Tibial Flexion Research Articles

Morphology of the central projections of physiologically characterised neurones from the locust metathoracic femoral chordotonal organ

The metathoracic femoral chordotonal organ of the locust (Locusta migratoria) is an internal proprioceptor composed of mechanosensory neurones which respond to tibial position, velocity, or acceleration, or to combinations of these parameters. Discriminant function analyses confirmed the visual observation that neurones with different responses to tibial movements had different central branching patterns. Some aspects of the projections were consistent for all neurones (e.g., the path taken by the main neurite through the metathoracic ganglion), whereas other regions of branches were consistently reduced or missing in some response classes. Some position-and-acceleration receptors had no main branches off the main neurite, and must therefore make relatively restricted contact with motor neurones and interneurones. Phasic or tonic neurones which responded in ranges of tibial extension had branches which projected further medial in Dorsal Commissures III and IV than similar neurones which responded in ranges of tibial flexion. I compare my results to previous studies of mapping in the insect CNS.

Mechanism for range fractionation in chordotonal organs of Locusta migratoria (L) and Valanga sp. (Orthoptera : Acrididae)

The femoral chordotonal organ (FCO) of Locusta migratoria and Valanga sp. (Orthoptera : Acrididae) is a leg stretch receptor containing scolopophorous sensory neurones embedded in a ligament, which emerges distally from the body of the organ and connects to a distal apodeme. The ligament is pulled when the tibia is flexed. Thus the FCO bridges the femur-tibia joint. The ligament is divided into separate strands, each of which is composed of several or more, long attachment cells. These cells link individual scolopidia to the apodeme. An additional unloading strand connects the body of the FCO to a static point on the femoral integument. Because the strands are inserted along the apodeme in a sequential array, and because the unloading strand holds all the tension on the FCO when the ligament is relaxed (tibia extended), a mechanism for gradual, sequential uptake of tension by the ligament strands exists when the ligament is pulled (tibia flexed). This leads to a range fractionation of stretch-sensitive neurone responses during tibial flexion, and of relaxation-sensitive neurone responses during tibial extension. Observations on the ultrastructural distribution of desmosomes suggest that groups of attachment cells may be functionally connected and may collectively transmit force to specific groups of neurones.

The firing pattern of the locust ( Schistocerca gregaria americana) mesothoracic femoral motor axons in resistance reflexes and during walking on a treadmill

The firing pattern of the locust mesothoracid femoral motoneurones during passive extension of the tibia (resistance reflexes) has been examined. Of the flexor excitors, some are activated only by very fast tibial movements producing a few spikes. Others produce a discharge which lasts as long as the imposed tibial extension. The flexor slow motoneurones are the only spontaneously active neurones and their frequency increases and remains high as long as the tibial extension lasts. The inhibitors remain silent during active tibial flexion (or extension) and they are active only during maintained extension. From the mesothoracic extensor tibiae motor axons, the slow extensor tibiae fires during tibial flexion and the inhibitor during tibial extension. The fast extensor tibiae is silent during tibial movement. The activity of the femoral motoneurones was also studied in a tethered locust walking on a treadmill. First, the similarities in the firing motor pattern between a deafferented and a normal walking leg were established and then the activity of the flexor tibiae motoneurones, recorded from a deafferented leg of a walking locust, was analysed. A modification in the resistance reflexes during the active stage of the animal was also demonstrated. The resistance reflexes seemed to become assistant reflexes during walking.

Prey capture in mantids: The role of the prothoracic tibial flexion reflex

The role which the prothoracic tibial flexion reflex plays in prey catching by the mantis Tenodera aridifolia sinensis (Sauss.) is examined. This reflex is elicited both by tactile stimulation of the movable spines on the ventro-medial border of the raptorial foreleg femur, and by pulling against the tibia. The reflex elicited by spine stimulation is inhibited when the ipsilateral tarsus is resting on the substrate, but is not if the tibia rests on the substrate after removal of the tarsus. Immobilizing the femoral spines by covering them with paraffin wax eliminates the ipsilateral tibial reflex to spine stimulation but not to tibia pulling. If either the right or left set of femoral spines are immobilized, the waxed foreleg fails to grip prey, and is readjusted around captured prey more frequently than the normal leg. If both sets of femoral spines are immobilized, the mantid's ability to successfully capture prey is impaired but not eliminated. It is concluded that proprioceptive feedback from the movable femoral spines and the tibiae play roles in, but neither are solely responsible for maintaining a continuous grip on prey captured by T. sinensis.

Research Note: Development of a Quantitative Method for the Evaluation of Varus-Angular Bone Deformity in Chickens

A quantitative technique was developed to measure the degree of flexion (twisting) and torsion (angulation) of the tibiotarsus bone from chickens affected with varus-angular bone deformity (varus-ABD). A plexiglass device was constructed consisting of X, Y, and Z-axis planes. The Y-axis plane was used to position the tibia in a constant reference position. The distance in millimeters from the (0, 0, 0) coordinate to the (X′, 0, 0) coordinate was used to measure medial tibial flexion (TF), and the distance from the (0, 0, 5 cm) coordinate to the (X′, 0, 5 cm) coordinate was used to measure lateral TF. The X-axis plane was fitted with a protractor to measure the angle of the proximal head of the tibia as a measure of tibial torsion (TT). The Z-axis plane was used to measure tibial length. Tibias with mild varus-ABD had TF values of >0 but ≤5 mm, whereas severe varus-ABD tibias had TF values of >5 mm. The TT values ranged from 10 to 60°, with the lower values associated with severe varus-ABD.

The femoral chordotonal organs of Decticus albifrons (Orthoptera: Tettigoniidae)—II. Function

1. 1. The electrophysiological properties of the pro-meso and metathoracic chordotonal organs of Decticus albifrons were studied. 2. 2. All three show minimum tonic response at a femur-tibiae angle of 90°, maximum response during tibial flexion (FTA of 0°) and they show a relatively small increase in their firing frequency during extension (FTA of 180°). 3. 3. The tonic activity of the COs adapts faster in the metathoracic than in the pro and mesothoracic. 4. 4. There are indications that some tonic sensory units are bi-directionally sensitive. 5. 5. The sensory neurons which respond only to tibial movement (phasic response) are much larger than those which are active when the tibia is stationary. 6. 6. The responses of the femoral motoneurons to the tibial movement represent resistance reflexes.

Prey capture in mantids: Prothoracic tibial flexion reflex

We describe a prothoracic leg tibial flexion reflex (PTFR) of the praying mantis Tenodera aridifolia sinensis which is initiated by tactile stimulation of the movable spines of the ventro-medial border of the femur. This flexion reflex may be responsible for the continuous grasping of a captured prey by the mantid.

The physiological mechanism of catalepsy in the stick insectCarausius morosus Br.

1. The phenomenon of catalepsy in the stick insect,C. morosus, during thanatosis (death feigning) was investigated quantitatively by applying controlled flexions of known amplitude, rise-time, and hold-time to the femorotibial joint of the prothoracic leg and observing the behaviour of the leg on release. 2. After release the leg always returned towards its fully extended resting position. An initial rapid extension (the fast phase), was followed by a slower movement (the slow phase), which often took several minutes. In some preparations the leg returned completely to its fully extended position (non-cataleptic). In others there was a maintained displacement of the leg after bending (partial catalepsy). 3. This misalignment between the initial extended position of the leg and its final position was proportional to the angle through which it had been bent. Rate of bending and time held bent had no effect on the final position of the leg. However the amplitude of the fast phase of the return curve was greater with slow rates of bend and with short times held bent. 4. Repeated bending caused a decline in the rate and extent of return and hence an increase in the misalignment between initial and final leg positions. 5. Denervation of the flexor tibiae had no effect on the return curve or on the final resting position of the leg, whereas extensor tibiae denervation resulted in the leg assuming a 90 ° flexed position, as did total denervation or CO2 anaesthesia. 6. Ablation of the femoral chordotonal organ, which causes considerable modification of locomotory behaviour, also had complex effects on the characteristics of the return curve following imposed tibial flexion. 7. Recordings of motor output to the extensor tibiae muscle indicated that imposed leg flexion was accompanied by a reflex increase of slow extensor excitor (unit 1) output and recruitment of a larger fast extensor unit (unit 2) during bending. Peak frequency and steady state (held) frequency of unit 1 in the flexed position were related to the angle of bend and to the rise time (inversely related to the rate of bend). This anomalous velocity response is an unusual feature of the reflex. 8. The behaviour of the leg after release from bending and the shape of the return curve could be accounted for by the operation of normal reflex pathways involving the extensor tibiae and the femoral chordotonal organ. The misalignment between the initial and final positions of the leg in insects showing partial catalepsy was found to be due to a maintained depression of unit 1 frequency after a bend/hold/ release cycle. This frequency depression was also found in non-cataleptic insects where no maintained misalignment was observed. 9. The relationship between leg position and extensor tension was found to be non-linear, and large increases in extensor tension are required to maintain the leg at femorotibial angles greater than 160 °. 10. The overall frequency of unit 1 output was found to be greater in non-cataleptic insects than in those showing partial catalepsy. This suggests that in non-cataleptic insects the maintained frequency depression after imposed flexion is not sufficient to depress the overall frequency below the critical level required to maintain the fully extended position, whereas in insects showing partial catalepsy reduction of the already lower extensor unit 1 frequency results in depression below this critical frequency and hence in maintained leg displacement. 11. It is suggested that the instances of “catalepsy” reported by previous authors were the result of repeated bending and hence cumulative depression of extensor unit 1 frequency.

Responses of perfused isolated leg preparations of the cockroach, Gromphadorhina portentosa, to L-glutamate, gaba, picrotoxin, strychnine and chlorpromazine.

AbstractA perfused leg preparation of Gromphadorhina portentosa (Orthoptera) was developed for use in pharmacological studies and bioassay procedures. Study of tibial flexion with increasing stimulation intensity at low frequency revealed five fast motor units. Chlorpromazine (2.5 × 10−4 M) progressively blocked these motor units. GABA generally failed to affect fast system responses, even at high concentration (2.5 × 10−4 M). A high concentration (2.5 × 10−4 M), picrotoxin produced effects consistent with the interpretation that motor axon excitability was affected. Strychnine (2.5 × 10−4 M) produced no effect on isolated leg preparations. L‐Gultamate (pH 7.2) produced contractures; the threshold for this response was 2.5 × 10−4 M. Contractures were produced after application to resting muscle, and were also observed in preparations receiving low frequency indirect stimulation. The response to glutamate under the latter condition closely resembled incomplete tetanus. L‐Glutamate (2.5 × 10−4 M) produced a reversible depression of kick force in locusts. These responses are compatible with the hypothesis that L‐glutamate is an excitatory neuromuscular transmitter in insects.