Muscular system Flashcards
Physical Activity is…
a movement that occurs due to the combined and coordinated efforts of the muscular, nervous and skeletal systems.
muscles produce movement by…
generating forces to rotate bones around joints
3 muscle types are..
smooth – internal organs
cardiac – heart muscle
skeletal – attaches to bone and causes them to rotate around joints
A skeletal muscle structure
- Epimysium –connective tissue that covers the muscle belly
- Fascicle/fasciculus – bundles of muscle fibers which compose a muscle belly
- Perimysium – connective tissue surrounding the fascicle
- a single muscle fiber within fascicle
- Endomysium – connective tissue surrounding and separating muscle fibers within a fascicle.
the role of the connective tissue surrounding muscles
help to transmit the force of muscle action to the bone via Tendon.
Muscle fiber is
a cell which is specialized to contract and generate force/tension.
It has the same structural components as other cells.
A tendon is … and serves to …
A tendon is a fibrous connective tissue which attaches muscle to bone. Tendons may also attach muscles to structures such as the eyeball.
A tendon serves to move the bone or structure.
A ligament is … and serves to…
A ligament is a fibrous connective tissue which attaches bone to bone, and usually serves to hold structures together and keep them stable.
A muscle cell structural components are…
sarcolemma, nuclei, sarcoplasm, organelles, myofibril, myofilaments
sarcolemma is…
its function…
it’s a plasma membrane surrounding a cell.
It encloses cell content.
Functions to:
1) regulate into/out passage of materials (e.g. glucose)
2) receive/conduct stimuli or electrical impulses called action potentials
the nuclei in the muscle cell contains…and responsible for…
1) contains the genetic material (DNA)
2) responsible for initiating the processes associated with adaptation to exercise: e.g. muscle cell enlargement or hypertrophy
Sarcoplasm (cytoplasm) contains…
1) ATP (adenosine triphosphate)-the only direct source of energy for muscle action
2) phosphocreatine
3) glycogen
4) fat droplets
5) organelles
ATP (adenosine triphosphate) is….
an energy-carrying molecule found in the cells of all living things. A-P-P-P
What cells use ATP for?
for 3 general types of tasks:
1) to drive metabolic reactions that would not occur automatically;
2) to transport needed substances across membranes;
3) to do mechanical work, such as moving muscles.
reaction that turns ATP into energy
- Chemically, ATP is an adenine nucleotide bound to three phosphates.
- There is a lot of energy stored in the bond between the second and third phosphate groups that can be used to fuel chemical reactions.
- When a cell needs energy, it breaks this bond to form adenosine diphosphate (ADP) and a free phosphate molecule.
- In some instances, the second phosphate group can also be broken to form adenosine monophosphate (AMP).
- When the cell has excess energy, it stores this energy by forming ATP from ADP and phosphate.
- ATP is required for the biochemical reactions involved in any muscle contraction. As the work of the muscle increases, more and more ATP gets consumed and must be replaced in order for the muscle to keep moving.
3 systems to create ATP are…
1) Phosphagen system
2) Glycogen-lactic acid system
3) Aerobic respiration
Phosphagen system
A muscle cell has some amount of ATP floating around that it can use immediately, but not very much – only enough to last for about three seconds. To replenish the ATP levels quickly, muscle cells contain a high-energy phosphate compound called creatine phosphate.
The phosphate group is removed from creatine phosphate by an enzyme called creatine kinase, and is transferred to ADP to form ATP.
The cell turns ATP into ADP, and the phosphagen rapidly turns the ADP back into ATP. As the muscle continues to work, the creatine phosphate levels begin to decrease. Together, the ATP levels and creatine phosphate levels are called the phosphagen system. The phosphagen system can supply the energy needs of working muscle at a high rate, but only for 8 to 10 seconds.
glycogen lactic-acid system
Muscles also have big reserves of a complex carbohydrates called glycogen. Glycogen is a chain of glucose molecules. A cell splits glycogen into glucose. Then the cell uses anaerobic metabolism (anaerobic means “without oxygen”) to make ATP and a byproduct called lactic acid from the glucose.
About 12 chemical reactions take place to make ATP under this process, so it supplies ATP at a slower rate than the phosphagen system. The system can still act rapidly and produce enough ATP to last about 90 seconds. This system does not need oxygen, which is handy because it takes the heart and lungs some time to get their act together. It is also handy because the rapidly contracting muscle squeezes off its own blood vessels, depriving itself of oxygen-rich blood.
There is a definite limit to anerobic respiration because of the lactic acid. The acid is what makes your muscles hurt. Lactic acid builds up in the muscle tissue and causes the fatigue and soreness you feel in your exercising muscles.
aerobic respiration
By two minutes of exercise, the body responds to supply working muscles with oxygen. When oxygen is present, glucose can be completely broken down into carbon dioxide and water in a process called aerobic respiration.
The glucose can come from three different places:
Remaining glycogen supplies in the muscles Breakdown of the liver's glycogen into glucose, which gets to working muscle through the bloodstream Absorption of glucose from food in the intestine, which gets to working muscle through the bloodstream
Aerobic respiration can also use fatty acids from fat reserves in muscle and the body to produce ATP. In extreme cases (like starvation), proteins can also be broken down into amino acids and used to make ATP. Aerobic respiration would use carbohydrates first, then fats and finally proteins, if necessary.
Aerobic respiration takes even more chemical reactions to produce ATP than either of the above systems. Aerobic respiration produces ATP at the slowest rate of the three systems, but it can continue to supply ATP for several hours or longer, so long as the fuel supply lasts.
energy supply systems used for:
100 m run
400m run
marathon
The muscle cells burn off the ATP they have floating around in about 3 seconds.
The phosphagen system kicks in and supplies energy for 8 to 10 seconds. This would be the major energy system used by the muscles of a 100-meter sprinter or weight lifter, where rapid acceleration, short-duration exercise occurs. If exercise continues longer, then the glycogen-lactic acid system kicks in. This would be true for short-distance exercises such as a 200- or 400-meter dash or 100-meter swim. Finally, if exercise continues, then aerobic respiration takes over. This would occur in endurance events such as an 800-meter dash, marathon run, rowing, cross-country skiing and distance skating.
Hydrolysis of ATP
Removing or adding one phosphate group interconverts ATP to ADP or ADP to AMP. Breaking one phosphoanhydride bond releases 7.3 kcal/mol of energy.
ATP+H2O→ADP+Pi ΔG = -30.5 kJ/mol
ATP+H2O→AMP+2Pi ΔG = -61 kJ/mol
2ADP+H2O→2AMP+2Pi ΔG = -61 kJ/mol
At pH 7,
ATP4−+H2O⇌ADP3−+HPO2−4+H+
ATP-PC system
The ATP-PC System
If you train any of your clients at high intensity you must understand how this energy system works. Here’s a short(ish) explanation…
As the name suggests the ATP-PC system consists of adenosine triphosphate (ATP) and phosphocreatine (PC).
This energy system provides immediate energy through the breakdown of these stored high energy phosphates. If this energy system is ‘fully stocked’ it will provide energy for maximal intensity, short duration exercise for between10-15 seconds before it fatigues.
Think of the ATP-PC system as the V8 of your energy systems – it provides you with the most ‘power’ because it produces ATP more quickly than any other system and because of this it fuels all very high intensity activities. It’s downfall however is that it burns out very quickly.
How does the ATP-PC system work?
There are only a few steps involved in the ATP-PC which is why it provides energy so quickly.
Steps of the ATP-PC system:
- Initially ATP stored in the myosin cross-bridges (microscopic contractile parts of muscle) is broken down to release energy for muscle contraction. This leaves the by-products of ATP breakdown: adenosine diphosphate (ADP) and one single phosphate (Pi) all on its own.
- Phosphocreatine (PC) is then broken down by the enzyme creatine kinase into Creatine and Pi
- The energy released in the breakdown of PC allows ADP and Pi to rejoin forming more ATP. This newly formed ATP can now be broken down to release energy to fuel activity.
ATPase in this case assists the synthesis of new ATP rather than the breakdown. We see how this works in the diagram below.
During the first few seconds of exercise regardless of intensity, the ATP-PC system is relied on almost exclusively, with energy coming from the breakdown of the ATP stores within the muscles.
These ATP stores last only a few seconds after which the breakdown of PC provides energy for another 5-8 seconds of activity.
Combined, the ATP-PC system can sustain all-out exercise for up to 10-15 seconds and it is during this time that the potential rate for power output is at its greatest.
If activity continues beyond this immediate period, the body must rely on other energy systems to produce ATP as the limited stores of both ATP and PC will be exhausted and will need time to replenish.
These stores are replenished after about two minutes rest.
If activity continues at a high intensity these stores may only partially replenish as there will not be enough energy available for creatine and Pi to reform PC and the rate of ATP breakdown through other energy systems will impede the replenishment of ATP stores in the muscle.
Training the ATP-PC Energy System
To develop this energy system, sessions involving repeats of up to 10-15 seconds of maximum intensity activity/work are required, with approximately two minutes rest between repeats to allow the system to replenish.
There is a more scientific formula for rest periods called the ‘work to rest ratio’. For the ATP-PC system the rest ratio is 1:10/12. This means that for every second of ‘work’ you need to allow 10 to 12 seconds for recovery.
Examples of training that focuses primarily on the ATP-PC system are:
Lifting the heaviest weight you possibly can for one or two repetitions. Sprinting as fast as you can for 50 – 100 metres with 2-3 minute recovery intervals before repeating. Punching a boxing bag as hard as you possibly can for 2 – 3 punches. Getting up out of your chair to go and make a coffee (alright it’s not really ‘training’ but as it requires immediate energy for movement the energy comes exclusively from the ATP-PC system).
Note that when you design training to condition the ATP-PC system you must build in adequate rest and stop the session if the quality of the movements or their power decreases significantly.
When this happens you are starting to work on power endurance (as fatigue is evident) and that is counter productive if your goal is purely to increase the ATP-PC system’s capacity.
For example, if you were training to increase your explosive leaping ability (say for basketball) by jumping as high as you could you would notice that after two or three leaps the next leap may not get you the same height.
You would then stop and rest as your ATP-PC system is depleted. If you continue you will be starting to train endurance which will be counterproductive to developing explosive leaping power.
glycogen is
The body breaks down most carbohydrates from the foods we eat and converts them to a type of sugar called glucose. Glucose is the main source of fuel for our cells. When the body doesn’t need to use the glucose for energy, it stores it in the liver and muscles. This stored form of glucose is made up of many connected glucose molecules and is called glycogen. When the body needs a quick boost of energy or when the body isn’t getting glucose from food, glycogen is broken down to release glucose into the bloodstream to be used as fuel for the cells.
