Cardiovascular Flashcards
What is blood pressure?
“Blood pressure” is the outward pressure/force exerted on the walls of blood vessels and the heart by the blood
What is the equation for blood pressure
Blood pressure = cardiac output x total peripheral resistance
What is the definition of cardiac output
Total volume of blood being pumped forwards into the systemic circulation by the heart
(HR x SV)
What is the definition of Total peripheral resistance
A measure of the constructive pressure from the vasculature resisting the forward movement of blood
What is cardiac output affected by
-sympathetic/parasympathetic activity to the heart
-cardiac filling/blood volume
-frank-starling’s law of the heart
-myocardial function/health
What is Total peripheral resistance affected by
-sympathetic nervous system activity to the vasculature
-humoral (bloodborne) factors : oxygen content, metabolites, angiotensin II, epinephrine, etc.
-vascular smooth muscle and endothelial function/health
True or false: blood pressure is pulsatile
True
What is systolic BP
The maximum pressure within the circulatory system while the heart is contracting (systole) and pumping blood forward from the left ventricle to the aorta and onward
What is diastolic BP
The minimum pressure within the circulatory system while the heart is relaxing (diastole) and refilling between beats
What are some examples of acute hypotension
- ORTHOSTATIC HYPOTENSION
-after a postural change (like standing up), blood volume “falls” down to the legs due to gravity
-upper-body blood pressure falls, lower body pressure rises
POST-EXERCISE HYPOTENSION
-after aerobic exercise, blood pressure may stay reduced for up to several hours before returning back to normal levels
How is blood pressure regulated.
Regulated by the heart and blood vessels
What is systolic pressure dictated by
The strength of the heart as it beats ;
What is diastolic pressure dictated by
The tension of the arterial system
How do we measure blood pressure
-oscillatory sphygmomanometer (“manual blood pressure”)
-continuous blood pressure measurement - (finger cuff or arterial catheter)
What are some advantages of the manual blood pressure cuff
-relatively easy to train for manual cuffs/no training required for automated cuffs
-inexpensive
-resting blood pressure is correlated to clinical disease outcomes (atherosclerosis, coronary artery disease, heart attack, stroke, etc.)
What are some DISADVANTAGES of the manual blood pressure cuff
More difficult to perform during movement/exercise
Provides only a single “point of measure” of blood pressure at one moment in time
Limited application
What is the benefit of using a continuous measurement of BP rather than a single measurement
A single measurement does not account for natural variability of blood pressure while multiple measures can account for variability
-by measuring blood pressure continuously we can gain far more info on the cardiovascular status and health of the individual
What are the PROS of the finger cuff BP measurement
-non invasive measurement of continuous blood pressure
-minimal training to operate
What are the cons of the finger cuff BP measurement
-less accurate - tiny arteries are harder to make precision measures from
-expensive
-cuff sensors are very fragile
What are some PROS of the arterial catheter BP measurement
-highly precise measurement of continuous BP
What are some CONS of the arterial catheter
-highly invasive
-extensive training required to insert catheters
-local anesthesia required- may become painful, which will increase BP through a stress response.
What is pulse-wave velocity
A simple, Non- invasive measure of vascular stiffness and constriction
When blood vessels constrict they also _______
Stiffen
What happens to pulse wave velocity if a vessel is stiffer than normal
The stiffer the vessel, the faster the pressure wave will travel along it. A more relaxed vessel will absorb, dampen and slow the pressure wave
How can we calculate pulse-wave velocity
By comparing when the pulse arrives at the carotid artery of the neck (very close to the aorta) versus the femoral artery in the leg (much further from the heart), we can calculate the pulse-wave velocity
What is the equation for pulse wave velocity
Pulse-wave velocity = distance travelled (between pulse points) / time between pulses
How do autonomic reflexes allow us to maintain BP
Depends on the reflexes responding appropriately
-if an individuals reflex is too sensitive, they may experience excessive and dangerous increases in BP
-reflexes that are too insensitive may risk hypotension and ischemia during day-to-day activities
How do we measure autonomic activity
Microneurography
-by inserting a small needle into a peripheral nerve branch, we can record the electrical signals from the sympathetic NS travelling towards the vasculature in the muscle. These signals cause vasoconstriction and are related to blood pressure
What is the baroreflex
The baroreflex adjusts sympathetic and parasympathetic activity in response to changes in blood pressure - the constant background regulator
What happens if the baroreflex has low sensitivity
- “under-correcting” and failing to swiftly correct drops in pressure
-risks syncope (fainting) and tissue ischemia during day-to-day activities
What happens if the baroreflex sensitivity is too high
- “over-correcting” causing excessive variations in pressure
-high-pressure oscillations cause cardiac and vascular damage over time
how is baroreflex sensitivity assessed?
By inducing a change in BP , then measuring the neural (MSNA), cardiac (HR), or vascular (vasoconstriction) responses
-large response indicates high baroreflex sensitivity
-small response indicates low baroreflex sensitivity
What are some examples of blood pressure challenges:
- Sit to stand test
- Pharmacological infusion
What is the sit to stand test (BP)
Standing up rapidly shifts blood towards the legs , evoking a baroreflex response. The magnitude of the HR response is a measure of baroreflex sensitivity
How does the chemoreflex influence BP regulation
The chemoreflex adjusts sympathetic and parasympathetic activity in response to changes in O2 and carbon dioxide
How does the chemoreflex influence BP regulation
The chemoreflex adjusts sympathetic and parasympathetic activity in response to changes in O2 and carbon dioxide
