Exercise Physiology Flashcards

Question

what is the functional organization of the nervous system

Answer 1

CNS (Brain & Spinal Cord): - Afferent: sensory-> Spinal Cord-> Brain (ascending) - Efferent: motor= brain-> spinal cord (descending) PNS (Sensory & Motor Divisions): -Autonomic Nervous System (ANS): Involuntary, sympathetic: fight or flight, parasympathetic: rest and digest Regulates involuntary body functions (e.g., heart rate, digestion). -Somatic Nervous System: voluntary

Answer 2

Central Nervous System (CNS): Includes the brain and spinal cord, responsible for processing information and controlling responses. Peripheral Nervous System (PNS): Includes all nerves outside the CNS, responsible for connecting the CNS to the rest of the body. Motor Division: Controls voluntary and involuntary movements (somatic and autonomic). Sensory Division: Transmits sensory information from receptors to the CNS. Ganglia: Clusters of neuron cell bodies outside the CNS, acting as relay stations. Neurons and Glial Cells: Neurons transmit electrical signals, while glial cells provide support and protection.

Answer 3

Neurotransmitters are chemical messengers that allow communication between neurons and between neurons and target cells (such as muscles and glands). They are essential for a wide range of bodily functions, including mood regulation, movement, cognition, and homeostasis. The balance and proper functioning of neurotransmitters are vital for maintaining health, and disruptions in neurotransmitter systems can lead to various neurological and psychiatric disorders.

Answer 4

A neurotransmitter is released from the presynaptic neuron (or nerve terminal) into the synaptic cleft, it travels across the cleft and binds to receptors on the postsynaptic membrane and causes depolarization. 2. Types of Responses in Postsynaptic Cells Excitatory Postsynaptic Potentials (EPSPs): can promote neural depolarization in 2 ways. Temporal summation- summing serval EPSPs from one presynaptic neuron or Spatial summation- summing EPSPs from several different presynaptic neurons Inhibitory Postsynaptic Potentials (IPSPs): they prevent synaptic transmission. They cause hyperpolarization (more negative resting membrane potential). Neurons with a more negative membrane potential resist depolarization. The combined result of all the EPSPs and IPSPs at any given time determines whether the postsynaptic neuron will reach the threshold for firing an action potential (i.e., whether the neuron will send a signal down its axon to communicate with other neurons or muscles).

Answer 5

Excitatory Postsynaptic Potentials (EPSPs): can promote neural depolarization in 2 ways. Temporal summation- summing serval EPSPs from one presynaptic neuron or Spatial summation- summing EPSPs from several different presynaptic neurons more likely to generate an AP Sodium (Na⁺) enters the neuron, making it less negative (depolarized). Which Increases the chance of firing an action potential. Causing the movement of the membrane potential closer to threshold (-55mV). Neurotransmitters: Glutamate, Acetylcholine, Dopamine, Norepinephrine. Result: If the threshold is reached, an action potential occurs.

Answer 6

Inhibitory Postsynaptic Potentials (IPSPs): they prevent synaptic transmission. They cause hyperpolarization (more negative resting membrane potential). Neurons with a more negative membrane potential resist depolarization. Negative ions (Cl⁻) enter or positive ions (K⁺) leave. Causing the Membrane Potential to becomes more negative (hyperpolarized). Causing a less likely to fire an action potential. Which prevents excessive neural firing or overactivity. Common Transmitters: GABA, Glycine, Dopamine (in certain regions). Function: Promotes relaxation, reduces muscle contraction, limits brain overactivity.

Answer 7

Muscle fiber recruitment, also known as motor unit recruitment, is the process by which the nervous system activates motor units to generate force in a muscle. A motor unit consists of a motor neuron and all the muscle fibers it controls, and when the motor neuron fires, all its muscle fibers contract simultaneously. According to the size principle, recruitment occurs in a specific order based on force demand: small motor units (Type I, slow-twitch fibers) are recruited first for low-force, endurance activities, followed by medium motor units (Type IIa, fast-twitch oxidative fibers) for moderate force, and finally large motor units (Type IIx, fast-twitch glycolytic fibers) for maximum force output during heavy lifting, sprinting, or explosive movements. If more force is needed, the brain recruits more motor units to increase contraction strength. Muscle recruitment also adapts with training, allowing athletes to recruit more muscle fibers during high-intensity tasks, enhancing strength, power, and performance. Additionally, during prolonged exercise, fatigue in slow-twitch fibers can trigger the recruitment of fast-twitch fibers to sustain muscle output. This sequential recruitment system is designed to conserve energy, prevent fatigue, and maximize force production when necessary.

Answer 8

Ultra-short (<10 sec) A. Phosphagen system i. Phosphocreatine depletion Short (10-180 sec) B. Anaerobic glycolysis ii. Lactic acid accumulation Moderate (2-10 min) C. Aerobic metabolism iii. Cardiovascular system limitations

Answer 9

Membrane potential refers to the electrical charge difference across a cell membrane, resulting from the uneven distribution of ions (Na⁺, K⁺, Cl⁻) inside and outside the cell. In a resting neuron, the resting membrane potential is typically around -70mV, meaning the inside of the cell is more negative relative to the outside. This resting potential is maintained by the sodium-potassium pump (Na⁺/K⁺ pump), which actively moves 3 Na⁺ out and 2 K⁺ in, and the membrane's permeability to K⁺ leakage, allowing potassium to slowly diffuse out of the cell. When a stimulus reaches the neuron, voltage-gated sodium channels open, allowing Na⁺ to rush into the cell, causing depolarization — the membrane potential becomes more positive (around +30mV). If the depolarization reaches the threshold (-55mV), an action potential is triggered, resulting in a rapid electrical impulse along the neuron. Following this, repolarization occurs as K⁺ channels open, allowing potassium to flow out of the cell, restoring the negative charge. Finally, a brief hyperpolarization may occur, where the membrane becomes slightly more negative than the resting potential before returning to its resting state. This rapid change in membrane potential, known as an action potential, is essential for transmitting electrical signals in neurons.

Answer 10

A motor unit consists of a motor neuron and all the muscle fibers it innervates, and it is responsible for generating muscle contractions. When the motor neuron sends an electrical signal (action potential), all the muscle fibers within that motor unit contract simultaneously. Motor units vary in size, with small motor units controlling slow-twitch (Type I) muscle fibers for endurance activities, and large motor units controlling fast-twitch (Type II) muscle fibers for power and strength movements. Over a lifetime, sedentary behavior can lead to motor unit loss (motor neuron death), particularly affecting fast-twitch fibers, resulting in muscle atrophy, decreased strength, and slower reaction times. Additionally, surviving motor neurons may attempt to reinnervate abandoned muscle fibers, converting them into slow-twitch fibers, causing a decline in power output. In contrast, a lifetime of exercise, especially strength and high-intensity training, can help preserve motor unit function, maintain muscle mass, and slow down motor unit loss, promoting better mobility, strength, and balance as a person ages. Exercise also helps enhance motor unit recruitment, allowing for more efficient muscle contractions, reducing the effects of sarcopenia (age-related muscle loss), and promoting overall neuromuscular health.

Answer 11

The principal functions of skeletal muscles are to facilitate movement, maintain posture, stabilize joints, and generate heat. Skeletal muscles attach to bones via tendons and produce movement by contracting and pulling on bones, allowing for activities such as walking, running, and lifting objects. They also play a critical role in maintaining posture by continuously contracting to keep the body upright and balanced, especially during sitting or standing. Additionally, skeletal muscles stabilize joints by supporting and reinforcing the bones, preventing dislocation or abnormal movement during physical activity. Another essential function is heat production, as muscle contractions generate body heat (thermogenesis), which helps maintain normal body temperature, especially during cold environments. Skeletal muscles also assist in protecting internal organs by providing a cushioning effect and supporting bodily structures. Beyond physical movement, skeletal muscles contribute to venous return, assisting blood flow back to the heart through rhythmic contractions during movement. Collectively, these functions are vital for mobility, stability, and overall body function.

Answer 12

1. Nerve Impulse Reaches the Neuromuscular Junction A nerve impulse (action potential) travels down the motor neuron to the neuromuscular junction (where the neuron meets the muscle fiber). This triggers the release of the neurotransmitter acetylcholine (ACh) from the axon terminal (end of the neuron) into the synaptic cleft (gap between neuron and muscle fiber). 2. Acetylcholine Binds to Receptors on the Sarcolemma Acetylcholine (ACh) diffuses across the synaptic cleft and binds to acetylcholine receptors on the sarcolemma (muscle cell membrane). This opens sodium (Na⁺) channels, allowing Na⁺ ions to rush into the muscle fiber, causing depolarization (a shift in electrical charge inside the muscle fiber). 3. Action Potential Travels Along Sarcolemma and T-Tubules The depolarization generates a muscle action potential (electrical impulse) that travels along the sarcolemma. The impulse travels deep into the muscle fiber through T-tubules (transverse tubules), ensuring the signal reaches the entire muscle fiber. 4. Sarcoplasmic Reticulum Releases Calcium Ions When the action potential reaches the sarcoplasmic reticulum (SR), it triggers the release of calcium ions (Ca²⁺) into the sarcoplasm (muscle cell cytoplasm). The influx of calcium ions is critical for initiating muscle contraction. 5. Calcium Binds to Troponin (Exposure of Binding Sites) Calcium (Ca²⁺) binds to a protein called troponin, which is attached to tropomyosin on the actin (thin) filament. This changes the shape of troponin, causing tropomyosin to shift and expose the myosin-binding sites on actin. 6. Cross-Bridge Formation (Myosin Attaches to Actin) The myosin head (from the thick filament) binds to the exposed binding site on actin, forming a cross-bridge. The myosin head is already "cocked" with energy from the breakdown of ATP (adenosine triphosphate).

Answer 13

fatigue is defined as a decline in muscle power. A decline in muscle power output occurs due to: decrease in muscle force production at the cross bridge level. A decrease in muscle shortening velocity. The cause of muscle fatigue is dependent on the exercise that produces the fatigue Very heavy exercise (1-10 mins): causes of fatigue are multifactorial-range from decreased Ca2+ release from SR to accumulation of metabolites that inhibit myofilament sensitivity to Ca2+. Key metabolites that contribute to fatigue include increases in Pi, H+ and free radicals, H= ions bind to Ca2+ binding sites on troponin-preventing Ca2+ binding and contracting, both Pi and free radicals modify cross-bridge head and reduces number of cross-bridges bound to actin. moderate intensity exercise (>60 min): causes of fatigue during prolonged endurance exercise include increase radical production and glycogen depletion. Accumulation of Pi and H+ in muscle do not contribute fatigue during moderate intensity exercise. Radical accumulation in muscle fibers modifies cross-bridge head and reduces number of cross-bridges bound to actin 9force production reduces). Depletion of muscle glycogen reduces TCA cycles intermediates and decreases ATP production via oxidative phosphorylation.

Answer 14

Human skeletal muscle fibers are classified into three main types based on their mechanical and biochemical properties: Type I (slow-twitch), Type IIa (fast-twitch oxidative), and Type IIx (fast-twitch glycolytic) fibers. Type I fibers are highly efficient at using oxygen to generate ATP through aerobic metabolism, making them suited for endurance activities. They have slow contraction speeds, but high endurance and are fatigue-resistant. Type IIa fibers have a moderate contraction speed and are capable of generating both aerobic and anaerobic energy, making them ideal for activities requiring both strength and endurance. Type IIx fibers generate rapid, forceful contractions but rely on anaerobic metabolism (mainly glycolysis), leading to rapid fatigue. These fibers are suited for short bursts of high-intensity efforts like sprinting or weightlifting. The regulation of force during muscular contractions is influenced by several key factors. The number of motor units recruited (motor unit recruitment) is a primary factor, with more motor units being activated for greater force. The frequency of action potentials (rate coding) also plays a role, where a higher frequency of neural firing leads to greater force production. Fiber type composition and the cross-sectional area of muscle fibers determine the maximum force a muscle can generate, with larger fibers producing more force. The length-tension relationship also affects force generation, as muscles generate the most force when they are at an optimal length for overlap between actin and myosin filaments. Additionally, muscle temperature, electrolyte balance, and neural drive can modify the force produced during contractions. Together, these factors work in coordination to regulate muscle force efficiently and adapt to varying demands.

Answer 15

During aerobic activities of progressively greater intensity, the recruitment of motor units follows a specific pattern based on the muscle fiber types involved. Initially, during low-intensity exercise, the body primarily recruits Type I (slow-twitch) fibers. These fibers are efficient at using oxygen and are highly resistant to fatigue, making them ideal for endurance activities such as walking or light jogging. As the intensity of the activity increases, the body progressively recruits Type IIa (fast-twitch oxidative) fibers. These fibers are capable of both aerobic and anaerobic metabolism, allowing them to sustain moderate-intensity efforts while also contributing to strength and power. At higher intensities, Type IIx (fast-twitch glycolytic) fibers are recruited to meet the demand for rapid, forceful contractions. These fibers rely on anaerobic energy systems, providing quick bursts of power but fatiguing rapidly. The progression of motor unit recruitment follows a size principle, where smaller, slower motor units (innervating Type I fibers) are recruited first, and larger, faster motor units (innervating Type IIa and IIx fibers) are recruited as the intensity of the activity increases. This systematic recruitment ensures efficient energy use and optimal performance across various intensity levels.

Answer 16

VO2max is the maximum rate at which an individual can utilize oxygen during intense exercise, and it is a key indicator of cardiorespiratory fitness. Several factors influence VO2max in both untrained and trained individuals undergoing an endurance training program. In untrained individuals, VO2max is typically lower due to less efficient cardiovascular and muscular systems. Factors such as heart rate, stroke volume (amount of blood the heart pumps per beat), and oxygen delivery to tissues are not optimized, leading to a lower VO2max. However, with endurance training, adaptations occur that improve cardiac output, mitochondrial density in muscle fibers, and aerobic enzyme activity, all contributing to an increase in VO2max. Trained individuals generally exhibit a higher VO2max due to increased stroke volume, greater capillary density in muscles, and more efficient oxygen utilization by muscle fibers. The degree of adaptation is influenced by factors such as genetics, age, sex, and training intensity. The duration and frequency of training also play a significant role; consistent and progressive endurance training increases VO2max over time. Moreover, muscle fiber type and dietary factors (e.g., iron levels) can further impact an individual’s ability to improve VO2max. Overall, while both untrained and trained individuals benefit from endurance training, the extent of improvement in VO2max is generally more pronounced in those who are initially untrained.

Answer 17

Strength development in both untrained and trained individuals is influenced by several key factors during a strength training program. For untrained individuals, the initial gains in strength are largely due to neurological adaptations such as improved motor unit recruitment, coordination, and neuromuscular efficiency. These neural adaptations enable better activation of muscle fibers and more effective force production. Additionally, muscle hypertrophy (increase in muscle size) starts to occur with continued training, further contributing to strength gains. For trained individuals, improvements in strength are more gradual and are driven primarily by muscle hypertrophy, which occurs due to the overload principle—progressively increasing the weight or intensity of the exercises. Trained individuals also experience muscle fiber adaptation, with Type II fibers (which generate more force) becoming more active in response to heavy lifting. Several training principles guide strength development, including the specificity principle, where the type of exercise should align with the goals (e.g., powerlifting or bodybuilding); the overload principle, which ensures the muscles are stressed beyond their usual capacity to promote growth and strength; and the progressive overload principle, which involves gradually increasing the intensity, volume, or load over time. The reversibility principle highlights that gains in strength will decrease if training stops, while the individualization principle acknowledges that training programs should be tailored to each individual’s needs, taking into account factors like age, sex, and fitness level. Proper recovery, periodization (cycling through various intensities), and nutrition (adequate protein intake) are also crucial in maximizing strength gains in both untrained and trained individuals.

Answer 18

Cross education refers to the phenomenon where training one limb or side of the body leads to strength and performance improvements in the untrained opposite limb. This occurs due to the neural adaptations that take place in the central nervous system. When one limb is trained, the motor cortex in the brain becomes more efficient at recruiting motor units, and this improved neural pattern can transfer to the opposite, untrained limb, even without direct training. This effect is particularly noticeable when strength training is focused on one arm or leg, resulting in some increase in strength or performance on the contralateral side. Cross education is thought to be beneficial in rehabilitation, as it can help maintain strength in an injured or immobilized limb by training the opposite limb. Factors influencing cross education include the type of training, the intensity, and the duration of the exercise. The effect is generally stronger for strength gains and less pronounced for endurance or skill-related tasks. This neural adaptation can help preserve functional capacity during recovery periods and may be used to speed up rehabilitation.

Answer 19

The FITT principle is a framework used to design effective exercise programs by adjusting Frequency, Intensity, Time, and Type of physical activity to meet individual goals. Frequency refers to how often an individual engages in physical activity (e.g., number of sessions per week), intensity is the level of effort required (e.g., low, moderate, or vigorous), time refers to the duration of each exercise session, and type refers to the kind of activity performed (e.g., aerobic, strength training, flexibility exercises). This principle helps tailor exercise programs to enhance fitness, improve health, and prevent injury. The U.S. guidelines for physical activity recommend that adults engage in at least 150 minutes of moderate-intensity aerobic activity or 75 minutes of vigorous-intensity aerobic activity per week, combined with muscle-strengthening activities on two or more days per week. For additional health benefits, the guidelines suggest increasing aerobic activity to 300 minutes of moderate-intensity or 150 minutes of vigorous-intensity weekly. These guidelines emphasize the importance of regular physical activity for maintaining overall health, reducing the risk of chronic diseases (e.g., heart disease, diabetes), improving mental health, and enhancing quality of life. Following the FITT principle in combination with these guidelines ensures a balanced and sustainable approach to fitness.

Exercise Physiology Flashcards

exam #2