BLOOD PRESSURE

What is blood pressure?

• Force of blood on inner walls of blood vessels

What alters blood pressure?

• Amount of blood in vessel

• Resistance against blood flow

Relationship between blood volume + resistance

• More blood volume + resistance = high BP

• Less blood volume + resistance = low BP

What causes an increased blood pressure (NOT HYPERTENSION)? (3)

• Decrease in vessel diameter

  • More resistance

• Increased heart rate

  • More blood volume

• Increased blood volume from osmosis

What causes a decreased blood pressure (NOT HYPOTENSION) (4)

• Hemorrhage

  • Less blood volume

• Dehydration

  • Less blood volume

• Increased vessel diameter

  • Less resistance

• Decreased heart rate

  • Less blood volume

How does blood pressure change across the body?

• Drops as it gets further from heart

  • Cross-sectional area increases from branching

    • Blood flow is less concentrated and more spread out across capillaries

• Highest in arteries + lowest in capillaries + veins

  • Capillaries = spread out

  • Veins = blood has lost all momentum (far distance)

    • Why it relies on muscle contractions

What is normal, high, and low blood pressure + what’s the units it’s measured in? (1) (3)

• UNITS = mmHg

• Normal: 120/80

• High: >120/80

  • Gets concerning when diastolic >95

• Low: <90/60

How to take blood pressure reading manually (1) [1] [2] [2] [2]

1) Wrap pressure cuff around upper left arm

2) Find brachial artery w/ stethoscope

• No sound cuz unobstructed flow = silent

3) Pump cuff to cut off blood flow

• Will stop hearing pulse when stethoscope if place on it

• Then you add 30mmHg of pressure on top

  • Exceeds systolic + diastolic pressure

4) Slowly release pressure until sound is heard

• Pressure weak enough for blood to pass in systole (source of sound) but strong enough to close off artery in diastole

• SYSTOLIC PRESSURE

5) Slowly release pressure until no sound

• Brachial artery = open

  • Pressure in artery > pressure of cuff

• DIASTOLIC PRESSURE

What causes hypertension

• Aterial plaques → vascular resistance

• Excessive blood volume

  • Pregnancy: To give blood to baby

  • Excessive salt consumption: Salt pulls water into blood stream

  • Stress: Increases vasoconstriction

• Can be genetic

• Fatigues cardiac muscle = increased cardiac problems

  • Heart works harder to move blood through smaller hole

What causes hypotension? (3)

• Low blood volume

• High vessel diameter

• Low heart rate

How does the body regulate blood pressure

1) BLOOD VESSEL:

• Carotid + aorta = baroreceptors

  • Detects amount of stretch during systole

    • Sends signals to medulla

LOW BP:

• Medulla simulates sympathetic nerves → vasoconstriction

HIGH BP:

• Parasympathetic nerves → vasodilation

2) KIDNEYS:

LOW BP:

• Renal arteries detect low BP in kidneys

  • Releases renin into blood

• Renin = plasma proteins → angiotensin

  • Angiotensin = powerful vasoconstrictor

• Vessels contract → increased BP

HIGH BP:

• Kidneys increase urine production

  • Removes water, urea, and salt from blood

• More urine = less blood volume

  • Lower pressure