Final answer:
The brain regulates blood pressure via the sympathetic nervous system by inducing vasoconstriction and increasing heart rate, thereby raising blood pressure to maintain homeostasis. These actions are facilitated by neurotransmitters like epinephrine and norepinephrine that bind to adrenergic receptors on blood vessels.
Step-by-step explanation:
The brain regulates blood pressure through a complex system involving the heart and blood vessels, mainly controlled by the sympathetic nervous system. When the baroreceptors in the cardiovascular system detect a change in blood pressure, they send signals to the cardiovascular center in the medulla oblongata. If blood pressure is perceived to be too low, maybe due to blood loss or dehydration, the cardiovascular center responds by triggering the sympathetic nervous system. This response leads to both vasoconstriction, which narrows the blood vessels and increases vascular resistance, and an increase in heart rate to boost cardiac output. These actions together help to elevate blood pressure to normal levels. When blood pressure is too high, the parasympathetic system is activated instead, leading to a decrease in heart rate and vasodilation, which lowers blood pressure.
Therefore, when the brain sends signals that cause the blood vessels to narrow (vasoconstriction) and the heart to beat faster, this mechanism helps to increase cardiac output and vascular resistance, effectively raising blood pressure to maintain homeostasis. The release of epinephrine and norepinephrine further enhances the sympathetic response, increasing blood pressure through their actions on adrenergic receptors in the blood vessel walls.