Introduction to circulation

Question 1

Circulation function

Answer 1

Supply O2 to Tissues & Remove Waste

Pathologies arise from:

• Diminished O2
• Diminished perfusion

Question 2

CVD function

Answer 2

PERFUSION (flow)

Flow requires a pressure difference

Flow, pressure & resistance closely interlinked

Question 3

Hypertension leads to

Answer 3

vessel damage, heart damage and many pathologies

Question 4

Circulation function

Answer 4

Carrying O2 glucose nutrients to the cells
Removing waste: CO2 and heat
Homeostasis of the extracellular fluid (via the kidneys)
Distribution of hormones
temperature regulation
defence against infections

Question 5

BP =

Answer 5

CO x PR

Question 6

Aorta 
Arteries 
Arterioles 
Capillaries 
Venules 
Veins

Answer 6

Aorta – stretch and recoil, stores energy
Arteries – distribute, volume adjust
Arterioles – regulate caps, resistance, set BP & TPR
Capillaries – Exchange (nutrients, gas, fluid)
Venules – collect blood, some exchange
Veins – reservoir for blood, muscle pump

Question 7

Pulmonary circulation

Answer 7

Right ventricle 
Thin walled 
Crescent X-shape 
Lungs only 
Low pressure + resistance 
High flow

Question 8

Systemic Circulation

Answer 8

Left ventricle 
Thick walled 
Circular X-section 
Multiple organs
High Pressure
Variable flow
Variable resistance

Question 9

Apex beats

Answer 9

at systole, apex of heart moves forward and strikes the chest wall

Question 10

Valves

Answer 10

Flaps of tissue inside a blood compartment that guarantee one-way flow of the blood.

Valves open when pressure is higher on the inflow side.

Question 11

Mitral & Tricuspid (AV) valves

Answer 11

Papillary fibres (prolapse)
Close during systole
S1: First heart sound (lub)

Question 12

Aortic & pulmonary valves (semilunar)

Answer 12

“moon-shaped”
Close during diastole
Diastole is longer than systole
S2: Second heart sound (dub)

Question 13

Heart muscle contraction

Answer 13

Myocyte become electrically activated
Action Potential (lecture 5)
Extracell ->  negative / Intracell  -> Positive
Free intracellular calcium increases
Muscle contracts

Calcium is removed & muscle relaxes

Question 14

Blood volume set by kidneys

Answer 14

Sodium and water central to volume setting - Depends on water intake

Formed elements do not contribute directly to pressure
Except when they block entire vessels

Blood pressure is determined by the balance between:
circulating blood volume & circulatory capacity

Question 15

Kidney review

Answer 15

By Filtering blood
Many small molecules go through filter
H2O, glucose, ions
Blood cells and proteins CANNOT go through filter
Desirable small molecule are re-absorbed back into blood
Excess fluid and undesirable small molecules left behind go to bladder and are excreted

Filtration unit is a nephron that contains a glomerulus (the filter)

Kidneys controlled by endocrine system and autonomic nervous system

Question 16

Glomerular filtration rate

Answer 16

Fluid entering all Bowmans capsules
In ml / min
Increase GFR -> fluid loss to urine
Increase renal blood flow   -> Increase GFR

Question 17

Hypoxia

Answer 17

Insufficient O2 supply to a region or to entire body

Question 18

Ischaemia causes

Answer 18

Vessel: clog, constriction, closure

Insufficient blood volume: e.g. haemorrhage

Heart: Insufficient Pressure Generation

Question 19

Hypoxaemia

Answer 19

low O2 content generally throughout arterial blood.

Typical causes would be: any serious respiratory problem, anaemia, or generally poor circulatory perfusion of the lungs.

Question 20

Angina Pectoris

Answer 20

Symptom

Chest pain due to over-exertion of (damaged) heart tissue

Can occur with or without physical exertion

Treat: Nitrates for immediate relief

Long term treatments: as per CAD

Immediate cause: Ischaemia of heart tissue due to an obstruction (or spasm) of a coronary artery.

Question 21

MI

Answer 21

Results from occlusion of a coronary artery
Treatment: MONA - immediate reperfusion

Sudden, crushing chest pain

Question 22

HF

Answer 22

Heart pumps out insufficient blood

Fatigue, dyspnoeia, oedema

Question 23

Shock

Answer 23

Critically low perfusion - SBP < 90 mmHg
Medical emergency
Affects critically ill patients

Example: haemorrhagic shock

Affects cerebral and renal function

Treatment: Aggressive intravenous fluid AND Oxygen + airway maintained

Question 24

Syncope causes

Answer 24

Shock

Arrhythmia