L12. Blood Pressure Control and Hypertension Flashcards Preview

02. Cardiovascular > L12. Blood Pressure Control and Hypertension > Flashcards

Flashcards in L12. Blood Pressure Control and Hypertension Deck (16):

What is the major mechanism for the circulatory system for measuring its cardiac output? What are the other means?

Blood pressure is the main readout

In desperate times, it can also use readings of pH, PCO2 and PO2


How is blood pressure and cardiac output controlled?

Mainly neurally in the brainstem centres


What is the baroreceptor reflex and what does it control?

A reflex mechanism that maintains blood pressure homeostasis.
A negative feedback system


What are the sensors of the baroreceptor reflex? And how do they relay information back?

Arterial baroreceptors in the carotid sinus and aortic arch and preglomerular arterioles

They sense changes in pressure (by stretch) and convey messages to the autonomic centres of the brain. (They are continuously firing information and and CHANGE in firing is interpreted as a rise or fall of blood pressure)


Where is the brainstem cardiovascular control centre?

In the medulla of the brainstem which has processor and depressor centres in it


What is the sympathetic and parasympthathetic innervations of the medullary cardiovascular control centres?

Sympathetic: Increases HR and decreases conduction time, increases contractility (increase intracellular Ca) and increases TPR (vasoconstriction) and increases venous tone (increaes venous return)

Parasympathetic: reduces HR and increases conduction time.


The baroreceptor reflex acts as a buffer. Explain this statement

The baroreceptor reflex is set to a small range of blood pressures and any ranges outside this, the reflex is caused to act to return it to the set range.

It also smooths out the large variations in pressure

Dennervating it = loose the control


Can the baroreceptor threshold change?

Yes, it is able to reset to new pressures but takes 1-2 days of adjustment


What range does the baroreceptor become silent to the brain? Why is this so?

When pressure reaches below below 60 mmHg (very dire and low) and the silence signals to the brain that there is not enough delivery of flow.
At this point the PO2 and PCO2 levels dramatically change and these chemoreceptors take over in sensing


What are the chemoreceptors, where are they located?

Respond to very low O2 concentrations and are located in the carotid and aortic bodies just outside the arteries. And are stimulated at low Mean Arterial Pressures


What does the blood pressure distribution (among the population) look like

Unimodal but not symmetrical (tends to skew towards the upper end)


How does blood pressure distribute in the population?

Men > Women
Age > young
Large body size > smaller


How does systolic and diastolic pressure change with age?

Both increase with age
Diastolic tends to plateau out earlier (meaning that pulse pressure rises) this is due to a decreasing compliance of the arteries with age (especially atherosclerosis)


Is there dirunal variation in BP?

Lower at night (by about 20 mmHg) with less variability
There is less sympathetic activity at night: the renin angiotensin system takes over the majority of control at night


What is the definition of hypertension?

Systolic pressure > 140 mmHg
Not necessarily disease state (operational definition)


What is the population paradox in terms of CVD disease?

The greatest numbers of deaths due to BP occur with those with average BPs (not high ends) because they have moderate risks and aren't the type to use drugs
The paradox states: more deaths occur in the larger number of people at moderate risk than the small number at high risk