neuron signalling

• What are the main structures of a neuron and their functions?

  • Dendrites: Receive nerve impulses from receptors or other neurons.
  • Cell Body (Soma): Contains the nucleus and cytoplasm; determines if signals are passed to the axon.
  • Axon: Transmits nerve signals in the form of action potentials to axon terminals.
• How does the sodium-potassium pump generate the resting potential?

  It pumps sodium ions out and potassium ions in, maintaining concentration gradients across the plasma membrane.
• What is the resting potential of a neuron?

  Approximately -70 mV.
• Why is the resting potential negative?

  Due to the distribution of ions inside and outside the plasma membrane of a neuron.
• What is the significance of myelination in nerve impulses?

  Myelination increases the speed of nerve impulses by acting as an insulating layer around axons.
• What is the speed of nerve impulses in myelinated axons compared to unmyelinated axons?

  Myelinated axons can transmit impulses at speeds up to 150 m/s, while unmyelinated axons transmit at 0.5 to 10 m/s.
• What is a synapse?

  A synapse is a junction between two neurons or a neuron and an effector, such as muscles or glands.
• How do neurotransmitters function in synaptic transmission?

  Neurotransmitters are released from the presynaptic membrane and diffuse across the synaptic cleft to bind to receptors on the postsynaptic membrane.
• What initiates the release of neurotransmitters at the presynaptic membrane?

  The arrival of an action potential at the axon terminal opens voltage-gated calcium channels, allowing calcium ions to enter.
• What is the role of acetylcholine in synaptic transmission?

  Acetylcholine binds to receptors on the postsynaptic membrane, opening voltage-gated sodium channels and generating an excitatory postsynaptic potential.
• What are the steps involved in synaptic transmission?

  1. Arrival of action potential at axon terminal.
  2. Opening of voltage-gated calcium channels.
  3. Calcium ions diffuse into the axon terminal.
  4. Movement of vesicles containing neurotransmitters to the presynaptic membrane.
  5. Exocytosis of neurotransmitters into the synaptic cleft.
  6. Binding of neurotransmitters to receptors on the postsynaptic membrane.
• How does the speed of nerve impulses correlate with animal size and axon diameter?

  Speed of nerve impulses decreases with increasing animal size (negative correlation) and increases with larger axon diameter (positive correlation).
• What is the diameter of axons in squids and their speed of nerve impulses?

  Axons of squids can have a diameter up to 1 mm and a speed of nerve impulses of up to 25 m/s.
• What is the function of myelin in neurons?

  Myelin acts as an insulating layer that increases the speed of nerve impulses.
• How does the release of acetylcholine generate an action potential in the postsynaptic membrane?

  Acetylcholine binds to receptors, opening voltage-gated sodium channels, allowing Na⁺ to flow into the neuron.
• What is the significance of the sodium-potassium pump in neurons?

  It maintains the resting potential by pumping sodium out and potassium in.
• What is the role of calcium ions in neurotransmitter release?


  Calcium ions trigger the movement of vesicles containing neurotransmitters to the presynaptic membrane for release.
• How does the structure of specialized cells relate to their function in neural signalling?

  Specialized structures like dendrites, axons, and myelin enable efficient transmission of electrical signals in neurons.