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Full-Text Articles in Medicine and Health Sciences
Neuronal Correlates For Neuroendocrine Habituation To Repeated Stress, Sara Matovic
Neuronal Correlates For Neuroendocrine Habituation To Repeated Stress, Sara Matovic
Electronic Thesis and Dissertation Repository
One way that the body actively responds to an impending stressor is by increasing systemic glucocorticoids through the activation of the hypothalamic-pituitary-adrenal (HPA) axis. While it is essential for short-term adaptation to stress, the sustained activation of the HPA axis during chronic stress can be detrimental and is linked to stress-related psychiatric conditions such as anxiety and depression. Therefore, it is important that the HPA axis adapts, or habituates, during chronic stress to minimize the negative consequences. Corticotropin releasing hormone (CRH) neurons in the paraventricular nucleus of the hypothalamus (PVN) function to assimilate incoming information from the stress circuitry and …
Functional Magnetic Resonance Imaging As An Assessment Tool In Critically Ill Patients, Loretta Norton
Functional Magnetic Resonance Imaging As An Assessment Tool In Critically Ill Patients, Loretta Norton
Electronic Thesis and Dissertation Repository
Little is known about whether residual cognitive function occurs in the earliest stages of brain injury. The overarching goal of the work presented in this dissertation was to elucidate the role of functional neuroimaging in assessing brain activity in critically ill patients. The overall objective was addressed in the following four empirical chapters: In Chapter 2, three versions of a hierarchically-designed auditory task were developed and their ability to detect various levels of auditory language processing was assessed in individual healthy participants. The same procedure was then applied in two acutely comatose patients. In Chapter 3, a hierarchical auditory task …
Age-Related Reductions Of Motor Unit Discharge Rates In The Human Hamstrings, Eric A. Kirk
Age-Related Reductions Of Motor Unit Discharge Rates In The Human Hamstrings, Eric A. Kirk
Electronic Thesis and Dissertation Repository
Neuromuscular age-related differences of human limb muscles have been widely described with the notable exception of the hamstring muscles. The purpose was to assess contractile function and spinal motor neuron output expressed as motor unit discharge rates in the hamstrings of 11 young (26 ± 4 y) and 10 old (80 ± 5 y) men. Maximal voluntary isometric contractions (MVC), stimulated contractile properties and motor unit discharge rates from sub-maximal to MVC were recorded from the lateral (biceps femoris) and medial (semimembranosus-semitendinosus) posterior thigh. In the old men, knee extension and flexion at MVC were lower (P < 0.05) and voluntary activation as assessed by the twitch interpolation technique was reduced (P < 0.05) compared with the young. Electrically evoked twitches were lower in amplitude and increased in duration of old hamstrings (P < 0.05) compared with the young. At sub-maximal to maximal contraction intensities the old had lower motor unit discharge rates as compared to the young (P < 0.001). At MVC, mean motor unit discharge rates in the biceps femoris and semimembranosus-semitendinosus of old hamstrings were 15.6 ± 6.4 and 15.3 ± 5.9 Hz, as compared to 26.1 ± 10.1 and 27.9 ±7.8 Hz in the young, respectively (P < 0.001). To date, the hamstrings show the greatest age-related reductions in motor unit discharge rates of any major limb muscle. These findings, in relation to motor unit discharge rates from other flexors and extensors support that in ageing, greater reductions are associated with limb flexor muscles.