In: Anatomy and Physiology
Why would blood pressure and heart rate increase under some circumstances but not others? (use baroreceptors, sympathetic system, and parasympathetic system)
When blood volume or sodium levels are low the body's blood pressure decreases, in response to this, there are receptors known as baroreceptors, which are the stretch receptors that senses this decrease in blood pressure and transmits this information along the vagus nerve to the central nervous system, this results in the decreasing of the firing of impulse, this causes vasomotor centere to activate sympathetic activity in heart and blood vessel and decrease the vagal tone on parasympathetic influence on SA node causing heart rate to increase, constriction of blood vessels, resulting in increase in blood pressure
In summary If blood pressure falls, such as on orthostatic hypotension or in hypovolaemic shock, baroreceptor firing rate decreases and baroreceptor reflexes act to help increase blood pressure by increasing heart rate
Sympathetic stimulation increases heart rate and blood pressure, while parasympathetic stimulation decrease heart rate and blood pressure.