Understanding Neuronal Communication and Brain Function

Overview

• The human brain processes millions of gigabytes of information daily and performs thousands of reactions.
• Information is received through the five senses, e.g., vision when driving.
• The brain integrates new information with existing data to direct behavior.

Neuronal Structure

• Neurons:
  • Billions in number, each connected to thousands of others.
  • Communicate via electrical and chemical signals.
  • Basic structure:
    • Cell Body: Contains the nucleus and genetic information.
    • Dendrites: Receive information.
    • Axon: Sends information to terminal buttons (end regions).
    • Axon Hillock: Connection point between cell body and axon.

Electrical State of Neurons

• Neurons have an electrical charge, around -70 millivolts at rest.
• Charge due to ion concentration differences inside vs. outside.
  • Outside: High in sodium (Na+) and chloride (Cl-).
  • Inside: High in potassium (K+) and protein ions.

Ion Channels and Membrane Potential

• Ion Channels:
  • Protein structures in cell membranes, acting as gates for ions.
  • Normally closed but open upon receiving a signal.

Synapse and Neurotransmitter Functions

• Synapse: Connection point between neurons.
• Neurotransmitters (NTs):
  • Released into the synapse.
  • Bind to receptors on receiving neuron.
  • Binding opens ion channels, causing biochemical events.

Postsynaptic Potentials

• Excitatory Postsynaptic Potential (EPSP):
  • Occurs with positive sodium ion influx, making membrane more positive.
• Inhibitory Postsynaptic Potential:
  • Occurs with negative ion influx, making membrane more negative.

Action Potentials

• Triggered when membrane potential at axon hillock hits a threshold.
• Involves a change in membrane permeability to sodium and potassium.
• Propagates down the axon, is an all-or-nothing response.
• Action Potential Characteristics:
  • Brief and larger reversal in membrane polarity.

Neurotransmitter Release

• Action potential reaching terminal buttons opens calcium channels.
• Calcium influx triggers neurotransmitter release via exocytosis.
• Cycle repeats with neurotransmitter binding to postsynaptic receptors.

Application

• Example: Visual input leads to neuronal messages that result in motor actions, like braking a car.