Short Term Control of Blood Pressure Flashcards
What formula describes mean arteriolar pressure?
MAP = CO x TPR
Why does mean arteriolar pressure (MAP) need to be regulated?
Too low leads to fainting (syncope)
Too high leads to hypertension
What is the medical name for fainting?
Syncope
What is syncope?
Fainting
What is the baroreflex?
One of the bodies homeostatic mechanisms that helps to maintain blood pressure at nearly constant levels
What is the process of the baroreflex?
1) Aortic arch baroreceptors detect changes in blood pressure and send this information to the medullary cardiovascular centres by the vagus nerve, carotid baroreceptors detect changes and sent this information by the glossopharyngeal nerve
2) Responds by innervating the parasympathetic nerve (vagus) or sympathetic nerve depending on what response is required to return blood pressure to normal
What do aortic arch baroreceptors send information to the medullary cardiovascular centre through?
Vagus nerve
What do the carotid baroreceptors send information to the medullary cardiovascular centres through?
Glossopharyngeal nerve
Where do the aortic arch and carotid baroreceptor sends information to?
Medullary cardiovascular centres
What are other inputs to the medullary cardiovascular centres other than aortic arch and carotid baroreceptors?
Cardiopulmonary baroreceptors
Central chemoreceptors
Chemoreceptors in muscle
Joint receptors
Higher centres
Can long term regulation of blood pressure be done by arterial baroreceptors?
No, revolves around blood volume
How is long term control of blood pressure achieved?
Main sensors are cardiopulmonary baroreceptors
Effects tend to be hormonal
Act on blood vessels and kidneys
Is long term control of blood pressure achieved neurally or hormonally?
Hormonally
Is short term control of blood pressure achieved neurally or hormonally?
Neurally
What do hormones act on to achieve long term control of blood pressure?
Blood vessels and kidneys
What are examples of things that are used to achieve long term control of blood pressure?
Renin-angiotensis-aldosterone system
Vasopressin (antidiuretic hormone)
Atrial natriuretic peptide and brain natriuretic peptide
How does the renin-angiotensin-aldosterone system regulate blood pressure in the long term?
Angiotensin II causes arteriolar construction and increases total peripheral resistance
Aldosterone increaes Na+ reabsorption and therefore increases plasma volume
What effect does angiontensin II have?
Causes arteriolar constriction and increases total peripheral resistance
What effect does aldosterone have?
Increases Na+ reabsorption and therefore increases plasma volume
What is another name for vasopressin?
Antidiuretic hormone
How does vasopressin (antidiuretic hormone) achieve long term regulation of blood pressure?
Causes arteriolar constriction and increases total peripheral resistance
Increases water permeability of collecting duct and therefore increases plasma volume
How does atrial natriuretic peptide and brain natriuretic peptide achieve long term regulation of blood pressure?
Causes arteriolar dilation which decreases total peripheral resistance
Increases Na+ excretion and therefore decreases blood volume
What is natriuresis?
Excretion of sodium in the urine
What is excretion of Na+ in the urine called?
Natriuresis
What are examples of when the baroreflex response would be used?
Due to posture
During the valva manoeuvre
What is the effect of standing?
Increases hydrostatic pressure causing pooling of blood in veins/venules of feet and legs:
Decreases venous return, EDV, preload, stroke volume, cardiac output and mean arterial pressure
Decreases baroreceptor firing rate
What is the baroreflex response to standing?
Decreases vegal tone
Increases sympathetic tone
What is the impact of decreasing the vagus tone by the baroreflex whilst standing?
Increases heart rate and cardiac output
What impact does the baroreflex increasing sympathetic tone when standing have?
Increase heart rate and cardiac output
Increases contractibility and increases stroke volume and cardiac output
Increases vasoconstriction which increases venous return, EDV, stroke volume and cardiac output
Increases arteriolar constriction which increases total peripheral resistance
What effect does vasoconstriction have?
Increases venous return, EDV, stroke volume and cardiac output
What does the tone of a nerve refer to?
Activity of the nerve
What is the valva manoeuvre?
Forces expiration against a closed glottis
What is the process of the baroreflex being used during the valva manoeuvre?
1) Increase in thoracic pressure is transmitted through the aorta
2) Increase in thoracic pressure causes decrease in venous return, EDV, SV, CO and MAP
3) Decrease in mean arterial pressure is detected by baroreceptors which initiates reflex which increases cardiac output and total peripheral resistance
4) Decrease in thoracic pressure is transmitted through to the aorta
5) Venous return is resorted, so is stroke volume but reflex effects are not worn of
6) Everything returns back to normal
