Physiology 3120 Lecture Notes - Lecture 35: Mean Arterial Pressure, Cardiac Output, Blood Vessel
15 May 2018
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Lecture 35 – Factors Influencing Mean Arterial Pressure
Control of MAP by the ANS
ANS neural control
- Involves rapid adjustments to both peripheral resistance (vasodilating and vasoconstricting
blood vessels) and cardiac output (by the ANS)
- Purpose of the cardiac system is to maintain normal mean arterial pressure for proper
perfusion of tissues throughout the body
o This is done rapidly by altering CO (HR, SV) or TPR
Tap and garden hose
- Cardiac output and TPR affect mean arterial pressure
- Imagine the cardiovascular system as a tap and garden house with a pressure gauge
- In the cardiovascular system, we are trying to maintain a particular MAP
- Tap: heart, hose: blood vessels
- Decrease cardiac output:
o If we reduced the flow, the pressure the hose is going to drop
o Decrease flow of blood out of the heart = drop HR = decrease MAP
- Increase cardiac output:
o Fully open the tap, lots of water flows in the hose and pressure goes up
o Increase HR or SV to increase CO → MAP increases
- TPR: constricting or dilating blood vessels
o Monitoring the pressure upstream of a vasoconstriction
o Location of the constriction and the location of where you are measuring the
pressure is very important
o Not concerned about what happens after because we are monitoring MAP
- Constriction:
o Decreases radius, increase resistance
o Increase MAP BEFORE the constriction and drops AFTER the constriction
- Dilation: increase radius, drop resistance, decrease MAP
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Heart and blood vessels
- There are baroreceptors that monitor the pressure and send signals into our brain so it can
then regulate the heart and blood vessels (CO and TPR) to maintain MAP
Control of MAP by ANS
In general:
- Cholinergic systems (systems that release Ach)
o → decreases arterial pressure
- Adrenergic systems (systems that release Epi and Norep)
o → increases arterial pressure
- SNS exception: sympathetic cholinergic vasodilator fibers
i) CO - Cholinergic control
- Cholinergic systems affect CO which in turn affect MAP
- Fibers to the heart are via the vagus nerve
- Stimulating vagus nerve to the heart releases Ach which binds to receptors on the SA node,
AV node and to a lesser extent to the contractile cells
find more resources at oneclass.com
find more resources at oneclass.com
Document Summary
Lecture 35 factors influencing mean arterial pressure. Involves rapid adjustments to both peripheral resistance (vasodilating and vasoconstricting blood vessels) and cardiac output (by the ans) Purpose of the cardiac system is to maintain normal mean arterial pressure for proper perfusion of tissues throughout the body: this is done rapidly by altering co (hr, sv) or tpr. Cardiac output and tpr affect mean arterial pressure. Imagine the cardiovascular system as a tap and garden house with a pressure gauge. In the cardiovascular system, we are trying to maintain a particular map. If we reduced the flow, the pressure the hose is going to drop: decrease flow of blood out of the heart = drop hr = decrease map. Increase cardiac output: fully open the tap, lots of water flows in the hose and pressure goes up. Increase hr or sv to increase co map increases. Increase map before the constriction and drops after the constriction.
