
Q
Define aponeurosis
A
Layers of flat, broad tendons> joins muscles to bone
e.g. epicranial tendon (top of skull between frontal and occipital bellies)
15
Q
Identify the 3 layers of connective tissue
A
> > extends from deep fascia
(From more superficial > to deep)
- Epimysium: encircles entire muscle
- Perimyium: separates fibers into bundles i.e. fascicles
- Endomysium: penetrates interior of each fascicle, and separates them into individual fibers
16
Q
What is the sequence of layers of a muscle? (starting at more superficial…
A
Skeletel muscle fascicle muscle fibers myofibrils sarcomeres filaments
17
Q
Define sarcolemma
A
=plasma membrane of muscle fiber or cell
18
Q
Define Transverse T Tubules
A
=tiny invaginations of the sarcolemma, filled with interstitial fluid. This is where AP’s travel to create equal stimulation and propagation across fiber and muscle
19
Q
Define sarcoplasm
A
=intracellular fluid/cytoplasm of glycogen and myoglobin(protein). Both of these substances are used for ATP production.
20
Q
Define myofibrils
A
= contractile organelles that shorten to contract muscle and cause movement
- diameter = 2 nm
- length = entire length of a muscle fiber
21
Q
Define sarcoplasmic reticulum
A
= fluid filled system of membranous sacs, which encircle each myofibril
22
Q
Define terminal cisterns
A
= end sacs of sarcoplasmic reticulum
> 2 cisterns + 1 tubule = ‘triad’
23
Q
Define filaments
A
= extend from myofibrils
- 2 nm diameter
- do NOT extend length of muscle fiber, are 1-2nm long
- give the striated look
24
Q
Define thick filaments
A
= composed of MYOSIN
- 16nm diameter
- 1-2 nm long
25
Define thin filaments
= composed of ACTIN
- 8 nm diameter
- 1-2 nm long
26
How are filaments arranged?
In Sarcomeres = individual compacted units of myofibril; contract to shorten muscle
= "the contractile unit"
Gives striated appearance
27
What are the components of a sarcomere? (5)
1. Z disc
2. A Band
3. I Band
4. H zone
5. M line
28
Define Z disc
separates sarcomeres, passes through the middle of the I band (shaped like a z)
29
Define A band
are the darkest portion of the sarcomeres; extends length of thick filament BUT also contains thin
30
Define I band
are the lightest portion of the sarcomere; contains ONLY THIN filaments
31
Define H zone
are the light band in the middle of the sarcomere, where thin filaments don't reach, ONLY THICK
32
Define M line
line in the middle of the sarcomere, consists of proteins which hold the THICK filaments in place (cuts thick in half)
33
Identify and define the 3 muscle proteins
= proteins are the foundation of myofibrils
1. contractile proteins: generate force during contraction
2. regulatory proteins: help switch the contraction process on/off
3. structural proteins: keep the thick and thin filaments in proper alignment; they also LINK the myofibrils TO the sarcolemma and ECM.
- alignment
- stability
- extensibility
- elasticity
34
Define titin- how big? what is it good for? What type of protein is it?
STRUCTURAL PROTEIN
3rd most plentiful
50x larger than average protein > each molecule spans half a sarcomere from Z disc to M line.
promotes elasticity of myosin > accounts for most of myofibrils elasticity and extensibility
Stabilizes thick filaments
35
define dystrophin- what is it good for? What type of protein is it?
STRUCTURAL PROTEIN
links thin filaments to proteins in the sarcomere membrane (sarcolemma).
Reinforces sarcolemma
36
Define a-actinin- what is it good for? What type of protein is it?
STRUCTURAL PROTEIN
Are found in z discs
Binds actin to titin
37
Define myomesin - what is it good for? What type of protein is it?
STRUCTURAL PROTEIN
forms the m-line (m-line binds to titian and myosin)
connects adjacent thick filaments together
38
Define nebulin - what is it good for? What type of protein is it?
```
STRUCTURAL PROTEIN
are long, non-elastic protein
wrapped around entire filament
helps anchor (thin filaments) to z discs
regulates length of thin filaments during development
```
39
Identify the three stages of the sliding filament contraction
= contraction and relaxation of muscles
1. @ relaxation: sarcomeres are normal
2. @ partial contraction: H zone decreases as thin filaments move towards each other. I band decreases and A band remains constant.
3. @ max contraction: thin filaments overlap and H zone disappears. I band also disappears.
40
The contraction cycle - identify and explain the (4) steps
1. ATP hydrolysis
2. Attachment
3. Power stroke
4. Detachment
41
ATP Hydrolysis
myosin heads hydrolize ATP > heads become energized and properly aligned. (ATP > ADP + P)
42
Attachment
Myosin heads bind to actin > form CROSS BRIDGES (P is released)
43
Power Stroke
Myosin cross bridges rotate towards centre of sarcomere, and force is generated in a stroke. Thick filaments walk along thin filaments, pulling them towards M line. (ADP is released)
44
Detachment
ATP binds to myosin head, cross bridges detach from actin. (ATP binds once again)
45
What is the KEY in the contraction cycle?
Calcium
46
Do filament lengths shorten during contraction?
NO. The sarcomere shortens and lengthens as filaments overlap in a cyclic process. If the sarcomere shortens > muscle fiber shortens > muscle shortens!
47
Define Myosin- what is it good for? What type of protein is it?
CONTRACTILE PROTEIN
Make up thick filaments
each molecule has one tail and two heads > they bind to myosin binding sites on ACTIN molecules of the THIN filaments
48
Define Actin - What is it good for? What type of protein is it?
CONTRACTILE PROTEIN
Make up thin filaments
each molecule has myosin binding site
49
Define tropomyosin- what is it good for? What type of protein is it?
REGULATORY PROTEIN
Component of thin filament
when the skeletal muscle fiber is realized > covers myosin binding site on actin, preventing myosin from binding
50
Define Troponin- what is it good for? What type of protein is it?
REGULATORY PROTEIN
component of thin filament
Ca ions bind to >> changes the shape of troponin >> moving the tropomyosin from binding sites on actin, muscle begins to contract
51
Identify the 5 structural proteins
1. A-actinin
2. dystrophin
3. titin
4. myomesin
5. nebulin
52
Identify the 2 contractile proteins
1. actin
| 2. myosin
53
Identify the 2 regulatory proteins
1. troponin
| 2. tropomyosin
54
Define Areolar tissue- where is it found?
loose connective tissue
- contains collagen fibers, elastic fibers, fat cells and fibroblasts
> is found in subcutaneous layer and binds muscles to layer of skin
55
What is the sarcoplasmic reticulum?
Fluid filled system of membraneous sacs
| ENCIRCLE EACH MYOFIBRIL
56
What are terminal cisterns?
Dilated end sacs of SR
| Butt against the t-tubercle from both sides forming a TRIAD
57
Define myofilaments
filaments within myofibrils
58
Define invaginations
cavities/pouches
59
The Ca event… 3 steps
1. In relaxed muscle > CA is stored in SR
2. the release of CA from SR occurs at terminal cisterns
3. This CA release triggers a muscle contraction > IS KEY
60
Define muscle tone. Do we exhibit muscle tone at rest? How does one sustain tone?
Does not generate enough force to produce movements, but muscles firm.
@ rest > skeletal muscle exhibits tone due to involuntary motor unit activation
In order to sustain tone, you must alternate activation of units
61
What happens when a neurone of a skeletal muscle is damaged?
The muscle becomes FLACCID = enters a state of limpness where muscle tone is lost
62
Define muscle contraction
overcoming force and producing movement
63
Identify the two types of muscle contraction
1. isotonic
| 2. isometric
64
Isotonic muscle contraction - identify two types
=muscles change in length
1. concentric isotonic: tension overcomes resistance and muscle shortens
2. eccentric isotonic: resistance overcomes tension, and muscle lengthens (i.e. myosin cross bridges resist movement and slows the lengthening process)
65
Isometric muscle contraction
= muscles stay the same length
i. e. tension generated is not enough to exceed the resistance of the object
- helps maintain posture
- stabilizes joints
- uses energy nonetheless
66
Identify the factors affecting force
= each cross bridge is an independent generator of force, therefore force production depends on the NUMBER of cross bridges…
1. Mechanical factors > velocity and length
2. Muscular factors > size and type
3. Neural factors > frequency of stimulation and motor unit recruitment
4. Other factors > time, age and training
67
Mechanical factor: velocity. Draw the force-velocity graph. What does it show?
Shows the relationship between velocity of contraction and the force subsequently generated.
During an eccentric movement (extension): as velocity increases, force generated increases (i.e. muscle lengthens, velocity increases, force increases)
>> more force with faster movement
During a concentric movement (flexion): as velocity increases, force generated decreases (i.e. muscle shortens)
68
Mechanical factor: length. Draw the muscle-length tension relationship. What does it show?
Shows that force is determined by number of cross bridges, which is related to the degree of overlap between actin and myosin. The degree of overlaps is related to length!
Forcefulness of a muscle contraction depends on sarcomere length!!
2-2.4. nm is the optimal sarcomere length (100% efficiency)
Resting muscle length is normally optimal for force generation
69
Neural factor: Motor unit recruitment. What is a MU? What will cause a strong forceful contraction? How do they fire?
A motor unit = a somatic motor neuron and ALL of the skeletal fibers that it stimulates
EACH MUSCLE FIBER is supplied by ONE motor neurone, and all nerve impulses are identical
The number and size of motor units will depict how forceful the contraction will be..
1 MU from a small muscle > small force
several MU from more muscle > more force
some contract, some relax >> is task dependent, will delay fatigue
70
Distinguish between muscles for fine motor skills and more general motor skills...
muscles for fine motor skills > SMALL MU with LESS fibres
Muscle for general motor skills > LARGER MU with MORE fibres
71
Explain the size principle
As force requirement increases, we must INCREASE the number of MU recruited.
Recruitment is orderly and specific, you recruit smaller units first, and as force requirement increases, your increase the size of recruited units.
72
Define a twitch contraction
a brief contraction of all muscle fibers in response to an AP
vary in duration: 20-200 ms
depend on muscle fiber type
73
Neural Factor: stimulation/firing frequency. Identify the 3 stages of a twitch contraction
```
To do with twitch contractions
There are 3 phases
1. latent
2. contraction
3. relaxation
```
74
Is a twitch contraction or an AP longer?
A TC is long compared to an AP. A TC: 20-200 ms, an AP: 1-2ms
75
Define refractory period
if 2 stimuli are applied one after another, the muscle will NOT respond to the 2nd stimuli. This is because the muscle has lost its excitability. The refractory period varies with muscle type
e. g. skeletal: 5ms
cardiac: 300ms
76
Draw the frequency graph of twitch contractions. Idenfity and explain the 4 types of twitches.
1. single twitch: a single AP
2. Wave summation: after refractory period, but before relaxation> 2nd AP applied increases the force of contraction
3. Unfused tetanus: stimulation occurs 20-30x/sec leading to sustained wavering contractions (unfused = incomplete)
4. Fused tetanus: stimulated 80-100x/sec leading to no relaxation period therefore individual twitches cannot be detected
77
Why does the force get stronger with increase in frequency?
Because Ca is already in the system readily available and muscle is already warm and ready to go. The elastic components of the tendons do not get time to relax.
78
How are smooth sustained muscle contractions achieved?
Through asynchronous unfused tetanus = different motor units acting at the same time!
- maintains a low level of force
- decreases fatigue ability
- only suitable for tasks requiring a low level of force
79
Muscle Factors: Type. Identify the three types of muscle fibers.
1. Type 1: SO ( slow oxidative)
2. Type 2x: FOG (fast oxidative glycolytic)
3. Type 2b: FG (Fast glycolytic)
80
(1) SO muscle fibers - identify characteristics: dia, power, colour, speed, fatuiability, mitochondria, capacity
smallest diameter, the least powerful
show as dark due to myoglobin
are slow, due to ATPase activity, take longer to reach peak tension
are fatigue resistant, with strong endurance
many mitochondria, with high aerobic capacity
81
(2x) FOG muscle fibers -identify characteristics: dia, power, colour, speed, fatuiability, mitochondria, capacity
Largest diameter, very powerful
contains many myoglobin, but are light in colour
are fast, due to ATPase activity in myosin head being fast
very fatigue able
few mitochondria, increase in glycogen
with anerobic capacity
82
(2b) FG muscle fibers - identify characteristics: dia, power, colour, speed, fatuiability, mitochondria, capacity
```
Intermediate diameter
have several myoglobin
faster than SO
moderate resistance to fatigue ability
aerobic capacity
```
83
Skeletal muscle fiber types can be divided into red muscle fivers and white muscle fibers. Distinguish between these
RED muscle fibers "dark meat": increases in myoglobin, mitochondria, energy stores and blood supply.
WHITE muscle fibers "white meat": decreases in myoglobin, mitochondria and blood supply
84
What are the 3 functional characteristics of muscle fiber types?
1. Force output (tension)
2. Speed of contraction
3. Fatigueability
85
How could you train FG fibres?
Through strength training- this results in hypertrophy(increase in size not quantity), strength increase and glycogen content.
e.g. weight trainer has 50% larger FG fibbers than a sedentary individual
86
What is the ration of muscle fivers in a MU? (a skeletal muscle)
a mixture of al 3 but 50% of which are SO
87
1 muscle > MANY types of fibres
:)
88
1 motor unit > ONE type of fibre
:)
89
What muscle fibres are involved in endurance tasks vs. powerful movements?
Endurance > SO increased
| Powerful > FG increased
90
What influences your muscle fibres?
BOTH training and genetics influence the proportion of fibres in your skeletal muscles. In fact, the distribution is LARGELY genetically determined. Most people have a 50-50 ration of Slow - fast fibres.
91
How can endurance exercises vs. resistance training induce changes in fibre type?
Endurance> gradual transformation of FG- FOG; increases mitochondria, blood supply and strength
Resistance > enhances ones tone; increases muscle mass (hypertrophy), and increases # of myofibrils and filaments within the fibers ( DOES NOT INCREASE NUMBER OF FIBERS)
92
What are the series of events that result in muscle contraction? (@ the neuromuscular joint)
1. nerve impulse > moves down the somatic motor neuron
2. causes Ca channels to open and diffuse in
3. causes the release of ACh from vesicles into synaptic cleft
4. ACh diffuses across cleft and binds to receptor sites
5. binding causes Na channels to open on post-synaptic neurone which stimulate the muscle contraction in that neuron
* 2 Ach molecules must attach to receptor site
* Excess Ach in cleft is either a) broken down by Achesterase or b) goes through reuptake
93
What is the relationship between muscle acidity and fatigue? Graph muscle fibre force vs. Ca levels. What does this graph illustrate? Why?
When pH is lower (i.e. more acidic), muscle fibre force decreases while Ca levels remain constant.
Why is this? Because lactic acid builds ip with exercise as it is a byproduct of anaerobic metabolism. THIS BUILD UP causes a decrease in pH
Ca levels remain constant as drop does not effect its release BUT ITS BINDING to troponin in order to initiate the contraction.
94
What is curare?
= an ACh antagonist >>> inhibits ACh from binding
| - essentially causes paralysis due to lack of muscle stimulation
95
What is botulinum Toxin?
=botox; is produced by bacteria, and prevents ACh release from vesicles (prevents exocytosis) WITHIN the end bulb
- causes relaxation or paralysis of skeletal muscles and wrinkles
96
What is Myasthenia Gravis? How can you treat?
=an autoimmune disease causing mostly voluntary muscles to experience WEAKNESS
- high levels of antibodies >> block or destroy receptor sites leading to a decrease in binding ACh
Treatment: ACh esterase inhibitors (PREVENT break down of ACH) leading to MORE available in system, leading to an increase in probability that ACh will bind to sites.
97
What is ATP? Why do we need it?
= adenosine tri-phosphate = energy in our system
> we need ATP for:
1. metabolic reactions
2. muscular contractions
- allows Ca pumps to activate in order to pump Ca out of SR (active transport)
- also ATP- thru hydrolysis leads to ADP + P >> this release of energy causes myosin head to bind to actin
I.E. If ATP is not available, CROSS BRIDGES do not form > NO CONTRACTION
98
If we cannot produce ATP, do we have a back up system?
1. break down creatine phosphate
2. thru anaerobic system
3. thru aerobic system
99
Creatine Phosphate energy system… uses? How does it provide energy?
Used for short, quick bests of hard exercise (1-15 seconds)
e.g. weight lifting, sprinting
How does it produce energy?
Creatine kinase takes phosphate from ATP and binds it to creatine >> creatine phosphate production during resting stages so CP is readily available for quick bursts of exercise
100
Explain. illustrate how intramuscular levels of ATP and CP would change in response to a 10 second "all-out" sprint.
They have an inverse relationships…
ATP starts low, CP starts high
With sprint > CP levels drop quick as it is used as energy and also converted in ATP in order to increase ATP levels for longer term energy.
101
What is the goal of CP levels?
To maintain ATP levels
102
What happens during a concentric movement? What would training result in?
as velocity increases, force decreases
Training would result in a change in the graph… we might expect a shift upwards of starting point, with the same general trend of curve following.
I.e. training allows for a greater force to be generated with a lesser velocity
103
With regards to the length-tension relationship, why would a constant load not provide the most strength gains when working with a machine? How would you improve this?
This is because a constant load assumes the same weight when you are both maximally and minimally contracting a muscle >> does not provide optimal gains throughout ROM of the exercise.
Improve… must design a system that exerts max exertion throughout all ROM. Must increase load during concentric movement for e.g. during a squat > provide weight during bend down.
104
Twitch contraction: explain the five stages
(TC= brief contraction of all muscles fibbers in a MU)
1. delay: muscle potential spreads across muscle
2. latent period: muscle AP waves over sarcolemma and Ca is released from SR
3. contraction: Ca binds to troponin, opens myosin binding sites on actin, cross bridges form
4. relaxation: Ca actively transported back into SR and binding sites close, muscle fibre tension decreases
5. refractory period
105
For an individual who wants to increase his endurance ability, but has 40% ST and 55% FT > what would you caution?
Improvements can be made, but only up until a certain point.
| only some FT can convert to oxidative (SO)
