Muscle Structure and Function Flashcards

1
Q

Provide an overview of muscle structure

A
  • Sarcomere, myofibril, muscle fibre, fascicle, muscle
  • Sarcomere: Smallest contractile unit, contain protein filaments (A and M) , between 2 transverse Z discs and H zone in middle
  • Myosin: Thick filaments with globular heads (attach to actin)
  • Actin: Thin filaments, twisted helix, tropomyosin and troponin
  • Postural (higher type I)
  • Power muscles (higher type II)
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

What are the mechanisms of muscle contraction at rest vs contracting

A
  • Rest: No connection between A and M, high affinity, unable to bind due to tropomyosin (covering bind site on A) and troponin (holds tropomyosin in place)
  • Ca: Facilitates removal of T and T
  • ATP: M head binds ATP and produces ADP, leads to cross bridge and power stroke
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

Describe the process of sliding filament model

A
  • AP triggers voltage sensitive proteins / Ca channels in sarcoplasmic reticulum to open
  • Ca floods into cell, troponin + Ca bind → movement of tropomyosin away from active sites
  • M heads + ADP + P + energy → head extends = binds to A
  • Releases stored energy and M changes shape → pull on strands and shrink sarcomere
  • Generate force (power stroke)
  • ADP + P unbind → new ATP binds in place on M head → release from A, breakdown ATP to ADP + P and repeat process on another A
  • Cross bridges detach, Ca unbinds and M cannot bind to A anymore
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

What is excitation contraction coupling

A
  • Sequence of events that begin with a neural impulse and end with contraction, excitation of a motor nerve, propagation of an action potential
  • Events at the neuromuscular junction, calcium release from sarcoplasmic reticulum
  • Sliding filament theory and muscle contraction
  • Power production is the key determinant of recruitment
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

What are type I muscle fibres

A
  • Slow twitch (slow contractile speed)
  • Small in diameter
  • Low force production
  • High oxidative (aerobic) capacity
  • Many mitochondria / capillaries / myoglobin
  • High aerobic enzyme activity and highly resistant to fatigue
  • Dominant muscle fibre during exercise below CP
  • Linear relationship between number of slow twitch and VO2max
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

What are type II muscle fibres

A
  • Fast twitch (fast contractile speed)
  • Large in diameter
  • High force production and glycolytic capacity
  • Many glycolytic enzymes, greater glycogen and PCr stores
  • Highly fatiguable, recruited during high-intensity exercise
  • A: Few mitochondria, highly fatiguable, anaerobic, low efficiency, exercise higher than CP
  • X: Many mitochondria, slightly fatiguable, combination, moderate efficiency, short high intensity exercise (<1min)
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

How do fibres respond to training

A
  • Aerobic training, conversion of type II X to type II A to type I
  • Distance runners 70-80% type I
  • Track sprinters 25-30% type I
  • Non-athletes 47-53% type I
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

How are muscle fibre types assessed

A
  • Muscle Biopsy
  • Site is anaesthetised, small incision is made (1-3cm)
  • Needle inserted into muscle
  • 10-100mg sample is extracted (grain of rice)
  • From metabolically active sites
  • Sample stained to identify fibre type
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

What is the purpose of training

A
  • Improvements in health and performance
  • Cardiorespiratory fitness
  • Muscular strength and endurance
  • Body composition, flexibility, speed, agility, power, adaptation
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

What is overloading

A
  • Principle of training
  • Training load beyond level athlete is accustomed to
  • Progressive overloading is required for continued improvement
  • Adequate recover and sufficient stress prevent overtraining
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

What is adaptation and reversibility

A
  • Principle of training
  • Training adaptation is not permanent, decay once stimulus is removed
  • Improvement only possible if stimulus increases over time
  • Same load = adaptation and then plateau
  • Excessive stimulus = inability to adapt, decrease in performance
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

What is the FITT principle

A
  • Training loads can be monitored / modified, assessing
  • Frequency (how often)
  • Intensity (how hard, energy expenditure, RPE)
  • Time (how long)
  • Type (training method(s))
  • Higher relative training intensity increases max VO2
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

What are the principles of training / their purpose

A
  • Specificity
  • Overload
  • Reversibility
  • Applying these principles promotes improvement through adaptation
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

What is specificity

A
  • Principle of training
  • Responses to training are specific to type of exercise, muscle groups and energy systems used
  • SAID Principle: Adaptations are specific to stimulus
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

What is karvonens HR reserve

A
  • HRR = difference between resting and maximal HR
  • HRR = HR max – HR rest
  • Training HR (THR) should be 80-90% of HR max for endurance athletes
How well did you know this?
1
Not at all
2
3
4
5
Perfectly