Skeletal Muscle pt 2 Flashcards
Exam 3
What are the 8 characteristics of skeletal muscles?
Largest contributor to body weight (non-obese)
Locomotion
Expression
Communication
Body temp
Storage of glycogen
“Effectors”/Targets of nerves
Large store of ions, fluids and proteins
What % of body weight do skeletal muscles contribute to (non-obese)
40%
Ligaments connect _____ to ______
bone to bone
Tendons connect ______ to _______
muscle to bone
- can be muscle-muscle via intermediate tendons
A single skeletal muscle cell is called a _______
muscle fiber
A single muscle fiber contains hundreds of _____
myofibril
What is the name of the cylinders that contain the actin and myosin
myofibril
What do we call a collection of one or more muscle fibers controlled by the same motor neuron?
Motor unit
Larger motor units are _________(easier/harder) to excite than smaller motor units
harder
What is the name of the functional/contractile unit of myofibril?
sarcomere - where myosin and actin overlap
Myosin filaments are also called _______ filaments
thick
Actin filaments are also called ______ filaments
thin
A group of muscle cells is a _________
fasciculous
many fasciculi = ______
muscle
skeletal muscles store energy as _____
glycogen
which two places is glycogen stored?
liver and skeletal muscles
The stronger the muscle cell, the more _______
myofibrils
how is myoglobin different from hemoglobin?
myoglobin has higher affinity for oxygen
Differentiate between type 1 and type 2 skeletal muscle classifications: speed
type 1 - slow
type 2 - fast
Differentiate between type 1 and type 2 skeletal muscle classifications: color
type 1 - red (more myoglobin)
type 2 - white
Differentiate between type 1 and type 2 skeletal muscle classifications: mitochondria
type 1 - a lot
type 2 - less
The _______ is the cell wall of the skeletal muscle cell
sarcolemna
_______ is the alternating color pattern of skeletal and cardiac muscle noted under a microscope
striations
The ____ extends from z disc to z disc
sarcomere
The area in which the thin filaments connect to each other is the _______
z disc
The area where there is only thin filaments is the _______
I band
The area where there is only thick filaments is the _______
H band
______ is the elastic connective tissue that anchors actin and myosin
Titin
A contracted myofibril pulls the two ______ closer together
z discs
The _______ usually doesn’t change width during contraction
A band
During contraction, the ______ shrink and the _____ disappear
I bands, H bands
Differentiate between the repair mechanisms of motor neurons vs skeletal muscle
motor neurons - train track system to carry proteins from nucleus down neuron
skeletal muscle - multi-nucleated
Myosin filaments are long strands of myosin molecules that are wrapped around at the ____
tail
____ myosin molecules make up each filaments
200
each myosin molecule has ___ chains that allow myosin molecules to attach
6 - 2 heavy and 4 light chains
What are the two types of myosin light chains?
Essential LC (2) - ATPase
Regulatory LC (2) - determines activity level of head
The myosin has an affinity for binding sites on the ______ filament called _____
actin - active sites (F-actin)
________ prevents myosin head from binding to F-actin active sites
tropomyosin
What are the 3 parts of the troponin complex?
- Troponin I: Binds Actin
- Troponin T: Binds Tropomyosin
- Troponin C: Binds Calcium
How does the troponin complex reveal the active sites?
When Ca++ binds to troponin C, the other two troponins (I and T) unravel strands and reveal active sites on actin filament
Differentiate between the AP of the following muscles: ocular muscle, gastrocnemius, soleus
Ocular Muscles - don’t do a lot of heavy lifting just need to respond quickly; eyes are light weight → fast, short contractions
Gastrocnemius - in between muscle, next to soleus muscle; quicker acting than soleus
Soleus - calf muscles, lots of force for extended periods of time; takes longer to get going but lasts longer
What is the mechanism of myofibril contraction?
“Sliding filament mechanism”
Describe the 6 steps of cross-bridge cycling
Attached
1. ATP binds to myosin head, releasing it from actin molecule
Released
2. ATP → ADP + phosphate, creating tension within myosin molecule
Cocked
3. Ca++ combines with troponin C → unravels tropomyosin blocking active sites on actin → myosin can see active sites and bind
Weak cross-bridge
4. phosphate released and myosin binds to active site on actin
Strong cross-bridge
5. head uses tension to pull on active site → sarcomere shortened
Post powerstroke
6. ADP falls off → back to attached state
What would happen in the cross-bridge cycle without ATP?
- Myosin heads couldn’t reset, couldn’t produce force
- Myosin head wouldn’t release from actin
_______ is the lack of ATP in the skeletal muscles
rigor mortis - muscle stiffness
If the sarcomere is over-stretched - not enough _______, wouldn’t be able to produce enough ______
surface area
force
What is the ideal sarcomere surface area on the graph?
B or C, but C is more optimal - a little more room to shorten than B
If the sarcomere is under-stretched - not enough _______, so won’t generate as much ______
room to shorten
force - start of the red line on the far left
The sarcomeres of the heart ventricular wall are a little ______-stretched
under - would look like A on graph; augments pumping to return more blood to the heart
After a tendon repair, the tendon is shorter and therefore the muscle is _____-stretched
over
Frank-Starling mechanism
Force of contraction directly dependent on stretch of heart muscle
Total tension =
passive + active tension
Professional athletes need to stretch more because their skeletal muscle is _____-stretched
under
Describe total, active, and passive tension on a graph
________ tension is the outside force used to achieve stress
Passive
______ tension is force generated by an AP
active - muscle contraction
Load/Contraction Velocity Diagram:
Increased load = decreased muscle contraction speed
- important in heart muscle
______ is skeletal muscle adaptation that occurs
from denervation/disuse of muscle
atrophy - loss of myofibrils 1st, then loss of skeletal muscles 2nd
______ is skeletal muscle adaptation that occurs
from exercising
hypertrophy - increased myofibrils, cell size, and vascular bed growth - increased muscle size
______ is skeletal muscle adaptation that occurs
from a lot of exercising (pro athletes), resulting in extra skeletal muscle cells
Hyperplasia
Quantal regulation or summation
number of motor units activated/recruited
more muscle = more force
Temporal (time) summation
force generation in comparison of rate stimulation (times per second)
Tettany occurs when? At how many Hz?
Ca++ coming out of SR faster than it can be put back in
40 Hz
temporal summation generates _____ force than quantal summation
more
_____ is the peak force that a muscle can generate
tettany
