Sarcomere Length During Post-Natal Growth of Mammalian Muscle Fibres

1968 ◽  
Vol 3 (4) ◽  
pp. 539-548
Author(s):  
G. GOLDSPINK
Keyword(s):  
Sarcomere Length ◽  
Biceps Brachii ◽  
Muscle Length ◽  
Muscle Fibres ◽  
Biceps Brachii Muscle ◽  
Newborn Animal ◽  
Maximum Tension ◽  
Mammalian Muscle ◽  
Extended Position ◽  
The Difference

The length of the sarcomeres, the A- and the 1-filaments and their percentage overlap were measured in the fibres of the biceps brachii muscle from mice of different ages. The sarcomere length with the limb in the fully extended position was found to increase from 2.3 µ in the newborn animal to 2.8 µ in the adult. This increase was due to a decrease in the percentage overlap of the filaments and not to any change in the filament lengths. The sarcomeres at the ends of the fibres were found to be shorter than those in the middle of the muscle, at all ages. When the muscles were stretched beyond their resting length, only about the middle 60 % of the sarcomeres in the young muscles increased in length. Length/tension plots were obtained for young and old muscles and the difference in the shape of these plots could be explained as being due to the non-functional terminal sarcomeres of the young muscles. The maximum tension developed by the young muscles was found to be attained at an initial muscle length about 10 % greater than their length at maximum limb extension. The adult muscles developed maximum tension at their length at maximum limb extension.

scholarly journals Muscle length and joint angle influence spinal but not corticospinal excitability to the biceps brachii across forearm postures

2019 ◽  
Vol 122 (1) ◽  
pp. 413-423 ◽  
Author(s):  
Davis A. Forman ◽  
Daniel Abdel-Malek ◽  
Christopher M. F. Bunce ◽  
Michael W. R. Holmes
Keyword(s):  
Isometric Contraction ◽  
Elbow Joint ◽  
Joint Angle ◽  
Biceps Brachii ◽  
Motor Evoked Potentials ◽  
Muscle Length ◽  
Elbow Flexion ◽  
Corticospinal Excitability ◽  
Biceps Brachii Muscle ◽  
Spinal Excitability

Forearm rotation (supination/pronation) alters corticospinal excitability to the biceps brachii, but it is unclear whether corticospinal excitability is influenced by joint angle, muscle length, or both. Thus the purpose of this study was to separately examine elbow joint angle and muscle length on corticospinal excitability. Corticospinal excitability to the biceps and triceps brachii was measured using motor evoked potentials (MEPs) elicited via transcranial magnetic stimulation. Spinal excitability was measured using cervicomedullary motor evoked potentials (CMEPs) elicited via transmastoid electrical stimulation. Elbow angles were manipulated with a fixed biceps brachii muscle length (and vice versa) across five unique postures: 1) forearm neutral, elbow flexion 90°; 2) forearm supinated, elbow flexion 90°; 3) forearm pronated, elbow flexion 90°; 4) forearm supinated, elbow flexion 78°; and 5) forearm pronated, elbow flexion 113°. A musculoskeletal model determined biceps brachii muscle length for postures 1–3, and elbow joint angles ( postures 4–5) were selected to maintain biceps length across forearm orientations. MEPs and CMEPs were elicited at rest and during an isometric contraction of 10% of maximal biceps muscle activity. At rest, MEP amplitudes to the biceps were largest during supination, which was independent of elbow joint angle. CMEP amplitudes were not different when the elbow was fixed at 90° but were largest in pronation when muscle length was controlled. During an isometric contraction, there were no significant differences across forearm postures for either MEP or CMEP amplitudes. These results highlight that elbow joint angle and biceps brachii muscle length can each independently influence spinal excitability. NEW & NOTEWORTHY Changes in upper limb posture can influence the responsiveness of the central nervous system to artificial stimulations. We established a novel approach integrating neurophysiology techniques with biomechanical modeling. Through this approach, the effects of elbow joint angle and biceps brachii muscle length on corticospinal and spinal excitability were assessed. We demonstrate that spinal excitability is uniquely influenced by joint angle and muscle length, and this highlights the importance of accounting for muscle length in neurophysiological studies.

Changes in Striated Muscle Fibres During Contraction and Growth with Particular Reference to Myofibril Splitting

1971 ◽  
Vol 9 (1) ◽  
pp. 123-137
Author(s):  
G. GOLDSPINK
Keyword(s):  
Sarcoplasmic Reticulum ◽  
Actin Filaments ◽  
Sarcomere Length ◽  
Biceps Brachii ◽  
Hexagonal Lattice ◽  
Muscle Fibres ◽  
Cross Sectional ◽  
Tension Development ◽  
Transverse Tubular System ◽  
Myosin Filaments

Ultrastructural measurements were carried out on the mouse biceps brachii and soleus muscles fixed at different states of contraction and stretch. At a sarcomere length of 2.7-2.9 µm the more peripheral actin filaments ran slightly obliquely from the Z-disk to the A-band. This is due to a mismatch between the rhombic actin lattice at the Z-disk and the hexagonal lattice at the M-line. For a perfect transformation of a rhombic lattice into a hexagonal lattice the ratio of the lattice spacings has to be 1:1.51. However, at this sarcomere length the ratio is about 1:2.0 (Z:M). During contraction the angle of the peripheral actin filaments remains approximately the same because the expansion of the M lattice is compensated for, partly by an increase in the Z-lattice spacing and partly by the bowing of the peripheral myosin filaments. When the sarcomeres are stretched beyond 3.0 µm the myosin filaments straighten out and the Z:M ratio decreases. The ratio of 1:1.51 is almost attained when there is no overlap of the actin and myosin filaments. Ultrastructural measurements were also carried out on biceps brachii muscles of different ages. The lattice spacings for a standard sarcomere length did not change during the post-natal growth period. The amount of myofibrillar material and sarcoplasmic reticulum plus transverse tubular system were estimated using linear analysis for muscles at 3 different stages of growth. It was found that the myofibrillar cross-sectional area in an individual muscle fibre may increase 40-fold during growth and that the transverse tubular and sarcoplasmic reticulum systems increase at about the same rate. In both the biceps brachii and the soleus muscles the myosin and actin filaments are not built into a continuous mass but they are divided into numerous discrete myofibrils. Subdivision of the myofibril mass occurs because the myofibrils split once they attain a certain size. The evidence presented in this paper supports the suggestion that the longitudinal splitting of the myofibrils occurs by the ripping of the Z-disks. When tension is rapidly developed by 2 adjacent sarcomeres a stress is produced at the centre of the Z-disk resulting from the oblique pull of the actin filaments. This causes some of the Z-disk filaments to rip and the rip then extends across the disk with the direction of the weave of the lattice. Evidence for the mechanism includes electron-micrographs showing Z-disks that are apparently just commencing to split; in these cases a hole can be seen in the centre of the disk. A model experiment is described which demonstrates the importance of the rate of tension development in causing myofibril splitting. Rapid tension development produces a snatch effect which causes the Z-disk filaments to break more readily. This may explain why the myofibrils in fast muscles tend to be small and discrete whilst those in slow muscles are larger and more irregular in shape.

Influence of Arm Positions on Emg-Reaction Time of the Biceps Brachii for Elbow Flexion and Forearm Supination

1984 ◽  
Vol 59 (1) ◽  
pp. 191-194 ◽  
Author(s):  
Reiji Taniguchi ◽  
Ryuichi Nakamura ◽  
Tatsuya Kasai
Keyword(s):  
Reaction Time ◽  
Elbow Joint ◽  
Biceps Brachii ◽  
Muscle Length ◽  
Elbow Flexion ◽  
Normal Subjects ◽  
Biceps Brachii Muscle ◽  
Prime Mover

The influence of starting positions of the arm on EMG-RTs of the biceps brachii muscle for elbow flexion and forearm supination was examined using 16 normal subjects. Two angles of the elbow joint, 45° and 110° flexion, and two positions of the forearm, 45° supination and 90° pronation, were used as the factorial combinations of all four. The EMG-RT for elbow flexion decreased in the order of 110° Pronation > 45° Pronation = 110° Supination > 45° Supination, and that for forearm supination decreased in the order of 45° Supination > 45° Pronation = 110° Supination > 110° Pronation. These results were kinesiologically interpreted that variations of EMG-RTs were based on the change in the number of synergic muscles participating in an intended movement and the muscle length of the prime mover at the start of the movement.

scholarly journals Histochemistry profile of the biceps brachii muscle fibres of capuchin monkeys (Cebus apella, Linnaeus, 1758)

2014 ◽  
Vol 74 (3 suppl 1) ◽  
pp. S177-S183
Author(s):  
CHF Bortoluci ◽  
LH Simionato ◽  
GM Rosa Junior ◽  
JA Oliveira ◽  
JRP Lauris ◽  
...  
Keyword(s):  
Biceps Brachii ◽  
Cebus Apella ◽  
General Analysis ◽  
Capuchin Monkey ◽  
Muscle Fibres ◽  
Capuchin Monkeys ◽  
Biceps Brachii Muscle ◽  
Biceps Muscle ◽  
Fast Twitch

A general analysis of the behaviour of “Cebus” shows that when this primate moves position to feed or perform another activity, it presents different ways of locomotion. This information shows that the brachial biceps muscle of this animal is frequently used in their locomotion activities, but it should also be remembered that this muscle is also used for other development activities like hiding, searching for objects, searching out in the woods, and digging in the soil. Considering the above, it was decided to research the histoenzimologic characteristics of the brachial biceps muscle to observe whether it is better adpted to postural or phasic function. To that end, samples were taken from the superficial and deep regions, the inserts proximal (medial and lateral) and distal brachial biceps six capuchin monkeys male and adult, which were subjected to the reactions of m-ATPase, NADH-Tr. Based on the results of these reactions fibres were classified as in Fast Twitch Glycolitic (FG), Fast Twitch Oxidative Glycolitic (FOG) and Slow Twitc (SO). In general, the results, considering the muscle as a whole, show a trend of frequency FOG> FG> SO. The data on the frequency were studied on three superficial regions FOG=FG>SO; the deep regions of the inserts proximal FOG=FG=SO and inserting the distal FOG>FG=SO. In conclusion, the biceps brachii of the capuchin monkey is well adapted for both postural and phasic activities.

The Proliferation of Myofibrils During Muscle Fibre Growth

1970 ◽  
Vol 6 (2) ◽  
pp. 593-603
Author(s):  
G. GOLDSPINK
Keyword(s):  
Electron Microscope ◽  
Phase Contrast ◽  
Biceps Brachii ◽  
Muscle Fibres ◽  
Biceps Brachii Muscle ◽  
Longitudinal Splitting ◽  
Stages Of Growth ◽  
High Incidence ◽  
Fibre Growth ◽  
Large Muscle

Myofibrils in muscle fibres of different sizes and different ages were examined and measured using phase-contrast and electron microscopy. During the post-natal growth of the mouse biceps brachii muscle the number of myofibrils in some fibres increases from about 75 to 1200 The range of myofibril size was from 0.4-1.2 µm. The distribution of myofibril sizes in muscles of all ages studied was bimodal A high incidence of longitudinal splitting of myofibrils was observed with the electron microscope in differentiating muscle fibres and in some medium and large muscle fibres. Size measurements with the electron microscope showed that the splitting myofibrils were about twice as large as non-splitting myofibrils and that the myofibrils split more or less down the middle. A possible explanation for the splitting is that the peripheral I filaments are pulled at an angle slightly oblique to the myofibril axis, because of the discrepancy in the A and I-filament lattice spacings. When the myofibril reaches a certain size the oblique pull of the peripheral I filaments is strong enough to cause the Z disks to rip. From data on the size, shape and number of myofibrils at different stages of growth it was concluded that longitudinal splitting is the means by which the number of myofibrils increases during post-natal growth.

Morphological Basis of the Disparity Between Muscle Length and Sarcomere Length in the Myocardium

1973 ◽  
Vol 31 ◽  
pp. 422-423
Author(s):  
G.E. Adomian ◽  
L. Chuck ◽  
W.W. Pannley
Keyword(s):  
Cardiac Muscle ◽  
Sarcomere Length ◽  
Muscle Length ◽  
Contractile Force ◽  
Direct Function ◽  
Morphological Basis ◽  
Tension Curve

Sonnenblick, et al, have shown that sarcomeres change length as a function of cardiac muscle length along the ascending portion of the length-tension curve. This allows the contractile force to be expressed as a direct function of sarcomere length. Below L max, muscle length is directly related to sarcomere length at lengths greater than 85% of optimum. However, beyond the apex of the tension-length curve, i.e. L max, a disparity occurs between cardiac muscle length and sarcomere length. To account for this disproportionate increase in muscle length as sarcomere length remains relatively stable, the concept of fiber slippage was suggested as a plausible explanation. These observations have subsequently been extended to the intact ventricle.

scholarly journals Is it the coracobrachialis superior muscle, or is it an unidentified rare variant of coracobrachialis muscle?

2021 ◽  
Author(s):  
Łukasz Olewnik ◽  
Nicol Zielinska ◽  
Łukasz Gołek ◽  
Paloma Aragonés ◽  
Jose Ramon Sanudo
Keyword(s):  
Case Report ◽  
Rare Variant ◽  
Shoulder Joint ◽  
Biceps Brachii ◽  
Coracoid Process ◽  
Biceps Brachii Muscle ◽  
Shoulder Region

AbstractThe coracobrachialis muscle (CBM) originates from the apex of the coracoid process, in common with the short head of the biceps brachii muscle, and from the intermuscular septum. The CBM demonstrates variability in both the proximal and distal attachment, with some extremely rare varieties, such as the coracobrachialis superior, coracobrachialis longus and coracocapsularis muscle. This case report describes an extremely rare variant of the coracobrachialis superior muscle, or a very rare variant of the CBM. Our findings highlight the importance of muscle variants in the shoulder region, especially the coracoid region, and are significant for radiologists, anatomists, physiotherapists and surgeons specializing in the shoulder joint.

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