4.Transmission of the excitation (inhibition) from one excitable cell to another. Synapses- types of synapses. Chemical synapses. Neurotransmitters and modulators. Postsynaptic potential. Summation of the postsynaptic potentials

synapses / types of synapses

🔹 Synapse = presynaptic terminal + synaptic cleft + postsynaptic membrane

transmission of excitation

• Depolarization of the presynaptic cell

• Action potential reaches the axon terminal

• Voltage-gated Ca²⁺ channels open, and Ca²⁺ enters the presynaptic terminal

• Neurotransmitters are released via exocytosis

• Neurotransmitters bind to ligand-gated ion channels (receptors) on the postsynaptic membrane

• Depending on the receptor:

  • Excitatory: Na⁺ channels open → Na⁺ influx → further depolarization

  • Inhibitory: Cl⁻ channels open → Cl⁻ influx → hyperpolarization

• If enough Na⁺ enters and threshold is reached → action potential generated in the postsynaptic cell

neurotransmitters and modulators

neuromodulators affect inhibitory or excitatory response of the RECEPTORS

post synaptic potential

post synaptic summation

Temporal summation = one neuron firing rapidly → each small signal adds up → possibly triggers an action potential in the next cell.