| 11. |
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| 12. |
- Wennergren, Göran, 1947, et al.
(författare)
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Interaction between the hypothalamic defence reaction and cardiac ventricular receptor reflexes.
- 1976
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Ingår i: Acta physiologica Scandinavica. - : Wiley. - 0001-6772 .- 1365-201X. ; 96:4, s. 532-47
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Tidskriftsartikel (refereegranskat)abstract
- The interference with regard to the cardiovascular and gastric motility responses which follows stimulation of the hypothalamic defence area (D.A.) and a simultaneous afferent input from cardiac ventricular receptors was analysed in chloralose-anesthetized cats. In spinalized animals with only the vagal efferent innervation of autonomic effectors from supraspinal structures intact, a D.A. stimulation increased the heart rate to the same level irrespective whether the cardiac receptor afferents were stimulated or not. This suggests that the vagal component of the reflex bradycardia of cardiac receptor origin was completely suppressed by the D.A. stimulation. The reflex gastric relaxation to cardiac receptor activation, mediated via vagal efferent non-adrenergic fibres, was similarly completely blocked by D.A. stimulation. In contrast, the reflex inhibition of the sympathetic outflow to the heart and vessels from cardiac receptors was still effective during a D.A. stimulation, a phenomenon which seems compatible with a simple summation of excitatory D.A. and inhibitory cardiac receptor influences on the sympathetic neurons. The modifying influence from ventricular receptors on D.A. responses closely resembles that exerted by the arterial baroreceptors. The two reflex mechanisms thus work in concert and synergistically with the hypothalamic influences to produce maximal cardiac output and skeletal muscle perfusion without undue increases of pressure load on the pump during a defence reaction.
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| 13. |
- Wennergren, Göran, 1947, et al.
(författare)
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Studies on the central integration of excitatory chemoreceptor influences and inhibitory baroreceptor and cardiac receptor influences.
- 1976
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Ingår i: Acta Physiologica Scandinavica. - : Wiley. - 0001-6772 .- 1365-201X. ; 96:1, s. 1-18
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Tidskriftsartikel (refereegranskat)abstract
- Experiments were performed on cats to explore the integrated cardiovascular responses when excitatory (chemoreceptor) and inhibitory (baroreceptor or cardiac receptor) influences are simultaneously presented to the medullary cardiovascular areas. At a given sinus pressure in the low or medium pressure range, the systemic blood pressure and the vascular resistance were higher when the chemoreceptors were stimulated, while a high, pulsating sinus pressure, i.e.a strong baroreceptor stimulation, could suppress completely even an intense chemoreceptor activation. Thus, the set point and the gain of the baroreflex were increased by a concomitant chemoreceptor activation. These effects are compatible with a simple, mutual 'summation' of excitatory and inhibitory influences on a common population of central vasomotor neurons. The reflex vasodilator effects elicited via vagal cardiac afferents were found to be more effectively suppressed by a concomitant chemoreceptor stimulation than were the baroreceptor effects, provided a primary chemoreceptor response (bradycardia) was at hand, while the heart rate responses were essentially uninfluenced by the prevailing chemoreceptor activity. This chemoreceptor suppression of the reflex vasodilatation from cardiac receptors, which may be of great importance in hypoxic situations, e.g. during a dive, suggests a more complex, neuronal interaction between the two reflex mechanisms in the CNS.
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| 14. |
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| 15. |
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| 16. |
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| 17. |
- Johansson, B, et al.
(författare)
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Effects of Tris on vascular smooth muscle
- 1979
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Ingår i: American Journal of Physiology - Heart and Circulatory Physiology. - 1522-1539. ; 237:3, s. 409-411
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Tidskriftsartikel (refereegranskat)
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| 18. |
- Johansson, B, et al.
(författare)
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Responses of smooth muscle to quick load change studied at high time resolution
- 1978
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Ingår i: Blood Vessels. - 0303-6847. ; 15:1-3, s. 65-82
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Tidskriftsartikel (refereegranskat)abstract
- Quick-release and quick-stretch experiments have been performed on preparations of smooth muscle from rat portal vein and rabbit urinary bladder. The low equivalent mass of the isotonic lever (8 mg) implied that inertial oscillations were limited to the first 5-10 msec after the load step. The high time resolution achieved in this way enabled us to separate three components in the length response to a step change in force: (1) an immediate passive elastic recoil, (2) an isotonic velocity transient lasting 50-75 msec and (3) shortening of the contractile element after its full adjustment to the new load. The maximal series elastic recoil was about 10% of the total muscle length in portal vein but only some 3% in urinary bladder. Stiffness of series elasticity increased in proportion to force and was about 3 times higher in bladder than in portal vein at any force level. Force-velocity relations for loads less than Po could be fitted to Hill's equation; Vmax in 4 AC-stimulated portal veins was 0.53 +/- 0.03 muscle lengths/sec and in 8 K+-activated bladder preparations 0.18 +/- 0.01 muscle lengths/sec. Application of loads greater than Po produced rates of lengthening greater than expected from an extrapolation of Hill's hyperbola. The nature of the transient component is discussed in the light of recent studies of force and velocity transients in skeletal muscle.
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| 19. |
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| 20. |
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