October 20, 2023 Flashcards
what is the relationship between lipolysis and training in regards to trained and untrained individuals as it pertains to FFA oxidation
Enhanced Lipolysis: Trained individuals often have greater capacity for lipolysis compared to UNTRAINED INDIVIDUALS, the breakdown of stored triglycerides into FFAs in adipose tissue. This means they can release more FFAs into the bloodstream during exercise.
Increased Fat Oxidation: Trained individuals have adaptations in their muscles that allow for more efficient FFA uptake and oxidation. Their muscle cells have a higher density of mitochondria and increased activity of enzymes involved in fat metabolism. This enables them to use FFAs as a more significant energy source.
Review graph on bottom left of page 69 for claritifcation
what is the relationship between lipolysis and training in regards trained and untrained individuals as it pertains to FFA in blood
Lower FFA Levels: Trained individuals tend to have lower FFA levels in the blood during exercise compared to untrained individuals.
This might seem counterintuitive, but it’s because trained individuals can more effectively take up and use FFAs, reducing the need for higher blood FFA concentrations.
review graph on bottom right of page 69
what is the ratio between fat and carbohydrates of total energy used during prolonged exercise at say, 50% Vo2 max between a trained and untrained individual
UT = 40% fat: 60% CHO
T= 60% fat: 40% CHO
All fibers within a Motor Unit (MU) have the same contractile and metabolic properties. True or false
true
briefly explain how a contraction occurs starting with the motor cortex
Motor Cortex Activation: The motor cortex, located in the brain, sends signals to initiate voluntary muscle movement. These signals travel down the spinal cord to motor neurons.
Motor Neuron Activation: Motor neurons in the spinal cord receive the signals from the motor cortex. Each motor neuron innervates a specific group of muscle fibers (motor unit).
Action Potential: When the motor neuron is activated, it generates an electrical impulse called an action potential. This action potential travels down the length of the motor neuron toward the neuromuscular junction.
THIS IS ALL WE LEARNED UP TO IN THIS LECTURE REVIEW PAGE 71
what determines the twitch characteristics of the muscle
The twitch characteristics of a muscle, including its contraction time, force production, and relaxation time, are primarily determined by the properties of the muscle fibers within that muscle
Muscle Fiber Type: Muscle fibers can be classified into different types, primarily Type I (slow-twitch) and Type II (fast-twitch) fibers. The type of muscle fiber in a muscle strongly influences twitch characteristics.
Type I fibers contract more slowly and generate less force but are highly fatigue-resistant. They are well-suited for sustained, low-intensity activities.
Type II fibers contract rapidly, produce greater force, but fatigue more quickly. They are better suited for high-intensity, short-duration activities.
how does calcium affect the twitch characteristics of the muscle
*Twitch Force and Tension: The amount of calcium released into the muscle fiber influences the force and tension generated during a twitch. A greater influx of calcium results in more cross-bridge formations and increased muscle force. A smaller calcium release leads to weaker twitch force.
*Twitch Amplitude: The amplitude of a muscle twitch, which represents the magnitude of force generated during the twitch, is directly related to the concentration of calcium ions available for contraction.
*Twitch Relaxation: Calcium also plays a critical role in twitch relaxation. When the action potential ends, calcium must be actively pumped back into the sarcoplasmic reticulum, and tropomyosin returns to its blocking position on the actin filament, preventing cross-bridge formation. This process allows the muscle to relax.
How do myosin isoforms and calcium release rates influence the kinetics of the contraction phase of muscle contractions
Myosin Heavy Chains: Muscle fibers contain different myosin heavy chain isoforms, which are part of the myosin protein complex responsible for generating force during muscle contractions. There are primarily two types of myosin heavy chain isoforms: fast-twitch (Type II) and slow-twitch (Type I).
Fast-Twitch Myosin (Type II): Fast-twitch myosin isoforms contract more rapidly and generate higher force. They are responsible for quick, powerful movements.
Slow-Twitch Myosin (Type I): Slow-twitch myosin isoforms contract more slowly and produce lower force but have greater endurance. They are involved in sustained, low-intensity activities.
Influence on Contraction Speed: The presence of fast-twitch or slow-twitch myosin isoforms within muscle fibers directly influences the speed of muscle contraction. Muscles with a higher proportion of fast-twitch fibers contract quickly, while those with a higher proportion of slow-twitch fibers contract more slowly.
Calcium Release Rates:
Excitation-Contraction Coupling: The rate at which calcium ions are released from the sarcoplasmic reticulum and become available for muscle contraction is a critical determinant of contraction kinetics.
Rate of Cross-Bridge Formation: Calcium binding to troponin allows the myosin heads to bind to actin filaments, initiating cross-bridge formation. The rate at which this occurs is directly influenced by the rate of calcium release.
relaxation phase kinetics are due to rates of calcium re-uptake
Role of Calcium in Muscle Contraction and Relaxation:To relax the muscle, calcium must be actively pumped back into the sarcoplasmic reticulum, and troponin must return to its blocking position on the actin filament, preventing further cross-bridge formation.
Rate of Calcium Re-uptake:
The rate at which calcium is actively transported back into the sarcoplasmic reticulum by the calcium ATPase pump, also known as the sarcoplasmic reticulum calcium ATPase (SERCA), is a crucial determinant of relaxation kinetics.
Faster calcium re-uptake by SERCA accelerates the removal of calcium from the cytoplasm and promotes muscle relaxation.
Muscle Relaxation Time: The rate of calcium re-uptake contributes to the speed of muscle relaxation. Faster calcium removal results in more rapid muscle relaxation, while slower calcium removal leads to a prolonged relaxation phase.
what is a tetanic contraction
A tetanic contraction, also known as tetanus, is a sustained and continuous contraction of a muscle in response to a rapid and repetitive series of stimuli or action potentials from motor neurons.
In a tetanic contraction, the muscle fiber remains in a state of maximal tension and does not fully relax between the individual contractions
how is a tetanic contraction achieved
increasing the frequency of action potentials to muscle via a-motorneuron firing
fast-twitch muscle fibers (40Hz) within a MU require higher action potential firing frequencies (Hz) to achieve contractions compared to slow twitch muscle fibers (20Hz) within MU. Why
because fast twitch muscle fibres have a faster relaxation rate.
firing rates of 10-20 Hz result in unfused tetanic contractions of the fibers within that single MU. So why aren’t submaximal contraction “jerky”?
related to motor unit recruitment
Because more than one MU is firing, and they fire asynchronously to smooth out the force produced
Two MUs generate more force than one!…. and they summate to “smooth out” jerky, single MU submaximal contractions. True or false
True
page 74
what is Tetanus
Tetanus, also known as lockjaw, is a serious bacterial infection caused by the bacterium Clostridium tetani (an anaerobic bacterium whose spores are found in soil and animal feces)
It primarily affects the nervous system and can lead to muscle stiffness and spasms, often starting in the jaw and neck but potentially spreading to other parts of the body.
Causing Bacterium: Tetanus is caused by the bacterium Clostridium tetani, which is commonly found in soil, dust, and animal feces. The bacterium can enter the body through wounds or injuries, especially deep puncture wounds.
Symptoms: The symptoms of tetanus typically include muscle stiffness, particularly in the jaw (hence the term “lockjaw”), neck, and face. Muscle spasms and rigidity can spread to other muscle groups, causing difficulty in breathing and potentially leading to severe complications.
Symptoms of the disease appear between 5-10 days later, produced by the action of Tetanus neurotoxin secreted by the bacteria at the site of the wound. The toxin exerts its effects after reaching the CNS, where it binds to synaptic terminals and blocks the transmission of signals that normally inhibit the activity of motor neurons. As a result motor neurons become *hyperexcitable, leading to inappropriate stimulation of skletal muscle
Prevention: Tetanus is preventable through vaccination.
If you have not had the vaccine, measures that can manage the symptoms include administration of the drugs that interfere with neuromuscular transmission and thus reduce muscle spasms.
Immunity: can be accomplished through infection of inactivated tetanus toxin vaccine which stimulates the body to produce antibodies against the toxin
Review page 75
