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Biology: The Human Nervous System
Question
What is the function of the nervous system?
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Answer
To detect stimuli, process information, and coordinate responses — allowing the body to react to its environment.
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Question
What are the two main divisions of the nervous system?
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Answer
The central nervous system (CNS: brain + spinal cord) and the peripheral nervous system (PNS: all nerves outside the CNS).
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Question
What are the three types of neuron?
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Answer
Sensory neurons (carry signals from receptors to CNS), motor neurons (carry signals from CNS to effectors), and relay neurons (connect sensory and motor neurons within the CNS).
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Question
What is a synapse?
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Answer
A junction between two neurons where nerve impulses are transmitted chemically via neurotransmitters across a small gap (synaptic cleft).
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Question
How does a signal cross a synapse?
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Answer
An electrical impulse triggers release of neurotransmitters from vesicles into the synaptic cleft. They bind to receptors on the next neuron, generating a new electrical impulse.
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Question
What is a reflex arc?
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Answer
The neural pathway for an involuntary reflex: stimulus → receptor → sensory neuron → relay neuron (in spinal cord) → motor neuron → effector.
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Question
What is the difference between a reflex and a voluntary action?
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Answer
A reflex is automatic and very fast (processed in the spinal cord without conscious thought). A voluntary action involves the brain and conscious decision-making.
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Question
What is the myelin sheath and what does it do?
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Answer
A fatty insulating layer around some axons. It speeds up nerve impulse transmission by allowing the signal to "jump" between gaps (nodes of Ranvier).
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Question
What is the resting potential of a neuron?
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Answer
The electrical charge across the membrane when not transmitting a signal: approximately −70 mV (inside negative relative to outside).
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Question
What is an action potential?
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Answer
A rapid change in membrane potential (from −70 mV to +40 mV) that travels along a neuron as the nerve impulse. Caused by ion movements across the membrane.
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