Quiz 3 Flashcards
1
Q
what is histochemical analysis
A
the analysis of tissues involving
- tissue extraction
- chemical treatment of the tissue
2
Q
what are the steps of histochemical analysis
A
- select suitable tissue (choosing appropriate muscle(s) to remove tissue sample)
- prep skin by cleaning and injecting area with anesthetic (xylocaine)
- insertion made with scalpel once area is numb (must be deep enough to penetrate subcutaneous tissue & fascia)
- needle inserted into incision
- tissue coaxed into space within notch
- blade pushed down to clip off tissue
- muscle tissue is treated once extracted
3
Q
what are the three parts of a biopsy needle
A
- outer tube has a notch
- middle portion consists of circular blade
- inner portion is used to push out any tissue that gets lodged in the blade
4
Q
what muscles are selected for histochemical analysis
A
- usually muscles that function as “prime movers”
- helps if the selected muscles are “superficial” and or sufficient size
5
Q
what is the advantage of using the needle biopsy technique
A
it is much less invasive than the suture biopsy technique and therefore more suitable for sports-related muscle research
6
Q
what controls muscle activity
A
enzymes
7
Q
what enzyme is being analyzed and stained for
A
acto-myosin ATPase
8
Q
why is it necessary to do the analysis as soon as possible
A
muscle activity fades over time
9
Q
characteristics of early onset muscle soreness
A
- localized discomfort
- felt immediately following the exercise
- can persist for several hours
- attributed to metabolic changes (increases in H+ associated with lactate appearance in the blood)
10
Q
characteristics of delayed onset muscle soreness
A
- gradual increase in intensity following activity
- peaks between 24 and 48 hours post exercise
- will decline over next 5-7 days
11
Q
what is the primary reason for the onset of DOMS
A
eccentric muscle contractions
- fewer motor units used to produce the same tension/active motor unit
- muscle soreness caused by fewer cross-bridges being called on to support the same tension when z-lines are moving away from each other
12
Q
what do the electron microscope pictures show (DOMS)
A
damaged/jagged z line
13
Q
what terms are used to refer to the mechanical disruption caused by DOMS
A
- muscle soreness
- z-line streaming
- sarcolemma damage –> cell necrosis
- inflammatory reaction
- macrophage activity
- increased pain
14
Q
describe the inflammatory reaction to DOMS
A
- necessary to eliminate damaged tissue & prepare for repair
- triggered by cytokines (interleukin-1)
- increased blood flow, muscle temperature, and macrophage activity
15
Q
describe macrophage activity caused by DOMS
A
- presence of cellular debris –> increased macrophage activity –> inflammation & swelling –> activation of immune system
16
Q
describe increased pain caused by DOMS
A
edema & chemical substances (Prostaglandins) –> increased sensitivity of pain receptors by stimulating muscle afferents –> increased pain (as long as 4-5 days, full effects manifested between 1 & 3 days)
17
Q
why is the lactic acid model inaccurate
A
lactic acid has a half life of 15-25 minutes, fully cleared from the mm within an hour
18
Q
what is the lactic acid model
A
DOMS caused by accumulation of lactic acid
19
Q
what is the mechanical trauma model
A
mechanical forces in contractile & elastic tissue result in structural damage
20
Q
what structural changes are caused by DOMS
A
- z-line streaming: significant disruption of z-line orientation (appear jagged)
- sarcolemma damage results in tissue permeability & blood flow –> results in disruption of calcium homeostasis –> leads to cell necrosis
21
Q
what is the function of structural proteins
A
- extrasarcomeric cytoskeleton
- stabilize hexagonal array of myosin lattice
- when they are selectively destroyed, “significant” myofibrillar disruption takes place
22
Q
why is desmin important
A
- filament that interconnects z-lines of adjacent myofibrils
- maintains cytoskeletal integrity by linking Z bands to plasma membrane
- contributes to muscle structural & cellular integrity, force transmission & mitochondrial homeostasis
23
Q
which fiber types are more likely to be disrupted with activity that results in DOMS
A
type II fibers may be selectively affected by high intensity eccentric activity
24
Q
describe the healing period from DOMS
A
- formation of protective proteins
- increase in remodeling collagenases, collagen, growth factors & enzyme inhibitors
- prevention of further incidence of DOMS during subsequent exercise sessions
- static stretching
- use of NSAIDS (ibuprofen, aspirin)
25
explain active insufficiency
- occurs when the muscle is already shortened by changing the joint angle
- prevents muscle from shortening further, reducing the ability to exert optimal force
26
explain passive insufficiency
occurs when the muscle is already stretched & not able to stretch further (reaching to your toes)
27
what is the PEC
Parallel Elastic Component of muscles
- derives from muscle membranes
- supplies resistance when muscle is passively stretched
- sarcolemma, epimysium, perimysium, endomysium (all parallel with contractile components)
28
what is the SEC
- Series Elastic Component of muscles
- determines the elasticity of skeletal muscle & human skeleton
- stores energy when stretched
- tendons
29
describe the stretch shortening cycle
- the cycle of muscle efficiency when muscles that are lengthened are shortened immediately to generate optimal force output
- muscle action where muscle is first actively stretched then immediately shortened
30
what is the importance of the stretch shortening cycle in sports
- elastic energy is stored during the stretch phase and released explosively during the shortening phase
- improves performance and increases power output in activities that require explosive movements (running, jumping, throwing)
- in sports, isometric contractions reduce muscle performance because the stored potential energy is lost in the form of heat
31
how does muscle force increase in the short term (two ways, order is important)
1. increase the frequency of active motor units
2. increase the number of active motor units through recruitment
32
describe viscoelasticity
- structures behave as both liquid & solid
- biological tissues have both viscous (fluid like) and elastic (solid like) properties that influence how they respond to mechanical stress, strain & deformation
33
how does viscoelasticity apply to muscle function in jumping and landing activities
- when potential energy is stored in SEC --> can be lost during isometric contraction --> decrease in jump height
- when recoil effect carried out immediately (instant concentric contraction post eccentric contraction) = little potential energy loss & jump height increases or is maintained
- jumping: tendons & muscles stretch & store elastic energy (act like springs), viscous component of tendons dissipate some energy = stretch more controlled & efficient
- landing: elastic components of tendons & muscles stores energy & viscous component dissipates some energy gradually = prevent muscles from being overloaded by sudden impact
34
what is the force velocity relationship
- forces generated by a muscle = function of its velocity
- faster contraction = less force
- slower contraction = more force
- loads move faster with less load & progressively get slower as load increases
35
describe concentric contractions and what happens at the myofibril level (cross-bridges)
- increase in cross bridge attachment
- more acto myosin filaments connecting when sliding toward center
- more cross bridges formed as actin moves toward z line
36
describe eccentric contractions and what happens at the myofibril level (cross-bridges)
- decrease in cross bridge attachment
- less acto myosin filaments connecting when sliding away from the center
- cross bridges are released as actin moves away from z line
37
what do we know about "reaction time"? what example did we use?
- amount of time required for the motor cortex to address the specific alpha motor neurons
- batting in baseball: amount of time for ball to arrive at plate (0.41 to 0.46 seconds) - amount of time it takes to swing bat (0.3 secs) = amount of time for batter to activate arm & hand muscles (0.16 seconds)
- ruler drop test: 6 inches = 0.175 seconds
38
describe the differences in architecture & function between sarcomeres arranged in series
- in line horizontally
- # of sarcomeres in series determines velocity of shortening of the fiber (velocities become additive)
- each individual sarcomere stays at its optimal length = preserves length tension relationship
- faster but longer & usually weaker
39
describe the differences in architecture & function between sarcomeres arranged in parallel
- in columns
- more arranges in parallel = greater capacity for exerting force
- slower but stronger
40
what is muscle architecture
arrangement of muscle fibers relative to the axis of force generated
41
what do we know about "specific force"
- between 22 to 28 N per sq cm
- more size/mass = more force production --> reason for weight classifications
42
how do we define specific force
- force that can be sustained by the muscle fibers themselves
- defines intrinsic property of muscle
43
explain PCSA and how it is defined
- Physiological Cross Section Area
- directly proportional to the max tetanic tension of the muscle
- sum of the x-sectional areas of all the muscle fibers within the muscles (usually in the direction of muscle fibers)
- two factors: whole muscle length, cross sectional area
44
explain temporal summation
- time required for activation, contraction, and relaxation
- stimulus gradually added over short period of time (successive stimuli = does not have to stretch the passive structures)
- pulses delivered consecutively with very short duration in between = less time for relaxation = higher force generated = external motion at joint
45
describe neural stimulation frequency
arrival of a single AP in muscle fiber produces very brief weak action of fiber (TWITCH), which does not result in full contraction of muscle
46
explain the length tension relationship
- each muscle has an optimal length that exists for development
- corresponds with maximum overlap of thick & thin filaments
- muscle's ability to produce force is greatest at ~120-130% resting length
47
what do we know about the force-velocity relationship when comparing concentric vs eccentric movement
- concentric: lighter loads can be moved at a faster velocity, heavier weights = velocity decreases until weight cannot be moved any more --> isometric hold
- eccentric: muscles will lengthen to act as resistors instead of producing force, load too heavy = muscles will lengthen and resist weight in opposite direction
48
how do we interpret the "untrained" and "trained" muscle curves for different sports
- untrained muscles move at a certain velocity when introduced for the first couple times
- over time, velocity increases as training progresses
- lighter loads = moved faster = shifts curve to right
- requires increase of load over time bc lighter weight no longer needed for training = max load limit increase
49
what is the effect of prestretching
muscles perform more work when they shorten immediately after being stretched than when in the state of isometric contraction
50
what is the underlying rationale for pennation
although there is a drop off in the portion of force developed by the sarcomeres, more fibers can be packed into a given area of muscle
51
factors affecting development of tension in muscles
1. firing frequency, muscle fiber recruitment, synchronization of active fibers
2. relative size of muscle
3. temperature of muscle
4. degree of muscle fatigue
5. degree of pre stretch
6. angle of muscle pull
52
how can a greater load be tolerated during eccentric contractions
- muscle is acting passively
- assumes role of resistance rather than force generator
