Lesson 4: The Brain, the Body, and Consciousness
Transcript
Welcome back to The Introduction to Psychology Series. I’m RJ Starr.
If the last lesson helped us understand how psychologists ask questions and gather evidence, this one brings us into the machinery behind those questions. Today we’re talking about the brain, the body, and consciousness—how biology shapes what we feel, think, remember, and believe.
This is where psychology overlaps with biology, neuroscience, and medicine. But you don’t need a medical degree to understand this. You just need to know one thing: everything you feel and think—every emotion, every reaction, every belief—is happening in a body. And that body has a system. A system that can be overloaded, regulated, stretched, trained, or injured. The mind is not separate from the body. They’re deeply connected. And if you want to understand yourself or anyone else, that connection matters.
Let’s start with the brain. Because while the mind is what you experience, the brain is where a lot of it starts.
Your brain weighs about three pounds and contains around 86 billion neurons. That number is hard to visualize, so just think of it this way: your brain is a dense, electrical city. These neurons are like little communication hubs, and they send messages across tiny gaps called synapses using chemicals called neurotransmitters. That’s how information moves—electrically and chemically—at lightning speed. Thoughts, sensations, emotions, all of it.
Different parts of the brain handle different tasks. The outer layer, called the cerebral cortex, is the most advanced part. It’s divided into four main regions or lobes. The frontal lobe is responsible for decision-making, planning, problem-solving, and impulse control. It’s what lets you pause before reacting, consider the consequences, or choose a higher goal. When people say someone lacks a filter, they’re often talking about frontal lobe function.
The parietal lobe handles sensory input. It helps you interpret things like touch, temperature, and spatial awareness. The temporal lobe, located on the sides of your brain, deals with hearing, language, and memory. And the occipital lobe, in the back, is all about vision.
Then there’s the limbic system, which sits deeper inside the brain and plays a major role in emotion and memory. This includes the amygdala, which helps you detect threats and process fear. The hippocampus, which is essential for forming new memories. And the hypothalamus, which regulates things like hunger, thirst, body temperature, and hormones.
There’s also the brainstem, which controls basic survival functions—heart rate, breathing, sleep. It’s not glamorous, but you wouldn’t last long without it.
What’s important to understand here is that the brain is not one unified voice. It’s a network of systems. And sometimes those systems are in conflict. One part of your brain might want to take a risk. Another might scream that it’s not safe. One part wants connection. Another expects rejection. One part wants to stay calm. Another floods your body with adrenaline. These aren’t character flaws. They’re biology.
The nervous system plays a major role in all of this. It’s the body’s communication highway. The central nervous system includes the brain and spinal cord. The peripheral nervous system includes all the nerves that extend out into your body.
A key part of the peripheral system is the autonomic nervous system, which regulates things that happen automatically—like breathing, heart rate, digestion. Within that, there are two branches: the sympathetic and the parasympathetic nervous systems.
The sympathetic nervous system is your body’s alarm system. It gets activated when you perceive a threat. Heart rate increases. Breathing gets faster. Pupils dilate. Muscles tense. Blood moves to the parts of your body needed for action. This is often called the fight or flight response. But we now know it’s more complex. People also freeze, fawn, or collapse, depending on how their system interprets the threat.
Then, once the threat passes, the parasympathetic nervous system kicks in. That’s the rest and digest system. It slows everything down. It helps your body return to baseline.
This balance—between activation and regulation—is at the heart of emotional health. If your sympathetic system is always on, you’ll feel anxious, jumpy, irritable. If your parasympathetic system can’t bring you back down, you’ll feel drained, stuck, numb. So many of our mental health struggles are rooted not in weakness, but in nervous system dysregulation. The body remembers, even when the mind forgets.
Hormones also play a role. Hormones are chemical messengers released into the bloodstream by glands. The endocrine system is the network responsible for this. Key players include cortisol, which is released during stress. Adrenaline, which prepares you for action. Oxytocin, which promotes bonding. And dopamine, which is involved in reward and motivation.
These chemicals shape our behavior in powerful ways. For example, when you achieve something important—or even when you anticipate achieving something—your brain releases dopamine. That hit feels good. It reinforces the behavior. This is why habits form. It’s also why addiction develops. The brain learns what feels good, and it craves more.
Oxytocin, often called the love hormone, increases during touch, eye contact, and social bonding. It deepens feelings of trust and closeness. But it doesn’t just make you feel warm—it also reduces stress and promotes healing. Physical connection changes chemistry.
None of this is abstract. It’s not just trivia. It’s the foundation for how you show up in the world. Your ability to pay attention. To regulate your emotions. To connect with others. To access memory. To weigh a decision. It all comes back to the system that lives inside your skin.
Now let’s talk about consciousness. Because so far, we’ve been talking about structures and systems. But consciousness is the experience itself. It’s what you’re aware of. Your thoughts. Your sense of self. Your attention. The internal dialogue happening as you listen to this right now.
Consciousness isn’t fully understood. We don’t have a perfect definition. But we do know that it’s layered. There’s waking consciousness—your normal, alert state. There’s altered consciousness—things like dreaming, hypnosis, meditation, or substance use. There’s divided consciousness—when your attention is split between multiple things. And there are states where consciousness becomes disrupted or diminished, like in sleep, coma, or anesthesia.
Sleep, in particular, is fascinating. It’s not just rest. It’s a cycle. You move through stages—light sleep, deep sleep, REM sleep. During REM sleep, your brain is highly active. That’s when dreaming happens. And dreams, while not fully understood, may play a role in memory consolidation, emotional processing, or problem-solving.
Consciousness also relates to attention. Attention is limited. You can’t focus on everything at once. Your brain filters out what it thinks is irrelevant. This is why two people can be in the same situation and notice completely different things. It’s not just about bias. It’s about bandwidth.
And here’s something else: your experience of reality is constructed. Your senses gather information, yes—but your brain fills in the blanks. It interprets, edits, filters. What you perceive isn’t the world itself. It’s your brain’s best guess about what’s out there. That guess is shaped by your memories, your expectations, your emotional state, your culture, your history.
So when someone says, I saw it with my own eyes, or I know what I felt—yes, that’s true. But perception is not perfect. Memory is not a recording. Consciousness is not a mirror. It’s a lens. And that lens can distort.
Which brings us to a deeper point. Understanding the biology of the mind isn’t just about anatomy. It’s about compassion. When you realize that so many of our thoughts and behaviors are shaped by systems we didn’t choose—by brain chemistry, by trauma, by stress responses, by developmental wiring—it becomes harder to judge and easier to understand.
That doesn’t mean we don’t have responsibility. But it does mean that not everything we struggle with is a moral failure. Sometimes it’s a brain struggling to regulate. A nervous system stuck in survival mode. A body doing its best to protect us, even when the danger has passed.
And when we understand that, we can begin to work with the system, not against it. We can learn what calms us. What grounds us. What patterns show up in our bodies before they show up in our behavior. We can start to feel less broken—and more informed.
The mind is not separate from the body. It never was. And the more we recognize that, the more we can treat ourselves and others with wisdom, not just advice.
In the next lesson, we’re going to explore how we learn. How behavior changes over time. How patterns are formed—and how they can be unlearned. We’ll look at classical conditioning, operant conditioning, and real-life examples that explain everything from habit loops to emotional triggers.
Thanks for listening. I’ll see you in Lesson Five.