1.1 The Cardiovascular System

Heart

1. Deliver o2

2. Gather waste products

3. Transport heat

4. Atria - thin muscular walls

5. Ventricles - thick walls

6. Left - oxygenated

7. Right - deoxygenated

Blood vessels of the heart

1. Vena cava - brings deoxygented blood back to the right atrium

2. Pulmonary artery - leaves right ventricle with deoxygenated blood to lungs

3. Aorta - o2 to body

Cardiac Conduction System

Group of specialised cells located in the wall of the heart.

Cardiac Conduction Pathway

1. .The hearts myogenic beats send impulses to SAN

2. 2.The impulse spreads like a way through heart 3.

3. The impulses from SAN spread through atria walls. 4.

4. This causes atrium to contract, forcing blood into ventricles 5.

5. The impulses then passes through atrioventricular node (AVN) 6.

6. AVN delays transmission 7.

7. Allows atria to fully contracts before ventricular systole

8. 8.The impulse passes through Bundle of his

9. 9.Impulse then arrives at purkinje fibres

10. 10.Ventricular systole

CCC Pathway

1. San

2. Atrial walls

3. Avn

4. Bundles of his

5. Purkinje fibres

6. Ventricular systole

Factors affecting the change in rate of the conduction system

neural control mechanism

Role of AVN

1. Receive impulse from SAN

2. Delay transmission of impulse'

3. Allow atria wall to fully contract

4. Send impulse to Bundle of His

Myogenic

Heart generates its own impulses

Diastole

Relax (filling of chambers)

Systole

Contract (emptying of chambers)

Neural control mechanism

1. Sympathetic nervous system

2. Parasympathetic nervous system

3. 2 systems coordinated by CCC located in the medulla oblongata

4. Send impulse to SAN

Sympathetic Nervous System

stimulates hearts to beat faster

Parasympathetic Nervous System

returns heart to resting level

Nervous System Pathway

1.Receptors detect change

2.Send impulses to cardiac control centre in medulla oblongata

3.Send impulse to SAN to increase/decrease (sympathetic/para)

4.Atrial systole

5.AVN

6.Bundle of his

7.Purkinje fibres

8.Ventricular systole

Chemoreceptors

Detect increase in carbon dioxide/ acidity levels causing heart rate to increase

Baroreceptors

Detect decrease in blood pressure causing heart rate to increase

Proprioreceptors

Detect increase in movements causing heart rate to increase

Hormonal control mechanism

1. Release Adrenaline

Adrenalin

Stress hormone released by sympathetic nervous system and cardiac nerve during exercise, causing increase in heart rate.

1. Prior to exercise - anticipatory rise

2. Send to SA node

3. Increase CO

4. More blood to working muscles

Stroke Volume

Volume of blood pumped out of the heart ventricles in each contraction

What is stroke volume dependent on?

1.Venous return - increases, SV increases

2.Elasticity of cardiac fibres - the more stretched, greater ejection fraction

Stroke volume in response to exercise

1. Increases with intensity

2. Only up to 40-60% max effort (plateaus)

3. Increase HR near max effort results in shorter diastolic phase

4. Ventricles don’t have time to fill with blood - can’t pump as much out

Heart rate

number of times the heart beats per minute (72)

1. Trained perfromer has a greater HR range - resting HR is lower and max higher

Cardiac hypertrophy

thickening of muscular wall of heart so it becomes bigger and stronger

Bradycardia

decrease resting heart rate below 60 per min

Cardiac output

Volume of blood pumped out of the heart ventricles per minute'

1. HR X SV = CO

Cardiac Output in response to exercise

1. Increase as intensity increases until plateaus

2. Increase max CO - transport more blood to working muscles + o2

3. Less blood to organs

Venous return

Volume of blood returning to the heart via veins

Starling's law

1.Increased venous return

2.Greater diastolic filling

3.This causes cardiac muscles to stretch and strengthen

4.This leads to greater force of contraction

5.Increase ejection fraction

Elasticity of cardiac fibres

how much the cardiac tissues stretch during diastole

Ejection fraction

the percentage of blood pumped out the left ventricle per beat

Heart Disease

1. CHD

2. Cause (Atherosclerosis) - coronary arteries become blocked/narrow by gradual build up of fatty deposits (caused by: high blood pressure, high cholesterol, lack of exercise, smoking)

3. Atheroma = fatty deposits in inner lining of artery

4. Angina = chest pains that occur when blood supply through coronary arteries to heart muscles restricted - blood clot

5. Exercise keep heart healthy - pump more blood, bigger + stronger, increase SV, flexible blood vessels, blood flow

High blood pressure

Force exerted by blood against the blood vessel wall

1. Extra strain on arteries

2. Increase: heart failure/attack, stroke

3. Aerobic exercise - reduce

4. Lower systolic + diastolic pressure

Cholesterol

HDL - transport excess in blood back to liver where it’s broken down (lower heart disease)

LDL - transport cholesterol in blood to tissues (increase heart disease)

Stroke

Blood supply to brain cut off

1. Brain needs constant supply of o2 - maintain function (energy)

2. Brain cells die

3. Injury, death, disability'

4. Ischaemic - blood clot stops blood

5. Haemorrhagic - weakened blood vessel bursts

Skeletal muscle pump

1.Change in shape of muscles when they contract/relax

2.Presses on veins causing a pumping effect

3.Squeezes blood to heart

AO2 - Increased use of muscles during specific body parts in sport which presses veins pushing blood back to heart

AO3 - Avoid fatigue + lactic acid build up

AO3 - Starling’s law + venous return

Respiratory pump

1.During breathing, muscles relax and contract

2.Pressure changes occur in thoracic + abdominal cavities

3.Pressure changes compress veins + assist blood return to heart

AO2 - Increased breathing rate during exercise causes increased effect of respiratory pump returning more blood to heart

AO3 - More CO2 exchanged for O2

Pocket valves

Prevent back flow by forcing blood in one direction back to heart

Smooth muscle

found in veins and contacts to push blood back to heart

AO2 - suction pump of the heart increase as heart beats harder/faster during exercise

AO3 - more blood to working muscles supplying O2 for resynthesis of ATP

Gravity

Causes blood in upper body to return back to heart

Venous return relationship with blood pressure

1, Increase - increases systolic pressure

Decrease - decreases systolic pressure

Transportation of o2 during exercise

Haemoglobin - found in red blood cells'

1. Combines o2 = oxyhaemoglobin

2. PP lungs high = full saturation OH

3. PP muscles low - offloads o2 to oxides glycogen + fats

Myoglobin - muscle haemoglobin

1. higher affinity for o2 then haemo

2. addition o2 store in muscles

3. Released to working muscles - extend aerobic respiration

Oxyhaemo diss curve - relationship between blood transport + release of o2

Bohr shift - ODC shifts to right

1. lower pH due to increase CO2

2. Product of aerobic respiration

3. Increased dissociation of o2 to muscles

4. Greater quantity of o2 to mitochondria

Mitochondria - cell respiration

1. higher aerobic intensity

Myoglobin

oxygen stored in muscles (high affinity for oxygen)

Affinity

How easily a substance combines with another

Haemoglobin role during exercise

1.Transport oxygen in blood to muscles

2.Less saturation of haemoglobin during exercise

3.Increase in oxygen release

4.Muscle receive more oxygen

Myoglobin role during exercise

1.Stores oxygen in muscles

2.Has higher affinity for oxygen

3.Oxygen dissociates from myoglobin at lower P02

Bohr Shift

movement of the s-shaped oxygen dissociation curve shifts to the right

Bohr Shift Explained

1.Oxygen becomes more easily dissociated from haemoglobin in blood capillaries to the muscles.

2.Reduction of affinity of haemoglobin for oxygen

3.Muscles require more oxygen in exercise - leads to dissociation of oxygen from haemoglobin

Factors responsible for Bohr shift

1.Increase In Blood Temperature - when blood is in muscles, temp increases causing oxygen to dissociate from haemoglobin more readily

2. Increase in Partial Pressure Of C02 - C02 levels rising during exercise leads to oxygen dissociating quicker

3.Decrease in pH - more C02 will lower pH in blood, causing oxygen to dissociate quicker

Redistribution Of Blood

During exercise , skeletal muscles require more oxygen so more blood needs to be redirected to them as they require more oxygen

What control blood flow?

Vasomotor centre which control vasodilation and vasoconstriction

Blood flow and brain

Blood flow to the brain must remain constant to ensure brain function is maintained as the brain needs oxygen for energy.

Vasoconstriction

Narrowing of blood vessel diameter to decrease blood flow to capillaries

Vasodilation

Widening of blood vessel diameter to increase blood flow to capillaries

Redistribution Of Blood During Exercise

1.Vasodilation - more oxygen is needed at working muscles so vasodilation will occur in the arterioles supplying the muscles, increasing blood flow and bringing in oxygen that's needed.

2.Vasoconstriction - occurs in arterioles supplying non-essential organs (eg liver + intestines)

What happens when sympathetic stimulation increases?

1.Vasoconstriction occurs

2.Blood flow reduces

3.This means blood can be redistributed to muscles in exercise

What happens when sympathetic stimulation decreases?

1.Vasodilation occurs

2.Increases blood flow to that body part

Pre-capillary sphincters

1.Tiny rings located at opening of capillaries

2.Contract - restrict blood flow

3,Relax - increased blood flow

4.During exercise - relax to supply skeletal muscles

Why Is redistribution of blood important?

1.Increase supply of oxygen to working muscles

2.Remove waste products

3.Increase blood to skin - regulate body temp + remove heat (sweat)

4.Direct more blood flow to heart

Aterio-venous difference (A-V02 Diff)

The difference in volume of oxygen between arteries and veins

A-V02 Diff at rest

Low - little oxygen required at muscles

A-V02 Diff at exercise

High - lots of oxygen required at muscles

Increase of A-VO2 Effects

1.This increase will affect gaseous exchange at alveoli - more oxygen is taken in and more carbon dioxide is removed.

2.Training increases A-VO2 diff - trained performers can extract more oxygen from blood

A-VO2 Diff at start of exercise

1.Increase in difference

2.More oxygen is extracted by working muscles + stored in myoglobin

3.Venous blood therefore has less oxygen returning to heart

How training increases max A-VO2 Diff and how body systems adapt to allow this

1. Increased o2 content in arterial blood due to more haemoglobin carrying capacity

2. Increased gas exchange at muscle due to more myoglobin which has a greater affinity for o2 than haemoglobin so can store more o2 in muscle

3. Increased gas exchange at muscle due to more efficient mitochondria allowing for more o2 to be used in muscle so less return in venous blood

Cardiovascular drift

Increase in heart rate in order to try and maintain cardiac output due to decrease in stroke volume (cardiac output increases during prolonged exercise to cool body)

When does cardiovascular drift occur

1. After 10 minutes

2. Warm environment

3. Steady state exercise

What causes cardiovascular drift

1. Caused by reduction of fluid in blood plasma due to an increase in sweating - makes blood more viscous

2. 2.This means venous return increases - reduces atrial filling and SV

3. Vasodilation occurs at skin to cool it down

Anticipatory rise

increase in heart rate before exercise due to adrenalin

Bradycardia

decrease in resting heart rate

How does increased CO2 increase Breathing Rate

1. Increased blood acidity

2. Detected by chemorecpetors

3. Impulse sent to respiratory centre

4. Increased impulses to respiratory muscles to contract faster