Neuron and Nerve Impulse
Resting and action potential, and impulse conduction along axons. (Biology › Neural Control and Coordination, NEET UG syllabus.)
What is Neuron and Nerve Impulse?
The structural and functional unit of the nervous system, specialized for transmitting electrical signals.
Key formula / rule: Na+/K+ Pump Ratio
Key points
- Describe the structure of a neuron and its components.
- Explain how resting membrane potential is established and maintained.
- Detail the sequence of events during the generation and propagation of an action potential (depolarization, repolarization, hyperpolarization).
- Differentiate between continuous and saltatory conduction of nerve impulses.
Common exam trap
Confusing the roles of Na+ and K+ ions during depolarization and repolarization.
Definitions
- Term
Neuron
- Meaning
The structural and functional unit of the nervous system, specialized for transmitting electrical signals.
- Term
Nerve Impulse
- Meaning
An electrical signal transmitted along the axon of a neuron, also known as an action potential.
- Term
Resting Membrane Potential
- Meaning
The electrical potential difference across the plasma membrane of a neuron when it is not transmitting a signal, typically -70 mV.
- Term
Action Potential
- Meaning
A rapid, transient, all-or-none change in the membrane potential of an excitable cell, used for long-distance communication.
- Term
Depolarization
- Meaning
A decrease in the absolute value of a cell's membrane potential, making the inside less negative (or positive) relative to the outside, primarily due to Na+ influx.
- Term
Repolarization
- Meaning
The restoration of the resting membrane potential after depolarization, primarily due to K+ efflux.
- Term
Threshold Potential
- Meaning
The critical level of depolarization (-55 mV) that must be reached for an action potential to be generated.
- Term
Saltatory Conduction
- Meaning
The 'jumping' of an action potential from one Node of Ranvier to the next in myelinated axons, resulting in faster conduction.
Learning objectives
Describe the structure of a neuron and its components.
Explain how resting membrane potential is established and maintained.
Detail the sequence of events during the generation and propagation of an action potential (depolarization, repolarization, hyperpolarization).
Differentiate between continuous and saltatory conduction of nerve impulses.
Explain the 'all-or-none' principle and the concept of threshold potential.
Understand the role of the refractory period in nerve impulse transmission.
Formulae
- Name
Na+/K+ Pump Ratio
- Note
Maintains electrochemical gradient for resting potential.
- Expression
3 Na+ out : 2 K+ in
Prerequisites
Basic cell structure and function (cell membrane, cytoplasm, nucleus).
Understanding of active and passive transport mechanisms (diffusion, facilitated diffusion, active transport).
Knowledge of ions (Na+, K+, Cl-) and their roles in biological systems.
Basic understanding of electrical potential and gradients.
Common mistakes
Confusing the roles of Na+ and K+ ions during depolarization and repolarization.
Misunderstanding the active nature of the Na+/K+ pump vs. passive ion channel movement.
Not grasping the 'all-or-none' principle and threshold potential.
Confusing the refractory period with hyperpolarization.
Incorrectly identifying the function of myelin sheath or Nodes of Ranvier.
Keywords
Neuron
Nerve Impulse
Resting Potential
Action Potential
Depolarization
Repolarization
Hyperpolarization
Threshold Potential
Na+/K+ Pump
Myelin Sheath
Nodes of Ranvier
Saltatory Conduction
Refractory Period
Voltage-gated Channels
Practice preview
Which of the following is primarily responsible for maintaining the resting membrane potential in a neuron?…
easy
The nerve impulse is essentially a/an ___________ wave that travels along the length of the neuron.…
easy
What is the primary event that leads to the repolarization phase of an action potential?…
medium