Short Term Control of Blood Pressure Flashcards
MAP is
The driving force pushing blood through the circulation
Result if MAP is too low
Fainting (syncope)
Result if MAP is too high
Hypertension
Receptors of blood pressure involved in arterial baroreceptor reflex
Aortic arch baroreceptor and carotid sinus baroreceptors
Baroreceptors indirectly measure pressure by measuring
Stretch
As MAP increases, baroreceptor firing
Increases
Two sensory nerves of arterial baroreflex
Vagus nerve
Glossopharyngeal nerve
Two motor nerves of arterial baroreflex
Parasympathetic vagus nerve
Sympathetic nerves
Medullary cardiovascular centres
Several different groups of neurons in medulla communicating that take impulses of MAP and decide what to do about it
Outcomes of the arterial baroreflex via parasympathetic nerves
Decreases blood pressure via sinoatrial node depolarising less
Outcomes of the arterial baroreflex via sympathetic nerves (not including smooth muscle)
Increase blood pressure via sinoatrial node depolarising more, adrenal medulla releasing adrenaline, myocardium releasing more calcium ions from sarcoplasmic reticulum increasing contractility and so SV
Outcomes of the arterial baroreflex via smooth muscle (controlled by sympathetic nerves)
Vasoconstriction increasing stroke volume and arteriolar constriction increasing TPR
Other inputs to the medullary cardiovascular centres
Cardiopulmonary baroreceptors Central chemoreceptors Chemoreceptors in muscle Joint receptor Higher centres
Cardiopulmonary baroreceptors
In the walls of the vessels in heart and lungs which are the low pressure parts of circulation, detect increase in blood pressure
Central chemoreceptors
Detect carbon dioxide levels, more co2 = more o2 and so increase in blood pressure
Chemoreceptors in muscle
Respond to high potassium ion concentration or acidity, signify high metabolic activity, need more blood so increase blood pressure
Joint receptors
Greater work in joints requires more blood and so increases blood pressure
Higher centres
Feed forward effect in the cortex effected by emotions
Main sensors in the regulation of blood pressure in the long term
Cardiopulmonary baroreceptors
Long term regulation of blood pressure act on
Vessels and kidneys
Result of standing up
Increased hydrostatic pressure causes pooling of blood in veins and venules of legs and feet
Effect of standing on blood pressure
Decrease in VR, EDV, preload, SV, CO, MAP and baroreceptor firing
Reflex response to blood pressure changes due to standing
Decrease in vagal tone so no longer slowing down the heart increasing HR and CO
Increase in sympathetic tone increasing HR, contractility, venoconstriction and arteriolar constriction
The Valsalva manoeuvre
Forced expiration against a closed glottis
Result of Valsalva manoeuvre
Increases thoracic pressure which is transmitted through to aorta
Effect of Valsalva manoeuvre on blood pressure
Reverses pressure gradient, decrease in VR, EDV, SV, CO, MAP
Reflex response to blood pressure changes due to Valsalva manoeuvre
Decrease in MAP is detected by baroreceptors which initiates reflex and increases CO and TPR, the decrease in thoracic pressure is transmitted through to aorta and VR so SV is restored but reflex effects not worn off, then return to normal
Regulation of blood pressure in the long term revolves around
Blood volume
