The impact of physical activity on cardiac conduction system

What happens to the body during exercise

more O2 required by working muscles, heart works harder +> more blood pumped around the body and faster

What is stroke volume

• = volume of blood pumped out by heart ventricles in each contraction

• average = 70ml

What happens to stroke volume (SV) during exercise

• Increases with exercise up to 40-60% of max effort, then will plateau

• Due to shorter diastolic phase (lack of filling time)

What is venous return

 the volume of blood returning to the heart via veins

• Up to 70% of vol. blood = contained in veins at rest

• During ex. The amount of blood returning to heart increases

What is the relationship between venous return and stroke volume

• If VR increases then SV increases

Describe starlings law

increased venous return (VR) -> creates a greater diastolic filling of the heart -> meaning that Cardiac muscle gets stretched -> the greater the force of contraction ->the more increased ejection fraction

What is HR

number of beats per minute

avg. = 72 bpm

What is cardiac output

 the vol. of blood ejected by the heart ventricles per minute

how do you calculate cardiac output (Q)

 Stroke volume (SV) x Heart rate (HR)

• as HR and SV increases so does cardiac output

What happens to HR range in response to exercise

• HR increases with exercise dependent on the intensity of the exercise

• Increases in direct proportion to exercise intensity

• Regular aerobic training = more cardiac muscle => stronger => cardiac hypertrophy

What is cardiac hypertrophy and what are the benefits of cardiac hypertrophy

thickening of muscular wall of the heart

• Means more blood can be pumped around the body in a single beat =. Results in a decreasing resting heart rate = BRADYCAARDIA (rate below 60 bpm)

 

What happens to cardiac output in response to exercise

• Cardiac output increases to maximum (threshold) and then plateaus

• Maximum cardiac output changes during exercise = benefits : more blood with oxygen to working muscles, efficient waste removal

What happens to the distribution of blood during exercise

• During exercise distribution of blood flow changes => more blood to muscles which are working

• Less blood passes through organs such and intestines, blood flow stays the same for the heart and kidneys

 

What happens to stroke volume during exercise

• SV increases as intensity of exercise increases

• Plateaus as it reaches threshold for individual this is because the ventricles don't have as much time to fill up with blood => can't pump as much out

 

What is the leading cause of death in the UK

Coronary heart disease

Cardio vascular disease

What is atherosclerosis

Occurs when coronary arteries become blocked and start to narrow due to fatty deposits 

caused by:

• high blood pressure

• lack of exercise

• smoking

• angina = pain and discomfort

Prevented by:

• regular exercise = aids flexibility of the blood vessels

What is blood pressure

It is the force exerted by the blood against the blood vessel wall

What does a high blood pressure do

it puts extra strain on the arteries and heart

if untreated =>  higher risk of Heart attacks, heart failure, kidney disease, strokes and dementia

What does regular aerobic exercise do

•  lowers BP

• Lowers both Systolic and Diastolic pressure by up to 5-10 mmHg => reduces risk of a heart attack by up to 20%

What are the 2 types of cholesterol

1. LDL (low density lipoproteins)

2. HDL (high density lipoproteins)

What is the function of LDL (low density lipoproteins)

 transport cholesterol in the blood to the tissues and = bad as linked to an increase risk of CHD (coronary heart disease)

What is the function of HDL (high density lipoproteins)

 transport excess cholesterol inn blood back to liver => broken down = good cholesterol as lower risk of developing heart disease

How does exercise help with cholesterol levels

• Regular exercise lowers LDL and increases HDL levels

What is cardio-vascular drift

• Steady inc. = cardiovascular drift

• Characterised by progressive decrease in SV and aBP (arterial blood pressure), together with a progressive rise in HR

• Occurs during prolonged exercise after 10 mins -> in warm environment despite intensity of the exercise remaining the same

Why does cardio-vascular drift occur during exercise

• When we Sweat = portion of fluid = lost from plasma volume

• This Decrease in volume. = reduce of venous return and SV

• HR inc. To compensate and maintain higher Q to make energy to cool body down

RESPONSE => maintaining high fluid intake before and during exercise = minimise drift

 

Blood vessels carry

blood containing…

• nutrients

• O2

they work with the heart and lungs to ensure muscles have enough O2 during exercise

What are the 2 types of circulation

PULMONARY

• Deoxygenated blood from heart to lungs

• Oxygenated blood back to heart

SYSTEMIC

• Oxygenated blood to the body from the heart

• Return of de-oxygenated blood from the body to heart

 

describe the pathway of blood vessels

1. Heart

2. Arteries

3. Arterioles

4. Capillaries

5. Venules

6. Veins

7. Heart

 

What are the characteristics of Veins

Thinner muscle/elastic tissue layer

Blood at low pressure

Valves

Large lumen

What are the characteristics of arteries

Thicker muscle/elastic tissue layer

Blood at high pressure

Smooth inner layer

Small lumen

what are the characteristics of capillaries

One cell thick

Only allow one red blood cell at a time

Slow blood flow to allow for nutrient exchange

What is blood pressure

the force which is exerted by the blood against the blood vessel wall

What are the venous return mechanisms

1. the muscle skeletal pump

2. the respiratory pump

3. pocket valves

describe the role of the skeletal muscle pump

• when Muscles contract/relax

=> change shape => pressing on veins = pumping effect

During exercise

• the skeletal muscle pump works harder because muscle contractions are more frequent and powerful.

• This squeezes veins and pushes more blood back to the heart, increasing venous return and helping maintain high cardiac output and oxygen delivery.

describe the role of the respiratory pump

• when Muscles contract/relax during breathing

=> changes thoracic + abdominal cavities => compressing veins

describe the role of pocket valves

Prevent backflow of blood

=> closing once blood has passed through

how does gravity aid venous return

 helps blood return to the heart from upper body

Suction pump action of heart draws blood back towards it

what it the role of venous return during exercise

• Ensure skeletal muscles receive enough O2

• During rest the valves and smooth muscle in veins are suff. To maintain VR

• During ex. Need to support skeletal muscle and respiratory pumps

• Performing an active cool down = maintain to prevent blood pooling

 

What are the effects that BP has on VR

• When sBP (systolic blood pressure) increases VR increases

• When sBP (systolic blood pressure) decreases the VR decreases

• Venous pressure (Pv) - right atrial pressure (PRA) / venous vascular resistance (Rv)

• Increases Pv or decrease in Pra or Rv leads to increase VR

• Increase in PRA decreases VR

What is venous return determined by

• VR is determined by a pressure gradient, which is the mean systemic pressure minus the right atrial pressure and resistance is the total peripheral vascular resistance

During exercise what happens to O2

• 3% dissolves into plasma in blood

• 97% combines with haemoglobin => making oxyhaemoglobin

Describe the transportation of O2

1. O2 combines with haemoglobin in RBC’s making => oxyhemoglobin

2. Fully saturated haemoglobin carries 4 oxygen molecules

=> occurs when the partial pressure of oxygen (concentration) in the blood is high i.e. alveolar capillaries

3. Oxygen released into the tissues due to the lower partial pressure of oxygen

4. Oxyhaemoglobin dissociation =>  O2 binds with haemoglobin = oxyhemoglobin => travels to tissues and unbinds = oxygen and haemoglobin

5. Stored in muscles by myoglobin => higher affinity for oxygen (binds more easily)

6. Store oxygen for the mitochondria (centre for aerobic respiration)

What does the oxyhaemoglobin dissociation curve help us to understand

• Helps us to understand how O2 is transported and released by haemoglobin

• Lungs: partial pressure of O2 = high --> haemoglobin fully saturated

• Tissues: partial pressure of O2 is low --> haemoglobin lower saturation 23%

What is the Bohr shift

additional O2 releases from haemoglobin at lower PH (higher CO2 conc.)

• In tissues there is a low partial pressure of O2 + a higher partial pressure of CO2 => Haemoglobin unloads at this point

Meaning that O2 is available to the tissues

• During exercise => curve shifts to the right => muscles require more O2

• Dissociation of O2  from haemoglobin in the blood capillaries to shift the right known as the Bohr shift

What 3 factors are responsible for the increase in Bohr shift

• increased blood temperature

• Partial pressure of CO2 increase

• pH levels

What happens during increased blood temperature

when blood and muscle temp inc. during exercise O2 will dissociate from haemoglobin more readily

What happens when the partial pressure of CO2 increases

 level of blood CO2 rises during exercise => O2 will dissociate faster from haemoglobin

What happens when pH increases

•  more CO2 will lower pH in blood

• A drop in blood pH will cause O2 to dissociate from haemoglobin faster (Bohr shift)

Describe the redistribution of blood during exercise

During exercise, the skeletal muscles require more O2 => more blood needs to be redirected to them in order to meet the increase O2 demand

• Redirection of blood flow to the working muscles mean that sports performers should ensure they don't eat less than an hour before competition

• Full stomach = more blood being directed to stomach instead of working muscles => effects amount of O2 going to performers muscles

• Blood flow to the brain must remain constant to ensure brain function in maintained as the brain needs O2 for energy

• In addition more blood needs to go to the heart as the heart needs oxygen for energy to beat faster and more blood goes to the skin as energy in needed to cool the body down

What is the vascular shunt

Redirecting of blood flow to areas where it is most needed

What is vasodilation

 widening of blood vessels to increase the flow of blood into capillaries

What is vasoconstriction

 narrowing of blood vessels to reduce blood flow into capillaries

The vascular centre of the brain located in the medulla oblongata controls…..

Blood pressure and blood flow around the body

What happens to blood flow during exercise

• During exercise chemical changes such as inc. CO2 and lactic acid = detected in chemoreceptors

• Receptors stimulate the vasomotor centre which will redistribute blood flow through vasodilation and vasoconstriction 

• During exercise more O2 = needed at working muscles => vasodilation will occur in arterioles supplying the muscles => increases blood flow and brings in muscles needing O2

• Vasoconstriction occurs in arterioles supplying non-essential organs such as intestines and liver

Why do we need blood redistribution

• Inc the supply if O2 to the working muscles

• Remove waste products from the muscles such as CO2 and lactic acid

• Ensure more blood goes to the skin during exercise to regulate body temp. + get rid of heat through radiation, evaporation and sweating

• Direct more blood to the heart as it is a muscle which requires extra O2 during exercise

• Atrio-venous (AV) difference = difference between O2 content of the arterial blood arriving at the muscles and the venous blood leaving the muscles

What is A-VO2 difference

= the difference between the o2 content of the arterial blood arriving at the muscles and the venous blood leaving the muscles