Neuron’s Cellular Structure

Neurons are the fundamental signaling units of the nervous system. Their structure is highly specialized for communication:

• Cell Body (Soma): Contains the nucleus (with genetic material) and organelles (like mitochondria, endoplasmic reticulum) necessary for the neuron’s survival and metabolism. It integrates incoming signals.
• Dendrites: Branch-like extensions projecting from the cell body. They receive signals from other neurons and conduct these signals towards the cell body. Most neurons have multiple dendrites.
• Axon: A long, singular projection that conducts electrical signals (action potentials) away from the cell body towards other neurons or target cells (like muscle fibers). Many axons are covered by a myelin sheath, a fatty insulating layer produced by glial cells (oligodendrocytes in the CNS, Schwann cells in the PNS). The myelin sheath speeds up signal transmission, with gaps called Nodes of Ranvier where the axon is exposed, allowing the electrical signal to “jump” rapidly.
• Axon Terminals (Synaptic Terminals): Small branches at the end of the axon that form connections with other neurons or cells. They contain synaptic vesicles filled with neurotransmitters.

4. Synapses

• Definition: A synapse is the specialized junction or gap where communication occurs between two neurons (or between a neuron and a target cell like a muscle fiber). It’s the site where information is transmitted from one cell to another.
• Structure (Neuronal Synapse): Typically involves:
  • Presynaptic Terminal: The axon terminal of the sending neuron, containing neurotransmitter vesicles.
  • Synaptic Cleft: The microscopic gap (about 20-40 nanometers wide) between the presynaptic and postsynaptic elements.
  • Postsynaptic Membrane: The dendrite or cell body membrane of the receiving neuron, containing receptor sites for neurotransmitters.
• Significance:
  • Nervous System: Synapses are the fundamental units of neural circuitry. They allow neurons to form complex networks, process information, and coordinate functions throughout the body. The strength and pattern of synaptic connections underlie learning, memory, sensory perception, movement, and emotional responses. Neurotransmitters released at synapses can either excite or inhibit the receiving neuron, determining whether it will fire an electrical signal.
  • Psychological System: Synaptic function is directly linked to psychological states and mental processes. The balance of excitatory and inhibitory signals at synapses influences mood, thought patterns, consciousness, and behavior. Many psychiatric and neurological disorders (e.g., depression, schizophrenia, Parkinson’s disease, Alzheimer’s disease) are believed to involve disruptions in synaptic communication, often related to imbalances in specific neurotransmitters. Drugs used in psychopharmacology primarily target synaptic processes (e.g., blocking reuptake of serotonin, mimicking dopamine).

In essence, neurons are the building blocks, psychopharmacology studies how drugs affect their function, pharmacodynamics explains the drug’s mechanism, and synapses are the crucial communication points where much of this activity, and the influence of drugs, occurs.