Short term control of blood pressure Flashcards
What is the driving force pushing blood through the circulation?
Mean arterial pressure
which is determined by CO x TPR
What happens when your MAP is too low?
fainting ( syncope)
What happens when your MAP is too high?
Hypertension
Where are the arterial baroreflex receptors?
Carotid sinus and aortic arch baroreceptor
Describe how baroreceptors work?
They fire when the elastic arteries stretch. More MAP, the more longer artery stretches and the more AP are fired
What is the normal MAP value for the normal baroreceptor firing rate?
80mmHg
Which nerve does the aortic arch barorecptors send signals to?
Vagus nerve
Where does the carotid sinus baroreceptors send signals to?
Glossopharyngeal nerve
Where do the vagus and glossopharyngeal nerve synapse?
Medullary cardiovascular centres
What is the first nerve effected by the medullary cardiovascular center if the MAP value needs to be changed?
Parasympathetic
What node does the parasympathetic system innervate?
Sinoatrial node
What node does the sympathetic system innervate/area it affects?
Sinoatrial node
and the adrenal medulla ( due to hormonal component )
Myocardium of the ventricle
Venoconstriction and arteriolar constriction
What are other inputs to the medullary cardiovascular centres?
Cardiopulmonary baroreceptors
central chemoreceptors
Chemoreceptors in muscle
Joint receptors (All feedback responses that detect action but thats not it)
Higher centres
(Feedforward response that causes increased HR before doing something)
How do you regulate long term blood pressure?
Revolves around blood volume
What are the main sensors for detecting blood volume?
Cardio-pulmonary baroreceptors
What types of effects does long term blood pressure have on body?
Hormonal
acts on blood vessels and kindey
What is the effect of standing on hydrostatic pressure, EDV, preload, SV, Co, MAP and baroreceptor firing rate?
Increased hydrostatic pressure causes pooling of blood in veins/venules of feet and legs
Decreased EDV, preload, SV, CO, MAP and therefore, baroreceptors firing rate
What is the reflex response to standing?
Decreased vagal tone
Increased sympathetic tone
What does decreased vagal tone effect?
Increased heart rate
and Cardiac output
What does increased sympathetic tone cause?
Increased HR and CO
Increased contractility
Increased venoconstriction, VR, EDV, SV, CO
Therefore increased arteriolar constriction and TPR
Define the valsalva manoeuvre
forced expiration against a closed glottis
eg: during defecation
Describe what occurs during valsalva manoeuvre
Increased thoracic pressure which is transmitted through the aorta
This causes decrease in venous return, EDV, SV, CO, MAP
MAP detected by baroreceptors which activate the reflex to increase CO and TPR
This causes a decrease in thoracic pressure transmitted through to the aorta
VR is restored so SV increases but reflec effects not worn off
eventually back to normal
