Skeletal muscles process muscle bundle containing number of muscle fibres each muscle fibre is lined by the plasma membrane called Sarcolemma in enclosing the sarcoplasm.
muscle fibre is a syncitium as the sarcoplasm contain many nuclei the endoplasmic reticulum that is sarcoplasmic reticulum of the muscle fibre is the store house of calcium ion . A characteristic feature of the muscle fibre is the presence of large number of parallel arrangement of elements in the sarcoplasm called myofilaments aur myofibrils. Each myofibril has alternate dark and light bands on it , that is too important proteins actin and myosin the light to band contain actin and is called I or isotropic band where as dark band called A or anisotropic band contain myosin . Both the proteins are arranged as rod like structure parallel to each other. actin filaments are thinner as compared to the myosin filaments hence are commonly called thin and thick filaments respectively in the centre of I band is an elastic fibres called is z line which bisect it . The thin filaments are firmly attached to the z line. the thick filament in the a band are also held together in the middle of this band by thin fibrous membrane called M line . The A and I band are arranged alternatively throughout the length of myofibrils . The portion of the myofibril between two successive is a line is considered as the functional unit of contraction and is called sarcomere.
structure of contractile protein .
Each actin filament is made of two filamentous actin for or F actin helically wound to each other . Each F actin is a polymer of monomeric globular actin or G actin.
to filaments of another protein tropomyosin also run close to F actins throughout its length . A complex protein troponin is distributed at regular intervals on the tropomyosin. Inthe resting state a subunit of troponin mask reactive binding sites for myosin on the actin filaments. Each myosin is a monomeric protein of Mero myosin constitutive and thick filament . Each meromyosin has two important parts a globular head with the short arm and a tail . The globular head is an active ATP is enzyme and has binding site for ATPase and active site for actin.the head and short arm project outwards at regular distance and the angle from each other from the surface of polymerized myosin filament and is known as cross arm.
mechanism of muscle contraction.
mechanism of muscle contraction is best explained by the sliding filament theory which state that contraction of a muscle fibre takes place by the sliding of thin filaments over the thick filament. Muscle contraction is initiated by a signal send by the central nervous system through a motor neuron and motor neuron along with the muscle fibre connected to it constituted motor unit . The junction between a motor neuron and the sarcolemma of the muscle fibre is called neuromuscular junction or motor end plate. neural signals reaching this junction release a neurotransmitter acetyl choline which generate an action potential in the sarcolemma . This spread through the muscle fibre and causes the release of calcium ions into the sarcoplasm . Increasing calcium level lead to the binding of calcium with a subunit of troponin on actin filaments. This will remove the masking of active sites for myosin. In utilising the energy from ATP hydrolysis the myosin head bind to the exposed active site on actin to form a cross bridge. this police the attached acting filaments towards the centre of a band the sideline attached to this actings are also called in words there by causing a shortening of sarcomere which causes contraction. So during shortening of muscle contraction the I band get reduced whereas the A band retain the length. The myosin releasing the ADP and phosphate goes back to its relaxed state. A new ATP binds and the cross bridge is broken. The ATP is again hydrolysed by the myosin in head and cycle of crossbridge formation and breakage is repeated causing further sliding.the process continues till the calcium ions are pump back to the sarcoplasmic cisternae resulting in the masking of actin filaments this causes the return of the Z lines back to their original position which is called relaxation.
11. Explain how the myofilaments produce muscle contraction even though the length of each myofilament does...
1. Explain the steps involved in muscle contraction starting from stimulation of the sciatic nerve (somatic motor neuron) to contraction of the muscle fibers within the gastrocnemius. Be sure to include any movements of ions, neurotransmitters, myofilaments and other relevant structures/particles in your answer. (3 pts) 2. Why do we see a graded response (tension increasing) in single muscle twitch when increasing the voltage (strength) of the stimulus that is applied? Was there a point at which maximal tension was...
Match each type of contraction with the correct description. A muscle increases in length during its contraction 1. Isometric Contraction A muscle gets shorter (decreases in length) when it contracts 2. Isotonic Concentric Contra 3. Isotonic Eccentric Contract A muscle contracts, but does not change length Previous Page Next Page Next Page
In experimental situations, how does skeletal muscle length determine the force of contraction? Why, in life, is this muscle length versus active tension relationship not seen?
Explain how contraction the gastrointestinal smooth muscle is intrinsically controlled
1 Explain the events of inspiration and expiration in terms of muscle contraction, change in volume (space), change in pressure and flow of air. 2 What factors stimulate breathing? Between O2 and CO2, which is more important in terms of stimulation of breathing? Why? 3 What does GFR stand for? What happens in nephrons if GFR is too high? Too low? 4 Describe the positive feedback mechanism used by the nephron loop to make the medulla salty. What is the...
what is the energy source used for muscle contraction? how does recruitment of motor units work? do all muscle fibers in a motor unit contract every time the somatic motor neuron stimulates it?
There is a trade-off between speed and force in muscle contraction. a) Why does this trade-off exist (please explain in terms of force generation by myosin heads)? b) How do glycolytic muscle fibers circumvent this trade-off?
Choose any and all appropriate answers: How is the muscular contraction stopped (i.e.: how does a muscle relax after contraction)? The brain stops sending the nerve impulse that commands the muscle to contract, interrupting communication at the neuromuscular junction Acetylcholineesterase (AChE) is released into the synaptic cleft to destroy any remaining Acetylcholine No mechanism is necessary. When the antagonist begins to contract, it forces relaxation and stretch of the agonist muscle. Relaxation occurs as the myosin heads are "snapped" off...
How does biofeedback control blood flow and smooth muscle contraction which are controlled by the sympathetic and parasympathetic nervous systems?
number 17-20
10. A Muscle fiber is made up of mabcils 11. Myofibrils are composed of a series of repeated functional units calledSarComeces, which runs from z to z line. Within the myofibrils there are thin and thick myofilaments called achna and muosnSliding of these two myofilaments leads to the contraction of muscles. The thin myofilaments are composed of actinteeamjesinand troponin 12. What are the five physiological characteristics of muscles? hi 13. The junction between a motor nerve and a...