Lecture 10/9: Skeletal Muscle AP Flashcards
Test 3
Skeletal Muscle is ___% of our body mass
40%
Where is Glycogen stored?
Liver
Skeletal muscle
How is the skeletal muscle useful is defense?
Defense against cold temperatures. Acts an an insulator
What does the skeletal muscles store to use for energy?
Glycogen
What happens when the skeletal muscles need to use energy?
Stored glycogen is broken down into glucose
Describe glycogen
starch compound
glucose molecules stuck together in a chain
Skeletal muscles are ________ of the central nervous system
Effectors
Neutral targets
T/F: the skeletal muscle stores ions
T
What is a bone-bone connection?
Ligament
What are examples of liagments?
Patella
MCL
ACL
What is a muscle-bone connection?
Tendon
What is an example of a tendon?
Achilles
What is a muscle-muscle (“tendon bridge”) connection?
tendon
Another name for a skeletal muscle fiber is _____
Cell
What is a group of skeletal muscle cells?
Fasciculous
What is Fasciculous separated by?
Connective tissues
What is a group of Fasciculi?
Muscle
Fill in the blank:
Muscle -> _____ -> ______ -> ______ -> Sacromere
Fasciculous
Muscle cell
Myofibril
Where is actin and myosin located?
Inside the myofibiril
What is a myofibril?
Cylinder inside muscle fiber that contains actin and myosin
What is a sacromere?
functional/contractile unit of myofibril where actin/myosin overlap
What are the color differences when looking at a skeletal muscle under a microscope?
Thin (actin) and thick (myosin) filaments
What color is a thin filament?
Lighter color
What color is a thick filament?
darker color
Where in the sacromere do we have the ability to produce force?
Overlap of actin and myosin
A-zone
Define a motor unit
1 or more muscle cell/fibers that are controlled by ONE motor neuron
How many skeletal muscles can a motor neuron control?
1 - many
T/F: Small motor units activate 2nd
F
1st
Describe the difference between small muscles and large muscles
Small muscles: Easier to excite
– require less electrical activity
– activated 1st
– helps with fine motor skills
Large muscles: Activated 2nd if you need to produce more force
– requires more electrical activity
– harder to excite
How many myofibrils are in ONE regular muscle cell/fiber?
200
For stronger muscle cells, how many myofibrils can you have?
1000s
Muscles that have fewer myofibrils are normally used for what?
Fine motor skills
More precise movements
What gives Type 1 muscle its red color? Why?
Myoglobin
The iron in myoglobin gives off a red color
What is myoglobin?
Iron containing protein
helps O2 unload from blood to muscle to be used by mitochondria to make ATP
Describe type 1 muscle. Ex)
Produce slow, strong contractions that can be sustained a long time.
Red
-Lots of myoglobin and mitochondria
Ex) Geese breast
Describe type 2 muscle. Ex)
Can produce fast, strong contractions, but doesnt last long
White (lacks alots of myoglobin)
-very little myoblin/mitochondria
Ex) chicken breast
What type of muscle is the Ocular Muscles?
Type 2
What is the Soleus? What type of muslce is this?
Type 1
Cap muscle in the lower leg-helps with standing all day
What is the Gastrocnemius? What type of muscle is this?
Mixed Type 1 & 2 – Type 2 dominates
Located in leg next to soleus.
What type of muscles are mostly in our body?
Mixed Type 1&2
Define: Sarcolemna
Cell wall of skeletal muscle
Define: Sacroplasma
Fluid inside the muscle cell
Where is the sacroplasmic reticulum located? Why?
Near the cell wall and Transverse tubules (T-tubules)
Close to the DHP voltage sensors used to open the Ca++ channel.
What does the SR store?
Ca++
What is striation? What are the muscles called?
Alternating color pattern when skeletal and cardiac muscle are stretched out.
Striad muscle
What is thin filament?
Actin
What is thick filament?
Myosin
Contraction depends on the ______ of the sacromere
Shortening
Anatomy: Sacromere
Z disc - z disc
Anatomy: Z disc
End of the sacromere
Bundled up actin around each other
Anatomy: I band
Only actin
light in color
Anatomy: A band
Actin + Myosin
Darkest of bands (appears as a line)
Thin
Anatomy: H band
Myosin only
Dark
Anatomy: Titin
Elastic connective tissue protein
Anchors actin + myosin
Holds sacromere together and allows movement
H =
myosin
I =
actin
A =
actin + myosin
Which band needs space in order to produce a contraction?
I band
What happens to the I band during a contraction?
Disappears
T/F: A band allows actin/myosin to pull on each other closing the space in the I zone
T
What happens to the H band during a contraction?
Disappears
T/F: Myosin is very stretchable
F
Myosin has a fixed width
What is the Sliding filament mechanism?
The processes of the lengthening and shortening of the sacromere resulting in reducing overall length of the muscle resulting in a muscle contraction
Skeletal muscles can be very long. How do we repair damage and handle mechanisms down the cell?
The skeletal muscle cells are multinucleated to handle this.
How do you identify the nuclei in skeletal muscles?
They are little purple dots under the microscope
Describe how proteins get down a motor neuron?
There are some tracks
There is a cart
Load the proteins up in the cart. and roll them down the axon in the cart…….
There are _____ myosin molecules in a myosin filament
200
Each myosin molecule has ___ chains
6
What are the 6 chains in a myosin molecule?
2 heavy chains in the tail
2 regulatory light chains
2 essential light chains
What are the myosin heads?
The 2 essential light chains
What are myosin filaments?
long strings of myosin molecules wrapped together at the tail
Describe the tail of the myosin filament
2 heavy chains wrapped around each other
used to fasten to other myosin molecules
Describe the regulatory light chain
Influences activity of the “head”
More active in smooth muscle than skeletal muscle
Things get phosphorylated here
Where are the essential and regulatory light chains located?
essential is more towards the outside
regulatory is more inside
What does the myosin head do?
“essential light chain”
-Posses ATP activity
- has binding site for F-actin
When it contracts -> pulls on actin inward -> shortens sacromere
What does actin filaments consist of?
2 protein strands:
- F-actin
-Tropomyosin
Describe the F-actin strand
Has the binding sites for the myosin heads
Describe the tropomyosin strand
Functions as a shield
oriented in a way that myosin heads cannot see binding sites on F-actin strand
Has a troponin complex that allows the binding sites to be revealed
What is a troponin complex?
3 proteins stuck together that when activated by Ca++, allows tropomyosin to unravel a bit and reveal the binding sites on F-actin
What are the 3 proteins on the troponin complex?
Troponin I: binds to actin
Troponin T: binds to tropomyosin
Troponin C: has 4 Ca++ binding sites
– fastens I & T together
– twists to unravel tropomyosin
What is the binding site for Ca++ in skeletal muscle?
Troponin C
Describe a high energy myosin head
Resting state
ADP + Pi attached to head
loose spring (uncocked) – relaxed
Describe a low energy myosin head
contraction
ATP will bind
tight spring (cocked) – tension
What is required for a myosin head to be released from F-actin?
ATP
What is Excitation-Contraction Coupling?
Turning an electrical event into an event that generates force
EPP –> AP
What is the Ca++ channel called in the SR called?
Ryanodine receptor
What is rigor mortis?
Stiffening of the muscles
ATP deficiency where myosin head cannot leave F-actin
What happens within the sacromere if you run out of ATP?
Ability to produce force is limited
myosin head wont be released from F-actin
Describe the Cross-bridge cycling process.
What is passive tension?
“stretch”
outside force used to over/under stretch a sacromere
What is active tension?
Muscle contraction from an AP
What is total tension?
Passive + active tension
The cardiac sacromere is naturally _________ specifically in the ventricular wall to pump blood
understretched
_____ is the optimal stretch length for a sacromere
2 micrometers
Over/under stretched sacromere =
less force in contraction
What happens in the heart when the sacromere gets overstretched?
Less force produced in L ventricle –> Heart failure
T/F: If there is no overlap in actin and myosin then there is no force produced?
T
Where is your achilles tendon?
Back of heel
Why is your gait not the same after an achilles tendon injury?
The Sx required cutting the and sewing the tendon. It will be shorter and not in the optimal stretch position.
Can use a cadavier to try to help prevent the shortening of tendon
