Venous ReturnVenous Return

Learning Objectives...Learning Objectives...1)1) To be able to explain how venous return is To be able to explain how venous return is

maintained.maintained.2)2) Understand how venous return affects the Understand how venous return affects the

quality of performance.quality of performance.3)3) To be able to describe the effects that a To be able to describe the effects that a

warm-up and cool-down period has on the warm-up and cool-down period has on the cardiovascular system.cardiovascular system.

LO1 = Venous ReturnLO1 = Venous Return

Using your textbook define Venous Return.Using your textbook define Venous Return.

What have you written down?What have you written down?

Venous return is the volume of blood flowing Venous return is the volume of blood flowing back to the heart through the veins.back to the heart through the veins.

LO1 = Venous ReturnLO1 = Venous ReturnHow does your body maintain venous return?How does your body maintain venous return?

There are 5 main mechanisms that enable blow There are 5 main mechanisms that enable blow to flow back to your heart.to flow back to your heart.

Do you know/Can you find out what they are?Do you know/Can you find out what they are?

LO1 = Venous ReturnLO1 = Venous ReturnPocket ValvesPocket Valves

One-way valves, called pocket valves, in the One-way valves, called pocket valves, in the veins prevent backflow of blood and direct veins prevent backflow of blood and direct

blood flow back towards the heart.blood flow back towards the heart.

HANG ON!HANG ON!

BINGO........BINGO........

Define VENOUS RETURN!Define VENOUS RETURN!

LO1 = Venous ReturnLO1 = Venous ReturnMuscle PumpMuscle Pump

Veins are situated between skeletal muscle Veins are situated between skeletal muscle which when contracting and relaxing helps which when contracting and relaxing helps push/squeeze blood through the veins back push/squeeze blood through the veins back

towards the heart.towards the heart.

LO1 = Venous ReturnLO1 = Venous ReturnRespiratory PumpRespiratory Pump

During exercise, breathing becomes During exercise, breathing becomes deeper/faster. This causes pressure changes deeper/faster. This causes pressure changes

to occur in the thorax and abdomen. This to occur in the thorax and abdomen. This increases the pressure in the abdomen increases the pressure in the abdomen

causing the large veins in that area to be causing the large veins in that area to be squeezed/sucked. This forces the blood back squeezed/sucked. This forces the blood back

to the heart.to the heart.

LO1 = Venous ReturnLO1 = Venous ReturnSmooth MuscleSmooth Muscle

Contraction and relaxation of smooth muscle Contraction and relaxation of smooth muscle within the middle layer of the veins’ walls also within the middle layer of the veins’ walls also

helps to push blood through the veins and helps to push blood through the veins and back towards the heart.back towards the heart.

LO1 = Venous ReturnLO1 = Venous ReturnGravityGravity

Blood from the upper body, above the heart, is Blood from the upper body, above the heart, is aided by gravity, which helps blood flow back aided by gravity, which helps blood flow back

to the heart.to the heart.

Newbie...Newbie...

Stand up & Cover Stand up & Cover Your Eyes!Your Eyes!

Do we think that Chris can remember the 5 Do we think that Chris can remember the 5 mechanisms that enable venous return to occur?mechanisms that enable venous return to occur?

LO2 = VR Affecting PerformanceLO2 = VR Affecting PerformanceExam Style Question....Exam Style Question....

Using your textbooks answer the following Using your textbooks answer the following question.question.

How does maintaining venous return affect How does maintaining venous return affect performance? (5marks)performance? (5marks)

Peer Assessment TimePeer Assessment Time

Mark your partners work according to the mark Mark your partners work according to the mark scheme.scheme.

I will then mark your work when you hand it in.I will then mark your work when you hand it in.

LO2 = VR Affecting PerformanceLO2 = VR Affecting PerformanceMark Scheme.....Mark Scheme.....

VR determines SV and Q.VR determines SV and Q.Starling’s Law, SV/Q dependent upon VR so if VR increases, Starling’s Law, SV/Q dependent upon VR so if VR increases, SV/Q increases:SV/Q increases:increase in SV/Q increases blood/oxygen transport to the increase in SV/Q increases blood/oxygen transport to the working muscles increasing their ability to contract/work working muscles increasing their ability to contract/work aerobically;aerobically;exercise intensity/duration can be increased;exercise intensity/duration can be increased;more significant in prolonged aerobic-based exercise, more significant in prolonged aerobic-based exercise, dependant upon oxygen supply;dependant upon oxygen supply;also increases anaerobic performance as good VR speeds up also increases anaerobic performance as good VR speeds up recovery allowing performers to work anaerobically for recovery allowing performers to work anaerobically for longer.longer.

LO3 = Warm up & the CV systemLO3 = Warm up & the CV system

Write down what happens to your body during a Write down what happens to your body during a warm up (doesn’t have to be linked with the warm up (doesn’t have to be linked with the

CV system)CV system)

What have you got?What have you got?

Has anybody got any that are linked to the CV?Has anybody got any that are linked to the CV?

LO3 = Warm up & the CV systemLO3 = Warm up & the CV systemIncreases blood flow/Q due to the Increases blood flow/Q due to the

vascular shunt mechanism via:vascular shunt mechanism via:

Vasoconstriction of arterioles/pre-Vasoconstriction of arterioles/pre-capillary sphincters to organscapillary sphincters to organs

Vasodilation of muscle Vasodilation of muscle arterioles/precapillary sphinctersarterioles/precapillary sphincters

BETH......DESCRIBE VASCULAR SHUNTING PLEASEBETH......DESCRIBE VASCULAR SHUNTING PLEASE

LO3 = Warm up & the CV systemLO3 = Warm up & the CV systemIncreased body/muscle temperature which:Increased body/muscle temperature which: increases transport of the enzymes required for increases transport of the enzymes required for

energy systems and muscle contractionenergy systems and muscle contraction decreases blood viscosity, improving blood flow to decreases blood viscosity, improving blood flow to

working musclesworking muscles increases the dissociation of oxygen from increases the dissociation of oxygen from

haemoglobin in muscle tissueshaemoglobin in muscle tissues Decreased OBLA (onset of blood lactate Decreased OBLA (onset of blood lactate

accumulation) due to the early onset of anaerobic accumulation) due to the early onset of anaerobic work when a warm-up is not carried out.work when a warm-up is not carried out.