Lecture 19 Flashcards
When we are exercising, we are activating __________ muscles. This means that we need activate _________ systems to make energy, and for that he needs to get oxygen to the skeletal muscles, so the ____________ and _____________ systems have to kick in.
Skeletal
energy
cardiovascular
respiratory
What three things occur when we are exercising?
- muscles are contracting
- there is increased respiratory rate
- heart rate and contraction increases
What does muscle composition refer to?
the ratio of muscle fibre types
Describe the two types of muscle fibres
Type II (a and x)/ fast twitch: peak tension in 50ms
Type I/slow twitch: peak tension in 110 ms
What can the type II fibres be divided into? Describe these
Type II a (intermediate fibres) and type II x fibres (really fast explosive fibres)
Why are we interested in measuring the muscle fibre types in muscles of athletes?
Because muscle fibres have really large differences in their contractile speeds
Describe the power of the muscle types
Fast twitch fibres produce a lot lot power
Describe the fatigue of the muscle types
Type I has a lot more resistance to fatigue
Describe type 2 a fibres?
They are in the middle of fast and slow twitch and can be pushed in either direction. They have both metabolic and mechanical potential where they can become very very oxidative like Type 1 or be made to produce a lot of power like type 2 x
What determines what type of muscle fibres you have?
- 50% genetic link
- early life sports can influence adult levels of muscle types (in younger individuals there is a given proportion of hybrid fibres that share some of the characteristics of either one of these fibres, and those hybrid fibres can specialize and become either type 1 or type 2 depending on what you do at a very young age)
There can also be shifts in the fibre type composition but really only in those type 2 subtypes. Type IIx fibres for example if you went and did a whole lot of endurance training then after a few weeks they would shift into the type II a intermediate fibres. What doesn’t seem to happen in the short and moderate term, a type 1 will not shift into a type 2 fibre. So really in the short to moderate term, only shifts within the type 2 fibres.
What is magnetic resonance spectroscopy?
MRI technicians will scan different muscles in athletes measuring a particular metabolite in skeletal muscle called carnosine.
What is carnosine?
This is 2 times higher in your muscle fast twitch fibres than your slow twitch fibres. Carnosine is very stable in muscles in response to training, and is not very responsive to diet changes. However, one supplement that does affect is beta alanine.
Carnosine buffers H+ ions. Because more H+ is produced in type II fibres, we can estimate what type of muscle fibres you have
Describe the type 1 fibres during exercise
There is high aerobic endurance. This means that we can maintain exercise for prolonged periods and it requires oxygen for ATP production.
It efficiently produces ATP from fat and carbohydrate
Describe type II fibres during exercise
Poor aerobic endurance, fatigues quickly
- Type IIx (fast) is seldom used for everyday activities and is instead used for explosive sprints
- Type II a (intermediate)
there is more force, faster fatigue than type I for short, high-intensity endurance events
Summary of muscle fibre types are found on what slide?
15
As intensity increases, the recruitment order of muscle fibre types is
Type I, Type IIa, Type IIx
What is the energy for metabolism?
ATP
Where do we get ATP from?
We have very limited ATP stores because what we do have is converted to ADP and Pi by ATPase. We must constantly synthesise new fuel stores
What is the fast ATP generation pathway?
the phosphocreatine pathway
Describe the phosphocreatine (PCr) pathway to generate ATP
This is a fast ATP generation. When ATP is used by ATPase, the ADP and Pi can be recycled to make more ATP from PCr. PCr is broken down into creatine and Pi and free energy and then the Pi and ADP are combined to form ATP. PCr can recycle ATP during exercise until it is used up. It is anaerobic.
How many ATP are yielded from one PCr?
1
After how long are the PCr stores used up?
3-15 seconds
Describe the glycolysis pathway to generate ATP
This is a fast ATP generation. There is no O2 required. Glucose is converted to pyruvate via a series of steps which produces 2 ATP.
What is the energy substrate in the glycolysis pathway?
muscle glycogen stores
The amount of glucose stored in the muscle allows us to use the glycolysis pathway for how long until the stores are used up?
15s - 2 mins
What are the two slow ATP generation pathways?
the TCA pathway
oxidation of fat (lipids)
Describe the TCA pathway for generating ATP
Oxygen is required. Pyruvate is converted to acetyl-CoA and through many steps, CO2 is produced as waste, cofactors are produces and GTP. In the process, 32-34 ATP are made.
Describe the oxidation of lipids
Fat stores are converted into fatty acids and glycerol. Fatty acids can enter β oxidation and the glycerol is converted to acetyl-CoA to enter the CAC. Overall there is a total of 460 ATP produced
How can protein act as a fuel source?
This is normally due to starvation. Protein is converted to amino acids and then to glucose then to acetyl-CoA to enter the citric acid cycle
What is ATP needed for?
for contraction/relaxation
What slide is a good summary slide?
slide 26
Which muscle fibre type are termed fatigue resistant?
a. Fast twitch (Type IIx)
b. Intermediate twitch (Type IIa)
c. Slow twitch(Type I)
d. None of the above
c. Slow twitch(Type I)
Phosphocreatine (PCr):
a. is a substitute for troponin in smooth muscle
b. destroys excess acetylcholine (ACh) at the neuromuscular junction
c. stores energy from ATP in the muscle cell
d. is a neurotransmitter found in smooth muscle
c. stores energy from ATP in the muscle cell
A muscle fibre gains 60 ATP’s from metabolism. How many glucose molecules were consumed to yield this much energy if the muscle fibre is operating anaerobically?
a. 120
b. 30
c. 38
d. 2
30
Weightlifters training anaerobically (for strength rather than endurance) emphasize which muscle type?
a. Slow twitch (Type I)
b. Fast twitch (Type Iix)
c. Neither
d. Both
b. Fast twitch (Type Iix)
