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Human Physiology 2 > Unit 2 - Blood Flow & Blood Pressure PART D > Flashcards

Unit 2 - Blood Flow & Blood Pressure PART D Flashcards

1
Q

_____ ______ as a result of blood pushing against walls of blood vessels, however blood is moving, so the pressure falls over the distance it travels.

A

HYDROSTATIC PRESSURE

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2
Q

Highest pressure in…

A

arteries closest to pump (ventricles)

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3
Q

Lowest pressure…

A

in veins (in the circulatory route these are furthest from ventricular pump)

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4
Q

Hydrostatic pressure results when…

A

Results when flow (F) is opposed by resistance (R).

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5
Q

↓P occurs b/c…

A

energy is lost as a result of the resistance to flow offered by the vessels
- resistance to BF also results from friction b/t the blood cells

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6
Q

By convention all body pressure are given relative to…

A

By convention all body pressure are given relative to atmospheric pressure and are measured in mmHg (millimeters of mercury).

100 mmHg = 100 mmHg above atmospheric pressure (at sea level = 760 mmHg).

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7
Q

In the systemic circulation, the HIGHEST pressure occurs in the…

A

aorta & results from pressure created by the LV

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8
Q

4 important pressures:

A
  1. Systolic Pressure (SP)
  2. Diastolic Pressure (DP)
  3. Pulse Pressure (PP)
  4. Mean Arterial Pressure (MAP)
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9
Q

Pulse

A

pressure wave that is transmitted through the fluid of the CV system

  • the rapid pressure increase that occurs when the LV pushes blood into the aorta
  • transmitted through the fluid-filled arteries
  • travels about 10x faster than the blood itself
  • pulse felt in arm is occurring slightly after the ventricular contraction that created the wave
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10
Q

Systolic Pressure (SP)

A

Max. pressure in aorta (~120 mmHg).

Reached ~ half way through ventricular ejection (i.e. during ventricular systole/contraction).

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11
Q

Diastolic Pressure (DP)

A

Min. pressure in aorta (~80 mmHg).

Reached at end of isovolumetric contraction of ventricles (so technically during ventricular systole, just after diastole ends and before ejection begins).

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12
Q

Pulse Pressure (PP)

A
  • Strength of pressure wave produced by ventricular contraction

= Systolic Pressure - Diastolic Pressure

  • Decreases over distance due to friction (& finally disappears at the capillaries)
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13
Q

Mean Arterial Pressure (MAP)

A

(since atrial pressure is pulsatile, we use this single value - MAP - to represent the driving pressure)

  • Average aortic pressure over entire cardiac cycle (~93 mmHg)
  • Driving force pushing blood through the systemic circuit
  • Homeostatically regulated by body to ensure adequate perfusion of organs.
  • Calculated clinically as: Diastolic Pressure + 1/3 (Systolic Pressure – Diastolic Pressure)
  • Heart spends more time in diastole, so diastolic pressure has a larger contribution to MAP
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14
Q

Describe Figure 15.6 - Systemic circulation pressures

A
  • Pressure waves created by ventricular contraction travel into the blood vessels
  • Pressure in the arterial side of the circulation cycles but the pressure waves diminish in amplitude with distance & disappear at the capillaries

Pulse pressure = systolic pressure - diastolic presure

Mean arterial pressure = diastolic pressure + 1/3 (pulse pressure)

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15
Q

By the time blood reaches the veins,…

A

pressure has decreased b/c of friction, & a pressure wave no longer exists
- venous BF is steady rather than pulsatile (in pulses), pushed along by the continuous movement of blood out of the capillaries

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16
Q

Low pressure blood in veins below the heart must flow…

A

“uphill,” or against gravity, to return to the heart

17
Q

Blood return to the heart (venous return), is aided by valves, the respiratory pump, & the skeletal muscle pump. When muscles such as those in the calf of the leg contract…

A

they compress the veins, which forces blood upward past the valves

18
Q

What is something to notice from Figure 15.6 (systemic circulation pressures)?

A

the pressure in the ventricles falls to only a few mm Hg as the ventricle relaxes, but diastolic pressure in the large arteries reflects the ability of those vessels to capture & store energy in their elastic walls

19
Q

What happens if BP falls too low (hypotension)?

A

the driving force for blood flow is unable to overcome opposition by gravity
- therefore, BF & oxygen supply to the brain are impaired, & the person may become dizzy or faint

20
Q

What happens if BP is chronically elevated (hypertension or ↑BP)?

A

↑ pressure on the walls of blood vessels may cause weakened areas to rupture & bleed into the tissues

  • if rupture occurs in the brain (cerebral hemorrhage & may cause the loss of neurological function (stroke)
  • if a weakened area ruptures in a major artery, such as the descending aorta, rapid blood loss into the abdominal cavity causes BP to fall below the critical min. (without prompt treatment, rupture of a major artery is fatal)
21
Q

What is a Sphygmomanometry?

A

an instrument for measuring pressure of a fluid (arterial BP is measured)

  • consisting of an inflatable cuff & a pressure gauge
22
Q

What is the Sphygmomanometry method?

A

Method of measuring systolic and diastolic pressure clinically using a blood pressure cuff attached a pressure gauge (sphygmomanometer) and a stethoscope.

23
Q

Sphygmomanometry

A
  1. Inflate cuff to occlude brachial artery (~140mmHg on the gauge), then slowly release the pressure and listen for the first Korotkoff sounds.
  2. Korotkoff sounds are soft tapping sound heard in the in vessel as blood begins to spurt through (turbulent blood flow).
  3. Pressure when you hear the first sound is the systolic pressure (highest pressure in the artery).
  4. Pressure when you hear the last sound is the diastolic pressure (lowest pressure in the artery after flow has returned to normal laminar flow).
24
Q

What should BP be on average?

A

On average should be 120/80 mmHg, however there is a high degree of variability.

25
Q

What do signs of hypertension include?

A

Signs of hypertension include a systolic pressure over 140 mmHg at rest and/or a diastolic pressure above 90 mmHg.

26
Q

Sphygmomanometry theory

A
  • the cuff encircles the upperarm & is inflated until it exerts pressure ↑ than the systolic pressure driving arterial blood
  • when cuff pressure exceeds arterial pressure, BF into the lower arm stops
  • now pressure on the cuff is gradually released
  • when cuff pressure falls below systolic arterial BP, blood begins to flow again
  • as blood squeezes through the still - compressed artery, a thumping noise called a KOROTKOFF SOUND can be heard with each pressure wave
  • once the cuff pressure no longer compresses the artery, flow smooths out & the sound disappears

Human Physiology 2 (37 decks)

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