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Transcript of Muscle Biology
Tendons: Tough bands of connective tissue that envelope muscles and attach to the periosteum of bones to transmit the force that the muscle exerts.
3 Main Types of muscle tissue:
Skeletal - Voluntary - Striated - Joints
Smooth - Involuntary - Sheets - Organs
Cardiac - Involuntary - Striated - Heart
Properties of Muscle
Irritability - Responds to stimulus
Contractibility - Can shorten in length
Elasticity - Can stretch and return
Extensibility - Ability to extend in length
Conductivity - Transmits nerve impulses
The Neuromuscular System
Generally refers to the complex linkages between the MS and the CNS. Regular practice will enhance the quality and efficiency of the two systems and their ability to work together.
While the video delves in to far more detail than we need, it gives a good visual understanding of how a contraction is transmitted to the surface of the muscle cell.
Key Points (very simplified):
1) Nerve impulse is transmitted along axon to SK at the motor plate
2) Ca+ gates in cell wall open and Ca+ floods into the SK
3) ACh is released from SV into the synapse
4) ACh receptors on motor plate open the gate to allow the interchange of Na+ and K+
5) The higher concentration of Na+ triggers a voltage change in the motor plate
6) Change propagates along the sarcolemma to the T-Tubes to the rest of the muscle
7) ACh is broken down and Ch is pumped back to the terminal
Ca+ = Calcium ions SK = Synaptic knob ACh = Acetylcholine Ch = Choline
Na+ = Sodium K- = Potassium T-tube = Transverse tubule
The ALL or NONE
Motor units comply to the ALL or NONE principle (or Law) which demands that any unit stimulated to contract will do so to its fullest potential. In other words, regardless of the number of fibres in the unit ALL will fire at the same time.
Motor units can be small (eye) or large (quads) meaning that the number of fibres in a unit varies depending on function. In general, slow-twitch units are smaller while fast-twitch units are larger.
Here again, the video uses language and concepts beyond what we need but the animation clearly outlines the process of muscle fibre recruitment.
Epimysium becomes a tendon
HANG ON! I've heard of ISOKINETIC Exercises?
ISOKINETIC exercises are performed on expensive machinery that allows a preset speed of contraction combining the best features of ISOMETRICS and ISOTONIC exercises because they control the speed at which the joint changes.
The Sliding Filament Theory
Muscular Response to Training
: This occurs when muscles are overloaded leading to enlargement of the fibres which, in turn, enlarges the overall muscle.
There are two types of hypertrophy: TRANSIENT & CHRONIC
: "The pump" is associated with a local edema when blood rushes into the recently exercised muscle fibres. This edema quickly fades.
: Hypertrophy that stays for days, months or even years depending on the intensity and frequency of the workouts as a result of increased capillary density, increased muscle proteins and increased storage capacity for glycogen, ATP and CP.
: Controversial theory that a muscle cell will split into TWO daughter cells. This has not bee proven in humans but has been documented in animals.
Excitation - Contraction Coupling
Muscles work essentially by converting chemical energy (ATP) into mechanical energy in a process often referred to as EXCITATION-CONTRACTION COUPLING.
The electrical signal that originates in the CNS transforms to a chemical signal at the neuromuscular junction to cross the synapse and is regenerated in the sarcoplasm. It then travels through the TRANSVERSE TUBULES - a set of interconnecting rings that surround the myofibrils. The T-Tubules cause a rapid release of Ca+ from ATP catabolism which in turn affects the actin and myosin chains producing a ratcheting contraction action.
The Ca+ ions released come from the Terminal Cisternae which are a part of the sarcoplasmic reticulum - a membrane that surrounds the myofibrils. The binding of Ca+ to the Myosin chain permits the bonding of actin to myosin and the fibres contract as the actin changes shape.
Creatine is a combination of three different amino acids - glycine, arginine, and methionine. That's it, it is nothing more than a combination of amino acids. No, creatine is not a steroid, and is totally different working in a different manner. Creatine is also produced by the body (in the liver) and found in high protein sources of meat such as fish and red meat. It is NOT a lab synthesized compound, it is natural.
How Does It Work?
After creatine enters the body (or after it is produced by the body) it firsts binds with a phosphate molecule to form Creatine phosphate. ATP (Adenine Tri-Phosphate) IS the body's energy source. When your body oxidizes carbs, protein, or fat it is doing this process in order to produce ATP. ATP is responsible for driving almost every body process there is. ATP is even involved in creating ATP. Energy is needed to drive all bodily processes and ATP provides this energy by hydrolyzing (cutting off) a phosphate group.
When a phosphate group is hydrolyzed, energy in the form of heat is given off and this energy is used to drive whatever process is being performed (ie: muscle contraction). Since one phosphate has been lost from the ATP it is now called ADP (adenine Di-phosphate) ...
ATP (hydrolysis) = ADP + Energy
. Now you have free ADP as a product from the ATP hydrolysis. ADP is pretty much useless in the body unless it is converted back into ATP. Creatine now comes into play. The phosphate bound creatine donates it's phosphate group to the ADP to re-form ATP! By allowing you to return ADP to ATP creatine will increase your ATP stores, thus allowing you to train harder and longer.
Another benefit of creatine is that creatine itself is a fuel source. In fact your body's first choice of energy when performing anaerobic activity (such as weightlifting) is your creatine phosphate stores. By supplementing with creatine phosphate you will increase these stores, thus giving you more energy for your workouts. Another anabolic property that creatine holds is it's ability to hydrate muscle cells. When muscle cells are hydrated a few things happen but the most notable is an increase in protein synthesis. The second being an increase of ions into the cell. Since the cell is holding more water, it can also hold more ions since the ions will follow water into the cell in order to keep the concentration the same. When more ions are present in muscle cells (the most important being nitrogen) muscle protein synthesis also increases.
While it is possible to convert slow-twitch to fast twitch it generally happens on a very small scale meaning genetics plays a large role in the ratio.
Key Points in Contraction:
1) AP transmits past the motor plate via excitation-contraction coupling
2) AP transmits along the sarcolemma to the T-tubes (tunnels into the sarcolemma)
3) AP transmits down the T-tubes to the interior of the muscle fibre
4) T-tubes in contact with SR at the terminal cisternae (Ca+ storage)
5) The change in voltage causes opening of Ca+ gates in the TC
6) The rapid influx of Ca+ into sarcoplasm causes the contraction sequence
7) Ca+ pump actively moves the Ca+ ions back to the TC to stop contraction
AP = Action Potential T-tube = Transverse tubules TC = Terminal cisternae (pl)
SR = Sarcoplasmic reticulum
I like to move it move it
Your Body has
Pg 66 from your text
1) Increased Hypertrophy- Increased size and efficiency of fast or slow twitch fibres (program design) that results in
(a) increased strength/power/endurance
(b) increased mitochonrion density
(c) increased capillary density
(d) increased actin/myosin levels which creates an increase in metabolism
2) Increased motor recruitment improving efficiency and coordination of fibre contraction coupled with increased NMJ efficiency
3) Connective Tissues (a) Increased bone density
(b) Increased ligament strength
(c) Increased tendon strength
4) Fuel Storage- More tissue means
(a) Increased ATP and CP storage
(b) Increased glycogen storage
(c) Increased overall anaerobic threshold which results in more efficient fuel untilization
5) Blood Supply- Increased tissue results in increased capillary density which means increased nutrient delivery (O2, glucose, amino acids), waste removal (CO2, lactic acidosis) and tolerance to anaerobic glycolysis
*results will vary with program design and individual genetics
From P34-35 from text
From P36 in the text
From P40 in text
From P42 in text
The benefits of resistance training:
From P38 in text
The Truth and Science about Steroids - Nat Geog
1) Ca+ ions bind to the troponin causing a shape change to the tropomyosin
2) Tropomyosin shape change exposes the actin binding sites
3) The stored ATP energy in the myosin head is used to bind to the actin
4) Actin binding causes shape change in myosin
5) Myosin heads "ratchet" the actin filament toward the M line
6) ATP is used to break actin bond returning the myosin head to its resting state
7) SR pumps the Ca+ ions out of the sarcoloplasm and back into TC
Ca+ = Calcium ATP = Adenosine triphosphate M line = Middle of sarcomere
SR = Sarcoplasmic reticulum TC = Terminal cisternae
But where does the ATP come from?
Okay ... But What Is Creatine?
When a muscle is exercised a phenomenon called hypertrophy causes the fibers to react in two ways which contribute to it's size and strength.
But ... What are contractions?
Previously, we learned how actin and myosin work together to shorten the length of the sarcomere.
When the entire muscle is prompted to contract it can result in 3 types of action:
(a) NO movement = ISOMETRIC
(c) LENGTHENING = ECCENTRIC
(b) SHORTENING = CONCENTRIC
These machines use hydraulics to slow the rate of movement causing an increase in fibre recruitment
Myosin is prevented from binding with the actin by the troponin & tropomyosin complex
Ca+ binds with the troponin causing a shape change exposing the tropomyosin
The myosin heads use the stored ATP energy to bind to the tropomyosin which causes a shape change pulling the actin filaments toward the M line
ATP-PC (Anaerobic Alactic)
Phosphocreatine gives ready supply of free phosphates to change ADP to ATP (10-15s)
PC + ADP >> ATP + CREATINE
Glycogen partially broken down in eleven biochemical reactions to Pyruvate BUT when there is not enough O2 present the Pyruvate is converted to Lactic Acid
Muscles feel the “BURN” (15-50s)
C6H12O6 + 2 ADP + 2 P >>> 2 C3H6O3 + 2ATP + 2 H20
During continuous activity Lactic Acid (LA) poses a serious problem. The point where blood LA levels abruptly rise beyond resting levels is called the Blood Lactate Threshold or Anaerobic Threshold. Reaching the AT at lower intensities of exercise suggests that the oxidative energy systems are not working or are over-taxed. Untrained athletes reach AT at 50-60% of VO2 max while higher trained athletes may not reach At until 70-80% of VO2 max. Thus the goal of training is to increase the concentration of mitochondria and myoglobin (O2 carrier in muscle fibres) to improve the efficiency of O2 transfers at the cellular level. Training also reduces the recovery time so activities with built in rest intervals eliminate LA quickly.
The build up of Lactic Acid is often seen as a negative but, in reality, is a by-product of a process. Lactate is transported to the liver where it is converted back into glycogen via gluconeogenesis. The Cori Cylce is the process where LA is converted to pyruvate for reformation of glucose or glycogen.
Same as anaerobic glycolysis but when in the presence of enough O2, the pyruvate is transformed to Aceyl CoA
Eight reactions that yield high energy protons
ELECTRON TRANSPORT CHAIN
The high energy electrons from the Krebs Cycle travel down a chain of free radicals
C6H12O6 + 6 O2 + 36 ADP + 36 P >>> 6 CO2 + 36 ATP + 6 H2O