Chloe White
\nProfessor Bell Lecture
\n11.7.2015 !
\nStress on the Brain: The HPA Axis and Behavior !
\nMargaret Bell, a researcher on Neuropsychology and Biological Psychology at the
\nUniversity of Texas at Austin, came to Trinity to give a lecture titled \u201cStress on the Brain: The
\nHPA Axis and Behavior.\u201d Since she may potentially be a professor at Trinity in upcoming years,
\nMs. Bell gave this lecture in the way that she would teach a class, so students could get a taste of
\nher teaching style. In her lecture, she diagrammed two main points: how the HPA axis is
\norganized, and what negative feedback is\/how it works with the HPA axis.
\nIn order to address the HPA system, we first need to talk about the basic endocrine system
\nin the human body. There are two main types of hormones that act in the human body: protein
\nhormones and steroid hormones. Steroid hormones, made up of fatty substances such as lipids
\nand cholesterol, can move right through the phospholipid bilayer of a cell. Hormones that cannot
\ndo this, such as protein hormones, must use membrane receptors in order to get inside of the cell,
\nand nuclear receptors to then get into the nucleus of that cell. These nuclear receptors activate
\n2nd messengers in the cell. The membrane receptors activate the creation of mRNA and can
\nchange protein expression: basically, they can change gene expression. The changes that occur
\nfrom these two receptors combined cause changes in the brain and in behavior.
\nThe HPA axis is a set of interactions, signals, and feedback systems between the
\nHypothalamus, Pituitary gland, and Adrenal Cortex (hence the name HPA). The main function of
\nthis axis controls the body\u2019s reaction to stress, however it also influences processes such as
\ndigestion and the immune system (functions that are influenced when the body goes through a
\nstress response). Each of the endocrine glands in the axis releases hormones and substances onto
\nthe next. The hypothalamus releases Corticotropin Releasing Hormone (CRH) onto the Anterior
\nPituitary, which then releases Adrenocorticotropic Hormone (ACTH) onto the Adrenal Cortex.
\nThe Adrenal Cortex releases multiple glucocorticoid hormones (mostly cortisol) in response to
\nreceiving the ACTH- however, these glucocorticoid hormones then act on the hypothalamus and
\nthe pituitary in a negative feedback cycle.
\nA negative feedback cycle is often compared to a thermostat. A thermostat works because
\nit knows what it\u2019s supposed to be at (set point), it senses the environment around it, and makes
\nchanges to adjust to the environment. Our body works this way as well. When the Adrenal
\nCortex receives ACTH from the pituitary, it starts producing cortisol. However, if it starts
\nreceiving too much ACTH, the cortisol will start acting on both the hypothalamus and the
\nanterior pituitary, signaling them to stop. It does this by binding with receptors on these two
\nglands, which notifies them to stop producing CRH and ACTH.
\nMs. Bell then had us do some problems in order to apply these theories on a real-life
\nstudy. The study concerned two different types of mother mice: High LG-ABN and Low LGABN.
\nHigh LG stands for High Licking\/Grooming, meaning this mother paid a lot of attention to
\nher newborns and created a lot of space for them. On the other hand, Low LG means the
\nopposite: she didn’t pay a lot of attention to her newborns. The study was looking at how
\noffspring of these two different types of mothers would respond to stress. Overall, it was found
\nthat offspring of High LG mothers responded to stress with less of a chemically-stressed
\nreaction, and they also returned to their baseline chemical levels quicker than Low LG offspring.<\/p>\n","protected":false},"excerpt":{"rendered":"
Chloe White Professor Bell Lecture 11.7.2015 ! Stress on the Brain: The HPA Axis and Behavior ! Margaret Bell, a researcher on Neuropsychology and Biological Psychology at the University of Texas at Austin, came to Trinity to give a lecture … Continue reading