The Nervous System
Year 9 ๐ซ Physiology & Health Neurons, synapses, reflex arcs, and the brain.
๐ง The Nervous System
The nervous system detects stimuli and coordinates rapid responses via electrical impulses.
- CNS (central nervous system) โ brain + spinal cord; processes information
- PNS (peripheral nervous system) โ nerves connecting CNS to receptors and effectors
- Sensory neurons โ carry impulses from receptors TO the CNS
- Motor neurons โ carry impulses FROM the CNS to effectors (muscles/glands)
- Relay neurons โ connect sensory and motor neurons within the CNS
Reflex arc pathway
Receptor โ Sensory neuron โ Relay neuron (spinal cord) โ Motor neuron โ Effector๐ง Synapses
A synapse is the tiny gap between neurons. Signals cross by diffusion of neurotransmitter chemicals.
- Impulse arrives โ Caยฒโบ enters terminal โ vesicles fuse with pre-synaptic membrane โ neurotransmitter released
- Neurotransmitter diffuses across synaptic cleft โ binds to receptors on post-synaptic membrane โ new impulse generated
- Neurotransmitter then broken down (e.g. by acetylcholinesterase) to allow rapid reset
- Synapses ensure one-way transmission; allow signal integration; are targets for drugs and toxins
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Interactive Demo โ The Nervous System
Reflex Arc Analyser