Understanding Synapses and Neurotransmission

Aug 4, 2024

Lecture on Synapses and Neurotransmission

Introduction

  • Synapses: Junctions between neurons
    • Crucial for the nervous system to function
    • Greek origin: "to clasp or join"
  • Importance: Enable learning, memory, and influence various experiences and disorders

Types of Synapses

  • Electrical Synapses

    • Direct ion current flow through gap junctions
    • Fast communication, synchronous activity
    • Common in heart muscle cells
    • Lack of control, unsuitable for all functions

  • Chemical Synapses

    • Use neurotransmitters to send signals
    • Slower, but more selective and controllable
    • Convert electrical signals to chemical and back to electrical

Structure and Function

  • Presynaptic Neuron

    • Sends the signal via presynaptic terminal
    • Contains synaptic vesicles with neurotransmitters

  • Postsynaptic Neuron

    • Receives the signal via receptor region
    • Receptor sites on dendrites or cell body

  • Synaptic Cleft: Gap between neurons

Neurotransmission Process

  1. Action potential reaches presynaptic terminal
  2. Voltage-gated calcium channels open, Ca2+ enters
  3. Synaptic vesicles fuse with membrane, release neurotransmitters
  4. Neurotransmitters cross synaptic cleft, bind to receptors
  5. Postsynaptic neuron may get excited or inhibited

Excitatory vs. Inhibitory Neurotransmitters

  • Excitatory: Depolarize postsynaptic neuron, increase likelihood of action potential
  • Inhibitory: Hyperpolarize postsynaptic neuron, decrease likelihood of action potential
  • Sum of excitations and inhibitions determines action potential

Neurotransmitter Lifecycle

  • Neurotransmitters bind briefly to receptors
  • Degraded, reabsorbed (reuptake), or diffused away

Impact of Drugs on Synapses

  • Cocaine: Blocks reuptake of serotonin, dopamine, norepinephrine
    • Leads to euphoria, paranoia, jitteriness
    • Prolonged use depletes neurotransmitter supply, reduces receptors

Conclusion

  • Healthy synapses balance excitation and inhibition
  • Both electrical and chemical signaling are crucial
  • Artificial imbalances (e.g., drug use) can lead to dysfunction

Credits

  • Lecture supported by Logan Sanders and Dr. Linnea Boyev
  • Written by Kathleen Yale, edited by Blake de Pastino
  • Consultant: Dr. Brandon Jackson
  • Directed by Nicholas Jenkins and Michael Aranda
  • Graphics by Thought CafĂ©