Tropism is the directional growth of a plant in response to an environmental stimulus, such as light (phototropism) or gravity (gravitropism).

The hypothalamus maintains homeostasis by regulating autonomic functions, controlling body temperature, hunger, thirst, and the release of hormones.

The human nervous system consists of the central nervous system (CNS), which includes the brain and spinal cord, and the peripheral nervous system (PNS), which includes sensory and motor neurons. It functions to receive, process, and respond to stimuli, enabling coordination, control, and communication within the body.