Intro to the CVS

Question 1

What are the 6 main reasons why we need the CVS?

Answer 1

1. Pump blood through Lungs & carry Oxygen, take away CO2
2. Transport nutrients to muscle and organs, take away waste and metabolises
3. Circulates hormones & immune mediators
4. Connection to lymphatic system
5. Human reproductive system (in ejection/ejaculation)
6. Temperature regulation (need to distribute heat)

Question 2

What is passive diffusion?

Answer 2

Random movement of undirected thermal movement of molecules

Question 3

What is the time needed to diffuse a given distance proportional to?

Answer 3

square of the distance

Question 4

At what distance does diffusion become time consuming?

Answer 4

> 1mm, then diffusion becomes inappropriate as the mode of transport throughout the body

Question 5

Time taken to diffuse across 0.1 um

Answer 5

0.005 ms, e.g. Synapse

Question 6

Time taken to diffuse across 10 um

Answer 6

50 ms, e.g. from Capillary to Cell

Question 7

Time taken to diffuse across 1 mm

Answer 7

8 min, e.g. through Cartilage

Question 8

Time taken to diffuse 1 cm

Answer 8

13 hours, e.g. through Left Ventricle Wall

Question 9

what does pressure difference drive?

Answer 9

blood flow

Question 10

Systole

Answer 10

Contraction

Question 11

Diastole

Answer 11

Relaxation

Question 12

Cardiac output=

Answer 12

Volume of blood ejected from the heart per minute, normally around 5 litres/min

Question 13

What is the main method of molecule movement within the CVS?

Answer 13

• CVS uses convection (movement by a pressure gradient)
• provides fast and directional transport
• diffusion still crucial for transport over short distances

Question 14

Distribution of cardiac output

Answer 14

• Liver & GI: 25%
• Muscle: 20%
• Brain: 13%
• Kidneys: 20%
• Myocardium: 4%
• Other: 18%

Question 15

Oxygen consumption at rest

Answer 15

• Liver & GI: 30%
• Muscle: 20%
• Brain: 18%
• Kidneys: 10%
• Myocardium: 10%
• Other: 12%

Question 16

What two areas are of clinical significance to cardiac output distribution?

Answer 16

• The brain and myocardium (muscular heart tissue)
• Places are relatively under-perfused
• Whenever there is a problem with blood supply, these two places are at risk (Stroke, Heart attack, angina, MI)
• Therefore, need to carefully control cardiac output

Question 17

What three factors control cardiac output?

Answer 17

1. Filing pressure (Starling’s law)
2. Sympathetic and parasympathetic autonomic nerves
3. Chemical factors & hormones (adrenaline)

Question 18

What is the equation for calculating cardiac output?

Answer 18

• Cardiac output = heart rate x stroke volume

- CO = HR x SV

Question 19

Why are blood flow and pressure important?

Answer 19

• Blood flow and pressure are critical for correct bodily functioning
• Because they are linked in the proper distribution of blood
• E.g. if there is poor perfusion in the kidneys: could cause renal failure and death

Question 20

Blood flow is…

Answer 20

1. Proportional to pressure across blood vessel

2. Inversely proportional to resistance of blood vessel

Question 21

What is the equation for calculating blood flow?

Answer 21

• Blood flow = (Pa -Pv) / resistance
• Pa is the pressure at the artery
• Pv is the pressure at the vein

Question 22

BP for Systemic circulation

Answer 22

120 (systolic) / 80 (diastolic)

- high pressure to pump around the body

Question 23

BP for Pulmonary circulation

Answer 23

25 (systolic) / 15 (diastolic)

- low pressure allows gas exchange

Question 24

What type of vessels are arterioles?

Answer 24

Resistance vessels

- They control arterial BP by determining total peripheral resistance (TPR)

Question 25

Why does blood slow down at the capillaries?

Answer 25

The velocity of blood is much slower at the capillaries to allow for gaseous/nutrient exchange to occur

Question 26

What is the equation for calculating blood velocity?

Answer 26

- Blood velocity (cm/s) = blood flow (cm3/s) / cross sectional area (cm2) - To calculate cross sectional area, do a number of vessels x (pi r squared) per vessel

Question 27

Describe how dual circulation can be in parallel or in series?

Answer 27

``` • IN SERIES (PORTAL): - Same blood supply between organs - Lower perfusion pressures - Medically significant if the first organ is being under perfused • IN PARALLEL: - Cardiac output is split up - Safeguards O2 supply in organs - Most organs are supplied this way ```

Question 28

Difference between structure of arteries and veins

Answer 28

• ARTERIES: - Thicker elastic wall to maintain blood pressure - Have high pressure that ensures blood flow in one direction • VEINS: - Thinner elastic walls - Have valves to ensure no blood backflow

Question 29

ELASTIC VESSELS: ARTERIES function

Answer 29

Large arteries accommodate stroke volume and convert intermittent ejection into continuous flow

Question 30

RESISTANCE VESSELS: ARTERIOLES function

Answer 30

Control arterial blood pressure and regulate local blood flow

Question 31

EXCHANGE VESSELS: CAPILLARIES function

Answer 31

Nutrient delivery to cells and tissues for water and lymph formation, and removal of metabolic waste

Question 32

CAPACITANCE VESSELS: VENULES AND VEINS function

Answer 32

Control the filling pressure and provide a reservoir of blood, so the veins can constrict and send blood to the heart if needed

Question 33

Distribution of blood volume

Answer 33

- Small veins and venues: 24% - Capillaries: 5% - Arteries: 10% - Heart: 10% - Lungs: 10% - Large veins: 24% * Systemic veins and venues serve as a reservoir holding 65% of volume

Question 34

Two types of circulation?

Answer 34

1. Systemic circulation | 2. Pulmonary circulation

Question 35

Systemic circulation

Answer 35

Takes oxygenated blood and nutrients (e.g. glucose) around the body and removes waste like amino acids and lactate

Question 36

Pulmonary circulation

Answer 36

Takes oxygen from lungs and releases carbon dioxide into the lungs