Topic 7b - Exercise Flashcards
The cardiac muscle can contract and relax without the input of neurones this makes it …
Myogenic
What causes the heart to contract?
Electrical activity in the heart
Where does the process of the heart beating start? And what is the role of the SAN?
The right atrium (SAN) - acts as a pacemaker which sets the rhythm of a heartbeat by sending regular waves of electrical activity to the vertical walls. This causes both atria to contract at the same time.
What does the non conducting collagen tissue do?
Prevents the waves of electrical activity from the SAN from being passed directly from the atria to the ventricles.
Where does the SAN transfer the electrical waves to?
The AVN
What is the AVN responsible for? why is there a delay before the AVN reacts?
Passing waves of electrical activity to the bundle of His. There is a slight delay to make sure that the ventricles react AFTER the atria have emptied.
What is the bundle of His?
A group of muscle fibres that are responsible for conducting waves of electrical activity to finer muscle fibres in the left and right ventricles called purkyne fibres.
What is the role of purkyne fibres?
To carry waves of electrical activity into muscular walls of the left and right ventricles which causes the ventricles to contract simultaneously from the bottom up.
What does an ECG do?
Records the electrical activity of the heart.
True or false? The heart muscle repolarises when it contracts.
False. The heart muscle depolarise when it contracts (loses its charge
True or false? The heart muscle depolarises when it relaxes.
False. The heart muscle polarises (regains charge) when it relaxes.
How does an ECG record changes in electrical charge?
Using electrodes placed on the chest.
What is the P wave in an ECG caused by?
The contraction (depolarisation) of atria.
What is the QRS complex and what is it caused by?
The QRS complex is the main peak of a heart beat, with the dips at either side. It is caused by the contraction (depolarisation) of the ventricles.
What causes the T wave?
The relaxation (repolarisation) of the ventricles.
What does the height of the wave in an ECG indicate?
How much electrical activity is passing through the heart - a bigger wave means more electrical charge (so for the P and R waves) a bigger waves means a stronger contraction.
State the order of an ECG (3 stages):
1) p wave = contraction of atria (depolarisation)
2) main peak = QRS complex = caused by contraction of ventricles
3) t wave = relaxation (repolarisation) ventricles
Draw an example of an ECG…
In book or OneNote
What do doctors use ECG’s for?
To diagnose heart problems
What could problems with the hearts rhythm indicate?
Cardiovascular disease
What’s the condition where your heartbeat is too fast?
Tachycardia
What is the name of the condition where your heart beats too slowly?
Bradycardia
What is an ectopic heartbeat?
An extra heart beat, can be caused by early contraction of atria or early contraction of ventricles
What is fibrillation? And what can it result in?
Irregular heart beat. It can result in chest pain, fainting, death
Give one possible cause of an ECG which has a QRS complex that is not as high as normal
The ventricles are not conducting properly/ could be because of muscle damage/ because AVN is not conducting impulses to the ventricles properly
What happens to breathing and heart rate when exercising?
It increases
Why does breathing rate and depth increase when we excersise?
To have a higher volume of oxygen going in for respiration and more co2 out.
Why does heart rate increase when we exercise?
To deliver more oxygen to the muscles and remove and extra co2 produced by respiration
What controls breathing rate?
Medulla oblongata
What does the medulla oblongata have that controls breathing rate?
Ventilation centres: inspiratory and expiratory
Describe the process of breathing (5 steps):
1) inspiratory centre in medulla oblongata sends nerve impulses to the intercostal muscles and diaphragm to make them contract
2) this increases the volume in the lungs and therefore decreases the pressure of the lungs
3) air enters the lungs due to the concentration difference in lungs and air
4) lungs inflate so stretch receptors in lungs are stimulated, stretch receptors send nerve impulses back to medulla oblongata (these impulses inhibit the action of inspiratory centre)
5) expiratory centre (no longer inhibited) sends nerve impulses to the diaphragm + intercostal muscles which causes the lungs to deflate, expelling air. As lungs deflate stretch receptors = inactive
Cycle repeats
How does exercise trigger an increase in breathing rate (ph)
1) during exercise the levels of co2 increase which decreases the pH of the blood
2) there are chemoreceptors in the medulla oblongata which are sensitive to pH changes in the blood
3) if chemoreceptors detect a decrease in blood pH they send nerve impulses to medulla oblongata, which sends more frequent nerve impulses to intercostal muscles and diaphragm - increases depth + rate of breathing
4) this causes gaseous exchange to speed up. CO2 levels drop and extra O2 is supplied to muscles - pH returns to normal as breathing rate decreases
Define ventilation rate
Volume of air breathed in or out in a period of time
