602 Flashcards
In a single muscle fiber, sarcomeres are arranged:
a. In parallel (side-by-side) b. In series (end-to-end) c. Partially overlapping d. Two or more of the above
D
What must be the physical relationship of actin to myosin for cross-bridges to form? How does this relationship affect the ability of the sarcomere to produce tension?
Overlapping
Must have an optimal length to work (z-lines can’t be too close or too far to work)
Which way do myosin head groups pull on the actin during an eccentric contraction? What ultimately determines whether an active muscle does a concentric, isometric or eccentric contraction?
Eccentric: head groups pull away from myosin
If the resistance force/effort force wins
What does the muscle look like when the parallel passive elastic elements are contributing most to the pull of that muscle on the tendon or bone?
When passive Is most relevant, it’s lengthened
When active is most relevant, it’s shortened
When a single alpha motor neuron fires in the anterior horn cell of the spinal cord:
a. One sarcomere depolarizes.
b. One myofibril depolarizes.
c. One fiber depolarizes.
d. Some of the fibers within the motor unit depolarize
while others rest.
e. All the fibers within the motor unit depolarize.
E
Muscle fibers within a motor unit fire synchronously
You are going to lift a box off the table that you anticipate is quite heavy. What motor units will you tend to recruit first and what characteristics do they have?
What if the box turns out to be empty?
What if you don’t know?
Larger
Smaller
Start with smaller then work up
If the shoulder flexion force generated by the anterior deltoid is inadequate to flex the shoulder, what options are available to you (or, more correctly, to your nervous system) to increase the force of shoulder flexion?
o Increase frequency
o Recruit another muscle
o Increase the other muscles (coracobrachialis)
o Motor units
o Larger motor units
o Type of fiber
o It would recruit surrounding motor units to compensate
Given the Physical Stress Theory (Mueller and Maluf), what is the response of a tendon to rapidly repeated forceful muscle contractions several hours a day for one or more weeks?
Injury
What structure contributes to the passive stiffness of a muscle?
Titin
What structure(s) is mainly responsible for extensibility or flexibility of a resting muscle?
Endomysium, perimysium
If you had prolonged muscle soreness of a muscle, the day after a workout. What type of muscle contraction would the muscle tolerate well?
Concentric high velocity or eccentric high velocity and why?
Concentric and high velocity
There is more tension during an eccentric contraction, so it wouldn’t make sense
Concentric produces less tension (because of Titin slack/tightening)
Is Titin slack/taut during concentric contraction?
Slack
Which has more Type I collagen? (Ligament or Tendon)
Tendon
Which is under more tensile stress at END ROM?
Under muscle contraction?
Ligament
Tendon
In which are collagen fibers parallel/same direction as force?
Densely packed in direction of many different forces?
(Ligament or Tendon)
Tendon
Ligament
Which has more elastin? (Ligament or Tendon)
Ligament
Enthesis
Fibrocartilaginous attachment of tendon/ligament that attaches to the bone
Sharpey’s fibers
The roots of the entheses
Importance of the 4 zones of Enthesis
Gradual change in tissue composition
Function goes from tendon resisting tensile forces»_space; bone resisting compressive forces
4 zones of enthesis
- Tendon proper
- Uncalcified fibrocartilage
- Calcified fibrocartilage
- Bone
Endotenon
Internal to tendon
Peritendon is…
aka. ..
fx. ..
Epitenon + Paratenon
aka “Tendon Sheath” (when filled with synovial fluid)
protects tendon by allowing slide over tendon
Fx of bursa
Reduce friction between moving tissues (bw skin/bone, tendon/bone, ligament/bone, muscle/bone)
Where is fibrocartilage found?
What type of cartilage does it have?
What forces does it resist?
In cartilaginous joints
Type I cartilage
Resist tensile AND compressive forces
Where is hyaline cartilage found?
What type of cartilage does it have?
What forces does it resist?
In synovial joints
Type II cartilage
Resist compressive forces
How does hyaline cartilage get nutrients?
Compression of joint from PGs and H2O leads to nutrients diffusing into the space after the load is removed
4 zones of hyaline cartilage:
- (Tangential) resists parallel movement, reduces friction between joints
- (Middle/Transitional) Type II collagen forms meshwork, keeps H2O + PGs contained, absorbs compressive forces
- (Radial) Perpendicular collagen fibers hold onto bone
- (Bone) Calcified cartilage layer that is impervious and prevents nutrients from crossing into bone
What is responsible for bone synthesis?
Bone resorption?
Osteoblasts
Osteoclasts
Where is Trabeculae found?
In cancellous/spongy bone
Cortical bone aka
compact bone
Cancellous bone aka
spongy
How are trabeculae organized
direction of stress/strain on bone
Fx of periosteum
1) Attaches ligaments, tendons, cartilage to deeper bone
2) Houses precursors to osteoblasts/clasts
3) Blood nutrients
Wolff’s law
What does it say about someone who is overweight?
Change in bone matches fx
Bone will be denser/thicker
SAID principle
Specific Adaptation to Imposed Demand
Load
Stress
Strain
Force applied
Force applied to a cross-sectional area
% in length/cross section of a structure
What happens to the stiffness of a tissue if it has bigger cross sectional area?
Increases stiffness
What happens to the stiffness of a tissue if it is longer?
Decreases stiffness
What is the inverse of stiffness
Compliance
How do you describe ultimate failure for:
- Ligament
- Tendon
- Cartilage
- Bone
- Sprain
- Tear
- Tear
- Fracture
How would you classify these joints by movement?
- Fibrous
- Cartilaginous
- Synovial
- Synarthrosis (little/no mvmt)
- Amphiarthrosis (some mvmt)
- Diarthrosis (free mvmt)
What are common features of synovial joints?
- Joint capsule
- Synovial membrane/fluid
- Hyaline cartilage
What are the 2 layers of synovial joint capsule?
What are their fx?
1) Fibrous
Encloses cavity, stability, sensory endings
2) Synovial
Lubrication, vascularized
What kind of joints are:
- Uniaxial
- Biaxial
- Triaxial
- Hinge/pivot joints
- Condyloid/saddle joints
- Plane + ball/socket joints
Convex on concave rule
Concave on convex rule
Roll and glide occur in opposite direction
Roll and glide occur in same direction
What affect do these have on joint mobility?
1) Large bony prominence
2) High elastin content
3) Hypertonic muscles
4) Joint capsule in plastic range
1) No effect
2) Hypermobility
3) Hypomobility
4) Hypermobility
What is the membrane that covers a muscle cell?
Sarcolemma
What is the contractile unit of a muscle? And how are they separated?
Sarcomere
Z discs