Question 1: The Minimum Stimulus Needed To Cause Muscle Cont

Question 1the Minimum Stimulus Needed To Cause Muscle Contraction Is C

Question 1 the minimum stimulus needed to cause muscle contraction is called the threshold. the latent period. twitch. recruitment. innervation.

Question 2 Release of acetylcholine at a neuromuscular junction decreases the release of Ca2+ from the sarcoplasmic reticulum. increases permeability of the sarcolemma to Na+. decreases the positive charge on the sarcolemma. lowers the threshold of the muscle fiber. overrides the inhibitory effect of acetylcholinesterase.

Question 3 One somatic motor neuron is stimulated by how many muscle fibers?

Question 4 To stimulate muscle contraction, acetylcholine is released from the ___________ into the synaptic cleft. synaptic knob junctional folds sarcoplasmic reticulum sarcolemma terminal cisterna

Question 5 Opening of sodium gates typically leads to repolarization of the plasma membrane. hyperpolarization of the plasma membrane. depolarization of the plasma membrane. drifting of plasma membrane voltage toward a more negative value. plasma membrane voltage returning to the resting membrane potential.

Question 6 The process of bringing more motor units into use during a muscle contraction is called wave summation. recruitment. treppe. incomplete tetanus. complete tetanus.

Question 7 A reason that muscle twitches become progressively stronger in treppe is Ca2+ accumulates in the sarcoplasm faster than the sarcoplasmic reticulum can reabsorb it. ATP is regenerated faster than it is consumed. myosin heads show faster and faster power strokes. more and more acetytlcholine is released with each stimulus. as the muscle warms up, aerobic respiration is accelerated.

Question 8 If one nerve stimulus arrives at a muscle fiber so soon that the fiber has only partially relaxed from the previous twitch, the most likely result will be fatigue. treppe. incomplete tetanus. complete tetanus. flaccid paralysis.

Question 9 Aerobic respiration produces approximately _____ more ATPs per glucose molecule than glycolysis does.

Question 10 The term for shortening of a muscle while maintaining constant tension is treppe. tetanus. isokinetic contraction. isometric contraction. isotonic contraction.

Question 11 An isometric contraction does not change muscle length. True False

Question 12 Which of the following is true concerning isotonic eccentric contraction? The muscle shortens but tension remains constant. The muscle lengthens but tension remains constant. The muscle tenses and shortens. The muscle tenses but length remains unchanged. The muscle lengthens and tension declines.

Question 13 Which muscle(s) can contract without the need for nervous stimulation? skeletal muscle smooth muscle cardiac muscle smooth and cardiac muscle skeletal, smooth and cardiac muscle

Question 14 Which of the following is very important for muscle to continue contraction during anaerobic respiration? cholinesterase inhibitors protease myokinase acetylcholinesterase acid phosphatase

Question 15 Athletes who train at high altitudes increase their red blood cell count and thus increase their oxygen supply during exercise. Increased oxygen supply results in increased glycolysis. increased use of myokinase. longer aerobic respiration. longer anaerobic fermentation. reduced ATP consumption.

Question 16 Use the image to name descibe what is happing in the electromyograpy Rapid shortening and relaxation a muscle fiber produces a quick jerk called [ Choose ] Treppe Twitch Incomplete Tetanus Complete Tetanus Fatigue Gradual, step-like increase of tensions separated by 1 sec [ Choose ] Treppe Twitch Incomplete Tetanus Complete Tetanus Fatigue Twitches that fuse with each other with no relaxation period [ Choose ] Treppe Twitch Incomplete Tetanus Complete Tetanus Fatigue Occurs when the metabolic components needed for muscle contraction are exhausted [ Choose ] Treppe Twitch Incomplete Tetanus Complete Tetanus Fatigue

Question 17 Creatine kinase donates one of its phosphate groups to ADP. phosphorylates and activates certain enzymes in the sarcoplasm. acts as a second messenger in muscle fibers. catalyzes the transfer of phosphate from CP to ADP. functions as a substitute for ATP during anaerobic fermentation.

Question 18 Which of the following best describes the resting membrane potential (RMP)? The intracellular environment is negatively charged. The intracellular environment has more positively charged sodium. The extracellular environment is negatively charged. It has a voltage of about +75 mV. It depends on the muscle fiber absorbing potassium ions from the ECF.

Question 19 Oligodendrocytes serve the same purpose in the CNS that satellite cells do in the PNS. True False

Question 20 Most of the myelin sheath is composed of lipids. carbohydrates. glycoproteins. proteins. polysaccharides.

Question 21 ___ form myelin in the spinal cord. Schwann cells Astrocytes Satellite cells Oligodendrocytes Microglia

Question 22 This image shows a representative neuron. What does "5" represent? synaptic knobs Schwann cells trigger zone node of Ranvier axon collateral

Question 23 This image shows a representative neuron. What does "1" represent? synaptic knobs axons Dendrites interneurons

Please Match the cell type with the function. You may Neuroglial cell that is related to immune tissue and phagocytizes dead nervous tissue [ Choose ] Schwann cells Oligodendrocytes Fibrous Astrocytes Protoplasmic Astrocytes Ependymal cells Microglia Forms the myelin sheath around most PNS axons [ Choose ] Schwann cells Oligodendrocytes Fibrous Astrocytes Protoplasmic Astrocytes Ependymal cells Microglia Line cavities of brain and spinal cord and secretes CSF [ Choose ] Schwann cells Oligodendrocytes Fibrous Astrocytes Protoplasmic Astrocytes Ependymal cells Microglia Star-like cells that form the blood brain-barrier [ Choose ] Schwann cells Oligodendrocytes Fibrous Astrocytes Protoplasmic Astrocytes Ependymal cells Microglia Forms the myelin sheath around most CNS axons [ Choose ] Schwann cells Oligodendrocytes Fibrous Astrocytes Protoplasmic Astrocytes Ependymal cells Microglia Star-like cell that forms a supportive framework in CNS and can form form scar tissue after injury [ Choose ] Schwann cells Oligodendrocytes Fibrous Astrocytes Protoplasmic Astrocytes Ependymal cells Microglia Spaces between these cells on an axon are called nodes of Ranvir [ Choose ] Schwann cells Oligodendrocytes Fibrous Astrocytes Protoplasmic Astrocytes Ependymal cells Microglia Aid in regeneration of damaged nerve fibers in the PNS [ Choose ] Schwann cells Oligodendrocytes Fibrous Astrocytes Protoplasmic Astrocytes Ependymal cells Microglia

Paper For Above instruction

The minimum stimulus required to induce a muscle contraction is termed the threshold stimulus. This concept is fundamental in neuromuscular physiology because it delineates the smallest electrical impulse necessary to trigger an action potential in muscle fibers, ultimately leading to contraction. When a motor neuron stimulates a muscle fiber, it releases acetylcholine at the neuromuscular junction, initiating depolarization of the muscle membrane. This depolarization opens voltage-gated Na+ channels, allowing sodium ions to flow into the cell, causing the membrane potential to become more positive. Once the threshold is reached, an action potential propagates along the sarcolemma, leading to muscle contraction through the sliding filament mechanism.

The process of muscle contraction involves several stages, beginning with the excitation-contraction coupling triggered by acetylcholine release. This neurotransmitter increases the permeability of the sarcolemma to Na+, resulting in depolarization. The depolarization wave travels along the muscle fiber, reaching the T-tubules, and triggers the release of calcium ions from the sarcoplasmic reticulum. The release of Ca2+ is pivotal because calcium binds to troponin, causing a conformational change that moves tropomyosin away from myosin-binding sites on actin filaments, thus enabling cross-bridge formation and contraction.

During contraction, the recruitment of motor units is essential for increasing the strength of muscle force. A motor unit comprises a single motor neuron and all the muscle fibers it innervates. The process of recruiting additional motor units during sustained muscle activity is known as recruitment. This process allows muscles to generate more force as more muscle fibers participate in contraction, which is crucial during physical activities demanding increased strength.

Muscle twitch is the response of a muscle to a single stimulus. When a nerve impulse is delivered, the muscle fiber exhibits a latent period, followed by contraction and relaxation phases. In treppe, or the staircase phenomenon, successive stimuli result in progressively stronger twitches without complete relaxation, primarily because calcium accumulates in the sarcoplasm faster than the sarcoplasmic reticulum can reabsorb it, enhancing contractile force. Alternatively, if stimuli occur in rapid succession, twitches can fuse into a sustained contraction called tetanus, which can be incomplete or complete depending on the frequency of stimulation.

A critical aspect of muscle energetics involves ATP production. Aerobic respiration, which requires oxygen, yields significantly more ATP—approximately 36 to 38 ATP molecules per glucose—compared to glycolysis alone, which produces only 2 ATP molecules per glucose. This high efficiency underscores the importance of oxygen supply in sustained muscle activity, especially during endurance exercises or high-altitude training. Athletes training at high altitudes adapt by increasing red blood cell counts, enhancing oxygen delivery and extending aerobic capacity, which supports longer and more efficient muscle function through prolonged aerobic respiration.

Muscle contractions can be classified based on tension and movement. An isotonic contraction involves changes in muscle length while tension remains constant, such as during the lifting of a weight. Conversely, an isometric contraction occurs when muscle tension develops without change in length, exemplified by holding a position. Eccentric contractions, a subtype of isotonic contractions, occur when a muscle lengthens under tension, as in controlled negative movements like lowering a weight. This type of contraction is crucial in movements that involve deceleration or controlled elongation of muscles.

Muscle tissues differ in their ability to contract autonomously. Cardiac and smooth muscles can contract independently of nervous stimulation, due to intrinsic pacemaker cells or a spontaneous depolarization mechanism. Skeletal muscles, however, rely exclusively on nervous stimulation for contraction. This difference highlights the autonomous contractile property of cardiac and smooth muscles, which are vital for involuntary functions such as blood flow regulation and gastrointestinal motility.

In anaerobic conditions, muscle cells depend heavily on glycolysis and other anaerobic pathways to generate ATP. One enzyme essential in maintaining energy balance during anaerobic respiration is myokinase, which catalyzes the transfer of phosphate groups between ADP molecules to form ATP and AMP. This process becomes critical when oxygen supplies are limited, as in intense exercise, and supports continued muscle activity despite the lack of oxygen. This mechanism is part of the broader adaptation that allows muscles to sustain activity temporarily without aerobic metabolism.

High-altitude training induces physiological adaptations such as increased erythropoiesis, which results in higher red blood cell counts. This adaptation enhances oxygen transport capacity, thereby prolonging aerobic respiration during exercise. The increased oxygen availability enables muscles to utilize aerobic pathways more effectively, delaying fatigue and improving endurance performance. Consequently, athletes develop a greater capacity for sustained activity through longer periods of aerobic respiration, reducing reliance on less efficient anaerobic pathways.

Electromyography (EMG) studies demonstrate different muscle activity patterns. Rapid muscle shortening and relaxation, characterized by quick jerks, correspond to twitch contractions. Stepwise increases in tension separated by a second reflect treppe, as the muscle warms and calcium handling improves. When twitches fuse into a continuous contraction without relaxation, it indicates tetanus—either incomplete or complete—depending on stimulation frequency. In fatigue, muscle force diminishes due to the exhaustion of metabolic reserves essential for sustained contraction, such as glycogen or ATP.

Creatine kinase plays a vital role in energy buffering within muscle cells. It catalyzes the transfer of a phosphate group from creatine phosphate (CP) to ADP, forming ATP, especially during periods of high energy demand. This rapid regeneration of ATP helps sustain muscle contractions temporarily during intense activity, highlighting its importance in muscle energetics and fatigue resistance.

The resting membrane potential (RMP) of a neuron is typically around -70 mV. It depends primarily on the high permeability of the neuronal membrane to potassium ions, which diffuse out of the cell, maintaining a negative charge inside relative to outside. The intracellular environment is negatively charged due to the distribution of ions, mainly because of the sodium-potassium pump and the differential permeability to various ions. Changes in this voltage are crucial in the generation and propagation of action potentials.

Oligodendrocytes and Schwann cells are specialized glial cells responsible for myelination in the nervous system. Oligodendrocytes are found in the CNS and form myelin sheaths around multiple axons, facilitating rapid electrical conduction. Schwann cells, located in the PNS, insulate individual axons. Both cell types are essential for efficient nerve transmission, but they are not interchangeable, reflecting their differences in location and structure.

In the CNS, oligodendrocytes produce myelin, whereas in the PNS, Schwann cells are responsible. Satellite cells in the PNS serve protective and supportive roles similar to astrocytes in the CNS, which regulate the extracellular environment and maintain the blood-brain barrier. Microglia are immune cells that monitor for injury or pathogens, capable of phagocytizing debris and pathogens, thus maintaining neural health. Ependymal cells line brain ventricles and produce cerebrospinal fluid (CSF), contributing to the nourishment and cushioning of neural tissue.

Overall, understanding the intricate processes involved in muscle contraction and neural function reveals the complexity of the human nervous and muscular systems. The precise regulation of stimuli, ion exchange, energy metabolism, and structural support highlights the sophisticated coordination necessary for movement, cognitive processes, and maintaining homeostasis. Advances in neurophysiology and muscular science continue to deepen our comprehension, with implications for treating muscular and neurological disorders.

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