What are IPSPs?

What are IPSPs?

• A. Excitatory signals that increase chance of firing
• B. Inhibitory signals that decrease chance of firing
• C. Signals that depolarize the membrane
• D. Modifications at the neuromuscular junction

Answer: (B)

IPSPs are inhibitory postsynaptic potentials, signals that decrease the likelihood that the postsynaptic neuron will fire an action potential. They occur when inhibitory neurotransmitters open ion channels that hyperpolarize the membrane—typically by allowing Cl− to enter or K+ to leave—or by increasing membrane conductance (shunting inhibition). This pushes the membrane potential away from the threshold or dampens incoming excitatory input, making it harder for the neuron to reach firing. Remember that neurons integrate inputs: if inhibition dominates, firing is less likely; if excitation dominates, firing is more likely. So IPSPs serve to dampen activity, unlike excitatory inputs that depolarize the membrane. The neuromuscular junction is a different type of synapse, so choices describing depolarization or muscle connections don’t fit IPSPs.

IPSPs are inhibitory postsynaptic potentials, signals that decrease the likelihood that the postsynaptic neuron will fire an action potential. They occur when inhibitory neurotransmitters open ion channels that hyperpolarize the membrane—typically by allowing Cl− to enter or K+ to leave—or by increasing membrane conductance (shunting inhibition). This pushes the membrane potential away from the threshold or dampens incoming excitatory input, making it harder for the neuron to reach firing. Remember that neurons integrate inputs: if inhibition dominates, firing is less likely; if excitation dominates, firing is more likely. So IPSPs serve to dampen activity, unlike excitatory inputs that depolarize the membrane. The neuromuscular junction is a different type of synapse, so choices describing depolarization or muscle connections don’t fit IPSPs.