Short Term Control of Blood Pressure Flashcards
What is the most essential equation in cardio?
MAP= CO x TPR
What is the driving force pushing blood through the circulation?
MAP
Why does MAP have to regulated?
- Too low= syncope
- Too high= hypertension
Where are the baroreceptors located?
- Aortic arch
- Internal carotid arteries
What are baroreceptors?
Stretch receptors which detect changes in pressure
How does MAP affect baroreceptors?
- Low MAP will cause a short burst of action potentials
- Elevated MAP will cause APs to be fired in quick succession as the vessels will be constantly stretched and therefore the receptors will constantly be sending signals
What nerve do impulses from the baroreceptor on the aortic arch go via?
Vagus nerve
What nerve do impulses from the carotid sinus baroreceptors go via?
Glossopharyngeal nerve
What area of the brain are impulses from the glossopharyngeal and vagus nerves received?
Medullary cardiovascular centres
What effect do sympathetic nerves have on the sinoatrial node?
Increases heart rate
What effect do parasympathetic nerves have on the sinoatrial nerve?
Decrease heart rate
What effect do sympathetic nerves have on blood vessels?
Vasocnstriction and arteriolar constriction
What happens if veins are constricted?
Increase preload
What happens if arterioles are constricted?
Increase TPR
What effect do sympathetic nerves have in the ventricles?
- Increases strength of contraction
- Increases conduction velocity
- Increase stroke volume
- Increase cardiac output
What other inputs to the medullary cardiovascular centres are there?
- Cardiopulmonary baroreceptors
- Central chemoreceptors
- Chemoreceptors in muscle
- Joint receptors
- Higher centres
Why do central chemoreceptors affect the CV system?
If there is more oxygen in the blood the body will respond in order to get it through systemic circulation quicker
What do muscular chemoreceptors respond to?
Physical activity
What do joint receptors respond to?
Physical activity
How will exercise affect MAP?
Increase
What are central chemoreceptors, chemoreceptors in muscle and joint receptors forms of?
Negative feedback control
How are higher centres involved in the CV system?
They anticipate change and respond with feed forward controls
What does regulation of blood pressure in the long term revolve around?
Blood volume
What are the main sensors in the regulation of blood pressure in the long term?
Cardio-pulmonary baroreceptors
What are most of the effects of the cardio-pulmonary baroreceptors controlled by?
Hormones
What do the hormones stimulated by the cardio-pulmonary baroreceptors act on?
Blood vessels and the kidneys
What are the effects of standing up?
Increased hydrostatic pressure causes pooling of blood in veins/venules of feet and legs
What do the effects of standing up cause?
- Decreased VR
- Decreased EDV
- Decreased preload
- Decreased SV
- Decreased CO
- Decreased MAP
- Decreased baroreceptor firing rate
What 2 effects does the reflect response exhibit?
- Decreased vagal tone
- Increased sympathetic tone
What are the effects of decreased vagal tone?
- Increased heart rate
- Increased CO
What are the effects of increased sympathetic tone?
- Increased heart rate and CO
- Increased contractility, SV and CO
- Increased venoconstriction, VR, EDV, SV and CO
- Increased arteriolar constriction and TPR
What is the Valsalva manoeuvre?
Forced expiration against a closed glottis
What is the purpose of the Valsalva manoeuvre?
To increase pressure in the thorax and abdomen
What a change in thoracic pressure transmitted through in the Valsalva manoeuvre?
Aorta
What does an increase in thoracic pressure?
Decreased
- VR
- EDV
- SV
- CO
- MAP
What detects a decrease in MAP?
Baroreceptors
What reflex do the baroreceptors initiate?
Increased CO and TPR
How is normal restored in the Valsalva manoeuvre?
VR is restored so SV increases
