Summary
The human nervous system is composed of the central nervous system (CNS), which includes the brain and spinal cord, and the peripheral nervous system (PNS), which connects the CNS to other organs. Information is transmitted as nerve impulses through neurons, which are specialized cells with long fibers called axons. Sensory neurons detect stimuli and send signals to the CNS, relay neurons transmit signals within the CNS, and motor neurons carry signals from the CNS to effectors like muscles. Reflex actions are involuntary and rapid responses to stimuli that do not involve the brain.
- Central Nervous System (CNS) — consists of the brain and spinal cord, controlling actions. Example: The brain processes information and the spinal cord relays signals.
- Peripheral Nervous System (PNS) — connects the CNS to other organs. Example: Nerves in your arm are part of the PNS.
- Neuron — a specialized cell that transmits nerve impulses. Example: Sensory neurons in the skin detect touch.
- Sensory Neuron — detects a stimulus and converts it into an electrical signal. Example: Found in sensory organs like the eyes.
- Relay Neuron — found in the CNS, relays signals to motor neurons. Example: Connects sensory neurons to motor neurons in the spinal cord.
- Motor Neuron — carries impulses from the CNS to effectors. Example: Signals muscles to contract.
- Reflex Action — an automatic and rapid response to a stimulus. Example: Pulling your hand away from a hot object.
Exam Tips
Key Definitions to Remember
- Central Nervous System (CNS)
- Peripheral Nervous System (PNS)
- Neuron
- Sensory Neuron
- Relay Neuron
- Motor Neuron
- Reflex Action
Common Confusions
- Mixing up the roles of sensory, relay, and motor neurons
- Confusing voluntary and involuntary responses
Typical Exam Questions
- What is the role of the CNS? It processes information and coordinates responses.
- How do sensory neurons function? They detect stimuli and send signals to the CNS.
- What is a reflex action? An automatic and rapid response to a stimulus.
What Examiners Usually Test
- Understanding the structure and function of neurons
- Differences between voluntary and involuntary responses
- The pathway of a reflex action