Exam 3 - Lecture 6 Flashcards
Skeletal muscles are the largest ________ of the body.
Container
Percent of body mass for a non-obese person that is skeletal muscle
40%
Skeletal muscles 3 tasks he said at beginning of lecture
Get away from danger/defend itself, communicate, regulate body temperature
Skeletal muscles are effectors means:
Takes action based on stimulus received from brain/reflex.
What does skeletal muscle store? and where else is it stored?
Glycogen which is a bunch of glucose molecules in a chain.
Muscle breaks it down into glucose to use energy.
Stored in liver too.
Ligaments are
Bone-bone connection such as patellar/ACL/MCL
Tendons
Vast majority are Muscle-bone, some can be muscle-muscle
e.g. achilles
Tendon bridge
Muscle-muscle connection
Order of muscle to sarcomere
Muscle -> Fasciculous -> muscle fiber (cell) -> Myofibril -> Sarcomere
Individual muscle cells are called
Muscle fiber
If we have more than one group of muscle cells, it’s called a
Fasciculous - Usually work as a unit
Plural for fasciculous
Fasciculi
Within a skeletal muscle fiber or cell, there will be ________ called ______ that contain _________ for skeletal muscle.
Cylinders; myofibrils; actin and myosin
cylinder looking thing inside skeletal muscle cell
Myofibril
There are over ________ myofibrils per one skeletal muscle cell, and if the muscle cells are larger it can get into the
200; 1000’s
Skeletal muscles with only few myofibrils will be used for
Fine/precise motor skills
Within myofibril, there are bands called
Sarcomeres
Basic contractile unit of a myofibril is a
Sarcomere
Z-discs
Two ends of each sarcomere
I-band
only actin
A-band
Actin and myosin
H zone/Band
only myosin
Whenever we have overlap of actin and myosin, we can produce
force
Grouping of functional units of skeletal muscle coupled with motor neurons are called
Motor units
Motor units
A collection of 1 or more muscle fibers that are controlled by a SINGLE motor neuron. Can control 1 to many skeletal muscle fibers/cell.
Smalls motor units (mu’s) control
Small motor neurons (mn’s)
Help fine motor tasks, dont contract super fast or lots of force, just fine motor control.
Large Mu’s control
Large motor neurons (mn’s)
Mu’s and Mn’s
Motor units and motor neurons
As the body contracts smaller Mn’s, and gradually need more, then
Larger Mn’s slowly get recruited
Typically, small mn’s are ________ while large mn’s are _______ to excite.
easy to excite; difficult to excite
Larger they are, require more stimulus to excite
Can you recruit a large mn without exciting small mn?
no.
Can you recruit small mn without exciting large mn?
Yes.
Type 1 skeletal muscle
Red, slow
Lots of myoglobin
lots of mitochondria
e.g. breast meat in ducks and geese cause they can fly at 30,000 feet.
Does type 1 skeletal muscle need to sustain force for extended period of time?
Yes.
Myoglobin
Iron containing protein that helps oxygen unload from muscles. Works very similar to hemoglobin.
Myoglobin has a higher _________ to oxygen which helps oxygen ________
Affinity; unload from blood
Mitochondria harnesses __________ to use ATP efficiently
oxygen
Why are type 1 skeletal muscles red?
From the iron bound in myoglobin
Type 2 skeletal muscle
White, fast twitched.
Very little myoglobin
Fewer mitochondria
e.g. chicken breast, can fly into low hanging tree but not 30,000 feet like geese and ducks.
Do white muscles sustain force for an extended period of time?
No, not designed that way.
Soleus muscle
calf muscle in back of leg for sustained force and heavy force.
Action potential of soleus muscle
Lasts the longest on AP graph, because its a sustaining muscle (type 1)
Ocular muscles (in regards to muscle type)
Quick and fast twitch muscles, quick and short action potential. (type 2)
In between muscle on action potential chart
Gastrocnemius. A mix between fast twitch and a more sustained muscle, but not nearly as much as soleus muscle.
Very first action potential on chart that just goes up and down is
The stimulus to move the muscle, soleus muscle takes the longest to get going, but its the most sustained force.
Soleus muscle takes almost ___________ milliseconds to reach peak force
100ms
Most muscles in our body can be
mixed of the two types.
What releases calcium in muscle cells?
Sarcoplasmic reticulum
Alternating color pattern in muscle cells
Striations
Thick filaments
Myosin
Thin filaments
Actin
Actin filaments wrap themselves around the
Z-disc
The light color of muscle cell under microscope
I-band (only actin)
Darker areas on microscope
Thicke filaments (h-zone) only myosin
Stretchy connective tissue that holds actin/myosin all together
Titin. its very elastic and allows sarcomere to move around a little bit.
Dar blobs on microscope hanging out into myofibrils
Mitochondria
Circle light color on microscope of skeletal muscle cell
Transverse tubule
Contraction of myofibril order
I-bands shrink -> H bands disappear -> Z discs move closer together -> Muscle decreases overall length = Sliding filament mechanism
Myosin has a _____ width
fixed. doesnt change much during contraction.
What doesnt change width during contraction?
A band
Muscles stretch from
tendon to tendon
What are the purple dots on microscopic picture thats colored of muscle cells?
Nuclei.
If we need to build something new and its far away on the other side of the neuron, you can transport it down the axon and it looks like
Train tracks with carts. Nucleus builds proteins, load it in cart, and wheel it down the neuron to where they are needed.
Skeletal muscle cells are ___ because the cells are so long. Do they have the train track method?
Multinucleated. No, they dont have room for it. they make up for it by being multinucleated.
Each of the tiny strands on colored microscope image of muscle cells, those are
Sarcomeres
How are thick filaments formed?
Myosin molecules that are wrapped and twisted together
How many myosin molecules make up a myosin filament?
200
Each myosin molecule has ____ chains. ________ make up the tail, and _________ make up the head.
6;2 heavy chains;4 light chains.
Head of myosin have _________ chains that are ______ chains and __________ chains. And the chains on the head are all considered to be _______.
4; regulatory; essential; light.
In skeletal muscle, _____ don’t do too much, but their activity can alter the myosin head in different types of muscle, but these chains will be phosphorylated in _________
Regulatory. smooth muscle.
Which chains provide ATP?
Essential chains on myosin head
Most superficial chain on myosin head
Essential chain
Myosin head has affinity for
active binding sites on f-actin filament strand
Does myosin head burn ATP?
yes, it has ATPase activity.
Which filament possesses active sites?
Actin
The actin filament strands are interwoven fibers that consist of
1 strand being f-actin, 1 being tropomyosin.
Tropomyosin acts as
a shield, oriented in a way to block myosin heads from binding to active sites on f-actin strand.
How is the shielding of tropomyosin moved in order to bind myosin heads?
3 troponin proteins that are bound to f-actin and tropomyosin strand at an intersection.
3 troponin molecules that bind to actin strand and tropomyosin
Troponin-T,I, and C
Troponin bound to F-actin?
Troponin-I
Troponin bound to Tropomyosin?
Troponin-T
Troponin bound to I and T, that allows calcium to bind to it?
Troponin C
How many binding sites does troponin C have for calcium?
4
When calcium binds to troponin C, it takes other 2 troponins and
twists them, which moves tropomyosin out of the way to loosen/unravel strand a little bit, exposing active sites to myosin head and allowing it to bind and contract muscle.
Myosin head has 2 orientations
One that is cocked and ready to go, and the other one is more relaxed and needs energy to reset itself.
drawing characteristics of Myosin head thats capable of binding to active site, cocked and ready to go
stretched spring from head to filament, ADP and Pi is bound, and head is ready
drawing characteristics of Myosin head thats awaiting ATP and is not ready to bind
Spring is much tighter, head is pulled back, awaiting for ATP which is floating around near.
Once ATP makes contact with myosin head, it will bind and
metabolizes into ADP and Pi, and use the energy thats liberated to put tension on myosin head.
Resting and healthy skeletal muscle should have myosin head in what state?
Cocked and ready to go!
During resting states when muscle isnt active, actin sites are
hidden and myosin head has nothing to bind to.
Adding calcium to inside of skeletal muscle will allow
Troponin-C is bound, unraveling actin, myosin head binds, and releases the phosphate, the tension in the head uses the stored tension and pulls on actin molecule, which brings ends of sarcomere closer together, contracting the muscle and ADP falls off. Myosin molecule now has neither ADP or Pi, and now stuck until ATP binds to it, then it can release from actin filament and reset for next cycle.
What do we need to release myosin head from actin molecule after contraction?
ATP to bind to it.
What happens if ATP doesnt bind to release myosin head?
Muscle will be stiff. This is why rigor mortis happens.
What happens once ATP is bound and myosin head is released?
Metabolized into ADP and Pi, restoring tension and cocking the head. Now ready to look for next active site.
vast majority of motor neurons innervate more than
1 skeletal muscle cell, thats why there is a branching pattern of the motor neurons with multiple NMJ
What determines how much force a muscle can generate?
Correct amount of stretch of muscle.
If we have an overstretched sarcomere, how much force will there be?
Either none or very very minimal. No actual real examples, muscles dont stretch this much. but in theory…
If we have an understretched muscle, there will be
less force generated because theres not alot of shortening.
B and C on graph.. what is gonna generate the most force?
C cause its just a little bit longer than B
In “normal anatomy” the muscles will be
held in place at an OPTIMAL stretch point
How do the heart sarcomeres compare to the rest of our muscles?
Typically understretched, between point A and B. Just below optimal.
Do average people have understretched muscles and do they need to stretch?
No… Professional athletes may have to because they have overdeveloped muscles.
But to perform optimally, yes muscles should be stretched.
If your achilles tears and you have to have a surgery that fixes it by overlapping it, what happens? How can we avoid this?
Makes it shorter, less than optimal, so now the muscle will be overstretched and the muscle it connects to wont be as strong.
You can do a surgery using a cadaver tendon, but these procedures are extremely expensive and typically used for professional athletes that can afford it.
What length of sarcomere is ideal according to the chart on lecture and how much percent tension is developed?
100%, 2 micrometers.
Increasing venous return to heart will cause sarcomeres to
become a bit more overstretched than they previously were. We can tolerate it this because at baseline theyre a little understretched, and adding filling pressure will make it perform better.
Frank-starling mechanism
Force of contraction is directly dependent on stretch of heart muscle. Cardiac output is roughly equal to venous return.
Passive tension means
stretch
Active tension
muscle contraction
total tension is
Passive + active tension
What is going to generate the most tension in the muscle?
Combining both active and passive tension
