The Nervous System - CrashCourse Biology #26

CrashCourse
23 Jul 201212:04
EducationalLearning
32 Likes 10 Comments

TLDRThe nervous system is composed of specialized cells called neurons that transmit signals to control behaviors, sensations, and bodily functions. It has a central nervous system (brain and spinal cord) that interprets signals and a peripheral nervous system of sensory and motor neurons to collect and act on data. These systems have both incoming and outgoing neuron pathways and somatic and autonomic branches driving voluntary and involuntary actions. The autonomic system is further divided into the activating sympathetic and calming parasympathetic nervous systems working in opposition. Action potentials allow rapid transmission of signals within and between neurons through changes in electrical potential across cell membranes.

Takeaways
  • 😀 The nervous system allows animals to have behaviors and be sentient
  • 😃 The nervous system is made of specialized neurons that transmit signals
  • 🧠 The central nervous system (brain & spinal cord) interprets signals, peripheral nervous system collects signals
  • 🤔 Afferent neurons carry signals to the central nervous system, efferent neurons carry signals away
  • 😮 The peripheral nervous system has somatic (voluntary) and autonomic (involuntary) parts
  • 😲 The autonomic system has sympathetic (fight-or-flight) and parasympathetic (rest-and-digest) parts
  • 🔌 Neurons have resting potentials, action potentials allow signals to propagate
  • âš¡ Signals jump along nodes of Ranvier in saltatory conduction to go faster
  • 🤯 Neurotransmitters cross the synapse between neurons
  • 😋 My brain says to eat more pizza!
Q & A

  • What are the two main departments of the nervous system?

    -The two main departments of the nervous system are the central nervous system (the brain and spinal cord) and the peripheral nervous system (all the nerves outside the brain and spine).

  • What is the difference between afferent and efferent neurons?

    -Afferent neurons carry information to the brain and spinal cord for analysis, while efferent neurons carry information away from the brain and spinal cord to muscles and organs.

  • What are the two divisions of the autonomic nervous system?

    -The two divisions of the autonomic nervous system are the sympathetic nervous system, which controls the fight-or-flight response, and the parasympathetic nervous system, which controls resting and digesting.

  • What is a reflex arc?

    -A reflex arc allows the spinal cord to respond directly to a stimulus without needing input from the brain. For example, quickly removing your hand from a hot stove.

  • What creates the voltage difference across a neuron's membrane?

    -The sodium-potassium pump moves 3 sodium ions out of the cell for every 2 potassium ions moved in, creating an excess negative charge inside the neuron.

  • How does an action potential propagate along a neuron?

    -An action potential is triggered when enough sodium channels open to reverse the voltage. This depolarization spreads to adjacent areas of the neuron and jumps along the axon between Nodes of Ranvier.

  • What causes the resting potential to be restored after an action potential?

    -The sodium channels close and potassium channels open, allowing positive potassium ions to exit. This repolarizes the membrane. Then the sodium-potassium pump restores ion gradients.

  • What stimulates the first neuron when you bite into pizza?

    -Chemicals from the pizza dissolve in saliva and stimulate the dendrites of taste receptor neurons in the tongue, generating action potentials.

  • What does the brain signal when you taste good pizza?

    -The brain signals the jaw muscles to chew, the neck muscles to lower the head for another bite, the throat to swallow, and the mouth to open for more bites.

  • What system will handle digesting the pizza?

    -The autonomic nervous system drives digestion of the pizza after it is swallowed.

Outlines
00:00
🧠 The Nervous System: An Overview

This paragraph provides an introduction to the nervous system. It explains that the nervous system allows organisms to have behaviors, makes you a sentient being, and is made up of specialized neurons that transmit signals. It distinguishes between the central nervous system (brain and spinal cord) and peripheral nervous system (nerves outside the CNS). It also introduces the concepts of afferent and efferent neurons.

05:02
🦵 The Peripheral Nervous System

This paragraph dives deeper into the peripheral nervous system. It explains the two components of the PNS - somatic (voluntary) and autonomic (involuntary). It also breaks down the autonomic system into the sympathetic (fight-or-flight) and parasympathetic (rest-and-digest) divisions, which have opposite functions but work together to maintain homeostasis.

10:02
âš¡ How Neurons Work

This paragraph provides an in-depth explanation of neuron anatomy and function. It covers dendrites, axons, myelin sheaths, nodes of Ranvier, membrane potential, ion channels, action potentials, neurotransmitters, and the role of sodium-potassium pumps. It explains how stimuli trigger signals that propagate along neurons through electrochemical changes.

Mindmap
Keywords
💡neurons
Specialized cells found throughout the nervous system that transmit signals between different parts of the body. The video explains how bundles of neurons form nerves and pathways to carry electrochemical signals. Different types of neurons like sensory, motor, afferent and efferent allow the nervous system to sense stimuli and initiate responses.
💡central nervous system
Made up of the brain and spinal cord. It is responsible for analyzing and interpreting sensory information sent from the peripheral nervous system before sending signals to initiate responses.
💡peripheral nervous system
Nerves and neurons outside of the brain and spinal cord. It collects sensory information from stimuli throughout the body and transmits it to the central nervous system.
💡reflex loop
A neural shortcut that allows the spinal cord to initiate quick muscle responses before sensory information reaches the brain. This is how you jerk your hand off a hot stove before feeling pain.
💡autonomic nervous system
Controls unconscious bodily functions like breathing, heartbeat and digestion through sympathetic and parasympathetic nerve pathways from the CNS.
💡action potential
The process of rapid change in a neuron's electrical membrane potential when it is stimulated. This is how neurons propagate signals down nerve pathways through saltatory conduction.
💡myelin sheath
An insulating layer around neuron axons. It allows signals to jump from node to node, increasing conduction speed down axons (saltatory conduction).
💡neurotransmitters
Chemicals like dopamine and serotonin which allow neurons to pass signals to each other across synapses. Their release is triggered by action potentials.
💡sympathetic nervous system
Branch of autonomic nervous system responsible for fight-or-flight stress response - increasing breathing and heart rates for action.
💡parasympathetic nervous system
Branch of autonomic nervous system responsible for rest-and-digest response - slowing heart rate and increasing digestion.
Highlights

Transcripts detail 8 key benefit areas of mindfulness meditation including reduced stress, pain, addiction and depression.

Studies show mindfulness meditation can permanently change the brain structure to promote wellbeing.

Meditation is linked to enhanced self-awareness, emotional regulation, focus and empathy.

MRI scans reveal meditation strengthens circuits related to calmness and internal focus.

Meditation may slow aging and promote longevity by reducing inflammation and cellular decay.

Mindfulness helps treat PTSD symptoms by reducing avoidance and aiding memory processing.

Studies indicate meditation boosts immune function and lowers blood pressure.

Meditation enhances creativity, cognitive flexibility and the ability to solve complex problems.

Meditators show increased gray matter in brain regions linked to learning, memory and emotion.

Meditation may benefit people with autism, ADHD, schizophrenia, depression and other disorders.

Mindfulness-based programs help treat addictions and prevent relapse in smokers.

Meditation improves emotional intelligence, social skills and relationship satisfaction.

Studies link meditation to improved academic performance, focus and stress management in students.

Mindfulness meditation reduces pain sensitivity by changing how the brain processes signals.

Meditation may help delay the onset of Alzheimer's and mild cognitive impairment.

Transcripts

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