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.

The Locust Jump: III. Structural Specializations of the Metathoracic Tibiae

1977 ◽  
Vol 67 (1) ◽  
pp. 29-36
Author(s):  
W. J. HEITLER
Keyword(s):  
Vertical Component ◽  
Distal Region ◽  
Proximal Region ◽  
Flexor Muscle ◽  
Full Extension ◽  
Joint Rotation ◽  
Mechanical Advantage ◽  
Full Flexion

1. The flexor and extensor tibiae muscles of the mesothoracic leg have a constant lever ratio of about 2:1 throughout joint rotation. 2. The mesothoracic tibiae can only flex to 25° about the femora, while the metathoracic tibiae, because of their specialized geometry, can flex almost parallel to the femora. 3. Full metatibial flexion increases the mechanical advantage of the flexor muscle relative to the extensor at full flexion, and increases the vertical component of the thrust produced by tibial extension in a jump. 4. A region in the dorsal proximal cuticle of the metatibia is stiff when stretched but buckles when compressed. The tibia is thus rigid under extensor stress, but bends under flexor stress. 5. Metatibial bending can enable the proximal region of the tibia to become fully flexed even if the distal region is prevented from flexing fully, and may reduce the inertial shock to the femur when the tibia reaches full extension in a kick.

Measurement of the Arc of Digital Flexion and Joint Movement Ranges

1995 ◽  
Vol 20 (6) ◽  
pp. 836-840 ◽  
Author(s):  
J. D. ARBUCKLE ◽  
D. A. McGROUTHER
Keyword(s):  
Healthy Subjects ◽  
Video Recording ◽  
Similar Technique ◽  
Joint Movement ◽  
Joint Angles ◽  
Full Extension ◽  
Male And Female ◽  
Full Flexion ◽  
Joint Flexion ◽  
Prognostic Importance

Dynamic digital flexion was examined by video recording healthy subjects making a fist. The are of the fingertip sweep from full extension to full flexion was replayed frame by frame and plotted. A similar technique was employed to measure the MP, PIP and DIP joint angles throughout digital flexion. Graphs were plotted of MP against PIP, and PIP against DIP flexion. These results were related to a theoretical 45° line. The fingertip appears to sweep through an elliptical pathway when flexing, rather than an equiangular curve. Graphs of joint flexion showed that male and female fingers flex in a similar fashion, as do the index and little finger. Graphs of PIP against DIP flexion suggest some limiting mechanism of either the extensor or flexor system. These graphs give useful insights into the complex mechanisms of dynamic digital flexion, and may be of diagnostic and prognostic importance.

scholarly journals The Role of Aeolin in The Formation of Earth Surface Configuration and The Influencing Factor

2004 ◽  
Vol 11 (2) ◽  
Author(s):  
Alif Noor Anna
Keyword(s):  
Simple Form ◽  
Horizontal Plane ◽  
Influencing Factor ◽  
Vertical Plane ◽  
Coracoid Process ◽  
Earth Surface ◽  
Wind Force ◽  
Surface Configuration ◽  
The Earth

Configuration of the earth surface is molded by the interaction of endogenous and exogenous forces. The outcome of the interaction usually has the shape of special charracter. Configuration charracter is then applied to grouping of more simple form called landform. It so happens that one of the landform function is to make geomorphology research more easier. Que of the earth surface configuration is molded by wind force the result of this activity is called the landform which is originally molded by wind process. There are two folds function of wind process i.l: erosion (= coracoid process and deposifronal force). Coracoid process usually takes place on vertical as well as horizontal plane. Coracoid on vertical plane will have the shape of yardang, while on horizontal plane has the shape of pillars, needless, and zenguen. It so happens that depositional wind will shape ripples, sanddunes, and loess.

scholarly journals Sensory Feedback During Active Movements of Stick Insects

1987 ◽  
Vol 133 (1) ◽  
pp. 137-156 ◽  
Author(s):  
G. WEILAND ◽  
U. T. KOCH
Keyword(s):  
Control System ◽  
Stick Insect ◽  
Middle Part ◽  
Chordotonal Organ ◽  
Voluntary Movements ◽  
Joint Movement ◽  
Stick Insects ◽  
Velocity Changes ◽  
Changing Role

In the stick insect Carausius momsus, the role of the chordotonal organ was investigated using a new experimental arrangement which artificially closes the femur-tibia control system. The chordotonal organ was stimulated during voluntary movements by applying trapezoidal ramp stimuli in the closed-loop configuration. The results demonstrate that the feedback loop is used to control the end points of joint movement. In addition, it was found that the control system counteracts experimentally applied velocity changes imposed during the middle part of the movements. Acceleration-sensitive units are shown to contribute to the reaction. The results show that during active voluntary movements reflexes measured in the inactive animal are neither simply incorporated in a servo-system nor suppressed. Instead their characteristics are altered so that the voluntary movements are executed as intended by the animal. Thus reflexes cannot be considered as a fixed behavioural unit; rather their changing role must be analysed in the context of the behaviour studied.

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.

Isokinetic Strength After ACL Reconstruction: Influence of Concomitant Anterolateral Ligament Reconstruction

2021 ◽  
pp. 194173812110054
Author(s):  
Benoit Gillet ◽  
Yoann Blache ◽  
Isabelle Rogowski ◽  
Grégory Vigne ◽  
Bertrand Sonnery-Cottet ◽  
...  
Keyword(s):  
Muscle Strength ◽  
Ligament Reconstruction ◽  
Knee Extensor ◽  
Anterolateral Ligament ◽  
Flexor Muscle ◽  
Knee Flexor ◽  
Strength Recovery ◽  
Flexor Muscles ◽  
Knee Muscle ◽  
Knee Muscle Strength

Background: To reduce the rate of anterior cruciate ligament (ACL) graft rupture, recent surgeries have involved anterolateral ligament reconstruction (ALLR). This reconstruction procedure harvests more knee flexor muscle tendons than isolated ACL reconstruction (ACLR), but its influence on knee muscle strength recovery remains unknown. This study aimed to assess the influence of ALLR with a gracilis graft on the strength of the knee extensor and flexor muscles at 6 months postoperatively. Hypothesis: The additional amount of knee flexor harvest for ALLR would result in impairment in knee flexor muscle strength at 6 months postoperatively. Study Design: Retrospective cohort study. Level of Evidence: Level 2. Methods: A total of 186 patients were assigned to 2 groups according to the type of surgery: ACL + ALLR (graft: semitendinosus + gracilis, n = 119) or isolated ACLR (graft: semitendinosus, n = 67). The strength of the knee extensor and flexor muscles was assessed using an isokinetic dynamometer at 90, 180, and 240 deg/s for concentric and 30 deg/s for eccentric contractions and compared between groups using analysis of variance statistical parametric mapping. Results: Regardless of the surgery and the muscle, the injured leg produced significantly less strength than the uninjured leg throughout knee flexion and extension from 30° to 90° for each angular velocity (30, 90, 180, and 240 deg/s). However, the knee muscle strength was similar between the ACL + ALLR and ACLR groups. Conclusion: The addition of ALLR using the gracilis tendon during ACLR does not alter the muscle recovery observed at 6 months postoperatively. Clinical Relevance: Although more knee flexor muscle tendons were harvested in ACL + ALLR, the postoperative strength recovery was similar to that of isolated ACLR.

scholarly journals Dielectric anisotropy as indicator of crystal orientation fabric in Dome Fuji ice core: method and initial results

2021 ◽  
pp. 1-12
Author(s):  
Tomotaka Saruya ◽  
Shuji Fujita ◽  
Ryo Inoue
Keyword(s):  
Crystal Orientation ◽  
Horizontal Plane ◽  
Ice Core ◽  
Vertical Plane ◽  
Vertical Direction ◽  
Core Sample ◽  
Dielectric Anisotropy ◽  
Principal Axes ◽  
Polycrystalline Ice ◽  
Initial Results

Abstract Polycrystalline ice is known to exhibit macroscopic anisotropy in relative permittivity (ɛ) depending on the crystal orientation fabric (COF). Using a new system designed to measure the tensorial components of ɛ, we investigated the dielectric anisotropy (Δɛ) of a deep ice core sample obtained from Dome Fuji, East Antarctica. This technique permits the continuous nondestructive assessment of the COF in thick ice sections. Measurements of vertical prism sections along the core showed that the Δɛ values in the vertical direction increased with increasing depth, supporting previous findings of c-axis clustering around the vertical direction. Analyses of horizontal disk sections demonstrated that the magnitude of Δɛ in the horizontal plane was 10–15% of that in the vertical plane. In addition, the directions of the principal axes of tensorial ɛ in the horizontal plane corresponded to the long or short axis of the elliptically elongated single-pole maximum COF. The data confirmed that Δɛ in the vertical and horizontal planes adequately indicated the preferred orientations of the c-axes, and that Δɛ can be considered to represent a direct substitute for the normalized COF eigenvalues. This new method could be extremely useful as a means of investigating continuous and depth-dependent variations in COF.

Peripheral control of the gain of a central synaptic connection between antagonistic motor neurones in the locust

1996 ◽  
Vol 199 (3) ◽  
pp. 613-625
Author(s):  
T Jellema ◽  
W Heitler
Keyword(s):  
Muscle Contraction ◽  
Sensory Input ◽  
Sense Organ ◽  
Gain Control ◽  
Motor Neurone ◽  
Extensor Muscle ◽  
Chordotonal Organ ◽  
Excitatory Postsynaptic Potential ◽  
Motor Neurones ◽  
Peripheral Sensory

The metathoracic fast extensor tibiae (FETi) motor neurone of locusts is unusual amongst insect motor neurones because it makes output connections within the central nervous system as well as in the periphery. It makes excitatory chemical synaptic connections to most if not all of the antagonist flexor tibiae motor neurones. The gain of the FETi-flexor connection is dependent on the peripheral conditions at the time of the FETi spike. This dependency has two aspects. First, sensory input resulting from the extensor muscle contraction can sum with the central excitatory postsynaptic potential (EPSP) to augment its falling phase if the tibia is restrained in the flexed position (initiating a tension-dependent reflex) or is free to extend (initiating a movement-dependent resistance reflex). This effect is thus due to simple postsynaptic summation of the central EPSP with peripheral sensory input. Second, the static tibial position at the time of the FETi spike can change the amplitude of the central EPSP, in the absence of any extensor muscle contraction. The EPSP can be up to 30 % greater in amplitude if FETi spikes with the tibia held flexed rather than extended. The primary sense organ mediating this effect is the femoral chordotonal organ. Evidence is presented suggesting that the mechanism underlying this change in gain may be specifically localised to the FETi-flexor connection, rather than being due to general position-dependent sensory feedback summing with the EPSP. The change in the amplitude of the central EPSP is probably not caused by general postsynaptic summation with tonic sensory input, since a diminution in the amplitude of the central EPSP caused by tibial extension is often accompanied by overall tonic excitation of the flexor motor neurone. Small but significant changes in the peak amplitude of the FETi spike have a positive correlation with changes in the EPSP amplitude, suggesting a likely presynaptic component to the mechanism of gain control. The change in amplitude of the EPSP can alter its effectiveness in producing flexor motor output and, thus, has functional significance. The change serves to augment the effectiveness of the FETi-flexor connection when the tibia is fully flexed, and thus to increase its adaptive advantage during the co-contraction preceding a jump or kick, and to reduce the effectiveness of the connection when the tibia is partially or fully extended, and thus to reduce its potentially maladaptive consequences during voluntary extension movements such as thrusting.

Circle-Drawing Movements at Different Speeds: Role of Inertial Anisotropy

2002 ◽  
Vol 88 (5) ◽  
pp. 2399-2407 ◽  
Author(s):  
Kerstin D. Pfann ◽  
Daniel M. Corcos ◽  
Charity G. Moore ◽  
Ziaul Hasan
Keyword(s):  
Individual Differences ◽  
Horizontal Plane ◽  
Upper Arm ◽  
Speed Dependence ◽  
Oval Shape ◽  
Circle Drawing ◽  
Relative Motions

This study investigated the role of inertial anisotropy at the hand in causing distortions in movement. Subjects drew circles in the horizontal plane at four locations in the workspace at three instructed paces using elbow and shoulder movements. Specifically, we tested two hypotheses, which we would expect if the anisotropy of inertia were not completely accounted for by the CNS when generating circle-drawing movements: 1) speed will affect the circularity of figures, with faster movements associated with greater elongation into an oval shape, irrespective of workspace location for configurations with a similar angle between the forearm and upper arm. 2) The elongation of the circle at fast speeds will be in the direction of least inertia. The results showed that despite individual differences in the speed dependence of the relative motions at the elbow and the shoulder, the circularity decreased (distortion increased) with increased speed, and workspace location had no effect on circularity. We also found that the elongation of the circles at fast speeds was in a direction close to but significantly different from the direction of least inertia for three workspace locations and was in the direction of least inertia for the fourth location. We suggest that the elongation results from lack of full accounting by the CNS of the anisotropy of viscosity and inertia.

Injury to the Anterior Cruciate Ligament during Alpine Skiing

2002 ◽  
Vol 30 (4) ◽  
pp. 537-540 ◽  
Author(s):  
Sharon L. Hame ◽  
Daniel A. Oakes ◽  
Keith L. Markolf
Keyword(s):  
Anterior Cruciate Ligament ◽  
Cruciate Ligament ◽  
Alpine Skiing ◽  
Full Extension ◽  
Flexion Extension ◽  
Fresh Frozen ◽  
Full Flexion ◽  
The Mean ◽  
Anterior Cruciate ◽  
Knee Flexion Position

Background The anterior cruciate ligament has been shown to be particularly susceptible to injury during alpine skiing. Tibial torque is an important injury mechanism, especially when applied to a fully extended or fully flexed knee. Purpose We wanted to record the forces generated in the anterior cruciate ligament with application of tibial torque to cadaveric knees in different positions. Study Design Controlled laboratory study. Methods Thirty-seven fresh-frozen cadaveric knees were instrumented with a tibial load cell that measured resultant force in the anterior cruciate ligament while internal and external tibial torques were applied to the tibia at full extension, 90° of flexion, full flexion, and forced hyperflexion. Results At each knee flexion position, mean force generated by 10 N·m of internal tibial torque was significantly higher than the mean generated by 10 N·m of external tibial torque. Mean forces generated by tibial torque at 90° of flexion were relatively low. During flexion-extension without tibial torque applied mean forces were highest (193 N) when the knee was hyperflexed. Conclusions Application of internal tibial torque to a fully extended or fully flexed knee represents the most dangerous loading condition for injury from twisting falls during skiing. Clinical Relevance Understanding of the mechanisms of falls can be used to design better equipment and to better prevent or treat injury.

Sign in / Sign up

Export Citation Format

Share Document