EONS LEARNING

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      • Periodic Table
      • Common Ion Sheet
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    • Unit 1: Beginning Chemistry >
      • Lesson 1: The Atom >
        • What is an Atom?
        • The Structure of Atoms
        • The Periodic Table
        • Modeling Atoms
      • Lesson 2: Chemical Bonding >
        • Why Do Atoms Form Bonds?
        • Ionic Bonding
        • Covalent Bonding
        • Intermolecular Attraction
      • Lesson 3: Chemical Nomenclature >
        • Octet Rule
        • Ionic Compounds
        • Covalent Molecules
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        • Modeling Ionic Compounds
        • Modeling Covalent Molecules
      • Lesson 5: States of Matter >
        • States of Matter
        • Phase Changes
      • Lesson 6: Density >
        • What is Density?
        • Calculating Density
      • Lesson 7: Thermodynamics >
        • Temperature
        • Heat
        • Gas Laws
      • Lesson 8: Solution Chemistry >
        • Diffusion
        • Solutions and Molarity
        • Semi-Permeable Membranes
      • Lesson 9: Thermal Expansion >
        • Thermal Expansion
    • Unit 2: Earth Science >
      • Lesson 10: Earth at a Glance >
        • Perspective
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      • Lesson 11: Layers of the Earth >
        • Layers of the Earth
      • Lesson 12: Plate Tectonics >
        • Plate Tectonics
      • Lesson 13: Rocks and Minerals >
        • Rocks and Minerals
      • Lesson 14: Particle Sorting >
        • Differentiation
        • Deposition of Sediment
      • Lesson 15: The Atmosphere >
        • Composition of the Atmosphere
        • Layers of the Atmosphere
        • Change Over Time
        • Atmospheric Disruption
    • Unit 3: The Cell >
      • Lesson 16: Life >
        • What is Life?
        • Structural Hierarchy of Living Things
      • Lesson 17: Biochemistry >
        • Intro to Biochemistry
        • Water
        • Micromolecules
        • Energy, Carbohydrates, Lipids
        • Protein and Nucleic Acid
      • Lesson 18: Cells >
        • What are Cells?
        • Microscopy
        • Plant and Animal Cells
      • Lesson 19: Membrane Transport >
        • A Special Environment
        • The Structure of Membranes
        • Membrane Transport
      • Lesson 20: Energy and Cell Respiration >
        • Energy in Biology
        • Energy Diagrams
        • Glycolysis and Anaerobic Respiration
        • Aerobic Cellular Respiration
      • Lesson 21: Photosynthesis >
        • Plants Get Energy From The Sun
        • Photosynthesis Process
        • Energy, Ecosystems, and the Environment
    • Unit 4: Anatomy and Physiology >
      • Lesson 22: The Human Body >
        • What Are Bodies Made Of?
        • What Do Bodies Do?
      • Lesson 23: The Nervous System >
        • The Nervous System
        • Neuronal Communication
        • The Central Nervous System
      • Lesson 24: The Endocrine System >
        • The Endocrine System
        • Hormones
        • Hormones, Puberty, and Reproduction
      • Lesson 25: The Integumentary System >
        • The Integumentary System
      • Lesson 26: The Musculoskeletal System >
        • The Skeletal System
        • The Muscular System
        • Anatomy Of The Musculoskeletal System
      • Lesson 27: The Cardiovascular System >
        • Blood and Blood Vessels
        • The Heart
      • Lesson 28: The Respiratory System >
        • The Respiratory System
      • Lesson 29: The Digestive System >
        • The Digestive System
        • Nutrition
      • Lesson 30: The Excretory System >
        • The Excretory System
      • Lesson 31: The Immune System >
        • Disease and Infection
        • Immunity
    • Units 5-6 Coming Soon
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    • Unit 1 >
      • EIS >
        • Lesson 1: Atoms
        • Lesson 2: Chemical Bonding
        • Lesson 3: Chemical Nomenclature
        • Lesson 4: Molecular Models
        • Lesson 5: States of Matter
        • Lesson 6: Density
        • Lesson 7: Thermodynamics
        • Lesson 8: Solution Chemistry
        • Lesson 9: Thermal Expansion
      • Unit 1: Project
      • Unit 1: Exam Review
      • Unit 1: Exam
    • Unit 2 >
      • EIS >
        • Lesson 10: Earth at a Glance
        • Lesson 11: Layers of the Earth
        • Lesson 12: Plate Tectonics
        • Lesson 13: Rocks and Minerals
        • Lesson 14: Particle Sorting
        • Lesson 15: The Atmosphere
      • Unit 2: Project
      • Unit 2: Exam Review
      • Unit 2: Exam
    • Unit 3 >
      • EIS >
        • Lesson 16: Life
        • Lesson 17: Biochemsitry
        • Lesson 18: Cells
        • Lesson 19: Membrane Transport
        • Lesson 20: Energy and Cell Respiration
        • Lesson 21: Photosynthesis
      • Unit 3: Project
      • Unit 3: Exam Review
      • Unit 3: Exam
    • Unit 4 >
      • EIS >
        • 22: The Human Body
        • 23: The Nervous System
        • 24: The Endocrine System
        • 25: The Integumentary System
        • 26: The Musculoskeletal System
        • 27: The Cardiovascular System
        • 28: The Respiratory System
        • 29: The Digestive System
        • 30: The Excretory System
        • 31: The Immune System
      • Unit 4 Project
      • Unit 4 Exam Review
      • Unit 4 Exam
    • Units 5-6 Coming Soon
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  • Home
  • About Us
  • Classroom
    • Resources >
      • Study Skills
      • Periodic Table
      • Common Ion Sheet
      • The Scientific Method
      • Doing Background Research
    • Introduction and Course Philosophy
    • Unit 1: Beginning Chemistry >
      • Lesson 1: The Atom >
        • What is an Atom?
        • The Structure of Atoms
        • The Periodic Table
        • Modeling Atoms
      • Lesson 2: Chemical Bonding >
        • Why Do Atoms Form Bonds?
        • Ionic Bonding
        • Covalent Bonding
        • Intermolecular Attraction
      • Lesson 3: Chemical Nomenclature >
        • Octet Rule
        • Ionic Compounds
        • Covalent Molecules
      • Lesson 4: Molecular Molecules >
        • Modeling Ionic Compounds
        • Modeling Covalent Molecules
      • Lesson 5: States of Matter >
        • States of Matter
        • Phase Changes
      • Lesson 6: Density >
        • What is Density?
        • Calculating Density
      • Lesson 7: Thermodynamics >
        • Temperature
        • Heat
        • Gas Laws
      • Lesson 8: Solution Chemistry >
        • Diffusion
        • Solutions and Molarity
        • Semi-Permeable Membranes
      • Lesson 9: Thermal Expansion >
        • Thermal Expansion
    • Unit 2: Earth Science >
      • Lesson 10: Earth at a Glance >
        • Perspective
        • Maps
      • Lesson 11: Layers of the Earth >
        • Layers of the Earth
      • Lesson 12: Plate Tectonics >
        • Plate Tectonics
      • Lesson 13: Rocks and Minerals >
        • Rocks and Minerals
      • Lesson 14: Particle Sorting >
        • Differentiation
        • Deposition of Sediment
      • Lesson 15: The Atmosphere >
        • Composition of the Atmosphere
        • Layers of the Atmosphere
        • Change Over Time
        • Atmospheric Disruption
    • Unit 3: The Cell >
      • Lesson 16: Life >
        • What is Life?
        • Structural Hierarchy of Living Things
      • Lesson 17: Biochemistry >
        • Intro to Biochemistry
        • Water
        • Micromolecules
        • Energy, Carbohydrates, Lipids
        • Protein and Nucleic Acid
      • Lesson 18: Cells >
        • What are Cells?
        • Microscopy
        • Plant and Animal Cells
      • Lesson 19: Membrane Transport >
        • A Special Environment
        • The Structure of Membranes
        • Membrane Transport
      • Lesson 20: Energy and Cell Respiration >
        • Energy in Biology
        • Energy Diagrams
        • Glycolysis and Anaerobic Respiration
        • Aerobic Cellular Respiration
      • Lesson 21: Photosynthesis >
        • Plants Get Energy From The Sun
        • Photosynthesis Process
        • Energy, Ecosystems, and the Environment
    • Unit 4: Anatomy and Physiology >
      • Lesson 22: The Human Body >
        • What Are Bodies Made Of?
        • What Do Bodies Do?
      • Lesson 23: The Nervous System >
        • The Nervous System
        • Neuronal Communication
        • The Central Nervous System
      • Lesson 24: The Endocrine System >
        • The Endocrine System
        • Hormones
        • Hormones, Puberty, and Reproduction
      • Lesson 25: The Integumentary System >
        • The Integumentary System
      • Lesson 26: The Musculoskeletal System >
        • The Skeletal System
        • The Muscular System
        • Anatomy Of The Musculoskeletal System
      • Lesson 27: The Cardiovascular System >
        • Blood and Blood Vessels
        • The Heart
      • Lesson 28: The Respiratory System >
        • The Respiratory System
      • Lesson 29: The Digestive System >
        • The Digestive System
        • Nutrition
      • Lesson 30: The Excretory System >
        • The Excretory System
      • Lesson 31: The Immune System >
        • Disease and Infection
        • Immunity
    • Units 5-6 Coming Soon
  • Workbench
    • Unit 1 >
      • EIS >
        • Lesson 1: Atoms
        • Lesson 2: Chemical Bonding
        • Lesson 3: Chemical Nomenclature
        • Lesson 4: Molecular Models
        • Lesson 5: States of Matter
        • Lesson 6: Density
        • Lesson 7: Thermodynamics
        • Lesson 8: Solution Chemistry
        • Lesson 9: Thermal Expansion
      • Unit 1: Project
      • Unit 1: Exam Review
      • Unit 1: Exam
    • Unit 2 >
      • EIS >
        • Lesson 10: Earth at a Glance
        • Lesson 11: Layers of the Earth
        • Lesson 12: Plate Tectonics
        • Lesson 13: Rocks and Minerals
        • Lesson 14: Particle Sorting
        • Lesson 15: The Atmosphere
      • Unit 2: Project
      • Unit 2: Exam Review
      • Unit 2: Exam
    • Unit 3 >
      • EIS >
        • Lesson 16: Life
        • Lesson 17: Biochemsitry
        • Lesson 18: Cells
        • Lesson 19: Membrane Transport
        • Lesson 20: Energy and Cell Respiration
        • Lesson 21: Photosynthesis
      • Unit 3: Project
      • Unit 3: Exam Review
      • Unit 3: Exam
    • Unit 4 >
      • EIS >
        • 22: The Human Body
        • 23: The Nervous System
        • 24: The Endocrine System
        • 25: The Integumentary System
        • 26: The Musculoskeletal System
        • 27: The Cardiovascular System
        • 28: The Respiratory System
        • 29: The Digestive System
        • 30: The Excretory System
        • 31: The Immune System
      • Unit 4 Project
      • Unit 4 Exam Review
      • Unit 4 Exam
    • Units 5-6 Coming Soon
  • Donate

neuronal communication

nerves communicate quickly

Let’s say you touch something hot, like a stovetop or a pot of boiling water. What’s next? You pull your hand away. Super fast. That’s it. If you’ve ever done this before (in which case, I’m sorry for your pain), you might have even noticed that you pulled your hand away before even feeling any pain or realizing that you had touched a hot stove. There was just an automatic reflex that pulled your hand away, along with the realization: This is hurting you! Get away!
Picture
This kind of super speedy reaction is called a reflex arc (more on this later), and it is an excellent example of just what makes the nervous system so useful: it’s really, really fast. When we want to send a signal super fast, we use the nervous system. It’s like the superhighway of communication in the body, and it’s really good at its job.

the neuron

As you might be able to guess, in order to do this really specialized, awesome function, the nervous system has a specialized, awesome structure. It is made up of millions of cells called neurons, which look something like this:
Picture
I’ve pointed out the most important parts of the neuron. It has lots of spindly bits that help to take in information from all over and a long axon that helps to send some signal about this information onto another cell. In other words, it takes in information and passes on a signal. Every part of your nervous system—your brain, your spinal cord, and your peripheral nervous system—is made up of neurons. (The neurons in each place are actually a little different from each other, but we won’t worry about the details of that in this class).

action potentials and neurotransmitters

The signal that a neuron sends is called an action potential. An action potential is a very fast signal that uses the movement of electrolytes (sodium and potassium ions) to generate electricity and allow a neuron to tell the next cell that it was just “on”. There’s only one type of action potential in neurons, and action potentials from a single cell all put out the same voltage. In other words, the action potential doesn’t actually tell you anything other than that the neuron was just “on”. The effect that the neuron being “on” has on the next cell depends on what type of neuron it is and what type of neurotransmitter it sends. 

This video gives a nice overview of how nerves communicate with each other:
You don’t need to know all of the details, but if you’d like to get into a bit more of the biochemistry behind these “magical” electrical and chemical signals, this video gives a nice overview:
Neurotransmitters are chemical signals sent across a synapse. A synapse is a gap between a neuron and the next cell. The next cell could be another neuron, it could be a muscle cell, or it could be some other cell type in the body. A neurotransmitter tells the next cell what to do. For example, the neurotransmitter acetylcholine is sent from a nerve cell to a muscle cell to tell the muscle to start contracting, to make the muscle move. Neurotransmitters like GABA are inhibitory, meaning they tell the next cell to not do anything, while others like glutamate are excitatory, meaning they tell the next cell to do something. Neurotransmitters like dopamine and serotonin control lots of different pathways in the brain, including the ones that make you feel happy. The action potential sends a “go-ahead” signal, but what the signal actually says is determined by the neurotransmitter. 

If you’d like a little more detail on neurotransmitters, this video gives a nice overview:
To summarize, a neuron receives an input through its dendrites (spindly bits), which could be from the outside environment or from another cell. Based on that signal, it sends an action potential, or electrical signal using ions, down its axon (nerve fiber). This action potential causes the release of neurotransmitters, which are chemical signals that determine the effects of that signal. Electrical signal down the neuron, chemical signal to a new neuron.

the reflex arc

The reflex arc is a good demonstration of the simplest version of how all of these systems come together in a cause-and-effect pathway. A sensory neuron senses a hot stove. It sends this message (via an action potential) to the spinal cord, which turns that signal around to a motor neuron to tell your hand to move (more action potentials). Touch a hot stove. Move hand away. Without even involving the brain to think about it!
Picture
This video gives a nice summary of what a reflex arc is, and why it’s important that we have fast signals in the body:

more complex signals involve more nerves

You’ll note that, in addition to the relatively simple reflex arc that only involves a few cells, this video also mentions some complex CNS processes, like learning. Every nervous system process that happens in your body can be traced back to nerves firing regular, simple action potentials, just like they do in the reflex arc: more complex processes just involve a lot more nerves and a lot more action potentials.

If you’re having trouble wrapping your brain around how such a simple “ON-OFF” signal can be responsible for all of the advanced processes that happen in the brain, just think: This is exactly how computers work, too! Everything a computer does ultimately comes down to a bunch of “ON-OFF” signals called binary code (which is a series of zeroes and ones). Making complex and unique things happen is just a matter of putting together a lot of zeroes and ones in very complex and unique ways.
Picture

Summary

You should understand that:
  • Nerves are used to send really fast signals, which help us to quickly turn sensory inputs into actions in the PNS and to do things that take a lot of really complex steps, like learning and memory, in the CNS. 
  • Nerves receive an input, which causes them to fire an action potential (electrical signal), which causes them to release a neurotransmitter (chemical signal), which determines what effect that action potential will have on the next cell.
  • The simplest pathway that demonstrates the main idea of the nervous system is the reflex arc: we have some sort of sensory input which travels up a sensory neuron, which tells something in the CNS what’s going on, which tells a motor neuron what to do to fix that thing (like moving your hand away from a hot stove).

Learning Activity

Picture
Next: the central nervous system

Contributors: Megha Kori, Emma Moulton
​Some images made with biorender.com

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