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Skeletal Muscle I
components & fibers
82
Anatomy
Undergraduate 2
03/07/2014

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Term
What is the basis for classifying muscle fibers?
Definition
Their enzymes & enzymatic activities (aerobic vs anaerobic metabolism)
Term
Do most muscles have more white fibers or red?
Definition
white
Term
Do adductor muscles primarily use oxidative or glycolytic metabolism? What colour are they?
Definition
oxidative ; red
Term
Do longissimus muscles primarily use oxidative or glycolytic metabolism? What colour are they?
Definition
glycolytic ; pale, more pink
Term
What is the main muscle in pork chop?
Definition
longissimus
Term
Order the following types of meat in increasing degree of pigmentation

Pork, Beef, Lamb, Poultry
Definition
Poultry
Pork
Lamb
Beef
Term
True or False

Differences in pigmentation between muscles can be observed with beef and lamb
Definition
false
Term
True or False

Differences in pigmentation between muscles can be observed in poultry and pork
Definition
true
Term
What is myoglobin?
Definition
an iron-containing compound that stores O2 in muscle fibers
Term
Describe the following characteristics of oxidative fibers

Colour
Mitochondria
Cytochromes
Enzyme activity
Twitch/contraction speed
Size
Definition
-redder in colour
-more, larger mitochondria
-more cytochromes
-succinate dehydrogenase & cytochromse oxidase activities are strong
-ATPase and phosphorylase activitise are weak
-slow twitch
-smaller diameter than white fibers
Term
How does myoglobin differ from hemoglobin?
Definition
Myoglobin stores oxygen in muscle, hemoglobin transports oxygen in blood
Term
Are red fibers oxidative or glycolytic?
Definition
oxidative
Term
What is the value of fat droplets found in oxidative fibers?
Definition
source of energy used aerobic metabolism
Term
Are muscles involved with respiration, chewing, maintaining posture etc. slow or fast twitch? Why?
Definition
slow twitch, don't want these muscles to be easily fatigued
Term
Why do oxidative fibers tend to have more capillaries than glycolytic fibers?
Definition
to facilitate oxygen and nutrient transfer
Term
Why do oxidative fibers tend to be smaller in diameter than glycolytic fibers?
Definition
to reduce diffusion distance & speed up the transfer process
Term
Why do glycolytic fibers appear to be more white?
Definition
because they have very small amounts of myoglobin
Term
Describe the following characteristics of glytolytic fibers

Colour
Mitochondria
Cytochromes
Enzyme activity
Twitch/contraction speed
Size
Definition
-white in colour
-smaller & fewer mitochondria
-fewer cytochromes
-weak aerobic enzyme activity
-strong ATPase and phosphorylase activity
-fast twitch
-larger in diameter
Term
What is the energy reserve used by fast twitch muscles?
Definition
glycogen
Term
What muscles are more easily fatigued, fast twitch or slow twitch?
Definition
fast twitch
Term
Why do white fibers have a more developed sarcoplasmic reticulum & T-tubules?
Definition
-used for transmitting AP across muscle fiber & stimulating contraction, important for achieving fast contraction
Term
Do intermediate fibers more closely resemble the metabolic pathway of red or white fibers? Why?
Definition
white, because the enzyme activities predominantly involve ATPase and phosphorylase
Term
What colour are intermediate fibers?
Definition
pink
Term
What bundles of muscle fibers called?
Definition
fasiculi
Term
What is another term for muscle fibers?
Definition
myofibers
Term
What is a myofibril?
Definition
contractile organelle inside the muscle fiber
Term
What are myofilaments?
Definition
protein filiments found inside myofibrils
Term
What is the basic contractile structure of a a muscle fiber cell?
Definition
myofibril
Term
What volume of the muscle fiber is attributed to myofibrils?
Definition
80%
Term
What are the two striations of myofibrils? Which is dark in regular light, and which is light?
Definition
anisotropic (dark)
isotropic (light)
Term
What causes the transverse striations of myofibrils?
Definition
arrangement & overlapping of thick & thin myofilaments
Term
Where is a Z disk (Z line) relative to the I band?
Definition
in the center of the I band
Term
What is a sarcomere?
Definition
repeating structural unit of myofibril, basic unit for contraction/relaxation cycle of the muscle
Term
How many A & I bands are found in one sarcomere?
Definition
1 full A and 2 half I
Term
When is sarcomere length the greatest?
Definition
during muscle relaxation (even greater when stretched)
Term
What is cold shortening and when does it occur?
Definition
shortening of the sarcomeres due to rapid chilling of meat
Term
When sarcomere length decreases, what happens to the distance between Z lines?
Definition
decreases
Term
How can you manipulate the carcass postmortem to increase sarcomere length?
Definition
use the weight of the carcass to stretch muscles, make selective cuts to stretch certain muscles
Term
How many thin filaments surround 1 thick filament?
Definition
6
Term
How many thick filaments surround 1 thin filament?
Definition
3
Term
What type of filament is found in A bands?
Definition
thick filaments
Term
What is the predominant protein in thick filaments?
Definition
myosin
Term
What is the effect on myosin when treated with trypsin?
Definition
Can produce...
light meromyosin: backbone of thick filament
heavy meromyosin: can be split into 2 subfragments
Term
What is HMM-1 composed of?
Definition
the two active heads of myosin
Term
What is the function of HMM-1?
Definition
-bind actin in thin filaments
-hydrolyse ATP to ADP
Term
Describe the arrangement of myosin in a thick filament
Definition
-1/2 of molecules face 1 Z line, 1/2 face the opposite Z line
-short headless zone in the middle of the filament
Term
What filaments make up the I band
Definition
thin filaments
Term
True or False

Thin filaments overlap a portion of the A band
Definition
true
Term
What is the predominant protein found in thin filaments?
Definition
G-actin
Term
What is the function of tropomyosin & troponin
Definition
tropomyosin changes depth in response to troponin, allowing myosin heads to row against actin molecules
Term
What happens when Ca2+ is available?
Definition
-it attaches to troponin
-conformation of the protein changes
-cross bridge binding sites on actin is exposed
-myosin heads can attach
Term
what are the 3 subunits of troponin?
Definition
C, I, T
Term
Where is a flexor muscle located on a limb, relative to the joint to which it bends? What do flexor muscles do?
Definition
on the same side
flexes
Term
Where is an extensor muscle located on a limb, relative to the joint to which it bends? What do extensor muscles do?
Definition
on the opposite side
extends/straightens out
Term
What side of the limb is the biceps brachii located on? Does it flex or extend the elbow?
Definition
cranial side
flexes
Term
What side of the limb is the triceps brachii located on? Does it flex or extend the elbow?
Definition
caudal side
extends
Term
What are some functions of muscles?
Definition
-produce a desired movement
-stabilize joints
-provide smooth control over a movement
Term
What do adductor muscles do?
Definition
pull the limb towards the median plane
Term
What do abductor muscles do?
Definition
pull the limb away from the median plane
Term
Are sphincters striated or smooth?
Definition
can be either
Term
These muscles surround an opening....
Definition
sphincters
Term
Do humans have cutaneous muscles?
Definition
no
Term
Where are cutaneous muscles found?
Definition
between the skin & deep fascia
Term
What is an agonist? Antagonist?
Definition
Agonist: a muscle that directly produces a desired movement

Antagonist: muscle that opposes the action of the antagonist
Term
A muscle that assists the agonist is known as...
Definition
a synergist
Term
A muscle that stabilizes a joint is known as...
Definition
a fixator
Term
Is a prime mover an antagonist or agonist?
Definition
either!
Term
What is the most stable point of muscle attachment?
Definition
the origin
Term
Where does most of the movement occur when a muscle contracts?
Definition
at the insertion
Term
What are the components of skeletal muscle? (5)
Definition
-muscle proper
-fasiculi
-myofibers
-myofibrils
-myofilaments
Term
What is the function of the epimysium?
Definition
covers & protects the muscle
Term
What effect does connective tissue have on eating quality?
Definition
more connective tissue = less tender
Term
Do locomotion muscles have more or less connective tissue?
Definition
more
Term
What binds muscle fibers into fasiculi?
Definition
perimysium
Term
True or False

The perimysium is a form of connective tissue
Definition
true
Term
What covers & protects a myofiber?
Definition
the endomysium
Term
What is a sarcolemma?
Definition
a membrane which surrounds a muscle fiber
Term
Why is the elastic property of sarcolemma important?
Definition
-to be able to change shape during contraction & extension
Term
What are T tubules?
Definition
a series of tubules which carry AP across the muscle cell
Term
What is a sarcoplasm? What are the 3 major organelles found within it?
Definition
the 'cytoplasm' of a muscle fiber
-nuclei, mitochondria & sarcoplasmic reticulum
Term
Are muscle fibers mononucleated or multinucleated?
Definition
multinucleated
Term
What is the difference between tendon & fascia?
Definition
tendon connect muscle to bone
fascia connect muscle to other muscle
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