Peak Performance - Heart And Lungs Flashcards
What type of muscle is cardiac muscle?
Myogenic
What does myogenic mean?
It can contract and relax without receiving signals from neurons
Give three factors for why people have different resting heart rates
- Size of heart due to different body sizes
- How much exercise someone does
Genetic factors
What happens when a person exercises their heart over a long period of time?
- The heart muscle walls thicken
- More blood is pumped each time/increased stroke volume
- Resting heart rate is lower
How does a heart beat?
- The SAN, located on the right atrium wall, generates an electrical impulse
- This spreads across the left and right atria, causing them to contract at the same time
- A band of collagen tissue prevents the impulse being passed directly from the atria to the ventricles
- The impulse also travels to the AVN which conducts the impulse to the bundle of His
- During this there is a delay of about 0.13 seconds
- The bundle of His splits into right and left Purkyre fibres
- These Purkyre fibres carry the impulse to the apex of the ventricles
- The fibres divide into even smaller branches that penetrate the ventricular muscle
- Ventricular muscle cells at the apex of the heart are depolarised, causing contraction
- The impulse travels up the ventricles in a wave of contraction, pushing blood into the aorta and the pulmonary artery
What does SAN stand for?
Sinoatrial node
What is the sinoatrial node also known as?
The pacemaker
Why is there a delay of about 0.13 seconds when an impulse is travelling from the AVN to the ventricles?
- To ensure that the atria have finished contracting
- To ensure that the ventricles have filled with blood before they contract
What does AVN stand for?
Atrioventricular node
How is electrical activity measured?
On an electrocardiogram (ECG)
How does an ECG work?
- Electrodes are attached to a person’s chest
- There is a change of polarisation of cardiac muscle when they contract
- This causes a small electricalcurrent on the skin’s surface
- This is what is measured
When might an ECG be performed?
- When the patient is at rest, lying down
- In a stress test when an ECG is done before and after a period of exercise
What four things does an ECG trace show?
- P wave - depolarisation of the atria
- PR interval - The time taken for impulses to be conducted from the SAN to the ventricles
- QRS complex - The contraction (depolarisation of the ventricles)
- T wave - Repolarisation of the ventricles during diastole
What does an ECG not show? Why not?
- Artial repolarisation
- Because it generates small signals that are hidden by the QRS complex
What does the P wave show?
Depolarisation of the atria
What does the PR interval show?
The time taken for impulses to be conducted from the SAN to the ventricles
What does the QRS complex show?
- The contraction (depolarisation) of the ventricles
- It is the main peak of the ECG
What does a T wave show?
Repolarisation of the ventricles during diastole
What is the heart problem called when the heart is beating too fast? What might be causing this and what might it lead to?
- Tachycardia
- Heart can’t pump blood efficiently so heart rate increases to increase amount of blood being pumped
- Increases risk of a heart attack
When might someone be described as being tachycardic?
When their heart rate is greater than 100 beats per minute
What might an ECG that shows p waves without any waves in between suggest is wrong with a person?
- Atria are contracting as there are p waves
- No QRS complex which means impulses aren’t travelling from the atria to the ventricles
- This suggests there’s a problem with the AVN
What does fibrillation mean?
Irregular heartbeat
How is fibrillation shown on an ECG?
Irregular waves of various sizes
How long does a large square on an ECG represent?
0.2 seconds
How long does a small square on an ECG present?
0.04 seconds
How many squares make up 1 second on an ECG?
- 5 large squares (0.2 seconds each)
- 25 small squares (0.04 seconds each)
What does the vertical axis on an ECG show?
Electrical activity
What is it called when a resting heart rate is lower than 60 beats per minute?
Bradycardia
What might cause bradycardia?
- Hypothermia
- Heart disease
- Drugs - beta blockers
What might tachycardia be caused by?
- Fear
- Fever
- Exercise
- Drugs
- Heart failure
- Fluid loss
What happens in atrial fibrillation?
- Abnormal electrical impulses start firing from sites in the atria
- The SAN can no longer control the rhythm of the heart
- Atria contracts randomly and too quickly
- Heart muscles can’t relax properly between contractions which reduces their efficiency
Explain how the electrical activity of the heart ensures that the ventricles begin contracting from apex of the heart
- There is a delay at the AVN
- The impulse is then carried across the bundle of His and along the Purkyre fibres to the base
- The impulse travels from the base up through and stimulates contract of cardiac muscle
What controls heart rate? Where is it located?
- Cardiovascular control centre
- In the medulla oblongata region of the brain
What does the cardiovascular control centre detect?
- CO2 levels
- Lactate in the blood
- Reduction in oxygen
- Increase in temperature
How is heart rate increased?
- Mechanical activity in muscles and joints is detected by sensory receptors in muscles
- Impulses are sent to the cardiovascular control centre
- An impulse is sent from the cardiovascular control centre down the sympathetic nerve to the SAN
- SAN increases heart rate by increasing the frequency of impulses it produces
What does the sympathetic nerve do?
Where does it come from and where does it go to?
- Increases heart rate
- From the cardiovascular control centre to the SAN
A runner is about to start a race. Describe what changes occur in their body when they hear the starting pistol
- Skeletal muscles contract
- Stretch receptors in the muscles and tendons are stimulated
- They send impulses to the cardiovascular control centre
- Impulse is sent along sympathetic nerve
- This increases heart rate
- Increased venous return leads to higher stroke volume
- Increased heart rate + greater stroke volume result in a higher cardiac output
- This means oxygen and fuel is transported to muscles faster
What is a negative factor when cardiac output increases? How can it be controlled?
- Blood pressure increases
- Pressure receptors in the aorta and the carotid artery send impulses back to the cardiovascular control centre
- Impulses are then sent from the cardiovascular control centre to the SAN along the vagus nerve
- This decreases the amount of impulses sent by the SAN
- This is an example of negative feedback
What is result of sympathetic stimulation of the intercostal muscles?
Increases breathing rate
What is the effect of parasympathetic stimulation of the heart?
Decreases heart rate and stroke volume
The carotid artery at the side of the neck is sometimes used for measuring heart rate.
Explain why pressing on the carotid artery might reduce pulse rate, thereby giving a false reading
- Pressing on neck causes an increase in blood pressure in the carotid artery
- Blood pressure sensors in the carotid artery signal to the cardiovascular control centre
- This would stimulate the vagus nerve
- This would reduce heart rate and therefore pulse rate
Explain why the heart rate rises before the start of exercise and why this may be an advantage
- Anticipatory rise due to the effect of adrenaline on the heart
- This increases oxygen supply to muscles in preparation of activity
Describe and explain the changes that occur in blood distribution after a person has started to exercise
- Increased blood flow to active skeletal muscles
- Reduced blood flow to non-essential organs such as digestive system
- This means more oxygen and glucose goes to respiring muscle cells
What is one complete heartbeat equal to?
One complete cardiac cycle
What does a cardiac cycle consist of?
- Atrial systole
- Ventricular systole
- Diastole
What is the purpose of valves in the heart?
To prevent the back flow of blood
What does an impulse consist of?
A wave of depolarisation followed by a wave of repolarisation
What happens if parasympathetic stimulation is increased?
- Decreases the impulse frequency of the SAN
- Increases the delay time at the AVN
- This reduces the frequency and the forces of the heart beat
What happens when parasympathetic stimulation is decreased?
-Impulse frequency of the SAN is increased
–Decreases delay time at the AVN
-This then increases the frequency and force of a heart rate
What is the heart rate a balance of?
Sympathetic and parasympathetic stimulation
What is tidal volume?
The volume of air we breathe in and out in each breath
What is vital capacity?
The maximum volume of air we can inhale and exhale
How can tidal volume and vital capacity be measured?
Using a spirometer
How are accurate results ensured when using a spirometer?
A nose-clip is worn
What happens to heart and breathing rate once you start to exercise? Why?
- Heart rate increases to supply more oxygen and glucose to the muscles and to remove CO2 being produced
- Breathing rate increases to increase oxygen uptake and CO2 removal
Explain the effect of adrenaline on the body
- Travels in the bloodstream as it is a hormone
- Directly stimulates the SAN which causes an increase in heart rate
- Causes dilation of the arterioles supplying skeletal muscles
- Causes constriction of the arterioles going to the digestive system and other organs not involved in exercising
- Causes an anticipatory increase in heart rate
What controls breathing rate? Where is it?
- The ventilation centre
- Medulla oblongata (brain)
How does the medulla oblongata control breathing?
- The ventilation centre sends nerve impulses to the external intercostal muscles and diaphragm muscles every 2-3 seconds
- This causes these muscles to contract, increasing the volume of the lungs
- This causes a decrease in pressure inside the lungs
- Air from the outside enters the lungs due to this pressure difference
- As the lungs inflate, stretch receptors in the bronchioles are stimulated
- These send inhibitiory impulses back to the ventilation centre which stops the impulses to the muscles which then relax
- The elastic recoil of the lungs and decreasing volume is why the air is forced out of the lungs
What is the remaining air in the lungs called after exhalation?
Residual air
What happens to the amount of residual air in the lungs during exercise?
-Decreases as more air is forced out
What is the most important stimulus affecting breathing rate?
pH of blood
What is the effect of a small increase in blood CO2 concentration on ventilation?
Big increase in ventilation
How does CO2 effect ventilation?
- CO2 dissolves in blood plasma, forming carbonic acid
- Carbonic acid then dissociates into H+ ions and hydrogencarbonate ions, HCO3-
- This causes a decrease in pH
- Chemoreceptors in the medulla oblongata detect rise in H+ ions
- Impulses are then sent from the ventilation centre to the intercostal and diaphragm muscles to stimulate them to contract faster and harder
How else is CO2 concentration monitored apart from by the medulla oblongata?
- Chemoreceptors in the carotid artery and the aorta
- These detect change in pH and send impulses to the ventilation centre
What is the benefit of breathing deeply in terms of CO2 and O2?
- Maintains a steep concentration gradient of CO2 between the air in the alveolar air and the blood
- This ensures efficient removal of CO2 and uptake of O2
How does a spirometer work?
- As the person breathes in and out of the spirometer, the change in air volume inside causes the floating lid to rise and fall
- The movement of the lid is recorded as a trace on a rotating drum
- Soda lime in the tube absorbs CO2
What does the trace produced by a spirometer show?
- Depth and frequency of breathing
- Rate of oxygen consumption
What does a fall on the trace produced by a spirometer represent?
-Consumption of oxygen by the person
Why does the total volume of gas in a spirometer decrease over time?
- Air breathed out is a mixture of CO2 and O2
- CO2 absorbed by soda lime
How would you test the effect of exercise on the breathing rate and tidal volume of a person?
- Connect a person to a spirometer using a mask so that continuous readings can be recorded
- Record readings for one minute at rest
- Have the person exercise for two minutes
- Record readings for a further minute after exercise
Equation for ventilation rate
Volume x breathing rate = ventilation rate
What happens when there is less CO2 in the blood?
- pH rises
- Decrease in rate and depth of breathing
What is the control of CO2 in the blood an example of?
Homeostasis
What is the motor cortex?
The region of the brain that controls movement
What effect does the motor cortex have on ventilation?
- Impulses sent from motor cortex to the ventilation centre
- This causes a sharp increase in ventilation
Apart from in the bronchioles, where else are stretch receptors found?
In tendons and muscles involved in movement
During vigorous exercise, the concentration of O2 in the lungs is higher than when at rest. Give the reasons for, and advantage of, this elevates oxygen level
- The depth and rate of breathing increases
- This means there is a greater volume of air is inhaled which increases the amount of oxygen taken in
- Increase in oxygen concentration creates a steeper concentration gradient between the alveolar air and the blood
- This increases the rate of gaseous exchange
- This increases metabolic rate
Explain why it is beneficial that stimulation of stretch receptors in the muscles increases ventilation
- Stretch receptors signal the start of movement
- They stimulate an increase in ventilation before there is a build up of waste products eg CO2
- This means these products are removed quicker than if the medulla oblongata noticed the change
When a person breathes air containing 80% oxygen, the minute ventilation is reduced by 20%. Explain how is occurs
- Increased oxygen levels in the blood
- This is detected by chemoreceptors
- This stimulates a decrease in breathing rate and depth
What is cardiac output?
The volume of blood pumped by the heart in 1 minute
Cardiac output = stroke volume x heart rate
What is stroke volume?
The volume of blood pumped out of the left ventricle each time the venticle contracts
What is venous return?
- Blood returning to the heart
- Increases during exercise
Why would exercise increase stroke volume?
- More blood fills heart during diastole
- This means the heart muscle is stretched to a greater extent
- Muscle contracts with greater force
- More blood is expelled
What is stroke volume measured in?
cm^3
What is the average resting stroke volume for an adult?
Between 50-90 cm^3
What determines how much blood is pumped out of the heart?
- How much blood enters during diastole
- Force of contraction
Which arteries are used to take a pulse?
- Radial (wrist)
- Carotid (neck)
A person has a resting stroke volume of 75 cm^3. They take their pulse rate and find that it is 70 beats per minute. Calculate their cardiac output
75 x 70 = 5250 cm^3 = 5.25 dm^3 min^-1
Give the units for cardiac output
dm^3 min^-1
What is the average cardiac output at rest?
5 dm^3 min^-1
A patient’s stroke volume was found to be 67 cm^3 per heartbeat and her resting heart rate was 73 BPM. Calculate the patient’s cardiac output and suggest if it is within the normal range
67 x 73 = 4891 cm^3 min^-1 = 4.9 dm^3 min^-1
-Average cardiac output is about 5 dm^3 min^-1 so it is within the normal range
A patient had a HR of 87 BPM. A dye was injected into blood circulation and sampled after circulation through the heart. Explain how cardiac output can be determined from the dye
- Concentration of dye measures stroke volume
- Lower the concentration of the dye in the sample, the larger the stroke volume
- If heart rate is known then cardiac output can be calculated
What is the cardiac output of the top end endurance athletes?
About 30 dm^3 min^-1
What is aerobic capacity?
The ability to take in, transport and use oxygen
What is VO2?
The volume of oxygen taken in per minute
What is the average resting value of VO2?
0.2-0.3 litres
What is VO2 max?
The maximum amount of O2 taken in per minute during aerobic exercise
What are the units of VO2 max?
ml^-1 kg^-1
What is VO2 max dependant on?
- Efficiency of uptake and transfer of oxygen
- Efficient use of oxygen by muscle cells
