Summary
Sense organs are specialized structures that detect changes in the environment and send information to the central nervous system for processing. They contain receptors that respond to specific stimuli, such as light, sound, or touch, and convert these into electrical impulses.
- Receptors — groups of specialized cells that detect changes in the environment and stimulate electrical impulses. Example: Light receptors in the eye detect light and send signals to the brain.
- Sensory Neuron — a neuron that detects a stimulus and converts it into an electrical signal. Example: Found in sensory organs like the eyes and skin.
- Relay Neuron — a neuron in the CNS that relays signals from sensory neurons to motor neurons. Example: Connects receptors to motor neurons in reflex actions.
- Motor Neuron — carries impulses from the CNS to effectors like muscles or glands. Example: Causes muscles to contract in response to stimuli.
- Reflex Action — an automatic and rapid response to a stimulus that does not involve the brain. Example: Pulling your hand away from a hot object.
Exam Tips
Key Definitions to Remember
- Receptors: Specialized cells that detect changes in the environment.
- Sensory Neuron: Neuron that detects stimuli and sends signals to the CNS.
- Motor Neuron: Neuron that carries impulses from the CNS to effectors.
- Reflex Action: Automatic and rapid response to a stimulus.
Common Confusions
- Confusing sensory neurons with motor neurons.
- Mixing up the roles of the CNS and PNS.
Typical Exam Questions
- What is the role of sensory neurons? Sensory neurons detect stimuli and send signals to the CNS.
- How does a reflex action differ from a voluntary action? Reflex actions are automatic and do not involve the brain, while voluntary actions are conscious decisions.
- What happens during the pupil reflex? The pupil changes size in response to light intensity to protect the retina.
What Examiners Usually Test
- Understanding the structure and function of neurons.
- Differences between voluntary and involuntary responses.
- The process of how sense organs detect and respond to stimuli.