Short Term Control of BP Flashcards
What is the baroreflex responsible for?
Maintenance of arterial blood pressure
How many sets of baroreflexes do we have?
2
Where can you find the baroreflexes?
Aortic arch
Carotid sinuses
What do the aortic arch and carotid sinuses have in common?
Both stretchy
How do the baroreceptors detect changes in pressure?
When pressure increases, the walls stretch and baroreceptors detect that change in stretch and they increase the firing rate of action potentials.
What happens to the firing rate of action potentials when pressure increases?
Firing rate increases
What happens to the firing rate of action potentials when pressure decreases?
Firing rate decreases
When are the aortic arch and carotid sinuses stretched the most?
During systole as there is an increase in pressure.
Where do the aortic arch baroreceptors send their signal?
Up the Vagus nerve
Where do the carotid sinuses send their signals?
Up the glossopharyngeal nerve.
Where are the integrating centres known as the medullary cardiovascular centres located?
Medulla oblongata
Name some of the responses that the medullary cardiovascular centres can evoke to bring MAP back to where it should be.
Parasympathetic outflow via vagus nerve
Sympathetic nerves
Which neurotransmitter is released in a parasympathetic response?
Acetyl choline
Where does acetyl choline bind to?
Cholinergic muscarinic receptors on the pacemaker cells.
What will happen when acetyl choline binds to the cholinergic muscarinic receptors on the pacemaker cells?
Cause them to hyperpolarise and will take them longer to reach threshold therefore decreasing HR.
Describe the sympathetic nerve response.
Release of noradrenaline which binds to beta-1 receptors causing pacemaker cells to depolarise faster and it will therefore increase heart rate.
Describe the sympathetic nerves which innervate the muscle of the ventricle.
Increased contractibility,.
Greater release of calcium causing more cross bridging of myosin and actin filaments, increasing the contraction and stroke volume.
List some of the other outputs to the cardiovascular centres.
Cardiopulmonary baroreceptors
Central chemoreceptors
Chemoreceptors in muscle
Joint receptors
Higher centres
What do cardiopulmonary baroreceptors do?
Sense central blood volume
What do central chemoreceptors do?
Sense changes in the partial pressures of oxygen and CO2
(guessing this is revision for resp. lectures…whoops? vaguely rings a bell ig)
What do chemoreceptors in muscles do?
Sense changes in metabolite concentration
What do joint receptors do?
Sense joint movement
Give two examples of higher centre.
Hypothalamus
Cerebral cortex
What is the hypothalamus responsible for?
Coordinating vascular responses for thermoregulation.
Also involved in flight or fight response.
->f you’re too hot then it will tell the medullary cardiovascular system to vasodilate.
What is the Valsalva Manoeuvre
Forced expiration against a closed glottis
->forcefully expiring with your mouth closed
What happens in stage one of the Valsalva Manoeuvre?
Increased thoracic pressure is transmitted through to aorta - immediate increase in BP
What happens in stage two of the Valsalva Manoeuvre?
Increased thoracic pressure reduces the filling pressure from the veins, which therefore ↓ VR, ↓ EDV, ↓ SV, ↓ CO, ↓ MAP
What happens in the late stage two of the Valsalva Manoeuvre?
The reduced MAP is detected by baroreceptors which initiate a reflex increase in CO and TPR
What happens in stage three of the Valsalva Manoeuvre?
At end of the manoeuvre, the decrease in thoracic pressure is transmitted through to the aorta, hence the drop in BP
What happens in stage four of the Valsalva Manoeuvre?
VR is restored so SV ↑, but reflex effects have not worn off
What function test can the Valsalva Manoeuvre be used for?
Test of autonomic function
In which individuals may the Valsalva Manoeuvre be reduced?
Elderly
Individuals w autonomic neuropathy*
*when nerves have been damaged, sometimes due to diabetes
Sometimes performing the Valsalva Manoeuvre can be dangerous. What can it cause?
Can increase risk of myocardial infarction
