The nervous system controls and coordinates all activities of the body. It is the body's main communication network and an important biology exam topic.
Divisions of the Nervous System
- Central Nervous System (CNS): brain and spinal cord.
- Peripheral Nervous System (PNS): nerves outside the CNS.
Parts of the Brain
- Cerebrum: largest part; controls thinking, memory and voluntary actions.
- Cerebellum: controls balance and posture.
- Medulla oblongata: controls involuntary actions like heartbeat and breathing.
The Neuron
The neuron is the structural and functional unit of the nervous system. It has three parts: dendrites (receive signals), cell body and axon (carries signals away). A neuron is the longest cell in the body.
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Reflex Action
A reflex action is a quick, automatic response to a stimulus, such as pulling the hand back from a hot object. It is controlled by the spinal cord, not the brain. The path it follows is the reflex arc.
Important Facts
The brain is protected by the skull and the spinal cord by the vertebral column. The gap between two neurons is the synapse. The cerebrum is the seat of intelligence and memory.
Quick Revision Points
- CNS = brain + spinal cord.
- Cerebrum is the largest part of the brain.
- Cerebellum controls balance.
- Medulla controls heartbeat and breathing.
- The neuron is the unit of the nervous system.
- Reflex actions are controlled by the spinal cord.
- The gap between two neurons is the synapse.