Action Potential/ Neurotransmission

• What is the approximate resting membrane potential of a neuron?

  -70 mV
• The resting membrane potential is maintained by the Na⁺/K⁺ ATPase pump, selective K⁺ permeability, and ion gradients
• Where is an action potential initiated in a neuron?

  Axon hillock
• An action potential is triggered when graded potentials depolarise the membrane to threshold
• Arrange the phases of the action potential in the correct order:

  1️⃣ Resting (-70 mV)

  2️⃣ Depolarisation (Na⁺ influx, +30 mV)

  3️⃣ Repolarisation (K⁺ efflux)

  4️⃣ Hyperpolarisation (undershoot)

  5️⃣ Return to resting via Na⁺/K⁺ pump
• The 'all-or-nothing' principle states that the size and duration of an action potential vary depending on stimulus strength.

  False
• Why does the action potential travel in only one direction?

  Refractory period
• After opening, Na⁺ channels become inactivated, creating a refractory period.
• Myelin is produced by Schwann cells in the PNS and oligodendrocytes in the CNS.
• What type of conduction does myelin enable in axons?

  Saltatory conduction
• Arrange the events at the synapse when an action potential arrives:

  1️⃣ Action potential depolarises the terminal

  2️⃣ Voltage-gated Ca²⁺ channels open

  3️⃣ Ca²⁺ influx causes vesicle fusion

  4️⃣ Neurotransmitter release into synaptic cleft

  5️⃣ Neurotransmitter binds to postsynaptic receptors
• Ionotropic receptors are ligand-gated and allow direct ion flow across the membrane.
• What type of receptors are metabotropic receptors coupled to?

  G-proteins
• EPSPs increase the likelihood of an action potential, while IPSPs decrease it.
• EPSPs result from Na⁺ influx, whereas IPSPs result from Cl⁻ influx or K⁺ efflux.
• What are two examples of neurotransmitters and their receptor types?

  Glutamate (AMPA, NMDA) and GABA (GABA-A, GABA-B)