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.