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From digestion to transport. The transport system. Link to presentation used in class (supplemented by additional slides…). Stephen Taylor transport presentation. Syllabus details relating to BLOOD.

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Presentation Transcript
link to presentation used in class supplemented by additional slides
Link to presentation used in class (supplemented by additional slides…)
  • Stephen Taylor transport presentation
syllabus details relating to blood
Syllabus details relating to BLOOD
  • 6.2.6 State that blood is composed of plasma, erythrocytes, leucocytes (phagocytes and lymphocytes) and platelets
  • 6.2.7 State that the following are transported by the blood: nutrients, oxygen, carbon dioxide, hormones, antibodies, urea and heat

6.2.1: Draw a heart, labelling the 4 chambers, associated blood vessels, valves and route of blood through the heart

let s draw a heart
Let’s draw a heart!
  • Drawing a heart...
control of the cardiac cycle
Control of the cardiac cycle
  • control of the cardiac cycle
  • conducrtion system of the heart
explain the basic cardiac cycle
Explain the basic cardiac cycle…
  • Animation 1
  • slightly more detailed cardiac cycle
control of heart rate
Control of heart rate

In order to understand control of heart rate, we need to understand WHY heart rate might increase or decrease….

Give me some reasons why heart rate might increase or decrease?

heart rate and force of contraction are controlled by the medulla brainstem
Heart rate and force of contraction are controlled by the medulla (brainstem)
  • Cardio-accelerator centre – cardiac nerve: increases heart rate (epinephrine)
  • Cardio-inhibotorycentre – vagus nerve – decreases heart rate (Ach)
the medulla responds to many factors
The medulla responds to many factors

An increase in carbon dioxide tension in the blood is sensed by chemoreceptors in the heart and carotid artery, and sent to the medulla for processing…


The sino-atrial node is affected by both sympathetic (adrenaline/noradrenaline) and parasympathetic (Ach) fibres

cardiac output
Cardiac output
  • Cardiac output = volume of blood pumped by the heart in L/minute.
  • Cardiac output is is the product of HEART RATE (BEATS/MINUTE) and STROKE VOLUME (ML/BEAT)
  • CO can be increased by means of increasing heart rate OR stroke volume
tissue oxygen delivery the bottom line
Tissue oxygen delivery:‘the bottom line’
  • depends on cardiac output (cardiac function and forward flow) and arterial oxygen content (CaO2)
  • Oxygen delivery (DO2) = cardiac output multiplied by the oxygen content of blood

DO2= CO X [Hb] X SpO2 X 1.34

(each 1 g of haemoglobin can carry 1.34 g of oxygen)

myocardial perfusion
Myocardial perfusion

myocardial perfusion occurs during diastole

  • A high heart ratemeans less time for diastolic filling and myocardial perfusion
  • A high heart rate increasesmyocardial work and increases myocardial oxygen requirement: the heart has to work harder’

Cardiac Output

(intrinsic ability of heart)

Heart Rate

Stroke Volume

(volume ejected/contraction)




 Vagal stim.

 Symp stim

  • (+)
  • Anticholinergics
  • Symp stim






Venous blood volume


 Depressant drugs

Fluid Therapy

total peripheral resistance
is resistance to blood flow provided by the vascular bed

determined principally by vascular tone

also affected by blood viscosity and ventricular wall tension

arterial blood pressure is the PRODUCT of CO and total peripheral resistance

If CO remains the same and afterload  then BP rises

If CO remains unaltered and afterload  (e.g. acepromazine) then BP falls

Total peripheral resistance
heart rate may affect cardiac output during anaesthesia
Heart rate can be influenced by MOST anaesthetic drugs:


α2 agonists


ACh inhibitors (anticholinergics)



severe bradycardia (not compensated by changes in stroke volume) or severe tachycardia will reduce cardiac output

Heart rate may affect cardiac output during anaesthesia
severe tachycardia decreases cardiac output
decreased preload (most of filling occurs in first half of diastole)

decreased stroke volume

decreased myocardial oxygenation potential (coronary arteries fill in diastole)

Severe tachycardia decreases cardiac output