Baroreceptor Reflex - Regulation Of Mean Arterial Blood Pressure Flashcards
What is blood pressure
The outwards (hydrostatic) pressure exerted by blood on blood vessel walls
What type of blood pressure is measured in clinical practice
Systemic arterial blood pressure
What is systolic arterial blood pressure
pressure from left ventricle contracting
What is diastolic arterial blood pressure
The pressure exerted by the blood on the walls of the aorta and systemic arteries during relax
What blood pressure values indicate hypertension
Clinic blood pressure of 140/90mmHg or higher
What is pulse pressure
Difference between systolic and diastolic blood pressures
Normal range 30-50mmHg
What is mean arterial blood pressure (MAP)
Average arterial blood pressure during a single cardiac cycle (systole and diastole)
Why is MAP not obtained by averaging systolic and diastolic pressures
Diastole lasts twice as long as systole
How is MAP estimated
(2x diastole pressure + systolic pressure) 3
Secondary method to estimating MAP
Diastolic BP + 1/3 pulse pressure
Normal MAP range
70-105mmHg
What MAP value is needed to perfuse vital organs
Minimum 60mmHg
What happens if MAP value is too high
Damage blood vessels
Place an extra strain on heart and other organs
What path do signals take during negative feedback
Detected by sensor (when not in narrow range)
Informs control centre
Sends instruction to effectors
Brings about compensatory results
What is the sensor used to regulate MAP
Baroreceptors
What is the cardiovascular control centre
Medulla
What are the effectors of the MAP
Heart - varies HR and SV
Blood vessels
How do blood vessels work to get MAP back to narrow range
By varying systemic vascular resistance
Which baroreceptors inform the medulla
Carotid baroreceptors
Aortic arch baroreceptors
What type of receptor are baroreceptors
Mechanoreceptors sensitive to stretch, the more stretch the more signals are fired
What cause the firing rate in baroreceptor afferent (outgoing) neurons to increase
When MAP increases
Where do baroreceptors send afferent impulses to
The cardiovascular control centre in the medulla of the brainstem
What is the role of the NTS in regulating MAP
Integrates and relays information to other regions that control pathways for the sympathetic and parasympathetic nervous system for the heart and blood vessels
What is stroke volume
The volume of blood pumped by each ventricle of the heart per heart beat
What is cardiac output
The volume of blood pumped by each ventricle per minute
What is the relationship between MAP, CO and SVR (systemic vascular resistance)
MAP = CO X SVR
What is systemic vascular resistance
Sum of resistance of all vasculature in the systemic circulation
What are the 3 ways MAP can be regulated
Heart rate
Stroke volume
Systemic vascular resistance
What term is used to describe the heart beating in absence of external stimuli
Autorhythmicity
What does the sympathetic division in the heart result in
Stimulation accelerates heart rate
Releases noradrenaline acting on beta1 receptors
What does the parasympathetic division of the ANS stimulate
Vagus nerve which slows the heart rate
Acetylchlorine acts on M2 receptors
How is stroke volume increased
If contractile strength of heart is increased
How is the contractile strength of the heart increased
Sympathetic nerves (found in myocardium) increases the force of contraction hence stroke volume
Which blood vessel shows the most resistance
Arterioles, pressure decreases when passing through due to smooth muscle layer
Which type of nerve fibre supplies the vascular smooth muscle
Sympathetic
Which type of neurotransmitters acts on the alpha receptors of the sympathetic nerves
Noradrenaline
What causes the vasomotor tone of vascular smooth muscle
Tonic discharge or sympathetic nerves resulting in continuous release or noradrenaline
What happens if there is a decrease in sympathetic discharge
Decrease in vasomotor tone resulting in vasodilation causing a decrease in MAP and SVR
When does baroreceptor firing decrease
If high arterial blood pressure is sustained
