Lecture 2: Muscle physiology & adaptations Flashcards
1
Q
epi
A
on
2
Q
peri
A
around
3
Q
endo
A
in
4
Q
Connective tissue
A
connects all components of the body
- why muscle does not rip off the bone
- continuous with each other around fibres, bundles, and belly
5
Q
Largest to Lowest
A
- Epimysium- continues with tendon
- Fasciculus- bundle of muscle fibres
- Perimysium-around each bundle of fibres
- Single muscle fiber-muscle cell
- Endomysium-around each fibre
- Myofibril- smallest unit
6
Q
Motor unit
A
motor neuron and all its associated fibres
7
Q
Nueromuscular Junction
A
junction between nerve cells and fibres
8
Q
All or None Principle
A
- either reaches threshold and fires or it doesn’t
- if stimulus reaches threshold then we get complete contraction
- can stimulate a few or large number of muscle fibres
9
Q
Myofibrils
A
Actin and Myosin
- arranged parallel with muscle fibres
- what gives muscle its striated appearance
10
Q
Sarcomeres
A
functional unit of contraction
11
Q
Cross-bridges
A
hook up to actin filament (like a hand over hand action pulling a rope)
12
Q
myosin
A
thicker and darker
13
Q
actin
A
thinner and lighter
14
Q
Muscle Contraction
A
-when a motor neuron stimulates muscle fibres they will contract due to the sliding filament theory
15
Q
Sliding filament theory
A
-cross bridges on the myosin attach to the actin and pull the thin filaments closer together, resulting in a shortening of the sarcomere (Z-lines more closer together)
16
Q
H-zone
A
thick filaments only, myosin only
17
Q
I-band
A
actin, light filaments
18
Q
more cross-bridges=
A
stronger contraction
19
Q
Stretched muscle
A
draw diagram
- has I-band, A-band, and H-zone
- z-line is not touching A-band
20
Q
Completely Contracted Muscle
A
- NO I-band or H-zone
- z-line tight with a-band
21
Q
Resting Muscle
A
- small I-band
- small H-zone
- z-line not touching but close to A-band
22
Q
What is necessary for myosin crossbridge cycling with actin filaments
A
- Calcium and ATP
- Ca binds with protein on actin causing the protein to move out of the way exposing the binding site to the myosin globular head
23
Q
What dictates the force of contraction
A
-number of cross-bridges that are attached to actin filaments at any instant in time
24
Q
Type II Fibres
A
- fast-twitch
- higher force productions
25
Type I
-contraction sustained longer, force production slow, fatigue resistant, limited force production
26
Type IIx
- ability to change to type IIa through training
| - high power capabilities
27
Type IIa
- more fatigue resistant than IIx
| - less power capabilities
28
Size principle
lower threshold units are recruited first
-type I=lower threshold=recruited first
type II=higher threshold=high force=recruited later
29
Exception to Size principle
with heavy resistance training all muscle fibres get bigger because they are all recruited in consecutive order by their size to produce high levels of force,
- in advanced lifters the CNS might adapt by allowing these athletes to recruit some motor units not in consecutive order
* Selective Recruitment
- ability to recruit type II fibers & inhibit lower threshold units
- adaption
30
Sports with low Type I
100m sprint
Olympic weight-lifting
Football wide receiver
Basketball
31
Sports with high type 1
```
800m run*
marathon
barbell squat*
soccer*
field hockey*
football lineman*
distance cycling
*=high in both
```
32
How can the force output of a muscle be changed?
- changing number of motor units activated
| - changing frequency of activation of individual motor units
33
Parallel (Fusiform) Muscle
more length
wide ROM
ex) bicep
34
Convergent muscle
more power
| wide surface area
35
pennate muscle
give more power due to wide surface area
| -bi, uni, multi (based on # of tendons)
36
Sphincter
open and close
37
Power
from surface area
38
ROM
from length
39
Isometric
muscle contraction that does not produce movement
40
Isotonic
contraction that does produce movement
| eccentric or concentric
41
Concentric
fibers and attachments move closer together causing joint movement
42
Eccentric
muscle fibers lengthen
- strongest
- gravity helps out
- more cross bridge alignment, keeping cross bridges on the actin=no reattaching, just continuous
43
Proprioceptors
-specialized sensory receptors that provideCNS with info needed to maintain muscle tone and perform complex coordinated movements
44
Muscle spindle
protects
- modified muscle fibres that provide info concerning muscle length and rate of change in length, help control activation of the muscle
- detects shortening and helps increase contraction
45
GTO
- relaxes the muscle
- located in tendon
- attached end to end with extrafusal fibres
- work to protect excessive tension by inhibiting muscle activation
- senses tension it sends signal to relax muscle
- inhibits contraction
46
Phosphagen system
ATP-PCr
- provides immediate ATP energy
- fast powerful movements
- short-duration, high intensity
- long rest periods
- peak= 1st few seconds
- capacity= 20 to 30s
47
Glycolytic system
breaks down glucose to lactic acid
- next readily available source of ATP
- longer, less intense exercise
- shorter rest periods
- peak=20-30s
- capacity=2-3min
48
Aerobic System
oxidative
- role in ,maintaing power output and recovering energy stores
- lower intensity
- long duration
ex) running, walking, skiing
49
Aerobic endurance training
-does not enhance muscle strength or size
-may compromise benefits of resistance training
why?-competing adaptations
-can start breaking down protein in muscle
50
when may aerobic training help increase strength?
- unfit sedentary people
- circuit training
- cross-fit
51
Does resistance training impact VO2 max?
no- not on aerobic power either
52
Major Adaptations to Resistance vs. Aerobic Training
See table 5.2 and 6.1
53
Overtraining
excessive frequency, volume, or intensity of training resulting in fatigue, illness, or injury
-can cause dramatic decrease in performance of all training levels
54
Stages of Training
acute stimulus-> overload -> acute fatigue -> overreaching (planned) -> chronic fatigue -> overtraining
55
Markers of Overtraining
- acute epinephrine and norepinephrine increases beyond normal exercise-induced levels
- psychological effects- low desire to train, low joy from training
- altered resting HR, ^submax HR, ^muscle soreness, ^injury, altered cortisol concentration, lower VO2 max, altered BP, low muscle glycogen
56
POMS
profile of mood states
- good profile vs. bad profile
- inverted profile can be an indication of overtraining/burnout (iceberg profile)
57
Detraining
- cessation of anaerobic training or large reduction in frequency, volume, intesnity or combination of variables
- can cause decrements in performance and loss of physiological adaptations
- can occur in 2 weeks with resistance+aerobic training
- can regain quicker if previously fit
58
Physiological Responses to Training and Detraining
-a detrained person is likely to be better at aerobic activities than resistance
FIG- 5.6
59
Neural Adaptations
- motor unit recruitment, firing rate, GTO inhibition take place first before increase in physical size
- will be able to lift more due to this
60
MES
minimal essential strain
- bone cells stimulated and migrate to area of stress to make bone thicker
- when forces that reach or exceed a threshold stimulus initiate new bone formation in the area experiencing mechanical strain
61
Stimulating bone formation
- use exercises that directly load particular regions- specificity of loading
- use structural exercises involving multiple joints ex) squat, dead lift, power clean
- Prgressively overload the musculoskeletal system and increase load
- vary exercise selection
62
Hypertrophy
- increase in synthesis of contractile proteins
- increase in number of myofibrils
- increase in diameter
63
Hyperplasia
- theory that preexisting muscle fibres splits or satellite cells, ^# of muscle fibres
- does not exist in humans
64
Strength Adaptations
high load, few repetitions, full recovery period
65
Muscle Size
moderate load
high volume
short to moderate rest periods
8-12 reps, building some muscle, more toning
66
Muscular Endurance
low intenisty
high volume
little recovery
-12-15-20 reps
67
Connective tissue adaptations
increased collagen metabolism
| -must adapt and grow and respond with hypertrophy
68
Collagen
building block of all types of connective tissue
69
If connective tissue doesn't grow at same rate...
compartment syndrome puts pain on muscle
70
Specific changes within a tendon that increase in its cross-sectional and strength in response to functional overload include...
- increase in collagen fibril diameter
- ^# of covalent cross-links within a fibre of increased diameter (ability to stick together)
- ^ in # of collagen fibres
- ^ in packing density of collagen fibres
- lead to stronger connective tissue
71
Stimulating Connective Tissue adaptations
- exercise of low to moderate intensity does not change collagen content of connective tissue
- high intensity loading results in a net growth of involved connective tissue
- the better the ROM the more efficient the diffusion throughout the ROM of the join
72
Cartilage as a connective tissue is...
avascular (does not get its own blood supply)
- meniscus injuries do not heal on their own
- must get diffusion from surrounding tissues
