Circulation 7

Question 1

net filtration pressure (NFP) (3)

Answer 1

• based on the Starling principle
• may result in net filtration or net reabsorption across capillary membrane
• creates a micro-circulation to mix interstitial fluids around the capillaries

Question 2

NFP formula

Answer 2

NFP = (Pcap - Pif) - (πcap - πif)

Question 3

NFP formula: Pcap

Answer 3

• hydrostatic pressure of blood in capillary

Question 4

NFP formula: Pif

Answer 4

• hydrostatic pressure of interstitial fluid

Question 5

NFP formula: πcap

Answer 5

• osmotic pressure in the capillary

Question 6

NFP formula: πif

Answer 6

• osmotic pressure of interstitial fluid

Question 7

what determines osmotic pressure (2)

Answer 7

• determines by concentration of salts and proteins in a solution
• water will move to solution with higher concentration of salts + proteins

Question 8

hydrostatic pressure (2)

Answer 8

• pressure of a column of fluid due to gravity
• the area with high hydrostatic pressure will force fluid to the area of lower hydrostatic pressure

Question 9

NFP: arterial side of capillary (3)

Answer 9

• Pcap > πcap
• NFP is positive
• net filtration occurs

Question 10

NFP: middle of capillary (3)

Answer 10

• Pcap = πcap
• NFP is ~0
• net movement is zero

Question 11

NFP: venous side of capillary (3)

Answer 11

• Pcap < πcap
• NFP is negative
• net reabsorption occurs

Question 12

lymphatic system: functions (2)

Answer 12

• collects excess filtered fluid and returns it to the circulatory system
• lymph nodes filter lymph to remove and kill pathogens

Question 13

how does fluid move through the lymphatic system (2)

Answer 13

• net water pressures and body movement drive fluid movement
• lymphatic veins and ducts contains valves to prevent backflow

Question 14

edema (2)

Answer 14

• accumulation of interstitial fluid
• can be due to ineffective lymphatic system

Question 15

gravity on blood pressure: formula

Answer 15

ΔP = p * g * Δh

Question 16

gravity on blood pressure: ΔP

Answer 16

• pressure difference between two points

Question 17

gravity on blood pressure: Δh

Answer 17

• height of the fluid column

Question 18

gravity on blood pressure: p

Answer 18

• density of the fluid

Question 19

gravity on blood pressure: g

Answer 19

• acceleration due to gravity

Question 20

what are the arterial and venous pressures at our heart due to gravity (standing) (2)

Answer 20

• arterial: 100 mmHg
• venous: 10 mmHg

Question 21

how much lower are venous pressures than arterial pressures due to gravity

Answer 21

• venous pressure at each height are ~100 mmHg lower to permit blood flow

Question 22

how does body position affect blood pressure

Answer 22

• changes in body position can alter blood pressure and flow
• changes relative to gravity, such as standing up

Question 23

body positions and blood pressure: standing up (2)

Answer 23

• causes pooling of blood in lower body
• due to low venous return, low SV, and low MAP

Question 24

how does our body regulate MAP when we stand up (2)

Answer 24

• baroreceptor reflex brings MAP back to normal
• increases HR and SV to raise MAP

Question 25

orthostatic hypotension (2)

Answer 25

• low blood pressure upon standing
• occurs when baroreceptor reflex is too slow and not enough blood flows to the head

Question 26

in what animals are the effects of gravity more important (2)

Answer 26

• snakes
• giraffe

Question 27

how do snakes deal with gravity

Answer 27

• heart is close to the brain so that it is guaranteed blood flow regardless of body position

Question 28

how do giraffes deal with body position changes (2)

Answer 28

• vasoconstriction occurs in vessels of lower body when the head is upright and aortic pressure increases
• vasodilation occurs in the vessels of the lower body when the head is feeding on ground and aortic pressure decreases

Question 29

giraffes and gravity: head problem

Answer 29

• heart must generate sufficient pressure to overcome hydrostatic pressure

Question 30

giraffes and gravity: head solution (2)

Answer 30

• thick-walled heart with low stroke volume & fast heartbeat
• generate very high MAP

Question 31

giraffes and gravity: feet problem

Answer 31

• giraffe must have solution to counter blood pooling in their legs and feet

Question 32

giraffes and gravity: feet solution (4)

Answer 32

• giraffe arteries are usually muscular
• skin on legs is very tight, acting as a compression stocking
• tight endothelium to prevent H20 loss
• venous valves

Question 33

gravitational effects on cardiovascular function in air

Answer 33

• pressure increases with height of the water column, causing pooling/high pressure at the bottom

Question 34

gravitational effects on cardiovascular function in water (2)

Answer 34

• blood and water have similar density and hydrostatic pressure
• effects outside the animal cancel out gravitational effect, acting as a large “compression stocking”