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Influence of Ovarian Hormones on the Regulation of Luteinizing Hormone and Prolactin Release by Angiotensin II
Published in Craig A. Johnston, Charles D. Barnes, Brain-Gut Peptides and Reproductive Function, 2020
M.K. Steele, L.S. Myers, C.F. Deschepper, W.F. Ganong, K.N. Stephenson, R.L. Shackelford
In terms of LH, it is clear that the facilitatory effects of AII are mediated by norepinephrine which then acts, probably directly, at LHRH neurons. The AII-norepinephrine interaction apparently occurs within the anterior hypothalamus. Future experiments are necessary to determine where, for example, neurotensin and oxytocin fit into this scheme. Do they act via norepinephrine, the opioids, or directly on the LHRH neuron? Do they act in parallel or in sequence with AII to affect LHRH release? Do they act at the anterior hypothalamus or at the median eminence? Similar questions can be raised regarding AII and prolactin. Although we have evidence that the suppressive effects of AII on prolactin are mediated by dopamine, we do not know where this interaction occurs or whether AII acts directly on dopamine neurons (cell bodies or terminals), or via an intervening substance? Hopefully, the work presented both in this chapter and this volume will facilitate answers to these questions and ultimately provide a map to understand brain and pituitary peptide control over anterior pituitary hormone secretion.
Unexplained Fever In Neurological Disorders
Published in Benedict Isaac, Serge Kernbaum, Michael Burke, Unexplained Fever, 2019
It is generally believed that the hypothalamus plays an important role in thermoregulation. The anterior hypothalamus controls thermoregulatory sweating by serving as an internal temperature sensing organ.50 The hypothalamus is capable of establishing the set point for body temperature by inborn ionic mechanism within the region of its posterior part.51 Bauer offered convincing clinical evidence by reporting abnormalities of body temperature in 13 out of 60 patients in whom hypothalamic disease was proven by biopsy. In four, fever was the presenting symptom.52 Although the common presentation of abnormal hypothalamic temperature regulation takes the form of bouts of hypothermia, hyperthermia has been described. Following operations in the region of the floor of the third ventricle, the temperature may rise to 4PC (106°F) or even higher. It usually remains elevated until death some hours or days later and is resistant to treatment with common antipyretic drugs. The temperature may, however, be reduced by the combination of phenobarbitol and physical cooling of the body.
Fluid management
Published in Hemanshu Prabhakar, Charu Mahajan, Indu Kapoor, Essentials of Anesthesia for Neurotrauma, 2018
Shumaila Hasan, Matthew A. Kirkman
In the healthy, awake human, thirst is stimulated by the activation of osmoreceptors in the anterior hypothalamus, which occurs at approximately ≥295 mOsm/kg. There are several hormones that influence sodium and fluid balance in physiologic conditions (Table 30.2).
Human cold habituation: Physiology, timeline, and modifiers
Published in Temperature, 2022
Beau R. Yurkevicius, Billie K. Alba, Afton D. Seeley, John W. Castellani
Reflex thermoregulatory responses to cold exposure are produced by a series of integrated neural mechanisms. Afferent signals from the skin are sensed in the preoptic area of the anterior hypothalamus, from which efferent signals arise causing cutaneous vasoconstriction and shivering thermogenesis [48]. Cutaneous vasoconstriction and NST are mediated by the sympathetic nervous system and downstream adrenergic and noradrenergic mechanisms, whereas shivering thermogenesis is driven by the somatic motor system (Figure 1). The control of these efferent responses during a reduction in mean body temperature (integration of core and skin temperature) is depicted in Figure 2. The threshold is defined as the temperature point where the effector response is initially activated, whereas the sensitivity of the response is denoted by the slope of the mean body temperature to effector response. A shift in the response threshold is often considered to be the result of a central modulation, whereas a change in the response sensitivity reflects modulation at the peripheral level (i.e., the cutaneous microvasculature) [49–52]. Changes in either the threshold or slope of the vasoconstrictor or shivering responses are a hallmark of adaptive responses to cold. In the context of habituation, higher skin temperatures and reduced shivering thermogenesis are likely due to an increased threshold (i.e., delayed onset due to a greater change needed to elicit the response) and/or a reduced slope (i.e., lower sensitivity) of the cutaneous vasoconstrictor and shivering effector responses.
Influences of ovarian hormones on physiological responses to cold in women
Published in Temperature, 2022
Andrew M. Greenfield, Nisha Charkoudian, Billie K. Alba
In response to body cooling, afferent signals from peripheral and central thermoreceptors are sensed by the pre-optic region of the anterior hypothalamus (PO/AH), from which efferent signals elicit insulative (i.e., cutaneous vasoconstriction) and metabolic (e.g., shivering and nonshivering thermogenesis) thermoregulatory effector responses. The early and sustained response to cold exposure is characterized by constriction of cutaneous blood vessels and a subsequent reduction in skin blood flow [17,18]. The vasoconstrictor response to skin cooling reduces the skin-to-air temperature gradient and thus minimizes convective heat loss during cold exposure. As cooling continues and cutaneous vasoconstriction becomes insufficient to prevent decreases in core temperature, metabolic heat production increases to offset heat loss [19,20].
Advances in the pharmacological management of non-24-h sleep-wake disorder
Published in Expert Opinion on Pharmacotherapy, 2021
Shohei Nishimon, Naoya Nishino, Seiji Nishino
The SCN, located in the anterior hypothalamus, plays a vital role in controlling circadian rhythms, and regulates physiological phenomenon in mammals such as the sleep-wake cycle, behavior, body temperature, and secretion of endocrine factors including cortisol and melatonin [5,14–16]. The cycle of the endogenous biological clock is slightly longer than 24 h in humans [17], but exposure to morning light resets the endogenous circadian rhythm to 24 h [18,19]. The SCN receives light information from the melanopsin-containing retinal ganglion cells, also called intrinsically photosensitive retinal ganglion cells (ipRGCs), via the retinohypothalamic tract (RHT) [20,21]. IpRGCs, along with rods and cones, are the photoreceptor cells known in mammals [20]. The pineal gland eventually receives environmental light information from the SCN via multiple synaptic pathways including the paraventricular nucleus, intermediolateral cell column of the spinal cord, and superior cervical ganglion [22]. Such a phototransduction leads to the melatonin synthesis cycle.