Blood Pressure
Force exerted by blood against blood vessels, arterial pressure
*Systolic: ventricles contracting
*Diastolic: ventricles relaxing
*Pulse: surge of bld entering atrial system, causing wall of
artery to swell & expand, relax is recoiling of artery wall
*Sounds of Korotkoff: sound heard over a blood vessel when
partially compressed
 Pressure points: point on body surface where pule felt
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Factors influence Blood Pressure
1. Cardiac Output: stroke volume per minute = avg. 5.04
stroke volume (70ml) X heartbeat (72bpm) = 5.04 ml/min
Stroke volume- volume discharged from L ventricle in
contraction (70ml)
If stroke volume or heartrate increases – cardiac input
increases- bld pressure increases
2. Blood Volume: amnt bld cells & plasma avg. 5L
Bld vol decreases ( hemmorrage) BP decreases
3. Peripheral resistance: friction btwn blood and walls of bld
vessels- hinders bld flow ex: constriction of arterioles
4. Viscosity: ease of which a fluid slides
BP rises when thicker
Control of Blood Pressure- cardiac output & peripheral
resistance. More bld enter heart, stronger contraction, greater
stroke volume, greater cardiac output
*Controlled by cardiac sensors in medulla oblongata
*Spyhgmomanometer: used to detect B.P.
Hypertension: chronic high BP 140/90
*Primary hypertension (essential) most common cause from
heredity, race, obesity, eating, salt
*Secondary: from drug, alcohol use, kidney disease once
stopped BP returns to normal
Factors that increase B.P.: increase in blood viscocity, pulse,
cardiac output, stress exercise, nicotine, stimulants,
arteriosclerossis
Factors that decrease B.P.: alcohol, width of arterioles,
hemmorrage, change in position, urine output, training
Venous Blood Flow
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depends on skeletal muscle contractions & breathing
B.P.decreases as moves thru system
veins contain valves to prevent backflow
vasoconstriction: increase in venous pressure with bld flow
constriction of vessel walls