The Chemical Mind: Crash Course Psychology #3

Summary

This script from Crash Course Psychology explores the intricate relationship between the nervous and endocrine systems, highlighting how they influence our thoughts, emotions, and actions. It delves into the structure and function of neurons, the role of neurotransmitters in communication, and the impact of hormones on our moods and physiological processes. The episode uses a relatable scenario of being startled at night to illustrate the body's chemical response, emphasizing the interconnectedness of psychological and biological phenomena.

Takeaways

• 🧠 The brain and nervous system are complex systems that use chemicals to regulate our thoughts, feelings, and actions.
• 🏃‍♂️ Sudden noises can trigger a 'fight or flight' response due to the release of chemicals in the brain, preparing the body for action.
• 🌐 Neurons are the fundamental units of the nervous system, transmitting messages through electrical impulses and chemical signals.
• 🧬 Neurons consist of a soma, dendrites, and axon, each with specific roles in receiving, integrating, and sending signals.
• 🚀 The myelin sheath around some axons acts like insulation, speeding up the transmission of electrical signals.
• 🔄 Synapses are the junctions where neurons communicate, with neurotransmitters bridging the gap between cells.
• 💊 Neurotransmitters are chemical messengers that can either excite or inhibit the activity of receiving neurons.
• 🌱 Hormones, secreted by the endocrine system, have a slower but longer-lasting effect on the body compared to neurotransmitters.
• 🔑 The pituitary gland is often referred to as the 'master gland' because it controls the function of other endocrine glands.
• 🔁 The nervous and endocrine systems work in a feedback loop, influencing each other to maintain the body's homeostasis.

Q & A

What is the primary function of neurons in the nervous system?

Neurons, or nerve cells, are the building blocks of the nervous system. They transmit messages to each other through electrochemical means, allowing for communication within the brain and body.

What are the three basic parts of a neuron?

The three basic parts of a neuron are the soma (cell body), dendrites, and axon. The soma contains the cell's life support, dendrites receive messages from other cells, and the axon transmits electrical impulses to other neurons or cells.

What is the role of the myelin sheath in a neuron?

The myelin sheath is a protective layer of fatty tissue that covers some axons. It acts like an insulated electrical wire, speeding up the transmission of messages along the neuron.

How do neurons communicate with each other?

Neurons communicate with each other through synapses, which are the contact points between neurons. When an action potential reaches the end of an axon, it activates chemical messengers called neurotransmitters that cross the synaptic gap to the receiving neuron.

What is the difference between excitatory and inhibitory neurotransmitters?

Excitatory neurotransmitters increase the chances of a neuron firing an action potential, while inhibitory neurotransmitters decrease that likelihood. They play opposite roles in the communication between neurons.

How do hormones differ from neurotransmitters in their function?

Hormones, like neurotransmitters, act on the brain and can be chemically identical to certain neurotransmitters. However, hormones are secreted by glands into the bloodstream and have a slower, more sustained effect on the body compared to the rapid, direct communication of neurotransmitters.

What is the role of the adrenal glands in the body's stress response?

The adrenal glands secrete adrenaline, the fight or flight hormone, which increases heart rate, blood pressure, and blood sugar, preparing the body for a quick response to stress.

Why are neurotransmitters like dopamine and acetylcholine considered to play both sides?

Neurotransmitters like dopamine and acetylcholine can both excite or inhibit neurons depending on the type of receptors they encounter. This dual functionality allows them to have different effects on neuron activity.

What is the pituitary gland's role in the endocrine system?

The pituitary gland is considered the master gland of the endocrine system. It releases hormones that regulate other endocrine glands and plays a crucial role in physical development, metabolism, and social bonding.

How does the hypothalamus control the endocrine system?

The hypothalamus controls the endocrine system by sending signals to the pituitary gland, which in turn releases hormones that regulate various glands and functions in the body.

Outlines

00:00

🧠 Neurons and the Startle Response

The script begins by describing a scenario of being startled awake at night, highlighting the body's immediate physical response to sudden noise. It explains that these reactions are due to the release of chemicals in the brain. The paragraph then delves into the biological basis of psychological experiences, emphasizing that our thoughts and feelings are rooted in our body's chemistry. The narrator introduces neurons, the fundamental units of the nervous system, explaining their structure and function. Neurons consist of a soma (cell body), dendrites (input branches), and an axon (output fiber). The paragraph also touches on the role of neurotransmitters in transmitting signals across synapses and the different types of neurons in the body, from tiny brain neurons to large ones that span the length of our limbs.

05:03

💊 Neurotransmitters and Hormones

This paragraph continues the discussion on how the body's chemistry influences our psychological state by focusing on neurotransmitters and hormones. It explains the role of excitatory and inhibitory neurotransmitters, providing examples such as norepinephrine, glutamate, GABA, serotonin, acetylcholine, and dopamine. The paragraph also discusses how neurotransmitters can either excite or inhibit neuron activity, depending on the receptors they interact with. Hormones are introduced as another type of chemical messenger that acts on the brain and the body, affecting mood, metabolism, immune function, and more. The endocrine system is described as a slower but longer-lasting communication system compared to the nervous system, with hormones being delivered via the bloodstream. The paragraph mentions various glands and their hormones, emphasizing the pituitary gland as the 'master gland' that regulates other endocrine glands.

Keywords

💡Neurons

Neurons, also known as nerve cells, are the fundamental units of the nervous system. They are specialized cells that transmit information through electrical and chemical signals. In the video, neurons are introduced as the building blocks of our nervous system, highlighting their role in communication within the brain and body. The script describes the structure of neurons, including the soma, dendrites, and axon, and how they function to transmit messages, which is crucial for understanding the video's theme of how our minds and bodies react to stimuli.

💡Dendrites

Dendrites are branch-like extensions of a neuron that receive signals from other neurons. They play a critical role in the communication between neurons by receiving and passing on information to the cell body. The video script uses dendrites as an example to explain how neurons receive messages, emphasizing their function as 'listeners' in the neuronal communication process.

💡Axon

The axon is a long, cable-like projection of a neuron that transmits electrical impulses from the cell body to other neurons, muscles, or glands. It is described in the video as the 'talker' of the neuron, responsible for sending out electrical signals. The script mentions that axons can be encased in a myelin sheath, which speeds up the transmission of these signals, illustrating the importance of the axon in the nervous system's communication speed and efficiency.

💡Synapses

Synapses are the junctions between two neurons where information is passed from one to another. They are described in the video as the contact points between neurons, with a tiny gap called the synaptic cleft separating them. The script explains how neurotransmitters cross this gap to transmit signals, which is essential for understanding how thoughts, feelings, and actions are coordinated in the body.

💡Neurotransmitters

Neurotransmitters are chemical messengers that transmit signals across a synapse from one neuron to another. The video script discusses various types of neurotransmitters, such as excitatory and inhibitory ones, and their roles in different functions like movement, emotion, and cognition. For example, dopamine is associated with pleasurable emotions and learning, while serotonin affects mood, hunger, and sleep, illustrating the broad impact of neurotransmitters on psychological states.

💡Endocrine System

The endocrine system is a collection of glands that produce hormones to regulate physiological processes in the body. In the video, it is contrasted with the nervous system, highlighting how it communicates through hormones rather than electrical signals. The script mentions that hormones like adrenaline and insulin have significant effects on the body, such as preparing for 'fight or flight' responses or regulating blood sugar, which ties into the video's exploration of how our bodies react to different stimuli.

💡Hormones

Hormones are chemical messengers secreted by the endocrine glands that travel through the bloodstream to target tissues. The video script explains how hormones influence a wide range of bodily functions, from mood and metabolism to growth and reproduction. The example of adrenaline being released during a fright or stress illustrates how hormones can have an immediate and powerful impact on the body's response to situations.

💡Myelin Sheath

The myelin sheath is a protective layer of fatty tissue that surrounds the axons of many neurons, aiding in the rapid transmission of electrical signals. The video script describes it as similar to an insulated electrical wire, emphasizing its role in speeding up neural communication. The script also mentions that damage to the myelin sheath, as in multiple sclerosis, can degrade these signals, leading to a loss of muscle control, which underscores the importance of the myelin sheath for neural function.

💡Pituitary Gland

The pituitary gland is a small, pea-sized gland located at the base of the brain that produces various hormones and is often referred to as the 'master gland.' In the video, it is highlighted as a central player in the endocrine system, controlling other glands through its hormone secretions. The script explains how the pituitary gland releases growth hormone and oxytocin, which are crucial for physical development and social bonding, illustrating its pivotal role in regulating various bodily functions.

💡Hypothalamus

The hypothalamus is a region of the brain that links the nervous system to the endocrine system via the pituitary gland. It plays a key role in regulating body temperature, hunger, thirst, sleep, and emotional functions. The video script describes how the hypothalamus initiates responses to stimuli, such as fear, by signaling the pituitary gland to release hormones like adrenaline, which in turn prepares the body for a 'fight or flight' reaction, demonstrating the hypothalamus's critical role in coordinating physiological responses.

💡Fight or Flight Response

The 'fight or flight' response is a physiological reaction that occurs in response to a perceived harmful event, attack, or threat to survival. The video script uses the example of a sudden banging at the door to illustrate this response, explaining how the release of adrenaline prepares the body for a quick physical reaction, such as running away or confronting the threat. This concept is central to the video's theme of how our bodies' biological systems react to and protect us from danger.

Highlights

The brain releases a surge of chemicals in response to sudden noises, triggering physiological reactions.

Psychological experiences are deeply rooted in biological processes.

Neurons are the fundamental building blocks of the nervous system, capable of transmitting electrochemical messages.

The brain is composed of billions of neurons, each playing a role in our thoughts, dreams, and actions.

Neurons vary in size, from less than a millimeter to the length of a human leg.

All neurons consist of a soma, dendrites, and axon, each with a specific function.

Dendrites receive messages from other cells and transmit them to the soma.

Axons transmit electrical impulses to other neurons, glands, or muscles.

The myelin sheath insulates axons, speeding up the transmission of signals.

Neurons communicate through synapses, the tiny gaps between their terminals.

Neurotransmitters are chemical messengers that cross the synaptic gap and bind to receptors on receiving neurons.

Neurotransmitters can be excitatory or inhibitory, influencing the likelihood of neuronal firing.

Endorphins are neurotransmitters that induce feelings of pleasure and well-being.

Norepinephrine and glutamate are examples of excitatory neurotransmitters with roles in alertness and memory.

GABA and serotonin are inhibitory neurotransmitters that calm neural activity and influence mood.

Acetylcholine and dopamine can act as both excitatory and inhibitory neurotransmitters.

The endocrine system, including hormones, works alongside the nervous system to regulate body functions.

Hormones, like neurotransmitters, can affect the brain and have slow, lingering effects on the body.

The adrenal glands secrete adrenaline, which prepares the body for fight or flight responses.

The pituitary gland is considered the master gland, controlling other endocrine glands and releasing essential hormones.

The hypothalamus in the brain regulates the endocrine system and maintains homeostasis.

The interaction between the nervous and endocrine systems is a complex feedback loop.

Transcripts

Say it's late at night, you're home alone drifting off to sleep, just, entering that

dream about Fritos, and then suddenly there's a banging at the door!

Suddenly you're wide awake and it feels like your heart's gonna explode.

You jump up ready to run out the back door, possibly grab a Phillips head screwdriver

and stab it into the darkness until it sticks into something.

Now whether it's a Weeping Angel or your neighbor looking to borrow a can of beans, it doesn't

really matter because when you heard that sudden noise, your startled brain released

an icy typhoon of chemicals.

And everything that's now going through your mind, like your urge to flee, your urge to

defend yourself, that internal debate about whether Weeping Angels are even real and "Woah!

Where's the cat?"

All that?

Is just a result of those chemicals.

Our brains and our nervous systems and the substances they produce and are always bathed

in are amazingly complex nuanced systems.

And even though we're always talking about our mental activities being somehow separate

from all the biological stuff going on in our bodies, in reality, the moods, ideas,

impulses, that flash through our minds are spurred by our biological condition.

As psychologists like to say, "Everything psychological is biological."

So one way to understand how your mind works is to look at how the chemistry of your body

influences how you think, sense, and feel about the world around you.

To do that, we begin at the simplest level, the system with the smallest parts, it's all

about the neuron, baby.

[Intro]

Neurons, or nerve cells, are the building blocks that comprise our nervous systems.

Neurons share the same basic makeup as our other cells, but they have electrochemical

mojo that lets them transmit messages to each other.

Your brain alone is made up of billions of neurons, and to understand why we think or

dream or do anything, you gotta first understand how these little transmitters work.

You actually have several different types of neurons in your body, from ones that are

less than a millimeter long in your brain to ones that run the whole length of your

leg!

Yes, you have cells as long as your legs, which is nothing compared to the hundred and

fifty feet the nerve cells of some dinosaurs had to be, I'm getting off topic, sorry.

No matter how big a nerve is, they all have the same three basic parts: the soma, dendrites,

and axon.

The soma, or cell body, is basically the neuron's life support; it contains all that necessary

cell action like the nucleus, DNA, mitochondria, ribosomes, and such.

So, if the soma dies, the whole neuron goes with it.

The dendrites, as bushy and branch-like as the trees they're named after, receive messages

and gossip from other cells.

They're the listeners, whispering what they hear back to the soma.

The axon is the talker.

This long, cable-like extension transmits electrical impulses from the cell body out

to other neurons or glands or muscles.

Whereas the dendrites are short and bushy, the axon fiber is long, and, depending on

what type of neuron it is, is sometimes encased in a protective layer of fatty tissue, called

the myelin sheath.

It's almost like an insulated electrical wire, the myelin sheath speeds up the transmission

of messages, and if it degrades, as it does with those affected with multiple sclerosis,

those signals are degraded as well, eventually leading to lack of muscle control.

Neurons transmit signals either when stimulated by sensory input or triggered by neighboring

neurons.

The dendrites pick up the signal and activate the neuron's action potential, or firing impulse,

that shoots an electrical charge down the axon to its terminals and towards the neighboring

neurons.

The contact points between neurons are called synapses.

All those bushy little dendrites are decorated with synapses that almost but don't quite

touch the neighboring axon in the tiniest game of "I'm not touching you!" of all time.

They're less than a millionth of an inch apart.

And that microscopic cleft is called the synaptic gap.

So, when an action potential runs down to the end of an axon, it activates the chemical

messengers that jump that tiny synaptic gap, flying like that little air kiss and landing

on the receptor sites of the receiving neuron.

Those messengers are neurotransmitters.

Although neurotransmitters slide right into their intended receptors like a key into a

lock, they don't stay bonded to the receiving neuron.

They just sort of pop out, having excited or inhibited the receiving neuron's trigger,

then the extras immediately get reabsorbed by the neuron that released them in the first

place in a process called reuptake.

Kinda like, "Here you go, oh, psych!"

So neurons communicate with neurotransmitters which in turn cause motion and emotion; they

help us move around, make jazz hands, learn, feel, remember, stay alert, get sleepy, and

pretty much do everything we do.

Some of them just make you feel good, like the endorphins we get flooded with after running

ten miles or falling in love or eating a really good piece of pie.

We've got over 100 different kinds of these brilliant neurotransmitters -- some are excitatory

and others are inhibitory, and all are good reminders that everything psychological is

also biological.

Excitatory neurotransmitters rev up the neuron, increasing the chances it will fire off an

action potential.

Norepinephrine is one you're probably familiar with, it helps control alertness and arousal.

Glutamate is another, involved in memory, but an over-supply of it can wig out the brain

and cause seizures and migraines which is why some people are sensitive to all that

MSG, or monosodium glutamate, in their Ramen.

Inhibitory neurotransmitters on the other hand, chill neurons out, decreasing the likelihood

that the neuron will jump into action.

GABA– gamma-aminobutyric acid– is a major inhibitory neurotransmitter, and you've probably

heard of serotonin which affects your mood and hunger and sleep.

Low amounts of serotonin are linked to depression, and a certain class of antidepressants help

raise serotonin levels in the brain.

Some neurotransmitters like acetylcholine and dopamine play both sides and can both

excite or inhibit neurons depending on what type of receptors they encounter.

Acetylcholine enables muscle action and influences learning and memory; Alzheimer's patients

experience a deterioration of their acetylcholine producing neurons.

Dopamine, meanwhile, is associated with learning, movement, and pleasurable emotions, and excessive

amounts of it are linked to schizophrenia as well as addictive and impulsive behavior.

So neurotransmitters are basically your nervous system's couriers.

But they aren't the only chemical messengers delivering the news; they've got some competition

brewing in the endocrine system.

And if you've been through puberty, you know what I'm talking about: hormones.

Like neurotransmitters, hormones act on the brain, and indeed some of them are chemically

identical to certain neurotransmitters.

Hormones affect our moods, arousal, and circadian rhythm, they regulate our metabolism, monitor

our immune system, signal growth, and help with sexual reproduction.

You could say that most of them boil down to the basics: attraction, appetite, and aggression.

Whereas neurons and synapses flick on and off, sending messages with amazing speed,

the endocrine system likes to take its time, delivering the body's slow chemical communications

through a set of glands that secrete hormones into the bloodstream where they're ferried

to other tissues, especially the brain.

So while the nervous and endocrine systems are similar, in that they both produce chemicals

destined to hit up certain receptors, they operate at very different speeds.

It's like, if the nervous system wants to get in touch with you, it sends you a text.

But if the endocrine system has a message, it will like lick the stamp, and put it on,

and write your address, and then a note and a pen on paper, and then fold it up and put

and mail it to you with the Post Office.

But fast isn't always better, and your body will remember that letter longer than the

text.

Hormones, they linger.

Which helps explain why it takes some time to simmer down after a moment of severe fright

or anger.

And our endocrine systems have a few important hormone brewing glands.

We've got a pair of adrenal glands snuggled up against our kidneys that secrete adrenaline,

that famous fight or flight hormone that jacks up your heart rate, blood pressure and blood

sugar, giving you that tidal wave of energy preparing you to run like heck or punch that

charging baboon in the throat; the pancreas sits right next to the adrenal gland and oozes

insulin and glucagon hormones that monitor how you absorb sugar, your bodies main source

of fuel.

Your thyroid and parathyroid glands at the base of your throat secrete hormones that

regulate your metabolism and monitor your body's calcium levels; if you have testicles,

they're secreting your sex hormones like estrogen and testosterone, and if you've got ovaries,

they're doing that job.

And all those glands are super important, but there is one gland that rules them all,

and in the darkness binds them: the pituitary gland.

Although it's just a little pea-sized nugget hidden deep in the bunker of the brain, it

is the most influential gland in this system.

It releases a vital growth hormone that spurs physical development and that love hormone,

oxytocin, that promotes warm, fuzzy feelings of trust and social bonding.

What really makes the pituitary the master gland is that its secretions boss around the

other endocrine glands, but even the pituitary has a master in the hypothalamus region of

the brain, which we will talk more about next episode.

So, AHHHHHHHHH!

if I managed to scare you, sorry, but I'm illustrating a point.

You have no control over being scared, but maybe now you do understand a little more

clearly how your nervous and endocrine systems worked together to call the shots.

First, the sensory input from your eyes and ears went to your brain, the simplest bits

of your hypothalamus without even letting you analyze it and were like ahhhh, and then,

that ran down the chain of command from your pituitary to your adrenal glands, to the hormone

adrenaline, to the rest of your body and then back to your brain, which then realized that

I was just messing with you and told everybody to just calm down for once!

The whole deal is a feedback loop: your nervous system directs your endocrine system which

directs your nervous system, brain, gland, hormone, brain.

And of course each of these systems is fantastically complex.

Way more than we can get into here.

So, in our next lesson, we're gonna get all up in your brain, and delve deeper into the

different components of your nervous system, find out what your old brain is, and learn

about how much of your brain you actually use.

In the meantime, thank you for watching this lesson in Crash Course Psychology which was

brought to you by Zane Ice, who wants to say hi to his friend Harrison.

Thank you, Zane.

If you'd like to sponsor an episode and give your own shout-out, you can learn about that

and other perks available to our subbable subscribers, just go to subbable.com/crashcourse.

This episode was written by Kathleen Yale, edited by Blake de Pastino, and our consultant

is Dr. Ranjit Bhagwat.

Our director and editor is Nicholas Jenkins, the script supervisor was Michael Aranda,

who was also our sound designer, and the graphics team is Thought Cafe.