Lecture 1. Cardiovascular system

Question 1

Describe the composition of fluid in the body

ie/ what % is total body water, what % is intracellular fluid, extracellular fluid

Answer 1

Total body water = 60%; intracellular fluid = 40%; extracellular = 20%
ECF: blood plasma 4%, interstitial fluid 16%

blood volume = 4% of BW

Question 2

Name the five functions of the CV system

Answer 2

transfer substrates and O2. to cells 
transfer metabolites and CO2 from cells
thermoregulation 
hormone distribution 
body defence mechanisms are carried in the CVS (eg/ antibodies)

Question 3

how are substances moved between organs?

Answer 3

bulk transport

Question 4

what is transport rate?

Answer 4

flow rate x concentration

Question 5

what is velocity?

Answer 5

total flow / total cross sectional area

Question 6

list x4 factors influencing diffusion rate

Answer 6

1. concentration difference
2. surface area
3. diffusion distance
4. permeability to that substance

Question 7

form = function, describe how capillaries optimise diffusion of metabolites

Answer 7

capillary network = extensive (less that than 1cm away from every cell in body - metabolites don’t have to travel far)
capillary barrier = 1 endothelial layer thin

Question 8

what is vascular resistance?

Answer 8

force required to move a given volume of fluid through a system of blood vessels in a specific period of time

Question 9

what is the flow equation?

Answer 9

Q = DP/R
DP = pressure difference (delta P)

Question 10

what are the determinants of resistance?

Answer 10

poiseuilles law: R = (8 x viscosity x length) / (pi x internal radius)

resistance proportional to viscosity and length, inversely related to internal radius eg/
thicker liquid or longer tube = more resistance
bigger radius = smaller resistance

Question 11

what are the determinants to blood flow

Answer 11

PRESSURE DIFFERENCE (M. A. P.) 
TOTAL PERIPHERAL RESISTANCE 
VISCOSITY (although this rarely changes)

Question 12

different types and sizes of vessels are arranged sequentially, describe the requirements of blood flow with vessels in a SERIES
Rs = R1 + R2 + R3 … etc

Answer 12

1. in a closed system blood flow must be equal in each segment preventing the build up of fluid
2. pressure drop will increase along the segments
3. the segment with the largest change in pressure will have the greatest resistance.

Question 13

vascular beds within organs are often arranged in parallel, describe the requirements of blood flow with vessels in PARALLEL

Answer 13

resistance is given by ohm’s law = 1/Rp = 1/ R1 + 1/R2 … etc
total flow = DP/Rp
= overall resistance of system is lower than in any one compartment therefore blood flow to one organ can be altered without altering blood flow to other organs.

Question 14

what are the four forces determining transcapillary fluid movement (bulk flow)

Answer 14

1. capillary blood pressure
2. plasma colloid osmotic pressure
3. interstitial fluid hydrostatic pressure
4. interstitial fluid colloid pressure

Question 15

describe the net movement of fluid across a capillary

Answer 15

(Pc + πif) - (πP + Pif)
net pressure higher at arteriole end = filtration
net pressure lower at venous end = reabsorption

Question 16

what is the role of the lymphatics?

Answer 16

not all blood reabsorbed at the venous end –> lymphatics responsible for returning excess interstitial fluid into venous circulation eg/ fluid and protein
- lymphatics dont have pressure gradient element generated by the heart and can therefore be affected by gravity

Question 17

list the 5 components of the CV system

Answer 17

heart - needed to generate pressure
arterials - distribution 
microcirculation - region of exchange
venous system - blood reservoir 
lymph vascular - return excess lymphatic

Question 18

x4 heart chambers = x4 valves, what are they?

Answer 18

x2 atrioventricular valves (mitral and tricuspid)
x1 pulmonic semilunar valve
x1 aortic semilunar valve

Question 19

what is the dual circulation of blood?

Answer 19

left = oxygenated blood to system circulation 
right = de-oxygenated blood to pulmonary

Question 20

name the 3 components responsible for effective functioning of the heart?

Answer 20

1. conductivity
2. contractility
3. autorhymicity

Question 21

describe the 5 components of effective cardiac pumping

Answer 21

1. regular and synchronised contractions
2. fully open valves - flow forward
3. no valve leaks - no flow backwards
4. adequate force of muscle contractions
5. adequate filling of ventricles