A neuron is the structural and functional unit of the nervous system that transmits nerve impulses as electrochemical signals. It is important for NEET Biology because NTA frequently tests resting and action potentials, saltatory conduction in myelinated fibres, and synaptic transmission involving neurotransmitters like acetylcholine.
Dendrites
Short, branching projections that receive nerve impulses from other neurons or sensory receptors and transmit them toward the cell body.
Cell body (Soma)
Contains the nucleus and most organelles; integrates incoming signals and maintains the neuron's metabolic functions.
Nucleus
Houses the genetic material (DNA) and controls protein synthesis essential for neurotransmitter production and cell maintenance.
Axon hillock
Cone-shaped junction between the soma and axon; the trigger zone where action potentials are initiated if threshold is reached.
Axon
Long cylindrical projection that carries nerve impulses (action potentials) away from the cell body toward the axon terminals.
Myelin sheath
Insulating lipid layer formed by Schwann cells (PNS) or oligodendrocytes (CNS); speeds up impulse conduction by enabling saltatory conduction.
Nodes of Ranvier
Unmyelinated gaps between adjacent Schwann cells where ion channels are concentrated; action potentials jump between nodes for faster transmission.
Schwann cells
Glial cells in the peripheral nervous system that wrap around the axon to form the myelin sheath; each cell covers one internode segment.
Axon terminals
Branching ends of the axon that form synapses with target cells; contain mitochondria for energy and vesicles with neurotransmitters.
Synaptic knob
Bulb-shaped swellings at axon terminal tips; release neurotransmitters into the synaptic cleft via calcium-triggered exocytosis.
Resting Potential (−70 mV)
NTA frequently tests the resting membrane potential value (−70 mV), the role of the Na⁺/K⁺ ATPase pump (3 Na⁺ out, 2 K⁺ in), and why the inside of the neuron is negatively charged at rest due to K⁺ leak channels.
Action Potential
Expect questions on depolarization (Na⁺ influx, threshold −55 mV), repolarization (K⁺ efflux), hyperpolarization, and the all-or-none principle. Know the sequence of events and the role of voltage-gated ion channels.
Saltatory Conduction
Questions on how myelin sheath enables faster impulse transmission — action potentials jump from node to node (saltatory = 'leaping'). Myelinated fibres conduct at 100 m/s vs 0.5 m/s in unmyelinated.
Synapse & Neurotransmitters
NTA tests the mechanism of chemical synaptic transmission — Ca²⁺ entry triggers vesicle fusion, neurotransmitter release into synaptic cleft, binding to post-synaptic receptors. Know acetylcholine and its degradation by acetylcholinesterase.
Solve previous year NEET questions on neural control and coordination.
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