The Antennal Motor System of the Rock Lobster: Competitive Occurrence of Resistance and Assistance Reflex Patterns Originating from the Same Proprioceptor

1980 ◽  
Vol 87 (1) ◽  
pp. 1-22
Author(s):  
JEAN-PIERRE VEDEL
Keyword(s):  
Motor System ◽  
Extensor Muscle ◽  
Chordotonal Organ ◽  
Rock Lobster ◽  
Neural Organization ◽  
Extensor Muscles ◽  
Flexor Muscles ◽  
Extensor Motoneurones ◽  
The Common

1. Skeletal, muscular and neural organization of the two distal joints (J2 and J3) of the antenna of the rock lobster Palinurus vulgaris has been described. 2. Motor innervation (nine motoneurones) of the two distal joints of the antenna has been determined by anatomical and physiological methods. Extensor and flexor muscles of J2 and J3 are each innervated by one specific excitatory tonic motoneurone. One excitatory phasic motoneurone is common to both the J2 and J3 extensor muscles, another to the J2 and J3 flexor muscles. The J3 extensor muscle also receives a specific phasic motoneurone. An accessory extensor muscle which spans J2 and J3 is innervated by one excitatory motoneurone. A common inhibitory motoneurone innervates the two flexor and the two extensor muscles of J2 and J3. 3. Movements of J2 and J3 are sensed by a proprioceptor (chordotonal organ). Reflex patterns involving this proprioceptor have been extensively studied. Sinusoidal extension-flexion movements imposed on the J3 joint induced intra-segmental reflexes (on the J3 muscle innervations) and inter-segmental reflexes (on the J2 muscle innervations) which exclusively involved the tonic excitatory motoneurones and the common inhibitory motoneurone. 4. Resistance reflexes (activation of the muscle stretched by the imposed movements) occurred whatever the excitability level of the animal and involved both flexor and extensor motoneurones. The motoneurones spiked at a higher frequency when the velocity of the imposed movement was increased. The common inhibitor motoneurone was activated during extension movements. 5. In preparations which became ‘more excitable’, assistance reflexes could be induced by joint stimulations which formerly induced resistance reflexes. Sometimes assistance reflexes could be induced by increasing the velocity of the movements imposed on J3. Assistance reflexes mainly involved extensor motoneurones. 6. The role of the tonic, phasic and inhibitory innervations and the functional significance of resistance and assistance reflexes are discussed in relation to the behavioural role of the rock lobster antenna.

Intersegmental reflex actions from a joint sensory organ (CB) to a muscle receptor (MCO) in decapod crustacean limbs

1978 ◽  
Vol 73 (1) ◽  
pp. 47-63 ◽  
Author(s):  
B. M. Bush ◽  
J. P. Vedel ◽  
F. Clarac
Keyword(s):  
Decapod Crustacean ◽  
Extensor Muscle ◽  
Chordotonal Organ ◽  
Flexor Muscle ◽  
Proprioceptive Reflexes ◽  
Co Activation ◽  
Extensor Muscles ◽  
Motor Activities ◽  
Central Excitability ◽  
Reflex Discharge

In the walking legs of decapod crustaceans, intersegmental reflex actions originate from various joint proprioceptors. The activity of the ‘accessory flexor’ (AF) muscle, which with the myochordotonal organ (MCO) constitutes a muscle proprioceptor for the mero-carpopodite (M-C) joint, is modulated by the sensory discharge of a joint receptor (CB chordotonal organ) for the more proximal, coxo-basal (C-B) joint. Selective mechanical stimulation of the CB organ also reflexly modifies the motor activities of the main M-C flexor and extensor muscles (recorded as EMGs). 1. Dynamic CB stretch (as would occur during a dorso-ventral C-B movement - i.e. ‘depression’ of the limb) stimulates motor discharge to the M-C extensor muscle, while dynamic release of CB (as during a ventrodorsal C-B movement - or leg ‘elevation’) excites the accessory flexor as well as the main flexor muscle. 2. Successive M-C muscle responses to repetitive sinusoidal changes of CB length differ quantitatively according to the direction (stretch or release) of the first CB movement, in some cases increasing but more commonly ‘adapting’ with repetition. 3. Reflex discharge frequencies of the extensor, flexor and accessory flexor motoneurones increase with velocity of CB movement. 4. Eye illumination, and spontaneous or other sources of increased central excitability, generally increase the CB reflex drive to the flexor and accessory flexor muscles and, in parallel, decrease the reflex action on the extensor muscle. The results are discussed in terms of the role of proprioceptive reflexes in intersegmental co-ordination of the leg joints. In particular the significance of the reflex regulation of the myochordotonal receptors, and thereby the gain of the M-C resistance reflexes, is considered in the light of the observed ‘co-activation’ of main flexor and receptor muscle motoneurones.

Intersegmental reflex coordination by a single joint receptor organ (CB) in rock lobster walking legs

1978 ◽  
Vol 73 (1) ◽  
pp. 29-46
Author(s):  
F. Clarac ◽  
J. P. Vedel ◽  
B. M. Bush
Keyword(s):  
Motor Units ◽  
Chordotonal Organ ◽  
Extensor Muscles ◽  
Decapod Crustacea ◽  
Complex Motor ◽  
Complex Picture ◽  
Receptor Organ ◽  
Proprioceptive Reflex ◽  
Length Changes

In the decapod Crustacea, Palinurus vulgaris and Fasus lalandii, the reflex influences of one particular proprioceptor organ, the coxo-basal chordotonal organ (CB), on all the muscles operating the proximal and distal joints of the same leg, have been analysed. The distal end of CB was clamped in fine forceps mounted on a servo-controlled stretcher, and CB length changes of 2 mm were applied. Motor unit activity of the different muscles was recorded as electromyograms (EMGs). 1. Two types of proprioceptive reflex evoked by CB length changes have been investigated: (a) resistance reflexes of the two levator and two depressor muscles of the same leg segment, the coxopodite, i.e. ‘intrasegmental reflexes’, (b) ‘intersegmental reflexes’ induced in the muscles operating the proximal (T-C) joint of the same leg, and in all eight muscles of the limb segments distat to CB. 2. Both levator muscles respond reflexly to imposed CB stretch (which normally occurs with limb ‘depression’), while both depressors respond during CB shortening (or passive “elevation” of the leg). 3. Intersegmentally CB stretch reflexly activates the M-C extensor muscle, and sometimes facilitates the T-C remotor and C-P bender muscles. Shortening of the single CB organ of a leg excites one or two tonic motor units of the T-C promotor and M-C flexor muscles, and also facilitates the remotor, I-M reductor, and the single stretcher-opener excitatory motoneurone. 4. Some of the muscles, particularly the M-C flexor and extensor muscles, are also influenced intersegmentally by the resting length of CB, usually but not invariably in the same direction as for the corresponding dynamic reflexes. The role of the CB chordotonal organ is discussed, with particular consideration of its intersegmental reflex influence on the posture of the entire leg, and on the more complex motor behaviour of locomotion, where it may be specially significant in coordination of the limb in lateral walking. A complex picture of both tonic and dynamic, inra- and intersegmental reflex regulation of the positions and movements of the limb segments, thus emerges.

Contributions of structure and innervation pattern of the stick insect extensor tibiae muscle to the filter characteristics of the muscle-joint system

1996 ◽  
Vol 199 (10) ◽  
pp. 2185-2198 ◽  
Author(s):  
U Bässler ◽  
W Stein
Keyword(s):  
Distal Portion ◽  
Stick Insect ◽  
Extensor Muscle ◽  
Chordotonal Organ ◽  
Movement Amplitude ◽  
Joint System ◽  
Pass Filter ◽  
Low Pass Filter ◽  
Flexor Muscles ◽  
Stimulation Of

It is shown that the low-pass filter characteristics of the muscle­joint system of the femur­tibia joint of the stick insect Cuniculina impigra result from co-contraction of the extensor and flexor tibiae muscles. The most distal region of the extensor muscle, which contains a high percentage of slow muscle fibres, is involved in this co-contraction. This conclusion results from the following evidence. (1) Inertial and friction forces do not affect the characteristics of the low-pass filter of the muscle­joint system. (2) There is some co-contraction of the extensor and flexor muscles during sinusoidal stimulation of the femoral chordotonal organ at high stimulus frequencies. Both muscles generate tonic forces that increase with increasing stimulus frequency and also increase with time from the beginning of stimulation until a plateau is reached. (3) For the extensor muscle, this tonic force is produced by its most distal portion only. (4) Electrical stimulation of the common inhibitory motoneurone (CI1) reduces the tonic force generated in this most distal portion of the extensor muscle. Therefore, CI1 stimulation reduces the amplitude of tibial movement in response to sinusoidal stimulation of the femoral chordotonal organ at stimulus frequencies below 0.5 Hz (over this frequency range, the tibial movement amplitude is a function of the force amplitude produced by the whole extensor muscle and there is no co-contraction), but at chordotonal organ stimulus frequencies of 1 Hz and above, CI1 stimulation increases the tibial movement amplitude (in this case, movement amplitude is limited by the degree of co-contraction of the extensor and flexor muscles). With repeated chordotonal organ stimulation at higher stimulus frequencies, the tibial movement amplitude steadily decreases. This must be a consequence of increasing levels of co-contraction of the extensor and flexor muscles, since at low stimulus frequencies (no co-contraction) there is no reduction in movement amplitude during repeated stimulations. It is concluded that co-contraction of the extensor and flexor tibiae muscles prevents instability in the reflex loop in spite of the high gain necessary for the generation of catalepsy. Therefore, the mechanism described can be considered to be an adaptation to the ecological niche occupied by this animal. The contribution of the distal part of the extensor muscle to this system can be switched off by the CI1 during active movements.

Neural mechanisms underlying the clasp-knife reflex in the cat. I. Characteristics of the reflex

1990 ◽  
Vol 64 (4) ◽  
pp. 1303-1318 ◽  
Author(s):  
C. L. Cleland ◽  
W. Z. Rymer
Keyword(s):  
Isometric Contraction ◽  
Tibialis Anterior ◽  
Time Course ◽  
Extensor Muscle ◽  
Neural Mechanisms ◽  
Medial Gastrocnemius ◽  
Reflex Inhibition ◽  
Golgi Tendon Organs ◽  
Extensor Muscles ◽  
Flexor Muscles

1. The goal of this study was to characterize the clasp-knife reflex by the use of stretch and isometric contraction of ankle extensor and flexor muscles in decerebrated cats with bilateral dorsal hemisections of their spinal cords at segment T12. 2. Stretch of an extensor muscle evoked inhibition in both homonymous and synergistic extensor muscles. The similarities between homonymous and synergistic inhibition suggest that similar neural mechanisms were responsible. 3. Homonymous and synergistic clasp-knife inhibition showed several characteristic features: 1) inhibition was evoked only by large stretches that produced significant muscle force. Short stretches that did not produce large forces evoked only excitation; 2) the magnitude of clasp-knife inhibition increased with increasing initial motor output, as reflected in the level of rectified EMG; 3) the time course of reflex inhibition evoked by ramp-and-hold stretch was characterized by segmentation of EMG during ramp stretch, dynamic overshoot of inhibition at the end-of-ramp stretch, and slow but usually complete decay of inhibition during maintained stretch; 4) inhibition persisted beyond the termination of stretch, and 5) inhibition showed adaptation to repeated stretch. 4. Isometric contraction of the soleus or medial gastrocnemius, produced by electrical stimulation of the muscle nerve, also evoked powerful synergistic-reflex inhibition via similar mechanisms as stretch-evoked, clasp-knife inhibition. Stretch evoked a greater degree of inhibition than did contraction, indicating that receptors responsive to both stretch and contraction contribute to clasp-knife inhibition. 5. The reflex effects produced by stretching the soleus or medial gastrocnemius were not confined to the homonymous and close synergistic muscles. Extensor muscles were inhibited and flexor muscles were excited throughout the hindlimb, which paralleled the pattern of a flexion-withdrawal reflex evoked by cutaneous stimulation. 6. Stretch of a flexor muscle, the tibialis anterior, evoked the same spatial pattern and time course of reflex action as stretch of an extensor muscle--inhibition of extensor muscles and excitation of flexor muscles throughout the hindlimb, including homonymous excitation of the tibialis anterior. 7. We conclude that neither Golgi tendon organs nor secondary spindle afferents are likely to contribute significantly to clasp-knife inhibition because their responses to stretch and isometric contraction differ from the reflex actions evoked by stretch and contraction.(ABSTRACT TRUNCATED AT 400 WORDS)

scholarly journals THE POSITION-DEPENDENT NATURE OF POSTURAL RESISTANCE REFLEXES IN THE LOCUST

1994 ◽  
Vol 188 (1) ◽  
pp. 65-88 ◽  
Author(s):  
L Field ◽  
M Coles
Keyword(s):  
Horizontal Plane ◽  
Vertical Plane ◽  
Motor Neurone ◽  
Chordotonal Organ ◽  
Joint Movement ◽  
Flexor Muscle ◽  
Full Extension ◽  
Flexor Muscles ◽  
Full Flexion

The resistance reflexes of tibial extensor and flexor muscles, of all six legs in the locust, show changes in gain at different femur­tibia angles (FTA). In all muscles the gain is high for small angles (near full flexion) and low for large angles (near full extension, approximately 160 °). An exception occurs in the mesothoracic flexor muscle, which shows two modes: one as above and another in which maximum gain occurs at 100­120 ° FTA. The position-dependent character is evident at each stage of the reflex pathway: motor neurone, non-spiking interneurone and femoral chordotonal organ (the afferent source of the reflex). We conclude that position-dependency originates from a decrease in the number of phasic femoral chordotonal organ neurones sensitive to joint movement as larger FTAs are approached. Position-dependency is only roughly correlated with the postural FTAs most commonly observed in the meso- and metathoracic legs of unrestrained resting locusts; no such correlation was evident for prothoracic legs. We propose that the major role of position-dependency is to allow resistance reflexes efficiently to counter torque introduced onto the femur­tibia joint by perturbations in the horizontal plane when the insect rests on a horizontal substratum and in the vertical plane when it rests on a vertical substratum.

Treatment of vertebral fractures due to osteoporosis

2015 ◽  
Vol 24 (01) ◽  
pp. 7-10 ◽  
Author(s):  
M. Pfeifer ◽  
M. Sinaki
Keyword(s):  
Exercise Program ◽  
Therapeutic Exercise ◽  
Training Support ◽  
Axial Stability ◽  
Extensor Muscles ◽  
Therapeutic Exercises ◽  
Increase Risk ◽  
Risk Of Falls ◽  
Risk Of Fall

SummaryThe objective of exercise in the treatment of osteoporosis is to improve axial stability through strengthening of back extensor muscles. Therefore, a back extension exercise program specific to one’s musculoskeletal competence and pain can be performed in a sitting position and later advanced to the prone position. When fragility is resolved, back extension is performed against resistance applied to the upper back. A significant reduction in back pain, kyphosis, and risk of falls and an improvement in the level of physical activity have been achieved through the SPEED (Spinal Proprioceptive Extension Exercise Dynamic) program. In addition, the application of a “Posture Training Support” (PTS) using a backpack may decrease kyphosis and pain related not only to compression fractures but also reduce iliocostal friction. Therapeutic exercise should address osteo - porosis-related deformities of axial posture, which can increase risk of fall and fracture. Thus, the role of a therapeutic exercise program is to increase muscle strength safely, decrease immobility-related complications, and prevent fall and fracture. As with pharmacotherapy, therapeutic exercises are individualized.

On everyday academic research

2017 ◽  
pp. 98-134 ◽  
Author(s):  
J. Tirole
Keyword(s):  
Common Good ◽  
Academic Research ◽  
Research Quality ◽  
Economic Research ◽  
Relevant Research ◽  
The Common ◽  
Verification Of Models ◽  
Science And Research

In the fourth chapter of the book “The economy of the common good”, the nature of economics as a science and research practices in their theoretical and empirical aspects are discussed. The author considers the processes of modeling, empirical verification of models and evaluation of research quality. In addition, the features of economic cognition and the role of mathematics in economic research are analyzed, including the example of relevant research in game theory and information theory.

Contemplative Principles of a Non-dual Praxis: the Unmediated Practices of the Tibetan ‘Heart Essence’ (sNying thig) Tradition

2015 ◽  
Vol 31 (2) ◽  
pp. 215-240
Author(s):  
Eran Laish
Keyword(s):  
Contemplative Practice ◽  
Tibetan Buddhist ◽  
Buddhist Tradition ◽  
The Common

This article focuses on the main contemplative principles of the ‘Heart Essence’ (sNying thig), a Tibetan Buddhist tradition that is characterized by a vision of non-duality and primordial wholeness. Due to this vision, which asserts an original reality that is not divided into perceiving subject and perceived object, the ‘Heart Essence’ advocates a contemplative practice that undermines the usual intuitions of temporality and enclosed selfhood. Hence, unlike the common principles of intentional praxis, such as deliberate concentration and gradual purification, the ‘Heart Essence’ affirms four contemplative principles of non-objectiveness, openness, spontaneity and singleness. As these principles transcend intentionality, temporality, and multiplicity, they are seen to directly disclose the nature of primordial awareness, in which the meanings of knowing and being are radically transformed. Therefore, the article will also consider the role of these non-dual contemplative principles in deeply changing our understanding of being and knowing alike.

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