Muscles Flashcards
(72 cards)
1
Q
What is the 60-40-20 rule for body water?
A
60% body is water
40% of body is intracellular water
20% of body is extracellular water
2
Q
____ ____ attach to the skeleton in order to accomplish a variety of movements
A
skeletal muscles
3
Q
humans have over ____ skeletal muscles!
A
600
4
Q
skeletal muscles attach to bone via ____ (____ ____)
A
tendons (connective tissue)
5
Q
muscle fibers essentially do one thing, and one thing only: ____ (____)
A
contract (shorten)
6
Q
each muscle in the human body is labeled as an ____ of the muscular system
A
organ
7
Q
muscles are attached to bones by tapered connective tissue endings called ____
A
tendons
8
Q
What are fascicles?
Where can they be observed?
A
a muscle organ is subdivided into bundles of muscle cells (fibers) called fascicles
fascicles can be readily observed in stringy cuts of meat such as flank steak
9
Q
each layer of organization within the muscle organ involves separation via ____ ____
A
connective tissue
10
Q
What two things do muscles contain in addition to muscle fibers and connective tissue?
A
muscles are both vascularized (contain blood vessels) and innervated (contain nerves)
11
Q
What is another name for a muscle fiber?
A
muscle cell
12
Q
Length of muscle fibers?
A
muscle cells are an unusually long cell that ranges from 10 to 100 μm in length
13
Q
How many muscle fibers can smaller muscle contain?
A
smaller muscles contain only a few hundred muscle fibers
14
Q
Muscle fibers are ____ – consisting of many nuclei?
What is this the result of?
A
multinucleate
the result from the fusion of many progenitor myoblasts
15
Q
What are muscle fibers filled with?
A
Myofibrils
16
Q
What are myofibrils?
A
contractile elements that run lengthwise in muscle cells
17
Q
What is sarcomere?
What is this similar to?
A
the sarcomere is the functional unit of skeletal muscle
similar to how the osteon is the functional unit of compact bone
18
Q
What do myofibrils consist of?
What appearance does this give skeletal muscle?
A
each myofibril consists of regularly arranged thin and thick filaments
alternating arrangement produces striated appearance of skeletal muscle
19
Q
What are the different regions of a sarcomere?
A
A-bands : stacked thick filaments and parts of thin filaments
H-zone consists of thick filaments only
M-line holds the stack of thick filaments together
I-band : (light) consists of parts of the thin filaments
Z-line protein disc at the center of the I-band to which thin filaments are attached
20
Q
What do the thick filaments consist of?
A
thick filaments consist of parallel bundles of myosin protein molecules
21
Q
myosin heads contact actin to form a ____ ____ during contraction
A
Cross bridge
22
Q
What do thin filaments contain?
A
thin filaments consist of 2 actin molecules arranged as a double helix
tropomyosin protein molecules are nestled in the actin groove – prevents myosin binding during resting conditions
23
Q
What is tropomyosin?
A
tropomyosin protein molecules are nestled in the actin groove – prevents myosin binding during resting conditions
24
Q
Describe muscular dystrophy?
A
muscular dystrophy is caused by an inherited mutation in the protein dystrophin
dystrophin connects the sarcolemma (muscle membrane) to myofibrils, particularly actin
dystrophin mutation (DMD) reduces the ability of the muscle structure to sustain the mechanical stress of normal muscle contraction
incurable; life expectancy is ~25 years
25
How do muscles get bigger?
Resistance training increases muscle mass through the process of hypertrophy
26
How does hypertrophy increase muscle size?
an increase in the size of a muscular organ is due to changes in myofibril volume
myofibril volume increases as the result of an increase in the synthesis of actin and myosin proteins
27
What is a second proposed why muscle get bigger?
some scientists think that the number of muscle fibers increase in response to exercise via hyperplasia (increased growth), but this is not a settled issue
28
Where is muscle contraction controlled at?
skeletal muscle contraction is consciously controlled via the neuromuscular junction
29
How does a nerve stimulate contraction?
muscles are stimulated to contract when a nerve impulse (discussed later in the course) reaches the axon terminal causing the release of neurotransmitter - acetylcholine
30
What does ACh do?
acetylcholine (ACh) molecules diffuse across the space between the axon terminal and the muscle membrane, called the synaptic cleft
acetylcholine (ACh) binds to ACh-gated cation channels causing a depolarization of the muscle membrane
31
What is sarcolemma?
the muscle membrane is often referred to as the sarcolemma
32
How much botulism toxin kill all people
600g
32
What is botulism toxin?
Botulism toxin (BoNT) is a neurotoxin produced by the bacterium Clostridium botulinum that blocks the ability of muscles to contract
33
How dos BoNT work?
BoNT blocks the release of ACh at the neuromuscular junction
with the diaphragm unable to contract, inhalation can no longer occur resulting in asphyxiation
33
How is BoNT used in medicine?
used in cosmetic formulations as BoTox® to reduce facial wrinkles (and used to treat migraines)
33
What does the depolarization of the sarcolemma cause?
the depolarization of the sarcolemma triggers release of Ca2+ ions within the muscle cell from the a storage organelle called the sarcoplasmic reticulum (SR)
34
What does calcium do when released?
Ca2+ ions diffuse into the myofibrils where they bind the regulatory protein troponin which prevents actin-myosin cross-bridge formation under resting conditions
35
Describe how cross-bridge formation occurs?
Cross-bridge Formation:
the binding of Ca2+ to troponin results in a conformational change that shifts tropomyosin filaments into the actin groove reveals the myosin-head binding sites on actin molecules
the actin-myosin cross bridge forms once ATP is hydrolyzed to ADP
cross-bridge formation causes a molecular “spring” to become compressed
36
What is the power stroke?
the power stroke occurs when cross-bridge formation triggers the release of the molecular “spring” resulting in a snapping action of the myosin head in the direction of the myosin tail
37
What happens after the power stroke?
ADP is released following the power stroke, which allows ATP to re-associate with the myosin head and effectively uncoupling the cross-bridge
38
How does muscle relaxation occur?
Relaxation of Muscle:
for relaxation to occur, intracellular Ca2+ levels must return to resting values
Ca2+ ions are resorbed via active transport back into the sarcoplasmic reticulum (SR)
ATP-requiring process
the nervous signal can be muted at the neuromuscular junction via the actions of the enzyme acetylcholinesterase
degrades ACh into choline and acetate neither of which can activate ACh-gated channels
39
How does rigor mortis occur?
complete rigor mortis occurs 6 – 8 hours post-mortem and involves the stiffening of the body’s muscles starting with the jaw (2hrs)
caused by Ca2+ ion accumulation in the sarcoplasm and an inability to resorb Ca2+ back into the SR
40
What does myostatin do?
myostatin regulates muscle development
41
What is myostatin?
myostatin is a growth factor secreted by muscle cells that inhibits the growth and development of muscle cells
42
What happens in animals that are homozygous for a loss-of-function mutation in myostatin?
animals that are homozygous for a loss-of-function mutation exhibit increased muscle mass
muscle mass increase is the result of hyperplasia, as opposed to hypertrophy
43
Can myostatin mutations appear in human population?
Yes
44
Skeletal muscles – attached to skeleton to facilitate ____
a. Muscles do just one thing = ____
b. ____: connective tissue that attaches muscle to bone
c. A given muscle in the body (eg., biceps brachii) represents an ____ in the muscular system
d. A muscle can be subdivided into ____ which are bundles of muscle fibers (cells)
e. Muscle fibers are ____ due to formation from multiple ____
f. Within a muscle fiber (cell) are ____ – the contractile element of a muscle fiber
Skeletal muscles – attached to skeleton to facilitate movement
a. Muscles do just one thing = shorten (contract)
b. Tendons: connective tissue that attaches muscle to bone
c. A given muscle in the body (eg., biceps brachii) represents an organ in the muscular system
d. A muscle can be subdivided into fascicles which are bundles of muscle fibers (cells)
e. Muscle fibers are multinucleate due to formation from multiple myoblasts
f. Within a muscle fiber (cell) are myofibrils – the contractile element of a muscle fiber
45
The ____ is the functional unit of skeletal muscle
a. Know the structure of the sarcomere, including:
i. Thick filament; thin filament; ____, ____, ____, ____, ____
1. Thick filaments = ____
2. Thin filaments = ____
3. Actin and myosin association results in ____-____ ____
The sarcomere is the functional unit of skeletal muscle
a. Know the structure of the sarcomere, including:
i. Thick filament; thin filament; A-band, I-band; H-zone; M-line; Z-line
1. Thick filaments = myosin
2. Thin filaments = actin
3. Actin and myosin association results in cross-bridge formation
46
____ and ____ regulates cross-bridge formation
Troponin and tropomyosin regulates cross-bridge formation
47
How do Troponin and tropomyosin regulates cross-bridge formation?
i. Troponin binds to Ca2+which affects tropomyosin configuration
ii. Tropomyosin moves away from the myosin-binding sites on actin
iii. Myosin heads bind to actin (myosin binding sites) resulting in cross-bridge formation
48
the ____ ____ ____ is the accepted understanding of how muscles contract
i. actin and myosin slide relative to one another (as opposed to any of these elements becoming shortened)
the sliding filament model is the accepted understanding of how muscles contract
i. actin and myosin slide relative to one another (as opposed to any of these elements becoming shortened)
49
Cause muscular dystrophy?
Muscular dystrophy is caused by a mutation in the gene coding for the protein dystrophin
a. Dystrophin helps attach actin molecules to the sarcolemma (muscle membrane)
b. Results in incurable condition that is marked by loss of motor function and eventually heart failure
50
What does botulism toxin do?
Affects the ability of axon termini to release ACh into the synaptic cleft
Prevents muscular contraction, results in asphyxiation due to effects on diaphragm
51
What is difference between hypertrophy and hyperplasia?
a. Hypertrophy: increase in myofibril volume due to addition of actin/myosin
i. Generally accepted view of how muscle organs increase in mass
b. Hyperplasia: formation of new muscle cells (fibers)
52
What is neuromuscular junction?
Neuromuscular junction: the synapse between a motor neuron and the motor end plate of a muscle
fiber
53
General order of muscle signal for contraction?
i. Action potential (nerve impulse) travels down axon
ii. ACh released from axon terminus and diffuses into synaptic cleft
iii. ACh binds to ACh-receptors on surface of muscle cell, triggering depolarization
iv. Depolarization is transmitted down T-tubules where it causes the opening of Ca2+
channels on the sarcoplasmic reticulum
v. Ca2+ released from SR binds to troponin in myofibrils
vi. Troponin activation causes a shift in tropomyosin position
vii. Myosin heads bind to exposed sites on actin molecules and ATP is hydrolyzed
viii. Power stroke occurs resulting in actin sliding past myosin, releasing ADP
ix. ATP reassociates with myosin head to uncouple cross-bridge
54
How does muscular relaxation occur? Rigor mortis?
i. acetylcholinesterase activity – enzyme that degrades ACh into acetate and choline in
the synaptic cleft
ii. ATP is used to pump Ca2+ ions back into the SR, effectively removing Ca2+ from the
troponin proteins
iii. rigor mortis is a stiffening of the muscles post-mortem:
1. Due to inability to reabsorb Ca2+ as a result of lack of ATP
55
What is myostatin?
Example?
myostatin: growth factor secreted by muscle cells that inhibits the growth (ie., hyperplasia) and development of new muscle fibers (cells)
b. egs., Belgian blue cattle; Texel sheep; bully whippets; GM. Swine; humans
56
What is strength of contraction influenced by?
Contraction strength is directly influenced by the number of actin-myosin cross-bridges formed which is
influenced by:
a. Number of muscle fibers stimulated
i. Muscle fibers (cells) are stimulated by motor units which correspond to a single efferent (motor) neuron
1. A single motor unit can innervate multiple muscle fibers
ii. Recruitment occurs when additional motor units become activated resulting in greater contraction force
1. If all motor units are activated then maximum contractile force is achieved
b. Relative size of the muscle fibers
i. Recruitment is based on muscle fiber size: smallest --> intermediate --> large
c. Frequency of the stimulation
i. A single action potential produces a single muscular contraction called a twitch
1. The muscle fiber completely relaxes after the contraction
ii. If the muscle isn’t given time to relax and a second action potential arrives, then summation occurs which helps to maintain sustained contraction of increasing force
iii. If repeated action potentials arrive in short succession, then tetanus occurs which results in maximum contractile force.
1. Eventually the contraction fails due to fatigue
d. Degree of muscle stretch
i. Optimal sarcomere length for generating maximum force is 80%-120% of resting length
1. If too shortened, the contractile force drops off sharply
2. If too lengthened, the contractile force also decreases, but at a more gradual decline
57
What is Tetanus (TeNT)? What does it result in?
Tetanus is a neurotoxin (TeNT) produced by Clostridium tetani which blocks the release of inhibitory neurotransmitters (eg. GABA).
a. Results in intense, unabated and extremely painful contractions which ultimately can cause asphyxiation
58
Know the characteristics of the (a) slow; (b) fast aerobic; and, (c) fast anerobic muscle fiber types?
Slow-Twitch (Type I) Muscle Fibers:
Contraction Speed: Slow and sustained contractions.
Energy System: Primarily aerobic metabolism (oxidative).
Fatigue Resistance: High fatigue resistance due to efficient energy production from oxidative processes.
Color: Red in color due to a high myoglobin content, which is involved in oxygen transport.
Force Production: Lower force production compared to fast-twitch fibers.
Activities: Well-suited for endurance activities like long-distance running or cycling.
Fast-Twitch Oxidative-Glycolytic (Type IIa) Muscle Fibers:
Fast-Twitch Oxidative-Glycolytic (Type IIa) Muscle Fibers
Contraction Speed: Faster than slow-twitch fibers but slower than fast-twitch glycolytic fibers.
Energy System: Primarily uses both aerobic and anaerobic (glycolytic) metabolism.
Fatigue Resistance: Moderate fatigue resistance.
Color: Pinkish in color due to a combination of myoglobin and glycogen content.
Force Production: Higher force production than slow-twitch fibers.
Activities: Suited for activities requiring both endurance and strength, such as middle-distance running or swimming.
Fast-Twitch Glycolytic (Type IIb or IIx) Muscle Fibers:
Fast-Twitch Glycolytic (Type IIb or IIx) Muscle Fibers:
Contraction Speed: Fast and powerful contractions.
Energy System: Primarily anaerobic metabolism (glycolytic).
Fatigue Resistance: Low fatigue resistance, fatigues quickly.
Color: White in color due to lower myoglobin content.
Force Production: Highest force production among muscle fiber types.
Activities: Suited for short bursts of intense, powerful activities like sprinting or weightlifting.
59
Understand how pyruvic acid is shunted to form lactic acid during anerobic conditions?
During anaerobic conditions, when there is a lack of oxygen, pyruvic acid generated during glycolysis is shunted or converted into lactic acid through a process known as lactic acid fermentation. This is a way for cells to regenerate NAD+ (nicotinamide adenine dinucleotide), which is necessary for glycolysis to continue. The conversion of pyruvic acid to lactic acid involves the following steps:
Glycolysis:
Glycolysis is the initial process where glucose is broken down into pyruvate.
It occurs in the cytoplasm and does not require oxygen.
Glycolysis produces ATP and NADH.
NADH Production:
During glycolysis, NAD+ is reduced to NADH as glucose is metabolized.
NADH is an electron carrier that temporarily holds high-energy electrons.
Anaerobic Conditions:
In the absence of oxygen (anaerobic conditions), the cell lacks an electron acceptor for NADH.
Without a way to regenerate NAD+, glycolysis would be inhibited.
Lactic Acid Fermentation:
To regenerate NAD+ and allow glycolysis to continue, pyruvic acid is converted to lactic acid through lactic acid fermentation.
This process occurs in the cytoplasm and involves the reduction of pyruvic acid to lactic acid.
Regeneration of NAD+:
In the process of lactic acid fermentation, NADH donates electrons to pyruvic acid.
This results in the reduction of pyruvic acid to lactic acid and the simultaneous oxidation of NADH back to NAD+.
Role of Lactate Dehydrogenase:
The enzyme lactate dehydrogenase plays a key role in the conversion of pyruvic acid to lactic acid by facilitating the transfer of electrons from NADH to pyruvic acid
60
What is myoglobin?
Myoglobin functions similar to hemoglobin by binding to O2 (but with greater affinity) which it delivers to oxygen-starved muscle tissues
61
Know the various ways in which muscles acquire energy?
a. Fatty acids broken down via beta-oxidation
b. Amino acids are deaminated to produce carbon molecules that can enter Krebs’ cycle
c. Glycosomes are intracellular vesicles within the muscle cell that store glycogen
d. Creatine is phosphorylated by creatine kinase (enzyme) to produce creatine phosphate which can be used to regenerate ATP (from ADP)
62
During short-duration, high intensity exercise, energy is consumed in the following order?
ATP (used within 6s) --> CP (used within next 10s) --> glycogen broken down to form glucose during remaining time
63
Muscles and bones function together to act as a ____-____ type mechanical system
lever-pulley
64
Describe levers?
a. Levers feature a pivot-point called the fulcrum
b. Allows the distance that the load can be moved to be increased
c. Basic formula: effort x length of effort arm = load x length of load arm
d. Three main types of lever systems:
i. 1st Class Lever: L – F – E (eg., occipital-C1 joint)
ii. 2nd Class Lever: F – L – E (eg., standing on toes)
iii. 3rd Class Lever: L – E – F (eg., bicep flexion – and most muscles)
65
What are agonists?
The muscle that causes an action is considered the agonist (or prime mover)
66
What are antagonists?
Using paired with an opposite action muscle called the antagonist (eg., extensor vs flexor)
67
What is origin and insertion?
The site of attachment of a muscle that experiences more movement is called the insertion; the site that moves less is called the origin
68
Critical dehydration thresholds?
12%, 20%
69
Stages of cancer?
There are five stages of cancer starting at stage 0.
Stage 0: This stage is where a tumor has not spread and can be somewhat easily cured
Stage 1: Often referred to as the “early stage”, this stage describes cancer that has not grown deeply into nearby tissues, or lymph nodes.
Stage 2 & 3: Both of these stages are similar in the detection of deeper growth on nearby tissue and possible spreading to lymph nodes.
Stage 4: This is the worst stage of cancer, where the cancer has spread to organs and other parts of the body that can make curing or controlling the cancer very difficult.
