Venous Return Learning Objectives... 1) To be able to explain how venous return is maintained. 2) Understand how venous return affects the quality of performance. 3) To be able to describe the effects that a warm-up and cool-down period has on the cardiovascular system. LO1 = Venous Return Using your textbook define Venous Return. What have you written down? Venous return is the volume of blood flowing back to the heart through the veins. LO1 = Venous Return How does your body maintain venous return? There are 5 main mechanisms that enable blow to flow back to your heart. Do you know/Can you find out what they are? LO1 = Venous Return Pocket Valves One-way valves, called pocket valves, in the veins prevent backflow of blood and direct blood flow back towards the heart. HANG ON! BINGO........ Define VENOUS RETURN! LO1 = Venous Return Muscle Pump Veins are situated between skeletal muscle which when contracting and relaxing helps push/squeeze blood through the veins back towards the heart. LO1 = Venous Return Respiratory Pump During exercise, breathing becomes deeper/faster. This causes pressure changes to occur in the thorax and abdomen. This increases the pressure in the abdomen causing the large veins in that area to be squeezed/sucked. This forces the blood back to the heart. LO1 = Venous Return Smooth Muscle Contraction and relaxation of smooth muscle within the middle layer of the veins’ walls also helps to push blood through the veins and back towards the heart. LO1 = Venous Return Gravity Blood from the upper body, above the heart, is aided by gravity, which helps blood flow back to the heart. Newbie... Stand up & Cover Your Eyes! Do we think that Chris can remember the 5 mechanisms that enable venous return to occur? LO2 = VR Affecting Performance Exam Style Question.... Using your textbooks answer the following question. How does maintaining venous return affect performance? (5marks) Peer Assessment Time Mark your partners work according to the mark scheme. I will then mark your work when you hand it in. LO2 = VR Affecting Performance Mark Scheme..... VR determines SV and Q. Starling’s Law, SV/Q dependent upon VR so if VR increases, SV/Q increases: increase in SV/Q increases blood/oxygen transport to the working muscles increasing their ability to contract/work aerobically; exercise intensity/duration can be increased; more significant in prolonged aerobic-based exercise, dependant upon oxygen supply; also increases anaerobic performance as good VR speeds up recovery allowing performers to work anaerobically for longer. LO3 = Warm up & the CV system Write down what happens to your body during a warm up (doesn’t have to be linked with the CV system) What have you got? Has anybody got any that are linked to the CV? LO3 = Warm up & the CV system Increases blood flow/Q due to the vascular shunt mechanism via: Vasoconstriction of arterioles/precapillary sphincters to organs Vasodilation of muscle arterioles/precapillary sphincters BETH......DESCRIBE VASCULAR SHUNTING PLEASE LO3 = Warm up & the CV system Increased body/muscle temperature which: increases transport of the enzymes required for energy systems and muscle contraction decreases blood viscosity, improving blood flow to working muscles increases the dissociation of oxygen from haemoglobin in muscle tissues Decreased OBLA (onset of blood lactate accumulation) due to the early onset of anaerobic work when a warm-up is not carried out.