Carbon Dioxide in blood Carbon dioxide is transported

Carbon Dioxide in blood… Carbon- dioxide is transported around the body in the following ways: � 5% dissolves in plasma � 20% combines with haemoglobin � 75% is transported in the blood as hydrogen carbonate (bicarbonate) ions - The CO 2 produced by the muscles as a waste product diffuses into the blood stream where it combines with water to form carbonate acid. This is a weak acid that dissociates into hydrogen carbonate ions.

Transport of oxygen in the blood… Oxygen plays a major role in energy production. Reduction- detrimental impact on performance. � Oxygen enters the red blood cells and combines with haemoglobin to form oxyhaemoglobin. � However, this depends on the amount of oxygen present. � When there is plenty of oxygen available all haemoglobin carries oxygen- haemoglobin is fully saturated. � When oxygen supplies are limited oxyhaemoglobin splits and releases oxygen into the muscles.

FORMING OXYHAEMOGLOBIN. . . During exercise Oxygenated blood to muscles In lungs – lots of oxygen – Haemoglobin becomes fully saturated with O 2 In working muscles – higher temperature and more CO 2 – more oxygen leaves the haemoglobin (dissociates) 3

What happens during exercise? The temperature of our muscles increase. As a result more CO 2 is produced. Both these increase the amount of O 2 in the muscles.

Oxyhaemoglobin Dissociation Curve…

The bohr shift… � Typically, the PO 2 in our arteries is 90100 mm. HG- blood leaving the lungs is about 97 - 98% saturated with haemoglobin. � When this blood reaches the tissues, the PO 2 falls to about 40 mm. HG, a point where haemoglobin is about 75% saturated. � As a result a large proportion of the oxygen being carried by the blood is released into the tissues.

THE BOHR SHIFT… What happens during exercise? � This release of oxygen occurs in greater amounts in exercise muscles, where the PO 2 may drop to well below 40 mm. HG, so nearly all the oxygen is released from the haemoglobin. � The amount of oxygen released is also affected by acidity levels. � In acid conditions (because of more CO 2 and lactic acid- during exercise) oxygen splits more readily from haemoglobin. * This effect is seen as a shift of the dissociation curve to the right, know as the BOHR SHIFT. *

Exam Question Describe how oxygen is transported to the working muscles and the effect that strenuous exercise will have on its delivery. Explain why strenuous exercise has this effect. (4 marks) EXAM ANSWER Simplistic circulation – heart – arteries – muscles; Oxygen as oxyhaemoglobin; Exercise increases temperature; More CO 2 in blood/increased acidity; Both increases release of oxygen from haemoglobin at muscles; Bohr shift; (4 marks)

Extraction of oxygen… Lots of oxygen- rich blood is delivered to our muscles. � Consequently, there is a difference between the oxygen content of the artery approaching the muscle and the vein leaving the muscle (a- VO 2 difference) � During exercise the a- VO 2 increases. �

A- VO 2 DIFFERENCE Artery carrying O 2 to muscle Vein carrying O 2 away from muscle Difference in oxygen concentrations between artery and vein = a-v. O 2 diff. 10

Oxygen into muscles… In the muscle, oxygen is stored by myoglobin. � *Myoglobin is a protein that stores oxygen in the muscle* � This has a high affinity for oxygen and stores the oxygen until it can be transported from the capillaries to the mitochondria. � *The mitochondria are the sites in the muscle where aerobic respiration takes place (power stations of the cells* � Energy is produced in the form of ATP. � *ATP is a molecule of energy* �

BLOOD VESSELS ARTERIES: CAPILLARIES: VEINS: Thick elastic walls Thin walls � Tiny, very thin Small lumen Take blood back walls Take blood away to the heart � Diffusion of O 2 from the heart High pressure and CO 2

BLOOD PRESSURE & VELOCITY TASK: Read the paragraph and answer the questions. • When the heart contracts it creates pressure in the blood vessels and pushes blood through the arteries. • This pressure and velocity depends on the blood vessels. ARTERIES CAPILLARIES VEINS High pressure and velocity. Low pressure and slow velocity. Low pressure but higher velocity.

BLOOD PRESSURE & VELOCITY Blood pressure Blood velocity Crosssectional area Arteries arterioles capillaries venules veins Velocity falls then rises increasing & decreasing crosssectional area Pressure falls friction & increasing crosssectional area 14

TASK: Complete the missing words using the word bank. Valves in the veins prevent the backflow of blood and ensures that blood only flows towards the heart. There is a contraction of the skeletal muscles to force the blood back through to the heart. The suction pressure of the heart helps the blood to flow back to the heart.

ACTION OF THE VALVES. . . 16

MUSCLE PUMP. . . 17

Exam Question (i) Arteries, capillaries and veins form part of the circulatory system. Explain the main features of capillaries in relation to their function. (3 marks) (ii) Blood supply is maintained by the venous return mechanisms. Explain how these mechanisms ensure the return of blood to the heart. (3 marks) EXAM ANSWER (i)One cell thick / think walls; Large surface area for the diffusion of gases; Narrow diameter single blood cell / short diffusion pathway; 3 marks (ii)Veins have one-way pocket valves; Muscle contractions (muscle pump) compress veins and push blood towards the heart; Breathing movements / respiratory pump alters pressure in thorax and assist flow back to the heart; Sympathetic nerves cause venous tone / veins contract to aid return of blood during exercise; Suction pump of the heart; 3 marks

Vasodilation and Vasoconstriction • During exercise our blood flow needs to be redistributed to accommodate for this. Vasodilation • During exercise we need more oxygen to go to our working muscles and the carbon dioxide needs to be removed. • Vasodilation means that our blood vessels dilate and get bigger to allow this process to occur. • This process happens around the muscles that our needed during exercise. • For example, during a football match this would occur to those blood vessels surrounding the quadriceps, hamstrings, and gastrocnemius. • This is controlled by the sympathetic nerve impulse. S from the brain. Vasoconstriction • This is the process of the blood vessels getting smaller to restrict the blood flow to certain muscles, to accommodate for the process of vasodilation. • This would happen in the blood vessels that surround those muscles that aren’t required during exercise such as the gut muscles.

LESSON OBJECTIVE • To understand the structure and function of the cardiovascular system. LESSSON OUTCOME • To be able to explain the structure and function of the cardiovascular system. 20

• The heart is a two sided pump. • The right side pumps blood to the lungs to collect oxygen. • The left side is slightly bigger and pumps blood to our muscles to deliver oxygen. • The right and left halves are separated by the septum. • The pumping parts (the bottom parts of the heart) are called the ventricles. • The blood collects in the atria.

The Cardiovascular System The four chambers of the heart have special names: An upper chamber is called an atrium (plural: atria). right atrium right ventricle left atrium left ventricle A lower chamber is called a ventricle.

The Cardiovascular System Deoxygenated blood is pumped from the heart to the lungs through the pulmonary artery. Deoxygenated blood returns to the heart through the vena cava. lungs body’s cells Oxygenated blood returns to the heart through the pulmonary vein. Oxygenated blood is pumped at high pressure from the heart to the body through the aorta.

The Cardiovascular System The pulmonary circulation carries: deoxygenated blood from the heart to the lungs oxygenated blood back from the lungs to the heart, ready to be pumped out to the body. The systemic circulation carries: oxygenated blood to the rest of the body through the arteries deoxygenated blood back to the heart through the veins. body’s cells

Right atria Left ventricle Right ventricle Septum 25

The valves in our heart stop the backflow of blood. The blood flows from the atria to the ventricles through the artio- ventricular valves (A- V valves). The blood flows from the ventricle to the arteries through the semi- lunar valves (S- L valves). vein valve open blood to the heart The valves allow blood to flow in the correct direction… backflow prevented vein valve closed …but close if blood starts to flow in the wrong direction.

Right S-L valve Right atria Left atria Right A-V valve Left ventricle Left A-V valve Right ventricle Septum 2 7

THE ARTIA. . • • The artia collects the blood. The left atria receives blood from the lungs through the pulmonary veins. The right atria receives blood from the body from the vena cava. There is an upper (superior) vena cava and a lower (inferior) vena cava.

Superior vena cava Right S-L valve Pulmonary veins Right atria Left atria Right A-V valve Left ventricle Left A-V valve Right ventricle Inferior vena cava Septum 2 9

THE VENTRICLES. . . • • • The ventricles pump the blood around the body. The left ventricle pumps blood to the body through the aorta. The right ventricle pumps blood to the lungs through the pulmonary artery. 30

Superior vena cava Aorta Pulmonary artery Right S-L valve Pulmonary veins Right atria Left atria Right A-V valve Left ventricle Left A-V valve Right ventricle Inferior vena cava Septum 31

THE HEART. . . TASK. . • Complete the paragraph on how the blood flows through the heart, using the word bank.

HEART BEAT • The chambers of the heart can contract and relax. • The period of contraction is called systole. • The period of relaxation is called diastole. • The atria and ventricles contract at different times and this is what makes the cardiac cycle.

HEART BEAT 1. Impulse for contraction is generated by a small mass of specialised cardiac muscle – sino- atrial node (SAN) 2. Artia contracts 3. Can’t get through to the ventricles 4. Atrio- ventricular node 5. Artria fully contracts 6. Septum 7. Bundle of His 8. Purkinje fibres 9. Ventricular wall 10. Ventricles contract

CONTROL OF HEART RATE. . . Spreads through atria first - systole Sino-atrial node Sets heart rate intrinsic Picked up by AVN Then down septum Then from tip of ventricle systole 35

SAN sets heart rate Impulses spread through atria Impulses picked up by AVN Valves act as barrier Down ventricle via bundle of His Ventricles contract via Purkinje fibres 36

EXAM QUESTION. . . EXAM QUESTION Describe how the sinoatrial node (SAN) and the atrioventricular node (AVN) control the increase in heart rate during exercise. (6 marks) ANSWER SAN initiates heart beat/sends impulses; intrinsic/myogenic/pacemaker; spread of impulses through atria; atria contracts/systole; role of valves as non-conducting material; impulse reaches AVN; initiation of impulse down interventricular septum/reduced delay of spread of impulses; Bundle of His; Purkinje fibres conducting impulses; ventricular systole/contraction; period of diastole/relaxation for filling; release of (nor) adrenaline from SAN (6 marks)

HEART RATE RANGE. . . During exercise our heart rate increases, as our body needs more energy for muscle contracts, so there is a higher demand for oxygen and when we finish exercising it needs to return to our resting heart rate. Our nerves act as a brake and an accelerator. Vagus nerve Slows the heart rate down Sympathetic nerve Speeds the heart rate up

Cause of change in heart rate… During exercise, more CO₂ is produced. This increases the acidity of our blood and lowers the PH. This is detected by the chemoreceptors, which sends a message to the medulla. This leads to changes in the heart rate via the vagus and sympathetic nerves.

INCREASE IN HEART RATE Exercise - blood CO 2 levels rise Medulla Detected by chemoreceptors Decreased vagus impulses to SAN - lets heart beat faster Increased sympathetic impulses to SAN - lets heart beat even faster

REDUCTION IN HEART RATE Medulla Stop exercise – CO₂ levels drop Detected by baroreceptors Increased vagus impulses to SAN - lets heart beat slower Decreased sympathetic impulses to SAN - allows heart rate to slow

HEART RATE VALUES TASK. . . • Use the internet to help you find the correct definitions of the key words. Stroke volume The volume of blood pumped out of one ventricle per beat Heart rate The number of times the heart contracts per minute Cardiac output The volume of blood pumped out of one ventricle per minute Cardiac output = Stroke volume x Heart rate 42

Effects of exercise on the cardiovascular & respiratory systems TASK. . . • Use the internet to find any short term and long term effects of exercise on the cardiovascular system. Short Term Effects Long Term Effects • Heart rate increases; faster contractions of the heart to make the blood flow around the body quicker. • Stroke volume increases; stronger contraction of the heart, increasing the volume of blood being pumped around the body. • Cardiac output increases; more blood is delivered to the working muscles. • Heart gets bigger and walls of the heart get thicker (hypertrophy). • Decrease in resting heart rate (bradycardia). • Increase in resting stroke volume. • Resting cardiac output stays the same. • Increased volume of blood, leading to a more efficient delivery of oxygen, which improves stamina. • Bigger capillary network. • High a- v. O₂ difference. • More efficient gas exchange.

EXAM QUESTION. . . EXAM QUESTION (i) Explain the terms cardiac output and stroke volume and the relationship between them. (3 marks) (ii) What are the effects of training on resting cardiac output and stroke volume? (2 marks) ANSWER (i)Cardiac output is the amount of blood leaving the heart/left ventricle per minute; Stroke Volume is the amount of blood leaving the heart/left ventricle per beat; Cardiac output = Stroke Volume x Heart rate/ Q = SV x HR/Pulse rate equiv. (3 marks) (ii)Cardiac output does not change; Stroke volume increases/equiv. (2 marks)

• The more blood that enters the blood during diastole, then the walls of the ventricle will stretch and contract with more force. • As a result of an increased blood flow to the heart there is a increased venous return because more blood is flowing around the body. • As a result of this higher workload the cardiac muscle contracts with greater force, giving a greater ejection of blood. • This occurs to make up for the shorter period of diastole, meaning that there is less time for the heart to fill with blood. THE GREATER THE VENOUS RETURN, THE GREATER THE STRENGTH OF CONTRACTION.

WHAT DOES THE GRAPH REPRESENT? 46

• During a steady state of exercise (60 minutes) the heart rate increases. • However, the cardiac starts to plateau and as a result the stroke volume needs to decrease. • This is thought to be caused by a reduction in fluid in the blood (due to sweating and loss of fluids because of the heat generated by muscle contraction), which in turn decreases the venous return and thus the stroke volume (Starling’s Law).

EXAM QUESTION (i) Explain why a performer’s stroke volume decreases during a run of constant pace and workload. (4 marks) (iii) Explain how it is possible for a trained an untrained individual to have the same cardiac output for a given workload. (2 marks) ANSWER (i) During exercise - loss of fluid at sweat; Hence reduced blood/plasma volume; Reduced venous return; Stroke volume decreases; Starling’s Law of the heart; Heart rate increases/beats more Maintain cardiac ‘Cardiovascular Drift’. (4 marks) (ii) Same physique/size/frame/weight; Untrained high heart rate and low stroke volume; Trained low heart rate large stroke volume; Can only occur at sub maximal workloads; At higher workloads untrained will not be able to increase their heart rate sufficiently; (2 marks)

What have you learnt in today’s lesson? LESSSON OUTCOME • To be able to explain Starling’s Law and the cardiovascular drift and apply this knowledge to exam questions. 49