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Nervous System and Neuron Function
Nervous System and Neuron Function
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The nervous system is the body's fast communication network, allowing you to sense the environment, think, move, and maintain internal balance. Its basic working unit is the neuron, a specialized cell that receives, processes, and sends signals. Understanding neuron function helps explain everything from reflexes and memory to muscle control and pain. It also connects cell biology to real body systems in a clear and practical way.
A neuron receives input through dendrites, integrates signals in the cell body, and sends an electrical impulse called an action potential down the axon. Myelin around the axon speeds signal transmission by allowing impulses to jump between nodes of Ranvier. At the axon terminals, the electrical signal triggers release of neurotransmitters across a synapse to the next cell. Together, billions of neurons form the central and peripheral nervous systems that coordinate rapid responses throughout the body.
Key Facts
- The nervous system is divided into the central nervous system, CNS, and peripheral nervous system, PNS.
- A neuron's main parts are dendrites, cell body, axon, myelin sheath, nodes of Ranvier, and axon terminals.
- Resting membrane potential is typically about -70 mV in many neurons.
- An action potential occurs when membrane voltage rapidly depolarizes and then repolarizes.
- Myelin increases conduction speed by saltatory conduction, where impulses move node to node.
- At a synapse, neurotransmitters diffuse across the synaptic cleft and bind to receptors on the next cell.
Vocabulary
- Neuron
- A neuron is a specialized cell that transmits information using electrical and chemical signals.
- Dendrite
- A dendrite is a branched extension of a neuron that receives incoming signals from other cells.
- Axon
- An axon is the long projection of a neuron that carries impulses away from the cell body.
- Myelin sheath
- The myelin sheath is a fatty insulating layer around some axons that speeds up signal conduction.
- Synapse
- A synapse is the junction where one neuron communicates with another cell by releasing neurotransmitters.
Common Mistakes to Avoid
- Confusing dendrites with axons, because both are extensions of the neuron. Dendrites usually receive signals, while the axon usually carries signals away from the cell body.
- Thinking myelin creates the nerve impulse, which is wrong because the action potential is produced by ion movement across the neuron membrane. Myelin mainly speeds conduction and reduces signal loss.
- Assuming all nervous system signaling is purely electrical, which is incomplete. Signals travel electrically along a neuron but are usually passed chemically across synapses.
- Believing the brain alone makes up the nervous system, which leaves out major structures. The spinal cord and peripheral nerves are also essential parts that carry information to and from the body.
Practice Questions
- 1 A nerve impulse travels along a myelinated axon at 80 m/s. How long does it take for the impulse to travel 1.6 m?
- 2 A signal must cross 5 synapses, and each synapse causes a delay of 0.5 ms. What is the total synaptic delay in milliseconds?
- 3 Explain why damage to the myelin sheath can slow movement or reduce coordination, even if the neuron itself is still alive.