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.
6.2.1: Draw a heart, labelling the 4 chambers, associated blood vessels, valves and route of blood through the heart
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?
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
DO2= CO X [Hb] X SpO2 X 1.34
(each 1 g of haemoglobin can carry 1.34 g of oxygen)
myocardial perfusion occurs during diastole
(intrinsic ability of heart)
Venous blood volume
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 fallsTotal peripheral resistance
ACh inhibitors (anticholinergics)
severe bradycardia (not compensated by changes in stroke volume) or severe tachycardia will reduce cardiac outputHeart rate may affect cardiac output during anaesthesia
decreased stroke volume
decreased myocardial oxygenation potential (coronary arteries fill in diastole)Severe tachycardia decreases cardiac output