neurons and synaptic transmission

• • Synaptic Transmission

  Synaptic transmission is the process by which neurons communicate with each other, relaying information to the central nervous system (CNS) via sensory neurons and executing responses dictated by the brain through motor neurons.
• The Process of Synaptic Transmission

  1. Action Potential Arrival: An action potential reaches the presynaptic membrane, causing depolarization by opening voltage-dependent calcium ion channels, leading to an influx of calcium ions.
• The Process of Synaptic Transmission

  2. Vesicle Fusion: The increased concentration of calcium ions within the presynaptic membrane causes vesicles containing neurotransmitters to fuse with the membrane and release their contents into the synaptic cleft through a process called exocytosis.
• The Process of Synaptic Transmission

  3. Neurotransmitter Diffusion: Neurotransmitters diffuse across the synaptic cleft down a concentration gradient and bind to complementary receptors on the postsynaptic membrane. This binding can result in either an inhibitory or excitatory effect on the postsynaptic membrane.
• The Process of Synaptic Transmission

  4. Propagation of Action Potential: The binding of neurotransmitters and the subsequent changes in ion flow can generate a new action potential in the postsynaptic neuron, continuing the cascade of neurotransmission along the neural pathway.
• Types of Neurotransmitters

  1. Inhibitory Neurotransmitters: These reduce the likelihood of an action potential in the postsynaptic neuron. For example, serotonin closes voltage-dependent sodium ion channels, decreasing the potential difference across the postsynaptic membrane and thus reducing the likelihood of an action potential.
• Types of Neurotransmitters

  1. Excitatory Neurotransmitters: These increase the likelihood of an action potential in the postsynaptic neuron. For example, dopamine opens more voltage-dependent sodium ion channels, increasing the potential difference across the postsynaptic membrane and thus enhancing the likelihood of an action potential.