The largest part of the human brain is the cerebrum which includes the cerebral cortex, the four lobes on both sides of the brain as well as the hippocampus, basal ganglia and olfactory bulb. This cerebrum controls voluntary action, emotions, hearing, vision and personality. Generally classified into four lobes which are attached on either hemisphere by the corpus callosum, the four bulbs are the frontal, parietal, occipital and temporal. The hemispheres have many ridges in them which help to increase surface area. Looking at the frontal lobe, there is the motor cortex which relays messages down the spinal cord to motor neurons for action and movement. The first long ridge or sulcus in the parietal lobe is the somatosensory cortex which receives sensory information from the environment. These two structures correspond to areas in the body directly. I'm highlighting some of the important structures that will tie into concepts that we cover in regards to yoga and mindfulness. So, when we talk about things like stress response, when we talk about things like breathing rate, there are certain areas of the brain that are valuable and important. In particular, we have the thalamus and this is a relay station for sensory impulses. So again, we have this ability to take in information from our environment and then we have transporting it to the cortex that think about it. Now, the hypothalamus is really important. Later on in endocrine and then again in stress, we're going to talk about the HPA axis which is one of the most foundational components of the stress response and the HPA axis stands for Hypothalamus Pituitary Adrenal. Now, the hypothalamus is the autonomic center. So, it regulates pretty much all autonomic responses that we can think of. So, body temperature, water balance, metabolism, emotions, fighting, fleeing, feeding, these are all going to be regulated by the hypothalamus that's going to in turn regulate not only the nervous system but the endocrinal as well. There's also the brain regions of the brain stem which help control breathing, heart rate, blood pressure regulation, the ability to swallow and some autonomic vomiting responses. So far, I've mentioned a few of the major components in the brain but would like to highlight aspects of the Limbic system which has an important role in stress. The limbic system includes many structures such as the hippocampus, olfactory bulbs, hypothalamus and amygdala, in addition to other structures. These are collectively important in their roles in basic emotions such as fear, pleasure and anger, as well as drives such as hunger, sex and caring for offspring. The limbic system is also important for conditioning reward pathways as well as potentially involved in addiction. The hippocampus' role and encoding long-term memory can be fundamental for allowing new pathways of behavior and practices such as yoga to get cemented. This is partly where we start to see the effect of changes to our lives through yoga, mindfulness and meditation. Lastly, the hypothalamus coordinates both the autonomic nervous system and the activity of the pituitary, controlling body temperature, thirst hunger and other homeostatic systems and involved in sleep and emotional activity. Again, for those of you interested, I encourage you to take a deeper look into the aspects of brain that is interesting to you. But of course, what we're really focusing on here is a lot about stress, a lot about breathing, a lot about establishing new patterns and so we're not going to dive too far into different brain regions. One thing I think is important is that protecting the CNS or the central nervous system is absolutely vital. So, not only do we have things like all of our skin, our skull, our scalp, but also all of our vertebrae has evolved to actually protect our spinal cord. So, the spinal cord is of course crucial, right? The spinal cord runs all the way from the base of our spine up into our brain and it is going to also be part of receiving and giving off messages. Okay. Cranial nerves. So, we have nerves running all throughout our spinal cord and we also have nerves that extend directly from the brain. We have 12 nerves that extend directly from the brain and of those, one of the most important ones in looking at yoga, meditation, mindfulness, stress reduction, is vagus nerve. Vagus nerve is associated with parasympathetic activation. The vagus nerve, the tenth cranial nerve, integrates with the regulation of the parasympathetic nervous system. Therefore, it's crucial in the ability to control heart rate digestion and lungs. Because of the ability of the vagus nerve to regulate breath and heart rate and decrease over activation and stress, it has been an important focus on research regarding yoga and meditation and the powerful effect that yoga and meditation can have on physiology and stress.
