A&P Test 3 Flashcards
what percent of body mass is contributed to skeletal muscle mass?
40%
What is skeletal muscle important for?
defend itself
provide for itself
communication
what does the skeletal muscle store to use as energy?
glycogen
what is stored in the muscle?
ions
glycogen
fluids
proteins
what are effectors?
something that receives instructions from the CNS
what is a glycogen?
a bunch of glucose molecules stuck together. a large starch compound.
Where is glycogen stored besides the muscles?
Liver
glycogen is broken down into
glucose
what does a ligament connect?
bone to bone
what does a tendon connect?
usually muscle to bone
however
sometimes it is muscle to muscle via an intermediary tendon (tendon bridge)
individual muscle cells are called
muscle fibers
more than one group of muscle cells are called a
fasciculous. These function as a unit
many fasciculous together are called
muscle
what are the internal cylinders called that are in a muscle fiber?
myofibril
what do myofibrils contain?
actin and myosin
how many myofibrils are in a muscle per skeletal muscle cell?
> 200 in smaller muscles
thousands in a larger cell in a larger muscle
what are skeletal muscle cells with little moyfibrils good for?
fine motor control
(don’t want to squeeze a glass with a ton of strength because it will crush it)
what is the basic contractile unit of a myofibril?
a sarcomere
what are the thick contractile units of a sarcomere called?
Myosin filament
what are the thinner contractile units of a sarcomere called?
actin filament
what is the area of overlap between a myosin and actin called?
A band
what does the overlap of actin and myosin allow for?
force
what is a motor unit?
one or more skeletal muscle fibers that are controlled by a single motor neuron
how many skeletal muscles cells can a motor neuron control?
one or many
what is a small motor unit?
a motor neuron controlling a small number of muscles
good for fine motor
what is a large motor unit?
a motor neuron controlling a large amount of muscles
good for strength
which is easier to excite, small or large motor units?
small motor units
it takes more and more action potentials in the ventral horn to elicit a large motor unit
how are skeletal muscles classified?
Type 1:
slow and sustained
red d/t iron
lots of myoglobin
lots of mitochondria
type 2
fast twitch- can’t sustain
white
very little myoglobin
fewer mitochondria
What is myoglobin?
a big protein similar to hemoglobin. A big iron containing protein that helps oxygen unload from the blood into the muscle.
higher affinity for O2 than hemoglobin. Oxygen is used by the mitochondria to create ATP efficiently.
duck or goose meat can be grouped into which type of skeletal muscle classification?
Type 1
chicken breast meat can be grouped into which type of skeletal muscle classification?
Type 2
how high can a goose fly?
30,000 feet. Can see them in a passenger airline
what is the soleus muscle?
the weight bearing calf muscle on the back of the leg. Is designed to produce and sustain a lot of force.
starts off kind of slow but can sustain for a while.
what is the gastrocnemius?
the muscle next to the soleus muscle in the back of the leg
an ocular muscle can be categorized into which skeletal muscle classification?
type 2
the soleus muscle can be categorized into which skeletal muscle classification?
Type 1
the gastrocnemius muscle can be categorized into which skeletal muscle classification?
Both type 1 and type 2, kind of falls in the middle
vast majority of our muscles can be classified in which skeletal muscle classification?
most muscles have characteristics of both Type 1 and 2
what is a sarcolemna?
the cell wall of the skeletal muscle cell
what is found near transverse tubules and or cell wall?
sarcoplasmic reticulum
Which 2 body systems have striated muscle fibers?
skeletal muscle
cardiac muscle
contraction of the skeletal muscles is dependent up the
shortening of the sarcomeres within the myofibrils.
what is the structure called that actin filaments come together and wrap themselves around at the end of the sarcomere?
Z disks
the 2 ends of the sarcomere are bound by the structures called the
z disks
what is attached to z disks?
actin filaments
what is the area in a sarcomere called that is only filled with actin?
I band
Why is the I band lighter colored?
the filaments are thin
what is the area in a sarcomere called that is only filled with myosin?
H band/zone
what is Titan?
large stretchy connective tissue/protein that anchors actin and myosin together. Found on the ends of the myosin. allows the sarcomere to move around a little bit without falling apart.
the z disk is the border between
2 sarcomeres
Label this:
- mitochondria
- T tubule opening
- I band
- Z band
- A Band
- H band
what is the container that holds sarcomere?
myofibrils
which part of the sarcomere does not change in length during contraction?
the area where myosin is located
what is the difference in these 2?
the top is relaxed the bottom is contracted
a skeletal muscle cells stretch from
one tendon to another tendon
how does the bottom of the axon get building blocks to build new proteins in an neuron?
Proteins are made in the nucleus
put in a “cart”
and sent down the “tracks” down the axon to the end of the axon
how do very long skeletal muscle cells get new material to build new proteins?
the skeletal muscle has routinely placed nuclei.
what makes skeletal muscle unique?
it is multinucleated
myosin filaments are long string of
myosin molecules that are wrapped together at the tail
how many myosin molecules make up a myosin filament?
200
each myosin molecules have how many chains?
6
2 heavy chains wrapped around each other at the tails
4 at the head called light chains
essential light chains
regulatory light chains
where are the essential light chains?
what does it do?
on the periphery of the head
it gives the myosin head it’s APTase activity
they are essential
where are the regulatory light chains?
what does it do?
between the essential light chains
they determine the activity level of the head.
they don’t really do a lot in skeletal muscle.
their activity can alter the activity of the myosin heads in smooth muscle. In smooth muscle we usually have phosphorylation of the myosin heads. This would turn the contraction on and off
the myosin head has an affinity for the binding sites on
actin filament
what are the active sites on actin?
the binding sites for myosin
What is the strand called where binding sites are found for myosin?
F actin
What are the 2 strands called that make up actin?
F actin
tropomyosin
what does tropomyosin act as?
a shield. It hides the active sites in a skeletal muscle at rest from myosin.
what is required for the tropomyosin to uncover the binding sites on actin?
troponin complex:
3 proteins stuck to each other
1. troponin T
2. Troponin I
3. Troponin C
Troponin C has 4 binding sites for Ca++
when Ca++ binds to Troponin C it twists the other two.
This unravels the tropomyosin and F actin twisting a little bit so that the binding sites are uncovered.
what is the troponin called that is fastened to the actin strand?
Troponin I
what is the troponin called that is fastened to the tropomyosin strand?
Troponin T
what is the troponin called that is fastened to the Troponin I and Troponin T molecules?
Troponin C
How many Ca++ binding sites does Troponin C have?
4
what is the binding site for Ca++ in skeletal muscle
troponin C
What are the 2 orientations that myosin heads can have?
ready to go: taught, pulled back, perpendicular to the actin filament
not ready to go: loose spring, needs to be “cocked”
what is attached to the myosin head in the cocked state?
ADP
P
what is required to “cock” a myosin head? Going from a low energy state to a high energy state
ATP being broken down into ADP and P
in a normal, healthy, resting skeletal muscle, what configuration should the myosin head be in?
the cocked state, ready to be used
Describe Cross-bridge cycling.
- The resting myosin head is in the cocked state with ADP and P attached. Actin binding sites are being covered by Troponin C.
- Ca++ comes in and binds to Troponin C. This changes the configuration of the troponin complex to reveal the binding sites on actin.
- Myosin now sees the active site and binds
- Phosphorous falls off
- The tension in the head is now used to grab on and pull on the actin molecule at the active site which pulls the two ends of the sarcomere closer together.
- ADP falls off and the tension is used in the head to it goes back to the released state, bent with a loose “spring” waiting for ATP to come and cock it.
What are the problems that can come about regarding cross-bridge cycling?
you can run out of ATP. This would leave the myosin head stuck to the actin but not contributing any force. RIGORMORTIS. Stiff muscles, not tense.
the neuromuscular junction on a foot long muscle cell a very ______ portion of the muscle
small
it took scientists forever to figure out that the DHP sensors are physically attached to Ryr gates. They were originally studying _____
chemical compounds.
the amount of strength of contraction that a muscle is able to generate is dependent on a number of things including:
the surface area involved with the thick myosin and thin actin filaments
i.e. really stretched out. If there is no overlap between actin and myosin, we won’t be able to create any force
If they’re too under stretched there’s no more room to pull them together so no force
what are of the body can tend towards an overstretched muscle where the actin and myosin heads don’t overlap as much as they should?
the heart specifically the L ventricle.
what is the optimal length of stretch in a sarcomere that would give us the maximum amount of tension in a skeletal muscle?
2 micrometers
if we have normal, healthy anatomy, our skeletal muscle is stretched to the
optimal length
if we have under stretched muscles, what do we need to do to ensure the muscle performs optimally?
what group of people have to do this?
stretch them out
athletes
what does the achilles tendon connect?
the gastrocnemius and soleus muscle to the calcaneous bone
how do surgeons repair a torn achilles tendon?
they take the 2 ends of the tendon and overlap them then sew them together
can use a piece of tendon from a cadaver but this is a specialized surgery and is very expensive. Usually reserved for elite athletes
what is the result of a achilles tendon repair?
it makes the tendon a little shorter, pulling the muscle a little longer (overstretched). For most people this won’t cause any issues. For elite athletes, this will impact coordination, gait, and performance.
the sarcomere of the heart looks a lot like the sarcomere in the
skeletal muscle
Why is it that the healthy heart can adapt to increases in preload and still pump out all of the blood that is brought in?
Because the sarcomere in the resting heart of a healthy adult are a tiny bit under stretched. an increase in preload stretches them optimally and we have a more forceful contraction to pump out the increased amount of blood.
what does the “upside down U or V” graph with tension developed on the Y axis and Length of sarcomere on the X axis tell us something about?
active tension: tension that is generated by shocking the muscle with an action potential
muscle contraction
what is passive tension in the skeletal muscle?
the outside force that has to be used to achieve the stretch of a skeletal muscle (pulling on the ends to stretch it out)
muscle stretch
what is the total tension?
the active and passive tensions added together.
