<p></p><h2><a>The Central Nervous System (CNS)</a></h2><p>The central nervous system includes the brain (contained within the skull), which weighs 1.3–1.4 kg in humans, and also the spinal cord, which extends into the vertebral canal. The brain is grossly divided into the brainstem, cerebellum, and cerebrum. The cerebrum is further divided into the basal ganglia, limbic system, and neocortex.</p><img src="@@PLUGINFILE@@/CNS.jpg" alt="Central Nervous System" width="424" height="839" class="img-responsive atto_image_button_left"><p></p><p></p><p><br></p><h2><a><br></a></h2><h2><a><br></a></h2><h2><a><br></a></h2><h2><a><br></a></h2><h2><a><br></a></h2><h2><a><br></a></h2><h2><a><br></a></h2><h2><a><br></a></h2><h2><a><br></a></h2><h2><a><br></a></h2><h2><a><br></a></h2><h2><a><br></a></h2><h2><a><br></a></h2><h2><a><br></a></h2><h2><a><br></a></h2><h2><a></a><a>Spinal cord</a></h2><p>The spinal cord descends from the brainstem down through the shielded tunnel of the vertebrae,&nbsp; and transmits information from the body to the brain and from the brain to the body. Thus, the central nervous system is composed of nerves the are rooted to both the surface of the brain, as well as to the spinal cord. Most nerves are peripheral nerves, which extend and branch toward the surface of the body.</p><img src="@@PLUGINFILE@@/Spinal%20Cord.jpg" alt="Spinal Cord Anatomy" width="600" height="760" class="img-responsive atto_image_button_left"><p></p><p><br></p><p style="text-align: center; "><i><br></i></p><p style="text-align: center; "><i><br></i></p><p style="text-align: center; "><i><br></i></p><p style="text-align: center; "><i><br></i></p><p style="text-align: center; "><i><br></i></p><p style="text-align: center; "><i><br></i></p><p style="text-align: center; "><i><br></i></p><p style="text-align: center; "><i><br></i></p><p style="text-align: center; "><i><br></i></p><p style="text-align: center; "><i><br></i></p><p style="text-align: center; "><i><br></i></p><p style="text-align: center; "><i><br></i></p><p style="text-align: center; "><i><br></i></p><p style="text-align: center; "><i><br></i></p><p style="text-align: center; "><i><br></i></p><p style="text-align: center; "><i><br></i></p><p style="text-align: center; "><i><img src="@@PLUGINFILE@@/Peripheral%20Nervous%20System.jpg" alt="Peripheral Nervous System" width="723" height="917" class="img-responsive atto_image_button_left"><br></i></p><p style="text-align: center; "><br></p><p style="text-align: center; "><br></p><p style="text-align: center; "><i><br></i></p><div><p>The brain grows, layer upon layer, like an onion. Brain cells generating grab onto a guidewire, which is a glial fiber, a glial highway, with the nucleus in the back. No other kind&nbsp;<span>of cell has to do this.&nbsp;</span></p><p><span>Neurons travel in waves, which scientists call <b>migration</b>. &nbsp;In terms of the distances relative to their size, they are making an odyssey, without mistakes telling them where to go in the brain.</span></p><p><span><br></span></p><p><span><br></span></p><p><span><br></span></p><p><span><br></span></p><p><span><br></span></p><p><span><br></span></p><p><span><br></span></p><p><span><br></span></p><p><span><br></span></p><p><span><br></span></p><p><span><br></span></p><p><span><br></span></p><p><span><br></span></p><p><br></p><p><br></p><p><br></p><p><br></p><p><br></p><p><br></p><p><br></p><p><br></p><p><br></p><p>Here is a cool video made by the Pasterkamp lab, outlining the signaling events and molecular mechanisms involved in the formation of neuronal connections during development.<br></p><p>&nbsp;<a href="https://www.youtube.com/watch?v=ZWACm6BkDVo&amp;t=2s">Pasterkamp Labs</a><br></p><p>&nbsp;</p><h2>The Triune Brain Theory</h2><br><p></p><p></p><p>The triune brain was first described by Maclean in 1990, as consisting of three layers that depict our evolution individually as a species. &nbsp;The first layer is the reptilian brain (its core), responsible for activation, arousal, homeostasis, and reproductive drives. This is the dinosaur brain, the same brain that has been around for 2,000,000 years. The reticular formation at the conjunction of the thalamus and the brainstem oscillates at 2Hz (delta) {Thatcher, 2015). At&nbsp;birth, this structure is already in place and fully functional.</p><p><br></p><p style="text-align: center;"><img src="@@PLUGINFILE@@/triune%20brain.jpg" alt="Triune Brain" width="699" height="455" style="font-size: 1rem;" class="img-responsive atto_image_button_middle"></p><p></p><p></p><p>The reptilian brain controls the body’s most basic, involuntary actions, like a heartbeat, breathing, body temperature regulation, and balance. It consists of the brainstem and the cerebellum (which joins the limbic thalamus by the reticular activating system). The cerebellum is the most densely packed area; surprisingly, this is where 80% of the brain’s neurons live (Herculano-Houzel, 2010). Used mostly for gross movements and balance, parts of the cerebellum are involved in the coordination of language, memory, and&nbsp;reasoning (Schmahmann, 1997). Interestingly, new literature suggests that the cerebellum plays a significant role in regulating the cerebrum, both via white matter (sub-cortically) and via grey&nbsp;matter (cortically) (Schmahmann, 1997, 1998, 2000; Teicher, Anderson, &amp; Polcari, 2012). This is the part of the brain that is cradled by the hand of a loving mother, and the part of the brain that also unconsciously senses the absence of her hand, in situations of neglect (Fisher, 2014, p. 23).</p><p><br></p><h2><a name="_Toc28940388"></a><a name="_Toc3535195">Brainstem</a></h2><p>The brainstem is responsible for carrying all information from the body to the cerebrum and cerebellum (hindbrain) and from the brain to the body. The pathways ascending from the body to the brain are the sensory pathways and communicate to your brain that which is going on with the body (pain, hunger, desires, temperature, sensations, etc). The descending pathways move from the brain to the body. The last job of the brain stem is its regulation of various systems, such as your cardiovascular system, respiratory system, pain sensitivity controls, as well as alertness, and consciousness.</p><p><b>The medulla oblongata</b>&nbsp;or simply&nbsp;<b>medulla</b>&nbsp;is a long stem-like structure which makes up the lower part of the&nbsp;brainstem.&nbsp;It is anterior and partially inferior to the&nbsp;cerebellum. It is a cone-shaped&nbsp;neuronal&nbsp;mass responsible for&nbsp;autonomic&nbsp;(inv<span style="font-size: 1rem;">oluntary) functions, ranging from&nbsp;</span><span style="font-size: 1rem;">vomiting</span><span style="font-size: 1rem;">&nbsp;to&nbsp;</span><span style="font-size: 1rem;">sneezing</span><span style="font-size: 1rem;">.</span><span style="font-size: 1rem;">&nbsp;The medulla contains the&nbsp;</span><span style="font-size: 1rem;">cardiac</span><span style="font-size: 1rem;">,&nbsp;</span><span style="font-size: 1rem;">respiratory</span><span style="font-size: 1rem;">,&nbsp;</span><span style="font-size: 1rem;">vomiting</span><span style="font-size: 1rem;">&nbsp;and&nbsp;</span><span style="font-size: 1rem;">vasomotor</span><span style="font-size: 1rem;">&nbsp;centers, and therefore deals with the autonomic functions of&nbsp;</span><span style="font-size: 1rem;">breathing</span><span style="font-size: 1rem;">,&nbsp;</span><span style="font-size: 1rem;">heart rate</span><span style="font-size: 1rem;">&nbsp;and&nbsp;</span><span style="font-size: 1rem;">blood pressure</span><span style="font-size: 1rem;">. The sleep wake cycle is associated with the pons.</span></p><p><span style="font-size: 1rem;"><img src="@@PLUGINFILE@@/Medulla%20Oblongata.jpg" alt="Medulla oblongata" width="500" height="378" class="img-responsive atto_image_button_left"><br></span></p><p>The brainstem plays a primary role in conduit functions. That is, all information related from the body to the cerebrum and cerebellum and vice versa must traverse the brain stem. The ascending pathways coming from the body to the brain are the sensory pathways. Descending tracts are upper motor neurons destined to synapses on lower motor neurons. The brain stem also has integrative functions. It is involved in cardiovascular system control, respiratory control, pain sensitivity control, alertness, and consciousness.</p>Here is a short video on the anatomy of the brainstem.<p></p><p>&nbsp;<a href="https://www.youtube.com/watch?v=T2zjlB4ctu4">brainstem</a><br></p><p></p><h2><a name="_Toc28940390">THE LIMBIC SYSTEM</a></h2><p>After the reptilian brain is formed, the next layer, the paleomammalian brain, better known as the limbic system, is primed and ready to be further developed by early life experiences. This area is largely responsible for the functions of memory, learning, and emotion. This second layer is responsible for basic autonomic functioning, as well as reflexes, and basic survival (DeRidder, 2014). The proliferation of the limbic system created higher frequencies, such as theta and alpha. The limbic structures include the amygdala, hippocampus, thalamus, hypothalamus, basal ganglia, and cingulate gyrus. These limbic structures are wrapped in the cerebral cortex, which is the outermost and third layer of the brain.</p><p><img src="@@PLUGINFILE@@/Limbic%20System.png" alt="Limbic System" width="600" height="357" class="atto_image_button_left"><br></p><p>From an evolutionary perspective, the reptilian brain is fully functional at birth and the second layer—the limbic system—is prepared for the organizational experiences of early life. The neuronal development of the brain’s first and second layers are virtually complete at birth; the branching of dendrites that occurs thereafter is dubbed “wiring,” since the growth of neurons and dendrites resembles wires (Seung, 2012). The wiring and creation of oligodendrocytes (glia cells&nbsp;<span style="font-size: 1rem;">responsible for myelination) now occurs from the limbic structures into the cortex. The self-reliance of the brain circuits has increased as we have evolved, and have moved to higher levels in the brain, ones that have less and less contact with sensory inputs.</span></p><p>Most of our significant early emotional and intellectual experiences, those that shape our later perceptions and reactions, occur when the limbic and reptilian structures are in dominance (Cozolino, 2002, p. 9). That is to say, many of our social-emotional reactions and behaviors are literally programmed beneath the surface of our consciousness. Indeed, empirical evidence suggests that processing emotion can occur without conscious awareness (Balconi &amp; Lucchiari, 2008; Bunce, Bernat, Wong, &amp; Shevrin, 1999; LeDoux, 1998a). What you smell goes directly into the limbic system, smell is the only sense that is not mediated by the thalamus. Head damage or virus (such as COVID-19) can affect this system, preventing the capability of smell. Severance of this connection is common in severe head trauma.</p><p>The sense of smell is tied directly to memory and emotion because the olfactory blub connect directly to the hippocampus, the seat of memory. Smells can create emotion because the olfactory projections link into the limbic system and the amygdala.</p><p>&nbsp;</p><h3><a name="_Toc28940391">Neuroanatomy of the Limbic System</a></h3><p><b>&nbsp;</b>The amygdala is located within the temporal&nbsp;lobes. It is essential to the experience of fear responses and its primary function is arousal. This complex structure controls the autonomic responses associated with fear; emotional responses {i.e. rage and anger) and Hormonal Secretions. The right-side amygdala is devoted to survival and reacts to threats, both real and perceived. The amygdala is an almond-shaped mass of nuclei located deep within the temporal lobes, medial to the hypothalamus and adjacent to the hippocampus. This area of the brain is prone to kindling, which is essentially repetitive neuronal firing that gives rise to high amplitudes until the pattern collapses. Each kindling lowers the threshold of the future ones, making them more likely.</p><p style="text-align: center;"><img src="@@PLUGINFILE@@/amygdala.png" alt="amygdala" width="400" height="513" class="img-responsive atto_image_button_middle" style="font-size: 1rem;"></p></div><div><span style="font-size: 1rem;"><br></span></div><div><span style="font-size: 1rem;"><br></span></div><div><span style="font-size: 1rem;"><br></span></div><div><span style="font-size: 1rem;">Check out this video of the Amygdala:</span><br></div><div><p></p><p>&nbsp;<a href="https://www.youtube.com/watch?v=JVvMSwsOXPw">Amygdala</a><br></p><p></p><h3><br></h3><h4>Basal Ganglia</h4><p>The Basal Ganglia are collections of nerve cells deep within the brain. Most of the basal ganglia are concerned with movement, though parts are devoted to language, thought, motivation and emotion. They include the caudate nucleus, the putamen, the thalamus, the globus pallidus, and the tail of the caudate nucleus.</p><p><br></p><p style="text-align: center; "><img src="@@PLUGINFILE@@/Basal%20Ganglia.png" alt="Basal Ganglia" width="500" height="350" class="img-responsive atto_image_button_text-bottom"><br></p><p style="text-align: center; "><br></p><p style="text-align: center; "><br></p><div><h4>Diencephalon</h4><p>This is the division of the forebrain, the forward most portion of the brain in vertebrates, which controls temperature, reproductive functions, eating, sleeping, and the display of emotions. The diencephalon includes the thalamus, hypothalamus, posterior portion of the pituitary gland and the pineal gland. The third ventricle is enclosed by the diencephalon.&nbsp;</p><p><br></p><p style="text-align: center; "><img src="@@PLUGINFILE@@/diencephalon.jpg" alt="diencephalon" width="500" height="376" class="img-responsive atto_image_button_text-bottom"><br></p><p style="text-align: center; "><br></p><h4>Hypothalamus</h4><p>The hypothalamus links the nervous system to the endocrine system via the pituitary gland (hypophysis). The hypothalamus controls body temperature, hunger, thirst, fatigue, anger, and circadian cycles. The hypothalamus is located below the thalamus, just above the brain stem. The hypothalamus is responsible for certain metabolic processes and other activities of the autonomic nervous system. It synthesizes and secretes neurohormones, often called hypothalamic-releasing hormones, and these, in turn, stimulate or inhibit the secretion of pituitary hormones.</p><p><br></p><p style="text-align: center; ">&nbsp;<img src="@@PLUGINFILE@@/hypothtrlamus.jpg" alt="hypothalamus" width="500" height="250" class="img-responsive atto_image_button_text-bottom"></p><p style="text-align: center; "><br></p><p>For your viewing pleasure, a short video on the hypothalamus:</p><p>&nbsp;<a href="https://www.youtube.com/watch?v=TVhm2rBGhB0&amp;t=15s">Hypothalamus</a>&nbsp;<br></p><p><br></p><h4>Hippocampus&nbsp;</h4><p>&nbsp;The hippocampus is a part of the forebrain, located in the medial temporal lobe. It belongs to the limbic system and plays major roles in short term memory and spatial navigation.</p><p>&nbsp;Here's a video on the hippocampus:&nbsp;&nbsp;<a href="https://www.youtube.com/watch?v=5EyaGR8GGhs">Hippocampus</a></p><p>This is a video about a famous person named "HM" and his life without a hippocampus.</p><p><a href="https://www.youtube.com/watch?v=KkaXNvzE4pk">HM</a></p><p><br></p><h4>Pituitary</h4><p>The pituitary is a small pea-size master gland of the endocrine system that sits in a bony depression beneath the hypothalamus. Its job deals with directing chemical changes to regulate the entire organic system.</p><p>Here is a short video on the hormones that come from the pituitary gland:</p><p><a href="https://www.youtube.com/watch?v=7rWPKHFMqEU">Pituitary</a><br></p><p>&nbsp;</p><h4>Reticular formation</h4><p>The reticular formation (also known as the reticular activating system) is at the core of the brainstem and plays a vital role in sleep, emotion, breathing, blood pressure, and heart rate.&nbsp;The reticular formation oscillates at 2 hz and is the dinosaur brain, roughly&nbsp;<i>2,000,000&nbsp;</i>years old in its evolutionary trajectory, is the same structure that we have.</p><p><br></p><p style="text-align: center; "><img src="@@PLUGINFILE@@/RAS.jpg" alt="RAS" width="600" height="600"><br></p></div><h4>Thalamus</h4><p>The thalamus is an egg-shaped structure deep within the brain that acts as a relay station, receiving information from all senses (except olfactory) &nbsp;processing the data and passing it between the spinal&nbsp;<i>cord,</i><i>&nbsp;</i>the medulla oblongata and the cerebral cortex. It relays sensory signals like motor signals to the&nbsp;<i>cortex,&nbsp;</i>and it also plays in the regulation of sleep and arousal states. It is the beginning of the brain's formation at 5 weeks in utero.</p><p>The thalamus is composed of the thalamic nuclei, which aids in the processing of various stimuli. Here is a general video of the thalamus and the thalamic nuclei:</p><p>&nbsp;<a href="https://www.youtube.com/watch?v=Szt_OkcMPmM">Thalamus</a></p><p>Here is a general video of the Basal Ganglia</p><p>&nbsp;<a href="https://www.youtube.com/watch?v=InJByqg1x-0">Basal Nucleus</a><br></p><h4>Caudate Nucleus</h4><p>The caudate nucleus is one of the structures that makes up the dorsal striatum of the basal ganglia. This part of the brain&nbsp;plays important roles in various other nonmotor functions as well, including&nbsp;<a href="https://en.wikipedia.org/wiki/Procedural_learning" title="Procedural learning">procedural learning</a>,&nbsp;<a href="https://en.wikipedia.org/wiki/Associative_learning" title="Associative learning">associative learning</a>&nbsp;and&nbsp;<a href="https://en.wikipedia.org/wiki/Inhibitory_control" title="Inhibitory control">inhibitory control</a>&nbsp;of action, &nbsp;among other functions. The caudate is also one of the brain structures which compose the&nbsp;<a href="https://en.wikipedia.org/wiki/Reward_system" title="Reward system">reward system</a>&nbsp;and functions as part of the&nbsp;<a href="https://en.wikipedia.org/wiki/Prefrontal_cortex" title="Prefrontal cortex">cortico</a>–<a href="https://en.wikipedia.org/wiki/Basal_ganglia" title="Basal ganglia">basal ganglia</a>–<a href="https://en.wikipedia.org/wiki/Thalamus" title="Thalamus">thalamic</a>&nbsp;loop.</p><p>And here is a little video of the Caudate Nucleus (It's a little funky, but helps explain anatomy):</p><p>&nbsp;<a href="https://www.youtube.com/watch?v=GcB5_gXka2g&amp;t=4s">Funky vid</a><br></p><p>&nbsp;</p><h4><a name="_Toc525053947">Parahippocampal Gyrus</a></h4><p style="text-align: center; "><a name="_Toc525053947"><img src="@@PLUGINFILE@@/Parahippocampal%20gyrus.jpg" alt="PArahippocampal gyrus" width="700" height="495" class="img-responsive atto_image_button_middle"></a></p><p><a name="_Toc525053947"></a><a name="_Hlk525136529">The parahippocampal gyrus is a region which is responsible for many functions, most notably for short-term working memory. The left-hand side is related to more verbal processes than the right, the right-hand side has more to do with forming associations. This area of the brain has much to do with the encoding and recognition of scenes; this area of the brain becomes active when taking in topographical scenes (images of cities, landscapes, and rooms—images of places).&nbsp; Furthermore, this area is involved in procedural memory consolidation, recognition, and recall. It is a component part of the networks for autobiographical memory, embarrassment, and regret.</a><br></p><p><a name="_Hlk525136529">The parahippocampal gyrus is a region which is responsible for many functions, most notably for short-term working memory. The left-hand side is related to more verbal processes than the right, the right-hand side has more to do with forming associations. This area of the brain has much to do with the encoding and recognition of scenes; this area of the brain becomes active when taking in topographical scenes (images of cities, landscapes, and rooms—images of places).&nbsp; Furthermore, this area is involved in procedural memory consolidation, recognition, and recall. It is a component part of the networks for autobiographical memory, embarrassment, and regret.</a></p><br><p></p><p><img src="@@PLUGINFILE@@/parahippocampal%20gyrus.png" alt="parahippocampal gyrus" width="566" height="651" class="img-responsive atto_image_button_left"><br></p><h4>Tiff Thompson's Depth Theory of Neuroanatomy</h4><p></p><p>Proponents of the collective unconscious theory in neuroscience have suggested that neurobiological correlates to the collective unconscious are the subcortical areas of the brain, specifically the thalamus (which oscillates in delta, theta, and alpha rhythms). The thalamus operates like a regulatory gateway, since all of the sensory input that comes into the brain, and all motor output, goes through the thalamus. The thalamus regulates what goes in and what goes out.&nbsp; Because these structures are located centrally, linking the brain with the rest of the nervous system, they are said to control vital processes, such as emotions and long-term memory (Hunt, 2012). Arousal occurs in the face of a threat, triggered by the amygdala, which is an almond-shaped structure in the brain responsible for mediating the fear response. The amygdala locks down the hippocampus so as to react by shutting down this structure, the seat of the memory (LeDoux, 1998b). LeDoux speculates, however, that psychoanalysis works by strengthening the cortical control of the amygdala. In fact, the face-to-face reciprocity between infant and mother is crucial for the development of the pre-frontal cortex, which serves to mediate the amygdala and regulate affect (Schore, 1994, 2003; Siegel, 1999; Stern, 2013; Tronick, 2007).</p><p>Sigmund Freud, quite rightly, believed that mental activity was rooted in phylogenically­ old emotion and motivation systems, which were constructed in early mental development, and instantiated throughout later adult life (LeDoux, 1998a;Panskepp, 1998). Thus, affective reactivity, such as dissociation, can be seen as a return to nonverbal, largely unconscious parts of the brain. These are areas that can influence the higher-ordered new-mammalian brain (Cozolino, 2002, p. 6). Furthermore, these older regions are innervated &nbsp;by the vagus nerve, which literally means "wandering nerve." The vagus nerve is also called the "wandering nerve" because it's the longest nerve in the human body and has countless branches that wind their way from the brainstem all the way down to the lowest part of the intestines, touching most major organs along the way. The vagus nerve is the tenth cranial nerve and is the main afferent pathway connecting the gut to the brain. This nerve modulates the parasympathetic nervous system, which counterbalances the fight, flight,&nbsp;or freezes stress response by eliciting the so­ called "relaxation &nbsp;response."</p><h4>The Vagus Nerve</h4><p>&nbsp;<img src="@@PLUGINFILE@@/Vagus%20Nerve.jpg" alt="Vagus Nerve" width="250" height="731" class="img-responsive atto_image_button_left">A study released in June of 2015 noted the discovery of vessels directly connecting the brain and the lymphatic system, a finding which will likely have continual substantial implications for major neurological diseases and also more common psychopathologies (Louveau et al., 2015). This finding changes the way scientists perceive neuro-immune interaction and may make the link between the body and the brain/mind something beyond esotericism.</p></div><br>Here's a short video pf Stephen Porges and his Theory on the Polyvagal Network:<br><a href="https://www.youtube.com/watch?v=ec3AUMDjtKQ">Porges</a><br><br><p></p>