The central nervous system
Organizational Management and Executive Thinking
In 2009, Karen Butler had surgery. When she woke up, she had picked up a foreign accent. Even though she was born and raised in America, waking up from the surgery, Karen sounded British! This is just one of the many weird and unusual things that can happen in our brains, which demonstrates just how many things our brains are responsible for and how it can compensate when something goes wrong. Understanding Karen’s mystery requires us to go into a little more depth on the Central Nervous System (CNS), which is the main coordinating unit in the body’s system of communication (with itself and with other people).
The way we speak and how we choose our words are just two of the many responsibilities of the CNS. As we briefly touched on earlier in this lesson (get it—touched on?—because of the stove thing?? *insert mandatory chuckle*), the CNS is made up of the brain and spinal cord. The CNS is responsible for controlling and coordinating essentially all of the actions of the body.
The actions that are regulated by the CNS include both conscious decisions and unconscious goings-on of the body. As we’ve learned, this is absolutely essential to complex life, because it allows different systems of the body to specialize in what they’re good at while still allowing the body as a whole to stay focused on keeping you alive. For example, the lungs get to be really good at just breathing, but they still have a boss telling them that they need to pick up the pace when we’re exercising and our oxygen demand goes up.
The actions that are regulated by the CNS include both conscious decisions and unconscious goings-on of the body. As we’ve learned, this is absolutely essential to complex life, because it allows different systems of the body to specialize in what they’re good at while still allowing the body as a whole to stay focused on keeping you alive. For example, the lungs get to be really good at just breathing, but they still have a boss telling them that they need to pick up the pace when we’re exercising and our oxygen demand goes up.
Nervous Control
The brain is also responsible for higher-level executive thinking, decision making, complex language skills (including the ones that decide our accent!), psychological processes, and all the other really complicated stuff (generally lumped into the term cognition) that humans do that helps us to stay alive, that helps to keep life interesting, and that keeps Karen talking like an American.
Cognition
parts of the brain
The brain is made up of 4 main sections:
1. The brainstem connects the brain to the spine and is in charge of automatic functions, like breathing, heart rate, swallowing, and consciousness (whether you’re asleep or awake).
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2. The hypothalamus (a part of the diencephalon, which also includes the thalamus and pituitary gland, but we won’t worry much about those in this class) controls your body’s temperature and connects closely with the endocrine system in order to maintain homeostasis of various body functions, like blood pressure and metabolism. It also orchestrates temporary and long-term changes in other body functions, like during stress, growth, puberty, and reproduction.
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3. The cerebellum controls coordination, timing, and precision of movement. It does not initiate movement (that is the job of the cerebrum), it just makes sure those movements aren’t super awkward and clunky.
Here’s a video of what happens when the cerebellum isn’t working right:
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4. The cerebrum controls memory, language, sensation and perception, initiating movement, executive-thinking, and all of those really complicated “thinking”-type things we normally associate with the brain. Because it has the most complicated functions, the cerebrum is also the biggest and most complicated part of the brain.
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In addition to these four parts of the brain, the CNS also includes the spinal cord, which is responsible for (1) relaying messages to and from the brain, and (2) coordinating reflexes.
This video provides a good summary of what the various parts of the CNS do:
temperature regulation and the cns
The process of temperature regulation is one of the simplest examples that demonstrates the importance of a complex governing system like the CNS in controlling a basic aspect of life—your internal temperature. It’s important for our internal temperatures to stay the same because all of our proteins are designed to work best at that temperature. Even minor swings in internal temperature can seriously slow down some life-sustaining reactions in our bodies, such as cell respiration.
As simple as temperature regulation may seem, it still requires that a lot of things come together! If we’re too hot, we can slow down our metabolism to make less heat, sweat to release heat by evaporative cooling (the hottest water molecules evaporate first, leaving us drenched in slightly chilled water), take off layers of clothing, go sit in front of a fan, or change our behavior in some other way to help us cool down.
As simple as temperature regulation may seem, it still requires that a lot of things come together! If we’re too hot, we can slow down our metabolism to make less heat, sweat to release heat by evaporative cooling (the hottest water molecules evaporate first, leaving us drenched in slightly chilled water), take off layers of clothing, go sit in front of a fan, or change our behavior in some other way to help us cool down.
If we’re too cold, we can speed up our metabolism to make more heat, we can shiver to use up more energy and make heat, we can turn up the thermostat in our house, we can go get a sweater, and so on.
Doing all of these things together and/or deciding which one is best in a given moment requires some coordination, which requires involvement of the CNS. Plus, even in order to do something as simple as, say, going to get a sweater, we need to do some pretty “complicated” things: we have to be able to remember what a sweater is, know where our sweater is, know how to put on a sweater, and coordinate all of our muscles in the process of putting on that sweater. Our brain is so good at all of these things that it makes them seem easy, but just think: Have you ever seen a simple animal like a caterpillar put on its own sweater? Or even a more advanced animal like a dog? Even simple things can get pretty complicated pretty quickly, and we need coordination and control from the CNS in order to make them all happen when we need them.
Even something as simple as putting on a sweater when it’s cold out requires a lot of brain power. Even advanced animals like dogs need help!
You should understand the idea of homeostasis, how this applies to temperature regulation, and how our bodies maintain a stable temperature when the environment gets either too hot or too cold, as explained in this video:
what happened to karen?
With so many nerves and so many complex functions happening in the brain, it’s no wonder that really weird things can go wrong when some of those nerves get damaged! In Karen’s case, her accent switch is a result of a very weird and unusual thing that can happen when the brain is damaged, called Foreign Accent Syndrome. Doctors later discovered that Karen had had a stroke during the surgery. Blood had stopped flowing to her brain and this had caused some parts of it to die. The other parts compensated for that death. She had “forgotten” how to speak in an American accent because of her stroke, but she was still able to speak in a British accent, which was probably a party trick of hers before the stroke. When neurons die, they can’t be easily replaced the way that, for example, skin gets replaced when the outer layer gets old and sloughs off. So, Karen’s brain compensated for the death of her American accent nerves by making her sound British. Doesn’t seem so bad!
(Doctors say that Karen can probably get back her American accent if she works really hard on it. But, Karen says that, even though it might confuse some people, she likes the way she sounds now!)
(Doctors say that Karen can probably get back her American accent if she works really hard on it. But, Karen says that, even though it might confuse some people, she likes the way she sounds now!)
Summary
You should understand:
Bonus Activity
You don’t have to understand the details of any specific process that happens in the CNS for this class. But, the brain does some really interesting and fascinating things! If you’re interested in learning about some of these, watch one or more of these videos and tell us what you found interesting about it in the Learning Activity form.
- The roles of each of the five main components of the CNS: the brainstem, the hypothalamus, the cerebellum, the cerebrum, and the spinal cord.
- The role of the brain in coordinating body processes generally, and temperature regulation specifically.
Bonus Activity
You don’t have to understand the details of any specific process that happens in the CNS for this class. But, the brain does some really interesting and fascinating things! If you’re interested in learning about some of these, watch one or more of these videos and tell us what you found interesting about it in the Learning Activity form.
Emotions and the Brain
Memory and the Brain
Learning and the Brain
Music and the Brain
Dancing and the Brain
Sleep and the Brain
Memory and the Brain
Learning and the Brain
Music and the Brain
Dancing and the Brain
Sleep and the Brain
Learning Activity
Contributors: Megha Kori, Emma Moulton
Some images made with biorender.com
Some images made with biorender.com