Involuntary actions like blood pressure, salivation, and vomiting are controlled by the autonomic nervous system (ANS) in the brain. The medulla oblongata, part of the brainstem, houses vital centers regulating these functions. The cardiovascular center manages blood pressure by adjusting heart rate and vessel diameter. Salivation is controlled by the salivary nuclei, and the vomiting center coordinates the complex reflex involved in vomiting. These centers receive sensory input and send motor signals via the ANS to regulate physiological processes. The sympathetic and parasympathetic branches of the ANS work in tandem, balancing involuntary actions to maintain homeostasis in response to internal and external stimuli.