Hemodynamics Flashcards
Factors that affect distribution of CO (x4)
Heart rate
Stroke volume
Pressure difference (high P –> low P)
Resistance to BF (opposition)
Water and BP
Water retention increases BP (hydrostatic pressure)
What generates most of BP?
Ventricular contraction
Drives blood through the system during contraction AND relaxation
Pressure: aorta –> capillaries
Pressure is high at aorta, steadily drops as it gets to the capillaries
Cross sectional area & velocity
Vary inversely with each other
At capillaries (smallest), velocity is slowest (helps with diffusion exchange)
What is systolic pressure?
Highest pressure in the arteries (occurs during ventricular systole)
What is diastolic pressure?
Lowest pressure (occurs during ventricular diastole)
Blood pressure cuff: how does it work?
Inflates to compress brachial a.
Deflates –> blood spurts (Korotkoff sound)
First sound = systolic pressure (force of BP on arterial wall right after ventricular contraction)
Last sound heard = diastolic pressure (ventricular relaxation)
Pulse pressure
Difference between systolic and diastolic pressures
Mean arterial blood pressure
Average blood pressure during the entire cardiac cycle
Mean ABP = HR x SV x TPR
Where are pulse points found?
Where arteries are at the surface of the body & can be pressed against a bony structure
Factors affecting BP (x3)
Cardiac output (HR, SV)
Blood volume (blood loss, H2O)
Peripheral vascular resistance
BP formula
Pressure = flow x resistance
What is vascular resistance?
Friction between blood and vessel walls
What affects vascular resistance? (x3)
Vessel radius: larger the lumen = lower resistance
Blood viscosity: ratio of RBCs to plasma, dehydration = more viscosity and depletion of RBCs = less viscosity
Vessel length: larger the vessel = greater the resistance
How do arterioles control BP?
By changing diameter
NO and BP
NO causes vasodilation of BVs –> decreased BP
Ways to regulate BP (x2)
Neural regulation (short term): baroreceptors + chemoreceptors
Hormonal regulation
Types of hormonal regulation (BP)
Short term: epinephrine & norepinephrine
Long term: RAA, ADH, ANP
How do baroreceptors work?
Detect changes in stretch
Aortic reflex: receptors in asc. aorta & aortic arch send signals through CN 10 –> medulla oblongata
Carotid sinus reflex: receptors in the internal carotid arteries send signals through CN 9 –> medulla oblongata
How do chemoreceptors work?
Located close to baroreceptors
Detect changes in blood levels in O2, CO2 and H2O
In response to low O2, low pH or high CO2 –> increased sympathetic stimulation (vasoconstriction and increased BP)
Chemoreceptors send signals to the MO and respiratory center to adjust rate of breathing
Epinephrine, norepinephrine & BP
Short term
Increased sympathetic stimulation causes the adrenal glands to release these catecholamines
Increases HR and force of contraction
Vasoconstriction of skin + abdominal organs
Vasodilation of cardiac muscle (increases BF)
RAA system and BP
Long term
Angiotensin II vasoconstricts arterioles
Aldosterone increases water reabsorption –> increased blood volume
ADH and BP
Long term
Released from post. pituitary in response to dehydration/decreased blood volume
Increases renal water absorption and increased systemic vasoconstriction –> increases BP
