Sex differences and stress resistance
Professor Bruce McEwen discusses differences between the sexes in coping with stress. These are mediated by hormonal, neural, and genetic factors.
Good question. First, letâ€™s talk about sex differences, and then letâ€™s talk about the concept of resilience, and what happens in the brain. If we talk about sex hormones and sex differences, we know that early in development â€“ in the human itâ€™s at mid-gestation and it also continues around early after birth â€“ there is the production of testosterone by the testes that causes what we call sexual differentiation of the brain. Certain brain structures from the hypothalamus to parts of the cerebral cortex, and probably a lot of other parts of the brain, are subtly changed by the testosterone, and also by genetic factors from the Y chromosome, so that the male brain develops in a somewhat different way from the female brain. At each stage the male and female are, of course, boys and girls, babies, are interacting with their environment, and processing things in somewhat different ways, so the combination of experience and these biases by the genetic and hormonal factors leads these brains to be somewhat different and to prioritize things, if you will, in different ways. The second part is that the adult brain, instead of just having the hypothalamus being the area that controls reproduction and is sensitive to sex hormones, the entire brain is, to some extent, responsive to sex hormones, and the reason for that is that there are receptors for steroid hormones that are found not just in the cell nucleus, where they regulate gene expression, but they are found in other parts of cells, in the synapses, in the dendrites, in glial cells, and they regulate not only genomic, genetic regulation of genes, but they also regulate second messenger systems, very much like neurotransmitters. We didnâ€™t know about these receptors until we began to use high-resolution techniques, electron microscopy, to look inside cells with antibodies for these receptors. Now we realize that the entire brain responds to all classes of steroid hormones, particularly the sex hormones, and in each case, whether its cerebellum or the movement control areas of the brain or the spinal cord or the hippocampus in memory or the amygdala in fear, or areas in the brainstem involved in pain, each of these areas responds to the sex hormones. So, if we put together what happens early in life, in addition to the experiences that people have, being a good supportive family life or a chaotic home life, plus these subtle sex differences, plus then the actions of circulating hormones in adult life, you have many different possibilities for producing different outcomes and vulnerabilities. For example, women are more vulnerable to anxiety and depressive disorders, but males are much more vulnerable to substance abuse and antisocial behavior. You could argue that these are just simply different ways that the male and female, on the average, sort of acts out or projects their response to, say, a toxic stress, and that it is not so much vulnerability, but a different strategy for dealing with these conditions.
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Professor Bruce McEwen describes the endocrine system, which regulates hormones, the autonomic nervous and immune systems.
Professor Bruce McEwen discusses the remodeling of dendrites, which are affected by BDNF, TPA, cell-adhesion molecules, and a number of other factors.
Professor Bruce McEwen describes some of the key players in the endocrine system - hypothalamus, pituitary gland, adrenal cortex, sex glands, and hormones.
Professor Bruce McEwen discusses how the amygdala is involved in processing fear and stress.
Professor Bruce McEwen describes how the interplay between life events and genes can lead to behavioral problems.
Professor Bruce McEwen describes the blood-brain barrier, which prevents most proteins from accessing the brain. Selective proteins can cross the barrier, instigating processes such as neurogenesis.
Professor Bruce McEwen introduces BDNF, a class of neurotrophic molecules released by excitatory neurotransmission and associated with key process and disorders.
Professor Bruce McEwen describes the interplay between reilience and stress, which can cause the brain to shrink or grow.
Doctor Daniel Pine explains that hormones are a contributing factor to the development of anxiety and depression. They interact with a number of other factors to cause to these disorders.
Matt Ridley talks about chromosome 10, gene which creates cortisol.