You rely on your sensory organs to collect information about the world around you. Once your brain has information from sensory organs, it triggers a response that will maintain homeostasis. For example, eyes adjust to bright and dim light by changing the size of your pupils. If your skin feels cold, you might shiver. You might get goose bumps, or your arm hairs might stand up, trapping the heat that would otherwise escape from your skin.
This power point presentation is a summary from your book: The senses
These other videos will help you with more details