Study Guides/Biology/What happens at the synapse between two neurons
Study Guide · Biology

What Happens at the Synapse Between Two Neurons?

In Class 10 Biology (Control and Coordination), we learn that our brain and body communicate through millions of nerve cells called Neurons. However, these neurons are not physically connected to each other like a continuous wire. There is a microscopic gap between them called a Synapse. So, how does a message cross this gap?

Question (Click to Flip)

What happens to the neurotransmitter chemicals after the message is passed?

Answer

Once the new electrical impulse is triggered, the leftover neurotransmitter chemicals in the gap are instantly destroyed by enzymes or sucked back up by the first neuron (Reuptake) so that the nerve doesn't fire endlessly.

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Key Facts

The Synapse acts like a biological 'One-Way Valve'. Because neurotransmitter chemicals are only stored at the axon terminal of the first neuron, and the receptors are only on the dendrite of the second neuron, a nerve signal can never travel backwards!

The Arrival of the Signal

A message travels down the axon of the first neuron (the Presynaptic neuron) in the form of a fast Electrical Impulse. When this electrical shock reaches the very end of the nerve fiber (the Axon Terminal), it cannot jump across the empty gap (Synapse) to the next neuron. The electrical signal stops.

The Chemical Conversion (Neurotransmitters)

To cross the gap, the signal must change its form.

  1. The arrival of the electrical impulse forces the axon terminal to burst open tiny sacs (vesicles).
  2. These sacs release special biological chemicals called Neurotransmitters (like Dopamine, Acetylcholine, or Serotonin) into the gap (the Synaptic Cleft).
  3. Thus, the electrical signal is converted into a Chemical Signal.

Receiving the Signal

  • The released neurotransmitter chemicals quickly float across the microscopic gap.
  • They bind to specific 'Receptors' located on the dendrite of the second neuron (the Postsynaptic neuron), acting like a key fitting into a lock.
  • As soon as the chemicals lock in, they trigger a brand new Electrical Impulse inside the second neuron.
  • The message continues its journey to the brain or muscle!

Questions and Answers

What happens to the neurotransmitter chemicals after the message is passed?+

Once the new electrical impulse is triggered, the leftover neurotransmitter chemicals in the gap are instantly destroyed by enzymes or sucked back up by the first neuron (Reuptake) so that the nerve doesn't fire endlessly.

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