Summary
Excitatory inputs depolarise the postsynaptic cell while inhibitory ones hyperpolarise it.
In depth
EPSPs depolarise (often via glutamate opening Na+ channels), IPSPs hyperpolarise (GABA opening Cl- channels). The balance of excitation and inhibition shapes neural circuits; too little inhibition can lead to seizures.
The net effect depends on the sum of excitation and inhibition. Dendritic location matters: inhibition near the soma is powerful.
Remember: whether a transmitter excites or inhibits depends on the receptor.
The balance of excitation and inhibition shapes neural activity, and in the cortex about 80 percent of neurons are excitatory (glutamatergic pyramidal cells) and 20 percent inhibitory interneurons (GABAergic, in many types such as basket and chandelier cells). Glutamate receptors: AMPA (fast), NMDA (slow, Ca2+), kainate. GABA-A receptors are Cl- channels (target of benzodiazepines, barbiturates, alcohol and anaesthetics); GABA-B are GPCRs. Glycine is the main inhibitory transmitter in the spinal cord, and strychnine blocks it, causing convulsions.
Shunting inhibition near the soma can veto excitation. Too much excitation causes seizures (epilepsy), and too much inhibition causes sedation. Excitotoxicity from excess glutamate kills neurons after stroke. In early development, GABA is depolarising.
Key idea: the effect of a transmitter depends on the receptor, not the transmitter itself.
Frequently asked questions
What is Excitatory and Inhibitory Synapses?
Excitatory inputs depolarise the postsynaptic cell while inhibitory ones hyperpolarise it.
Which area of biology covers Excitatory and Inhibitory Synapses, and how advanced is it?
Excitatory and Inhibitory Synapses is one of the 54 topics in Neuroscience. It is rated Intermediate, so it suits learners who already know the core vocabulary. Related topics in this area include NMDA Receptors, Neural Development, Neurotransmitters.
Can you give an example of Excitatory and Inhibitory Synapses?
Benzodiazepines enhance GABA-A receptor activity.
What should I learn before Excitatory and Inhibitory Synapses?
Work through the Beginner topics in Neuroscience first, such as Nervous System, Neuron, Central and Peripheral Nervous Systems, then return to Excitatory and Inhibitory Synapses. Intermediate topics assume the Beginner vocabulary.
What topics are related to Excitatory and Inhibitory Synapses?
The closest topics to Excitatory and Inhibitory Synapses are NMDA Receptors, Neural Development, Neurotransmitters, Neuropharmacology. Comparing them side by side is a good way to see how the ideas connect.
How can I check that I understand Excitatory and Inhibitory Synapses?
Read the summary and the in-depth section, then use the quick check on the interactive lesson for Excitatory and Inhibitory Synapses. To practise the whole of Neuroscience, use the Neuroscience quiz.
How is Excitatory and Inhibitory Synapses different from NMDA Receptors?
Excitatory and Inhibitory Synapses: Excitatory inputs depolarise the postsynaptic cell while inhibitory ones hyperpolarise it. NMDA Receptors: Glutamate-gated channels that act as coincidence detectors by needing both ligand and depolarisation. Read both side by side and note what each one explains.
How should I study Excitatory and Inhibitory Synapses step by step?
First, read the summary and write the definition in your own words. Second, read the in-depth section and note any example. Third, compare it with NMDA Receptors and explain the difference aloud. Finally, take the Neuroscience quiz and come back to this page for any question you miss.