Final answer:
Reflex actions are involuntary, rapid responses to stimuli, such as the knee reflex, and withdrawal from a hot surface. They are mediated by reflex arcs within the somatic nervous system, allowing for immediate reaction without brain involvement. The ANS controls other involuntary functions like heart rate and digestion.
Step-by-step explanation:
Reflex actions are involuntary and rapid responses of the nervous system to external stimuli. They serve to protect the body from harm by automatically engaging certain muscles or glands without the need for conscious thought. For example, the "knee" reflex is an automatic response to the tapping of the patellar tendon, used in medical examinations to test the integrity of the nervous system. Similarly, touching a hot stove instinctively triggers a with drawal reflex, causing one to pull their hand away to avoid burns. These reflexive actions happen via a reflex arc, bypassing the brain and involving only the spinal cord and peripheral nerves, allowing for immediate response. Such reflexes are a critical part of the somatic nervous system, which controls movements we can usually command at will. However, the reflex actions occur without conscious input, illustrating their involuntary nature. The autonomic nervous system (ANS), on the other hand, controls involuntary functions such as heart rate and digestion and is divided into sympathetic and parasympathetic divisions influencing the body's readiness for action and rest, respectively.