Nervous System

Summary

The Amoeba Sisters dive into the intricacies of the nervous system, highlighting the diversity and specialization of body cells. They explore the central nervous system (CNS) and the peripheral nervous system (PNS), detailing their functions and components. The video explains the structure of the brain and the roles of neurons and glial cells. It describes an action potential's process, emphasizing neuron communication through neurotransmitters. The video concludes by encouraging interest in neurological careers.

Highlights

• Cells in the body are incredibly specialized, each with unique structures for different functions! 🤯
• The brain is divided into hindbrain, midbrain, and forebrain, each with distinct functions! 🧠
• Neurons communicate via action potentials, carrying signals super fast! 🚀
• Glial cells do much more than just 'support'; they're crucial for neuron function! 🌟
• The "all or none" nature of action potentials makes neuron signaling unique! 💡

Key Takeaways

• Body cells are incredibly diverse, playing specialized roles in different systems! 🧬
• The CNS, comprising the brain and spinal cord, acts as the command center! 🧠
• Neurons and glial cells are vital to the nervous system's functioning! 🔗
• Understanding action potentials helps in grasping neuron communication! ⚡️
• The nervous system's complexity offers endless exploration and career opportunities! 🧑‍🔬

Overview

Ever wondered about the diversity of body cells? The Amoeba Sisters reveal the fascinating specialization of cells across different systems, like how stomach parietal cells produce acid while nerve cells send signals. They introduce the nervous system, emphasizing its complexity and integral components.

The video guides us through the nervous system's structure, from the brain's regions to neurons’ roles. It highlights the CNS as the brain and spinal cord hub, while the PNS channels information throughout the body. Neurons and glial cells come into play, each vital in maintaining nervous health and function.

Taking us deeper, the sisters explain action potentials and neuron communication. They showcase how signals zip through axons and trigger neurotransmitters to bridge synapses, painting a vivid picture of our intricate nervous network. Careers in this field are as exciting as the science itself, inviting curiosity and exploration.

Chapters

• 00:00 - 00:30: Introduction to Body Cell Diversity The chapter introduces the concept of body cell diversity, emphasizing the variety and specialization of cells within the human body. It challenges the simplistic view of cells as uniform 'little circle blobs' by highlighting specific examples of specialized cells. For instance, parietal cells in the stomach produce stomach acid, a unique function within the digestive system that is not shared by cells in other systems. Similarly, mast cells are part of the immune system, containing substances like histamine crucial for inflammatory responses. Additionally, skeletal muscle cells, also known as muscle fibers, are integral to the muscular system. The chapter aims to broaden the understanding of the functional diversity and significance of different cell types in maintaining bodily functions.
• 00:30 - 01:00: Neuron and Nervous System Overview This chapter provides an overview of neurons and the nervous system. It begins by discussing the specialized structures of various cells, essential for their functions, emphasizing muscle cells with their essential filaments for contraction. The chapter highlights the neuron's role, a specialized cell within the nervous system, sharing an admiration for its unique functions. It sets the stage to delve deeper into the nervous system, encompassing not just neurons but other integral components as well. The chapter concludes by preparing to introduce a comprehensive tour of the nervous system.
• 01:00 - 02:00: Central and Peripheral Nervous System The chapter titled 'Central and Peripheral Nervous System' provides an overview of the nervous system's division into two main regions: the central nervous system (CNS) and the peripheral nervous system (PNS). The CNS includes the brain and spinal cord, while the PNS comprises nerves throughout the body. The PNS is responsible for delivering sensory information to the CNS, which in return, acts as a command center by processing the information and executing motor responses or regulating body mechanisms. The chapter briefly mentions the role of cells within the nervous system and the concept of action potential.
• 02:00 - 03:00: Overview of the Human Brain The chapter introduces the human brain as part of the Central Nervous System (CNS), emphasizing a broad overview of its structure. The brain is divided into three main regions: the hindbrain, midbrain, and forebrain. A detailed look at the hindbrain reveals that it includes the medulla, pons, and cerebellum. The medulla is responsible for regulating essential functions such as breathing, blood pressure, and heart rate. The pons contributes to these regulatory functions and plays a role in coordinating signals between different parts of the brain.
• 03:00 - 04:00: Functions of the Cerebrum and Brain Myths The chapter starts by distinguishing different parts of the brain, focusing on the cerebellum, which is responsible for balance and movement coordination. It also discusses the midbrain, highlighting its role in alertness, the sleep/wake cycle, and motor activity. The 'brainstem' is introduced, encapsulating structures like the medulla, pons, and midbrain. The chapter culminates in the discussion of the forebrain, notably the cerebrum, which is divided into two hemispheres (left and right) and is responsible for numerous sophisticated functions.
• 04:00 - 05:00: Peripheral Nervous System Breakdown This chapter begins by discussing the cerebrum, highlighting its role in various functions such as speech, thinking, reasoning, sensing, and emotions. It encourages further reading for more exploration on these topics. The forebrain is briefly discussed, including structures like the thalamus, which deals with sensory and motor information, and the hypothalamus, known for its major control of the endocrine system. The chapter aims to debunk popular myths about the brain, notably the erroneous belief that humans only use 10% of their brain capacity.
• 05:00 - 06:00: Sympathetic and Parasympathetic Systems The chapter titled 'Sympathetic and Parasympathetic Systems' likely covers the divisions within the peripheral nervous system (PNS), specifically focusing on the somatic nervous system (SNS) and the autonomic nervous system (ANS). The SNS is responsible for motor functions of skeletal muscles and includes voluntary actions under conscious control as well as somatic reflexes. The autonomic system, on the other hand, manages the internal environment, likely discussing the roles of the sympathetic and parasympathetic systems in regulating bodily functions such as gastrointestinal and excretory processes.
• 06:00 - 07:00: Cells in the Nervous System This chapter delves into the various types of cells present in the nervous system, particularly emphasizing the autonomic nervous system (ANS). It explains how the ANS is responsible for controlling involuntary muscles and autonomic reflexes, and further divides into two main systems: the sympathetic and parasympathetic systems. The sympathetic system, known for its shorter name, is part of the body's quick fight or flight response, using the metaphorical example of encountering a fear-inducing situation like facing a 'personal nemesis'. The text aims to provide an understanding of how these systems help the body react to different stimuli and stressors.
• 07:00 - 08:00: Neuron Structure and Function The chapter 'Neuron Structure and Function' introduces the concept of the body's fight or flight response triggered by stressful situations, using the metaphor of a malfunctioning copy machine. It explains how this response accelerates heart rate and breathing while suppressing less critical functions like digestion. The chapter also touches on the contrasting role of the parasympathetic system, colloquially known as 'rest and digest,' which regulates and promotes bodily functions when at rest.
• 08:00 - 10:00: Action Potential Explained The chapter explains how the heart rate decreases and digestion occurs in the 'rest and digest' phase. It discusses how these responses can have opposite effects on the same organ. It further describes the two major types of cells in the nervous system found in both the central and peripheral nervous systems, focusing on the general structure of neurons, including the cell body, nucleus, and other organelles.
• 10:00 - 11:00: Neurotransmitters and Signal Transmission The chapter titled 'Neurotransmitters and Signal Transmission' begins by introducing key components of the neural anatomy: dendrites and axons. Dendrites are branched structures where signals are received, while axons carry signals away from the cell to another cell. The junction where a neuron communicates with another cell is called a synapse. The chapter also introduces glial cells (or glia), emphasizing that although they were initially known as supporting cells, they play a much more crucial role in neural function than previously thought. The chapter hints at a deeper exploration of these structural roles and their significance in signal transmission.
• 11:00 - 12:00: Recap and Final Thoughts In this chapter, the role of glial cells in the nervous system is highlighted. Often considered merely as the 'glue' in the brain, glial cells actually have a plethora of crucial functions. They maintain the balance of chemicals necessary for cell signaling in the intercellular space, are integral to upholding the blood-brain barrier that protects the nervous system from various substances, and are responsible for the production of myelin. Myelin sheaths insulate axons, enhancing the transmission of electrical impulses in neurons.

Nervous System Transcription

• 00:00 - 00:30 You know – sometimes we forget how  different the cells in the body can   be – we kind of imagine them as all as  little circle blobs when in reality,   there is so much body cell diversity.  Parietal cells in the stomach as part   of the digestive system – they can make stomach  acid! Thankfully, cells in other systems do not. Mast cells as part of the immune system  – they contain substances like histamine   that they can release which is critical  for the inflammatory response. Skeletal   muscle cells -which are also called muscle  fibers – as part of the muscular system,
• 00:30 - 01:00 they’re shaped like cylinders with  multiple nuclei – and their structure   includes thin and thick filaments which  are essential for muscle contraction. We could on with all the specialized  cells in all the body systems and   the cells themselves structurally sure  are different – specialized for their   function. And if I had to pick my favorite  specialized body cell – it’d be a neuron   –a cell that is part of the nervous system.  The system that is the topic of this video. But before we talk about neurons  or other cells in the nervous   system because it’s not just neurons – let’s give  a little general tour of the nervous system. Then
• 01:00 - 01:30 we’ll get to cells of the nervous system  and briefly mention the action potential! First, structure wise, you can divide the nervous  system into 2 very general regions: the central   nervous system (CNS) – which consists of the brain  and spinal cord - and peripheral nervous system   (PNS) –which consists of all other components of  the nervous system -such as nerves throughout the   body. The PNS can provide sensory information for  the CNS while the CNS can process that information   and act as a command center – the CNS can execute  motor responses or regulate body mechanisms.
• 01:30 - 02:00 So, we said the CNS consisted of the spinal  cord and brain. Let’s talk a bit about the   amazing human brain – although realize we  are being very general here – as we are   going to divide it into 3 general regions:  the hindbrain, midbrain, and forebrain. Let’s look at the hindbrain first.  It includes the medulla, pons,   and cerebellum. The medulla has many regulation  functions such as the regulation of breathing,   blood pressure, and heart rate. The pons is  involved with some of these type of functions   as well and also coordinating signals with  this area to the rest of the brain. And the
• 02:00 - 02:30 cerebellum? Balance and movement coordination  are some functions of the cerebellum. The midbrain: deep in the brain, this area is  involved in alertness and the sleep/wake cycle,   motor activity, and more. If you’ve heard  the term “brainstem,” this includes some   of the structures we just mentioned: the  medulla, pons, and midbrain specifically. Finally, the forebrain. Most notably, this  includes the cerebrum, which itself is   divided into two hemispheres: right and left. So many functions are done by our amazing
• 02:30 - 03:00 cerebrum depending on specific location whether  it’s our speech, our thinking and reasoning,   our sensing, our emotions – check out  the further reading to explore this!   The forebrain also technically includes some  structures in it like the thalamus – which is   involved with sensory and motor information-  and hypothalamus – which if you remember   from our endocrine system video, has  major control of the endocrine system. There are a lot of myths about the brain. One  quick myth I heard all the time as a kid that   I’d like to put to rest. It’s the myth that  “humans only use 10% of their brain” – it’s
• 03:00 - 03:30 not correct. We have a great reading suggestion on  that as well as some others that circulate around. Now, that was all the central nervous system  (CNS). What about the peripheral nervous   system or PNS? Functionally speaking, we can  further divide the PNS based on what it does.   The somatic nervous system (SNS) and autonomic  nervous system (ANS). The SNS is involved with   motor functions of skeletal muscle. This will  include voluntary actions under conscious   control but also somatic reflexes that involve  skeletal muscle. The ANS is all about what’s   going on in the internal environment in  regard to gastrointestinal or excretory
• 03:30 - 04:00 or endocrine or smooth and cardiac muscle  and it also includes autonomic reflexes. And the ANS itself can be further divided –  I know, I know, there’s a lot of dividing but   stay with me – the ANS can be divided into the  sympathetic and parasympathetic systems. The   sympathetic system – the shorter word of the two–  helps me remember it’s part of the quick fight   or flight response. I know the whole running  from a bear is a very popular example. For me,   it’d be more realistic if I was face to face with  my personal nemesis: the copy machine which I may
• 04:00 - 04:30 or may not have had some very bad experiences  with before – and the warning bell just rang   so you now know you have 60 seconds to get your  copies – but it’s making crazy machine noises   and giving you vague warnings– this also could  activate your fight or flight response. A response   that can cause your heart to race and breathing  rate to increase and some things to not be active:   like the digestive system. Because if you’re  desperately trying to run from a bear or take   on the copy machine, you don’t really need to be  digesting your food at that very moment…right? The parasympathetic system – longer word  – this is often called rest and digest.
• 04:30 - 05:00 Heart rate will decrease, digestion will  occur – again, rest and digest. Many times,   these two systems can therefore have  opposite effects on the same organ. So let’s talk about two major types  of cells in the nervous system that   makes up nervous tissue. That means  these are cells that you’ll find in   the central nervous system and  the peripheral nervous system. Most of the time, neurons are what come to mind.  There are different types of neurons but to focus   on general neuron structure: you have the cell  body – the nucleus and most other organelles
• 05:00 - 05:30 are here. There are dendrites, generally  these branched structures are where signals   are received. And you have an axon – I like  to think away axon! – because axons are the   fiber where normally a signal will be carried  away to some other cell. The junction area   where the neuron will be communicating  with another cell is called a synapse. And the other major cell type? Glial cells. Or  you can call them glia. When I was a student   and read that they were supporting cells – I  don’t think the word “supporting” emphasized   to me at the time how essential they really  are. Structurally, there was a lot of emphasis
• 05:30 - 06:00 on how they actually help the neurons connect  in place – the word “glia” comes from a Greek   word that means glue. But glia have huge roles  and they are SO much more than that. Some glial   cells keep a balance of certain chemicals  in the space between cells – essential for   signaling – and maintain the blood-brain barrier  which keeps a lot of substances in the body from   getting into the nervous system. Some glial  cells make myelin – which goes around the   axons of neurons as something called a myelin  sheath - insulates the axon and transferring
• 06:00 - 06:30 of the signal. Some glial cells produce  cerebrospinal fluid which is protective   to the brain and essential for homeostasis -  as well as many other critical functions. Some   glial cells have important immune function in the  nervous system. These are all just a few examples. As amazing as glial cells are, it’s time to  move on to the action potential. Generally,   action potentials are recognized as something  neurons do – but we did link some interesting   reads about certain glial cell types and  action potentials. We’re just going to touch
• 06:30 - 07:00 on what an action potential is but we may have  a future video to go into more detailed steps. The main idea is that neurons need to be able  to communicate with each other. And to do that   they’ve got to be able to receive a signal in the  dendrite and carry it down the axon. And they need   to do that fast – like less than 2 milliseconds  fast. The action potential makes that possible.   We can’t talk about an action potential without  talking about when the neuron is at rest – meaning   when there is no signal being carried – at  rest, a neuron has something called a resting   potential. The resting potential of a neuron is  more negative than its surroundings – in fact   it can be measured – it generally is around  -70 mv. Yes, mv, which is millivolts- it has
• 07:00 - 07:30 an electrical charge. That’s because there are  ions involved inside and outside of the cell:   ions like chloride (Cl-), sodium (Na+), potassium  (K+), certain anions (A-). Specifically,   sodium (Na+) and potassium (K+) play huge roles  in keeping the resting potential – they should   sound familiar because we talk about the sodium  potassium pump in another video and that is a pump   that helps maintain a neuron at resting potential.  At rest, generally the sodium (Na+) concentration
• 07:30 - 08:00 is higher outside of the cell and the potassium  (K+) concentration is higher inside the cell.   How can we remember that? How about it’s Kool  to be K+ resting in the cell. But overall,   at rest, the neuron is more negative  inside compared to its surroundings. So let’s say the dendrite of the neuron receives  a signal. This can generate an action potential   along the axon. An action potential is going to  rapidly change the charge in the neuron along   the axon - the signal carries from one area  of the axon to the next. Ion channels open   allowing Na+ to flood inside the first region  of the axon. Recall Na+ is a positive ion. This
• 08:00 - 08:30 event is called depolarization – as the electric  charge is becoming more positive in the axon as   Na+ floods in and most K+ channels at that moment  stay closed. This spreads to the next region of   the axon and carries along. But as the action  potential spreads to a new region of the axon,   the old region where the action potential  already occurred will start to be restored   back - to learn more about the different channels  that open and close to achieve this amazing   feat – or specific events like the undershoot or  refractory period- check out the further reading
• 08:30 - 09:00 links in the video description. Eventually we  hope to have an entire video on this process. Two things to point out about this  action potential. 1. If neurons are   myelinated – meaning they have myelin  sheaths that insulate the axon and   assist with the transfer of the signal  – the action potential can actually jump   from node to node – the nodes being  areas of where it’s not myelinated. 2. Important to realize, the action  potential is considered an “all or   none” thing. What we mean by that is that it  either happens or it doesn’t – like a light
• 09:00 - 09:30 switch it’s either on or off – there isn’t a  dimmer switch, there aren’t different levels,   it’s either off or it reaches a threshold  of when it’s on and if it’s on, it’s going. So that’s all good but what happens next? Let’s  say you have an action potential and it’s going   to signal another neuron – how? Well that’s one  way to introduce neurotransmitters. So the action   potential goes down the axon and gets to the axon  terminals – the ends of the axon. We had mentioned   there is this space called a synapse which  consists of the area between the two neurons.   The action potential can signal synaptic vesicles  in that neuron to release something called   neurotransmitters. There are different types  of neurotransmitters and they can be derived
• 09:30 - 10:00 from different substances: for example, amino  acids or amino acid precursors. Or even a gas   such as nitric oxide although the release  is different than other neurotransmitters. Generally, when neurotransmitters are  released from the synaptic vesicles,   the neurotransmitters only need to travel  a small space between the neurons specified   as the synaptic cleft. Then they can  bind specific receptors of the next   neuron – specific receptors to the type of  neurotransmitter that binds it. The dendrite
• 10:00 - 10:30 area of the other neuron receives the signal and  can start an action potential across its axon. When we cover a lot of things, we  think it’s important to recap: so,   we’ve talked about the peripheral  nervous system (PNS) and the central   nervous system (CNS). Since the CNS  includes the spinal cord and brain,   we also talked some about major areas of the  brain. Then we focused on the PNS- how it can   be divided into the somatic nervous system (SNS)  and autonomic nervous system (ANS) and then how   the autonomic nervous system (ANS) can be divided  into the sympathetic and parasympathetic system.
• 10:30 - 11:00 We then explored major cell types in the  nervous system: glial cells and neurons.   And since neurons can communicate with  each other using an action potential,   we gave a brief overview of the action  potential. We then mentioned that once   the action potential occurs, this can signal  the release of neurotransmitters in the synapse   between neurons. Those neurotransmitters bind  specific receptors of a neighboring neuron. Phew! So, with such a complex system that could be  so many videos long –there continues to be a
• 11:00 - 11:30 lot of research done to help diseases and  conditions of the nervous system. If you   have an interest in this field– there  are many careers involved in neurology   to explore. Well that’s it for the Amoeba  Sisters, and we remind you to stay curious.