exam 1: 1/16/25 Flashcards by Haley Walker

What is Clearance?
What’s the formula?

volume of plasma cleared of a substance per unit of time

C= U(x) x V /P(x)

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What’s the formula for GFR?

GFR= U(creatinine) x V/P (creatinine)

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Clearance of free water

Definition

volume of free water (no electrolytes) removed from the body per unit of time

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What is the effect of elevated ADH on free water clearance?

lowers free water clearance

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normal MAP and BP

MAP formula

MAP 100 mmHg
SBP 120 mmHg
DBP 80 mmHg
DBP + (1/3) [(SBP-DBP)]
*93 mmHg MAP more accurate

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Which vessels have the greatest amount of vascular resistance?

arterioles

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Normal RA pressure

0 mmHg

furthest from heart/aorta and downstream from chokepoint = end of systemic circulation

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Delta P of systemic circulation

aorta - RAP

100 mmHg - 0 mmHg

= 100 mmHg

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Normal mPAP and pulmonary BP?

mean pulmonary arterial pressure = 16 mmHg

Pulmonary BP= 25/8

not the same as MAP formula

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LA pressure

2 mmHg

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Delta P of pulmonary circulation

mPAP - LA

16 mmHg - 2 mmHg

= 14 mmHg

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What is pulse pressure?

SBP - DBP

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Delta P of the aorta

120 mmHg - 80 mmHg

= 40 mmHg

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Compliance meaning and formula

stretchiness

Delta V / Delta P

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As blood flow meets higher vascular resistance… what happens to pulse pressure?

reduced pulse pressure

from energy being “zapped”

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Adding more volume into a stiff/less compliant blood vessel…. effect on BP and PP?

increase SBP

widens pulse pressure

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Adding more volume into a more elastic/more compliant blood vessel… effect on BB and PP?

SBP not as elevated

more narrow pulse pressure

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What drives flow during diastole?

elastic recoil of the aorta during diastole acting like a secondary blood pump

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What’s the #1 reason for low pulse pressure in the PA?

**low resistance
stretchy

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Capillary hydrostatic pressures at the arteriolar end and venular end?

arteriolar 30 mmHg
venular 10 mmHg

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What effect does arterial stiffness have on pulse pressure?

blood into container -> HIGH pressure

not ejecting/not filling -> LOW pressure

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Why don’t we see a pulse pressure for veins?

stretchy/ more compliant than arteries

why giving 1L bolus doesn’t increase BP that much

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If compliance is constant, an increase in stroke volume will do what to pulse pressure?

increase

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What are 2 things that will increase stroke volume?

stiff walls
increased stroke volume

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What 3 things in the body does compliance apply to?

CV system, blood vessels, airways

LV pressure

filling = 0 mmHg ejecting = 120 mmHg

aorta pressure

100 mmHg

whats the end of systemic circuit?

RV pressure

filling = 0 mmHg ejection = 25 mmHg

Why do arterioles have high vascular resistance?

smooth muscle cells -> THICC walls narrow opening

What are properties of veins?

- stretchy/compliant - wide openings - thinner layers of smooth muscle compared to arterioles... veins don't constrict has much as arterioles

What are properties of capillaries?

very thin single layer endothelial layer for gas exchange

Where are endothelial cells located?

inner layer of entire CV system, LV, LA - single layer capillary cells are endothelial

What are properties of the aorta?

- THICC wall - really stretchy -

What effect does aging have on our aorta?

aorta becomes rigid -> high pulse pressure

Cardiac Output equation

CO= HR x SV 5 L/min = 72 x 70 cc

Velocity equation

Velocity (distance/time) = blood flow (vol/time) / cross sectional area v= F/A

What 2 things increase velocity?

- increased CO - decreased cross sectional area

cross sectional area of aorta

2.5 cm^2

cross sectional area of capillaries

2500 cm^2

cross sectional area of vena cava

8 x 2 cm^2

What type of system is the systemic circulation?

parallel system

What type of system is the pulmonary circulation?

parallel system * all blood passes through it vs the systemic cirulation has some choices

What are capillaries permeable to?

glucose, electrolytes, gases (lipid soluable) *brain capillaries are tighter

What happens to fluid/substances that are not reabsorbed by the capillary beds?

swept up by lymphatic system

Distance under a pressure source

distance of 13.6 mm (or 1.36 cm) below a pressure source... increases pressure by 1 mmHg

What is the reference point for pressure inside the heart called?

*Isogravimetric point: in the middle of tricuspid valve where gravity has ZERO effect on BP b/c its located in the middle of the pressure source We used to call it "phlebostatic axis"

Upright position pressure of a vein at: - umbilicus - above patella - foot

+22 mmHg +40 mmHg +90 mmHg (if standing still) All due to effect of gravity

Upright position pressure of a vein at: Internal jugular vein sagital sinus

0 mmHg *veins in neck very thin and wide. If they were a negative hydrostatic pressure -> vein would collapse -> little venous drainage from the brain -10 mmHg * large veins, thick walls, meningitis make up the walls of sinuses... meningitis are ridged/non-compliant

What happens if the superior sagittal sinus was exposed to the atmosphere?

suck air in (air embolism) due to negative or "sub atmospheric" pressure within the vessel

Why is a BP cuff on the arm a slightly higher BP in the upright position?

column of blood upright = basilic vein brachial vein +6 - +8 mmHg *arterial blood weights just as much as venous blood ex: brachial artery

How do veins withstand high pressures as a result of gravity?

one way valves that prevent retrograde flow contracting skeletal muscles push on the one way valves in veins

What are the valves in veins composed like?

- thinner than veins - delicate

What happens to our veins over time as we age or standing on feet long periods of time?

veins become over stretched leading to valvular insufficiency -> varicose veins blood clot risk

Recumbent pressures

aka supine Aorta 100 mmHg Foot 95 mmHg Pcap 25 mmHg venular end 5 mmHg RA 0 mmHg

In standing position, what's the pressure increase of the weight of blood in arteries and veins in the foot?

+ 90 mmHg - venular end recumbent 5 mmHg - valves not working in standing 90 mmHg

How to find artery BP?

BP from heart + gravity pressureW

Who's funeral did one of the honor guards pass out from standing?

Jimmy Carter

A pseroen upright without intermittent contraction of skeletal muscles in the legs, would loose consciousness in how long?

10-20 minutes decreased preload causing decreased brain blood flow

systemic volume in veins vs. arteries

veins 2.5 L Arteries 700 mL

vascular distensibility equation

aka expandability vascular distensibility= increase vol. / increase pressure x original vol.

A small original volume that can expand a lot... does what to distensibility?

increases it, more expandable

Large container that doesn't accept volume easily and need to use a lot of pressure... does what to distensibility?

decreases it, less expandable

normal SVR

800-1600

Resistance equation

R= Delta P / F

Conductance equation

How easy to move something ***1/ resistance low resistance -> high conductance *** conductance = diameter^4

What determines blood vessel blow flow?

tissue metabolism

Most important variable of blood flow?

changes in resistance or vessel diameter

small increase in diameter has what effect on blood flow?

Huge increase in conductance and blood flow

increased Delta P vs. low Delta P effect on BP

increased delta P results in increased blood flow low delta P results in low blood flow