Topic 7b - Exercise

Question 1

The cardiac muscle can contract and relax without the input of neurones this makes it …

Answer 1

Myogenic

Question 2

What causes the heart to contract?

Answer 2

Electrical activity in the heart

Question 3

Where does the process of the heart beating start? And what is the role of the SAN?

Answer 3

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.

Question 4

What does the non conducting collagen tissue do?

Answer 4

Prevents the waves of electrical activity from the SAN from being passed directly from the atria to the ventricles.

Question 5

Where does the SAN transfer the electrical waves to?

Answer 5

The AVN

Question 6

What is the AVN responsible for? why is there a delay before the AVN reacts?

Answer 6

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.

Question 7

What is the bundle of His?

Answer 7

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.

Question 8

What is the role of purkyne fibres?

Answer 8

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.

Question 9

What does an ECG do?

Answer 9

Records the electrical activity of the heart.

Question 10

True or false? The heart muscle repolarises when it contracts.

Answer 10

False. The heart muscle depolarise when it contracts (loses its charge

Question 11

True or false? The heart muscle depolarises when it relaxes.

Answer 11

False. The heart muscle polarises (regains charge) when it relaxes.

Question 12

How does an ECG record changes in electrical charge?

Answer 12

Using electrodes placed on the chest.

Question 13

What is the P wave in an ECG caused by?

Answer 13

The contraction (depolarisation) of atria.

Question 14

What is the QRS complex and what is it caused by?

Answer 14

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.

Question 15

What causes the T wave?

Answer 15

The relaxation (repolarisation) of the ventricles.

Question 16

What does the height of the wave in an ECG indicate?

Answer 16

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.

Question 17

State the order of an ECG (3 stages):

Answer 17

1) p wave = contraction of atria (depolarisation)
2) main peak = QRS complex = caused by contraction of ventricles
3) t wave = relaxation (repolarisation) ventricles

Question 18

Draw an example of an ECG…

Answer 18

In book or OneNote

Question 19

What do doctors use ECG’s for?

Answer 19

To diagnose heart problems

Question 20

What could problems with the hearts rhythm indicate?

Answer 20

Cardiovascular disease

Question 21

What’s the condition where your heartbeat is too fast?

Answer 21

Tachycardia

Question 22

What is the name of the condition where your heart beats too slowly?

Answer 22

Bradycardia

Question 23

What is an ectopic heartbeat?

Answer 23

An extra heart beat, can be caused by early contraction of atria or early contraction of ventricles

Question 24

What is fibrillation? And what can it result in?

Answer 24

Irregular heart beat. It can result in chest pain, fainting, death

Question 25

Give one possible cause of an ECG which has a QRS complex that is not as high as normal

Answer 25

The ventricles are not conducting properly/ could be because of muscle damage/ because AVN is not conducting impulses to the ventricles properly

Question 26

What happens to breathing and heart rate when exercising?

Answer 26

It increases

Question 27

Why does breathing rate and depth increase when we excersise?

Answer 27

To have a higher volume of oxygen going in for respiration and more co2 out.

Question 28

Why does heart rate increase when we exercise?

Answer 28

To deliver more oxygen to the muscles and remove and extra co2 produced by respiration

Question 29

What controls breathing rate?

Answer 29

Medulla oblongata

Question 30

What does the medulla oblongata have that controls breathing rate?

Answer 30

Ventilation centres: inspiratory and expiratory

Question 31

Describe the process of breathing (5 steps):

Answer 31

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

Question 32

How does exercise trigger an increase in breathing rate (ph)

Answer 32

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

Question 33

Define ventilation rate

Answer 33

Volume of air breathed in or out in a period of time