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Digital Image Processing and Three-Dimensional Reconstruction in the Basic Neurosciences
Published in Rangachar Kasturi, Mohan M. Trivedi, Image Analysis Applications, 2020
The second system is by (Hibbard et al./1986), who reported 3-D reconstructions of microcapillary modules in the median eminence of the hypothalamus of the rabbit. This portion of the hypothalamus physically connects the brain and the pituitary, and the capillary network within the median eminence is believed to play a role in controlling the two-way hormonal communication between the brain and the pituitary. To establish whether local control of blood flow within the median eminence is possible, a series of reconstructions was undertaken to study the placement of smooth-muscle sphincters within microcapillary loops and arbors. Hibbard et al./1986 report two reconstructions of small capillary bundles carried out entirely by programmed image segmentation, mosaicking, and two stages (coarse and fine) of alignment (Fig. 5.13). Thin tissue sections were imaged by transmission electron microscopy and digitized. The capillary interiors (lumens) were identified using an operator designed specifically to extract the lumens with their high gray-levels, low local variances, and long-range contiguity. Mosaics of multiple overlapping micrographs of the same section were obtained by matching lumen edges by cross-correlation (Moik/1980). The mosaic images were then aligned, first by superposing centroids and principal axes, and then by alternate cycles of translational and rotational cross-correlation, as described above for the metabolic 3-D reconstruction (Hibbard et al./1987).
Cellular and Molecular Basis of Human Biology
Published in Lawrence S. Chan, William C. Tang, Engineering-Medicine, 2019
The diencephalon, located deep in the brain and inferior to the middle cerebral cortex, has several components, each with distinct sensing and endocrine functions: Thalamus: Controlling the input of sensing from afferent (ascending) nerves.Hypothalamus: Regulating body temperature, regulating hunger, thirst, sexual behavior via pituitary gland, also initiating “fight-or-flight” response.Pineal gland: Regulating biorhythm.Pituitary gland: Regulating reproductive system in organ maturation.
The relation between psychosocial working conditions and work-related musculoskeletal complaints
Published in Richard Graveling, Ergonomics and Musculoskeletal Disorders (MSDs) in the Workplace, 2018
Leif W. Rydstedt, J. Paul Weston
Catecholamines respond almost immediately to acute stress exposure (not as immediate as neurally mediated responses) and prepare the organism for the ‘fight-or-flight’ response. The SAM system responds primarily to issues of control of the environment, manifesting the classic fight-or-flight response in reaction to acute physical threat. Perceived psychological stress activates the hypothalamus and sympathetic nervous system to secrete adrenaline and noradrenaline into the bloodstream. These catecholamines mobilise energy to the brain, heart and muscles and increase blood pressure, while reducing the activity of the gastrointestinal system, visceral activity and reproductive activity (Bishop, 1994). It has been shown that adrenaline secretion from the adrenal medulla is associated with the intensity of mental stress, as opposed to noradrenaline, which is more sensitive to changes in physical demands and body posture (Lundberg, 2005).
Attenuation of stress-induced cardiovascular reactivity following high-intensity interval exercise in untrained males
Published in Journal of Sports Sciences, 2021
Nor MF Farah, Amerull Daneal Amran, Ahmad Munir Che Muhamed
Cardiovascular reactivity refers to responsiveness of the cardiovascular system towards acute physiological or psychological stressors, eliciting changes to cardiovascular functions e.g., heart rate, cardiac output, and blood pressure, allowing the body to adapt to the stressor (Panaite et al., 2015). Stress-induced cardiovascular reactivity is a result of the interplay between activation of the sympathetic system and hypothalamic–pituitary–adrenal axis, along with parasympathetic or vagal withdrawal (Huang et al., 2013). Following cessation of the stress response, the cardiovascular functions are restored to pre-challenge or baseline levels, termed as cardiovascular recovery. This is mostly attributable to cardiac vagal reactivation, which commonly leads to reduction in blood pressure and heart rate responses (Stanley et al., 2013). Frequent exposure to stressful situations in day-to-day life can lead to cardiovascular responses that are exaggerated, prolonged, and repeatedly expressed resulting in heightened blood pressure and slower heart rate recovery.
Urinary Isoflavones Levels in Relation to Serum Thyroid Hormone Concentrations in Female and Male Adults in the U.S. General Population
Published in International Journal of Environmental Health Research, 2021
Patricia A. Janulewicz, Jeffrey M. Carlson, Amelia K. Wesselink, Lauren A. Wise, Elizabeth E. Hatch, Lariah M. Edwards, Junenette L. Peters
Thyroid hormones (TH) are controlled through the hypothalamic-pituitary-thyroid (HPT) axis and are crucial for the regulation of many biological systems. The HPT axis is complex and sensitive to perturbations. The hypothalamus, located in the central nervous system, produces thyrotropin-releasing hormone (TRH), and sends it to the pituitary gland, which releases thyroid stimulating hormone (TSH). TSH binds to receptors on the thyroid gland and stimulates the synthesis and release of thyroid hormones, thyroxine (T4) and triiodothyronine (T3), into peripheral circulation. Proper production of these hormones is largely dependent on iodine levels (Rousset et al. 2000). Circulating TH levels are maintained by a feedback mechanism between the hypothalamus, pituitary gland, and thyroid gland (Rousset et al. 2000; Pearce and Braverman 2009; Gilbert et al. 2012). Optimal circulating TH levels are essential for normal fetal and child growth (Meeker 2012; DiVall 2013) and brain development (Meeker 2012), reproductive function, and metabolism (Meeker and Ferguson 2014).
Human exposure to synthetic endocrine disrupting chemicals (S-EDCs) is generally negligible as compared to natural compounds with higher or comparable endocrine activity. How to evaluate the risk of the S-EDCs?
Published in Journal of Toxicology and Environmental Health, Part A, 2020
Herman Autrup, Frank A. Barile, Sir Colin Berry, Bas J. Blaauboer, Alan Boobis, Herrmann Bolt, Christopher J. Borgert, Wolfgang Dekant, Daniel Dietrich, Jose L. Domingo, Gio Batta Gori, Helmut Greim, Jan Hengstler, Sam Kacew, Hans Marquardt, Olavi Pelkonen, Kai Savolainen, Pat Heslop-Harrison, Nico P. Vermeulen
The function of the endocrine system is strictly regulated involving the hypothalamic/pituitary/gonad axis. The hypothalamus secretes stimulating and inhibiting factors that modulate the pituitary secretion of hormones. These then regulate diverse processes like the control of growth, metabolism, or reproductive cycles. The homeostasis of the endocrine system is regulated by feedback mechanisms. The more common negative feed-back cycles negatively affect stimulation from a preceding tissue. The less common positive-feedback mechanisms positively affect or increase stimulation from the preceding tissue.