Neurotransmitter receptors are found mainly on the postsynaptic membrane of the neuron, especially on the dendrites and the cell body (soma), and at some specialized synapses on the axon terminal of certain neurons. Summation (adding up excitatory and inhibitory inputs) takes place electrically across the dendrites and soma, with the final “decision” to fire happening at the axon hillock (the initial segment of the axon).

Quick Scoop: Neuron Receptors & Summation

Where are neurotransmitter receptors in a neuron?

Most classical neurotransmitter receptors sit where chemical signals arrive from other neurons.

  • On dendritic spines and dendritic shafts of the postsynaptic neuron.
  • On the cell body (soma), which also receives many synapses in some neurons.
  • At certain specialized axo-axonal synapses, on the presynaptic terminal of another neuron (these modulate neurotransmitter release rather than classic “input,” but still use receptors).

You can picture a neuron as a tree: dendrites are the many branches where receptors are clustered, catching neurotransmitter “messages” released into the synaptic cleft.

Many neurons receive 80–95% of their synaptic input onto dendrites, which is why so many neurotransmitter receptors are concentrated there.

Where does summation take place in a neuron?

Summation is how a neuron “votes” on whether to fire an action potential.

  • Spatial summation :
    • Multiple excitatory postsynaptic potentials (EPSPs) and inhibitory postsynaptic potentials (IPSPs) arrive at different synapses on dendrites and soma at roughly the same time.
* These graded potentials spread passively through the cell’s interior and algebraically add together (excitatory minus inhibitory).
  • Temporal summation :
    • Rapid, repeated firing from the same presynaptic neuron causes EPSPs (or IPSPs) to stack in time at a single synapse.
* Because each postsynaptic potential lasts longer than the interval between spikes, they overlap and add up.

All of this graded activity is spread over the dendrites and soma , but the crucial site where the net effect is “read” is the axon hillock/initial segment :

  • The axon hillock has a very high density of voltage-gated sodium channels and the lowest threshold in the neuron.
  • If the combined EPSPs and IPSPs that arrive there reach threshold, an action potential is triggered; if not, the neuron stays silent.

So in simple exam-style terms:

  • Neurotransmitter receptors: mainly on dendrites and soma (postsynaptic membrane).
  • Summation: spread over dendrites and soma, with the final summation “decision” at the axon hillock.

Mini multi-view: how different sources phrase it

Below is a compact view of how typical teaching sources describe summation sites:

[5][1][3] [7][1][3][5] [8][9][3][5] [9][3][5][7]
Aspect Common teaching phrasing
Where inputs arrive Synapses on dendrites and soma of the postsynaptic neuron.
Where spatial summation occurs Across many synapses on dendrites and soma at the same time.
Where temporal summation occurs At a given synapse when it is repeatedly activated in quick succession.
Final decision point Axon hillock / initial segment, where summed potentials reach or fail to reach threshold.

TL;DR

  • Neurotransmitter receptors: on postsynaptic membranes , especially dendrites and soma.
  • Summation: graded potentials combine over dendrites and soma; the axon hillock is where the neuron decides to fire or not.

Information gathered from public forums or data available on the internet and portrayed here.