Introduction to CVS

Question 1

why do we need the CVS?

Answer 1

→pump blood through the lungs and carry oxygen
→transport nutrients to the muscles and organs
→circulate hormones and immune mediators
→connection to the lymphatic system
→ human reproduction
→ temperature regulation

Question 2

what is passive diffusion?

Answer 2

→random, undirected thermal movement of molecules.

Question 3

what is the equation for passive diffusion?

Answer 3

→ time needed to diffuse a given distance is proportional to the square of the distance: t ∝ d².

Question 4

what is the main method of molecule movement within the CVS and what does it provide?

Answer 4

→CVS uses convection
→ movement by a pressure gradient
→ It provides fast and directional transport
→diffusion is still crucial for transport over short distances.

Question 5

what is the significance of having pressure differences?

Answer 5

→output of blood at high pressure creates a pressure difference with distant blood vessels.
→This pressure difference drives blood flow.

Question 6

where does cardiac output go?

Answer 6

→blood is distributed to various parts of the body, such as the kidneys, liver and GI

Question 7

what are the brain and myocardium relative to other tissues?

Answer 7

→relatively under perfused.

Question 8

what controls cardiac output?

Answer 8

→filling pressure (Starling’s Law)
→sympathetic and parasympathetic autonomic nerves
→chemical factors and hormones (eg. adrenaline)

Question 9

equation for calculating cardiac output?

Answer 9

→Cardiac Output = Heart Rate x Stroke Volume

→CO = HR x SV

Question 10

why are blood flow and blood pressure important ?

Answer 10

→Blood flow and blood pressure are critical for correct bodily functioning
→ linked in the proper distribution of blood

Question 11

what happens if there is poor perfusion of the kidney?

Answer 11

→ renal failure and death

Question 12

equation for calculating blood flow?

Answer 12

→Blood flow = (Pa - Pv)/resistance

→Pa is the pressure at the artery, while Pv is the pressure at the vein.

Question 13

what is blood flow proportional to and inversely proportional to?

Answer 13

1) proportional to pressure across the blood vessel

2) inversely proportional to the resistance of the blood vessel

Question 14

why does blood slow down in the capillaries?

Answer 14

→to allow for gaseous/nutrient exchange to occur.

Question 15

equation for calculating blood velocity?

Answer 15

→Blood velocity (cm/s) = blood flow (cm³/s) / total cross-sectional area (cm²)

→To calculate cross-sectional area, we do the number of vessels times the πr² per vessel.

Question 16

describe in series blood circulation

Answer 16

→same blood supply between organs
→lower perfusion pressures
→medically significant if the first organ is being underperfused

Question 17

describe parallel blood circulation

Answer 17

→cardiac output is split up
→safeguards O₂ supply in organs
→most organs are supplied this way

Question 18

what are differences between the structures of arteries and veins?

Answer 18

ARTERIES:
→ thicker elastic wall to maintain blood pressure
→ have high pressure that ensures blood flows in one direction

VEINS:
→thinner elastic walls
→ have valves to ensure no blood backflow

Question 19

what are elastic vessels?

Answer 19

ELASTIC VESSELS: ARTERIES

Question 20

what are resistance vessels?

Answer 20

RESISTANCE VESSELS: ARTERIOLES

Question 21

what are exchange vessels?

Answer 21

EXCHANGE VESSELS: CAPILLARIES

Question 22

what are capacitance vessels?

Answer 22

CAPACITANCE VESSELS: VENULES AND VEINS

Question 23

where is most of the blood volume distributed?

Answer 23

→mostly found in large and small veins and venules. →Systemic veins and venules serve as a reservoir, holding about 65% of the volume.

Question 24

What do large arteries do?

Answer 24

→Large arteries accomodate stroke volume

→convert intermittent ejection into continuous flow

Question 25

What do resistance vessels do?

Answer 25

→Control arterial blood pressure and regulate local blood flow

Question 26

What do exchange vessels do?

Answer 26

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

Question 27

What do capacitance vessels do?

Answer 27

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

Question 28

What is the typical resting blood pressure

Answer 28

120/80 mmHg is typical resting blood pressure- the systemic pressure

Question 29

What are the pressures in the aorta and large veins?

Answer 29

Aorta >100 mmHg | Large veins 5-10 mmHg

Question 30

Recall the resting and exercising cardiac output

Answer 30

Rest 70/min x 70 ml = 5 litres/min Exercise 180/min x 120 ml = 20 litres/min

Question 31

What happens if pressure at both ends are the same?

Answer 31

No flow if pressure at both ends is the same. The higher the pressure difference, the faster the flow

Question 32

Summarise the systolic and diastolic pressures in systemic and pulmonary circulation

Answer 32

``` Systemic= 120/80 Pulmonary= 25/15 ```

Question 33

How does venous pressure vary?

Answer 33

Venous pressure (Pv) varies with location & posture, generally around 3-12mmHg

Question 34

What are the roles of venules/veins?

Answer 34

Control filling pressure of the heart & provide a reservoir of blood. They can stretch and contract but do not as much. Have a lot of blood at anytime

Question 35

Where does the main drop in pressure occur?

Answer 35

arterioles and even lower in capillaries

Question 36

How do arterioles control BP?

Answer 36

by determining total peripheral resistance (TPR)

Question 37

What do the endothelium release?

Answer 37

nitric oxide which relaxes the vessels leading to vasodilation

Question 38

What is vascular tone?

Answer 38

innervations all the time and is balanced by the parasympathetic Noxide. Allows control of the dilation- held in the middle to react immediately

Question 39

What do the sympathetic nerves in the tunica adventitia do?

Answer 39

Sympathetic nerves in the tunica adventitia release noradrenaline which stimulates α1 receptors leading to vasoconstriction

Question 40

Where is the majority of blood volume at any given time?

Answer 40

Systemic veins and venules- 65% Lungs-10% Heart-10% Capillaries-5%

Question 41

Where does the cardiac output go? | Cardiac output and oxygen consumption

Answer 41

``` 1. Liver &GI Kidneys Brain Muscle Other ``` Oxygen consumption 1. Liver and GI 2. Muscle 3. Brain 4. Kidneys