Dehydration reduces blood volume. how would this affect cardiac output? explain.

Dehydration causes the brain to shrinks and require more work to complete the task when comparing with hydrated brain the do same work. Unlike the condition called hyponatremia or what we called as over hydration that dilute the Sodium ion ( Na+) Dehydration will make your blood more concentrated with Sodium +.This will cause the urine to appear darker. Dehydration will cause moody mood,dry mouth,dark urine and etc. Over hydration will cause nausea,vommitting,muscle spasms,or rare cases,death by damaged brain cell because the brain is inside the skull. Since the skull is solid bone,once the brain swell it take up spaces then having pressure between the swelled brain and the skull. That causes brain damage or brain death.