Reflex arch

Burke JR, Schutten, MC, Koceja DM et al. (1996) Age-dependent effects of muscle vibration and the Jendrassik maneuver on the patellar tendcm reflex. Arch Hiys Med Rehabil 77 (6) 600-604... 

The regulation of the total peripheral resistance also involves the complex interactions of several mechanisms. These include baroreflexes and sympathetic nervous system activity response to neurohumoral substances and endothelial factors myogenic adjustments at the cellular level, some mediated by ion channels and events at the cellular membrane and intercellular events mediated by receptors and mechanisms for signal transduction. As examples of some of these mechanisms, there are two major neural reflex arcs (Fig. 1). Baroreflexes are derived from high-pressure barorecep-tors in the aortic arch and carotid sinus and low-pressure cardiopulmonary baroreceptors in ventricles and atria. These receptors respond to stretch (high pressure) or... 

Feldman RG, Chirico-Post J, Proctor SP. 1988. Blink reflex latency after exposure to trichloroethylene in well water. Arch Environ Health 43 143-147. 

A decrease in plasma volume leads to decreased MAP, which is detected by baroreceptors in the carotid sinuses and the arch of the aorta. By way of the vasomotor center, the baroreceptor reflex results in an overall increase in sympathetic nervous activity. This includes stimulation of the heart and vascular smooth muscle, which causes an increase in cardiac output and total peripheral resistance. These changes are responsible for the short-term regulation of blood pressure, which temporarily increases MAP toward normal. 

Now I could see it better— tail up, back arched. Cats rarely contract rabies, but they are especially vicious when they do. A bite from a rabid cat must be one of the least pleasant ways of going to one s eternal reward, and I did not tmst my swordsmanship against feline reflexes. 

A newborn baby boy is unconscious after having suffered a seizure. A variety of dysmorphic facial features are evident, including a high forehead, a flat occiput, large fontanelles, and a high arched palate. All reflexes are depressed. There is hepatomegaly consistent with... 

Any sudden alteration in the mean arterial blood pressure tends to produce compensatory reflex changes in heart rate, contractility, and vascular tone, which will oppose the initial pressure change and restore the homeostatic balance. The primary sensory mechanisms that detect changes in the mean arterial blood pressure are stretch receptors (baroreceptors) in the carotid sinus and aortic arch. 

Lowenstein, O. and Lowenfeld, I.E., Mutual role of sympathetic and parasympathetic in shaping of the pupillary reflex to light, Arch. Neurology Psychiatry (Chicago), 64, 341, 1950. 

Ioffe S, Jansen AH, Russell BJ, Chemick V. Sleep, wakefulness and the monosynaptic reflex in fetal and newborn lambs. Pflugers Arch Eur J Physiol 1980 388 149-57. 

Sutton PM (1981) The interaction between reflex apnoea and bradycardia produced by injecting 5-HT into the nodose ganglion of the cat. Pflugers Arch 389 181-187... 

Fozard JR, Ali AT (1978) Receptors for 5-hydroxytryptamine on the sympathetic nerves of the rabbit heart. Naunyn Schmiedeberg s Arch Pharmacol 301 223-35 Frank K, Fuortes MGF (1957) Presynaptic and postsynaptic inhibition of neurosynaptic reflex. Fed Proc 16 39 40... 

Afferent neurons The afferent neurons (fibers) of the autonomic nervous system are important in the reflex regulation of this system, for example, by sensing pressure in the carotid sinus and aortic arch and signaling the CNS to influence the efferent branch of the system to respond (see below). 

Reflex arcs Most of the afferent impulses are translated into reflex responses without involving consciousness. For example, a fall in blood pressure causes pressure-sensitive neurons (baroreceptors in the heart, vena cava, aortic arch, and carotid sinuses) to send fewer impulses to cardiovascular centers in the brain. This prompts a reflex response of increased sympathetic output to the heart and vasculature, and decreased parasympathetic output to the heart, which results in a compensatory rise in blood pressure and tachycardia (see Figure 3.5). 

Piikivi L. 1989. Cardiovascular reflexes and low long-term exposure to mercury vapour. Int Arch Occup Environ Health 61(6) 391-395. 

Although CN can disperse rapidly at high temperatures, at lower temperatures CN provides stimulation of the chemoreceptors in the aortic arch activating a reflex respiratory gasp. It has been shown that it is not possible in the conscious human to prevent subsequent gasps following stimulation of the chemoreceptors. If the concentration of CN is sufficient, the subsequent inhalation of additional CN leads to unconsciousness, convulsion, and possibly death. 

Heymans, C., Bouckaert, J.J., and Dautrebande, L., Sinus carotidien et reflexes respir-tores. Ill SensibUite des sinus carotidiens aux substances chimiques. Action stimulante respiratoire reflexe du sulfure de sodium, du cyanure de potassium, de la nicotine et de la lobeline, Arch. Int. Pharmacodyn. Thera., 40, 54, 1931. 

Paintal AS (1969) Mechanism of stimulation of type J pulmonary receptors, J Physiol 203 511-532 Paintal AS (1973) Vagal sensory receptors and their reflex effects. Physiol Rev 53 159-227 Pinto A, Yanai M, Sekizawa K, Aikawa T, Sasaki H (1995) Conditioned enhancement of cough response in awake guinea pigs, Int Arch Allergy Immunol 108 95-98... 

Kamei J, Ogawa M, Kasuya Y (1987) Monoamine and the mechanisms of action of antitussive drugs in rats. Arch Int Pharmacodyn 290 117-127 Kamei J, Tanihara H, Igarashi H, Kasuya Y (1989) Effects of A-methyl-D-aspartate antagonists on the cough reflex. Eur J Pharmacol 168 153-158... 

Haeusler, G., and Osterwalder, R., 1980, Evidence suggesting a transmitter or neuromo-dulatory role for substance P at the frist synapse of the baroreceptor reflex, Naunyn Schmiedeberg s Arch. Pharmacol. 314 111-121. 

Our laboratory has recently investigated the reflex effects of carotid sinus hypertension on the coronary circulation (Ito and Feigl, 1984a). The carotid sinuses were vascularly isolated and perfused with a servo controlled pressure pump. The aortic depressor nerves were cut bilaterally to prevent aortic arch baroreceptor reflexes from buffering carotid sinus reflexes. The left main coronary artery was perfused at constant pressure, and the ventricles were paced at a constant rate following the production of heart block in a closed-chest preparation. Aortic pressure was stabilized with a pressure reservoir and propranolol was administered to block reflex sympathetic effects to the myocardium. Step increases in carotid sinus pressure resulted in graded reflex coronary vasodilation accompanied by increases in coronary sinus oxygen tension. Atropine administration demonstrated that the major portion of the reflex vasodilation was due to parasympathetic activation. These results indicate that parasympathetic coronary vasodilation is part of the carotid sinus baroreceptor reflex. 

Neymans C, Bouckaert JJ, Dautrebande L. Sinus carotidien et reflexes respiratoires. II. Influences respiratoires reflexes de I acidose, de Tanoxemie, de I anhydride carbonique, de respiratoires dans les poumons et au dela des poumons. Arch Int Pharmacodyn 1930 39 400-448. 

In mammals the carotid bodies are situated at the bifurcations of the cormnon carotid arteries into their internal and external branches and are irmervated by the sinus nerve, a branch of cranial nerve EX (Fig. 1). The aortic bodies in mammals, on the other hand, are located in the region of the aortic arch and the roots of the major arteries of the thorax. Their afferent fibers nm in the aortic nerve, a branch of the vagus (Fig. 1). They appear to make little contribution to the resting ventilatory drive in eucapnic normoxia and may not contribute to the hypoxic ventilatory response in many species. It would appear that they participate almost exclusively in cardiovascular reflexes in this group (see Ref. 25 for review). Glomus tissue that may... 

Based on reflex studies, the hypoxic bradycardia exhibited by most teleost fish appears to be triggered by activation of externally oriented receptors that monitor aquatic O2 levels. These receptors are found largely on the first gill arch but have been reported on other gill arches in some species (see Refs. 13,65 for reviews). Not all fish follow this pattern, however. In the gar and the tambaqui they appear to be sensitive to both internal and external changes in Pq (79,85) while in the neotropical fish the traira they appear to only monitor the P02 of the blood (84). By contrast, the 02-sensitive receptors instrumental in producing the increases in ventilation frequency and amplitude in most teleost fish appear to monitor both the blood and the water (13,67,84,85). 

The microscopic anatomy of glomus cells in vertebrates has been described in the aortic and carotid bodies of mammals (59,88) and birds (48,68,71) and the carotid labyrinth of amphibians (40,49). Although there is reflex and neurophysiological evidence for 02-sensitive chemoreceptors in the gills of larval amphibia (44,45,83), they have not been examined microscopically. Reptiles do not appear to have distinct carotid bodies or labyrinths. However, clusters of glomus cells have been identified microscopically in the central cardiovascular region, in connective tissue around the pulmonary, carotid, and aortic arches in turtles and lizards (4,42,75). 

---