Mechanisms Controlling The Heartbeat

Question 1

What important property does the heart have?

Answer 1

Automatism

Question 2

What does the automatism of the heart mean?

Answer 2

It can contract and relax without any external stimuli

Question 3

Where do the contractions of the heart begin?

Answer 3

In the muscle cells of the heart

Question 4

What is a heartbeat?

Answer 4

The sound that results from each cardiac cycle

Question 5

What instrument allows the heartbeat to be heard?

Answer 5

Stethoscope

Question 6

What sound does the heart make?

Answer 6

Lub-dub

Question 7

Which heartbeat sound is louder?

Answer 7

Lub

Question 8

What causes the heart to beat?

Answer 8

An electrical impulse

Question 9

What initiates the electrical impulse of the heart?

Answer 9

The SA node

Question 10

What does the SA node stand for?

Answer 10

sino-atrial node

Question 11

What is the SA node?

Answer 11

A group of specialised muscle cells

Question 12

Where does the SA node occur?

Answer 12

In the wall of the right atrium

Question 13

What is the SA node known as?

Answer 13

The pacemaker of the heart

Question 14

What is the AV node?

Answer 14

Another group of specialised conducting cells

Question 15

What does the AV node stand for?

Answer 15

Atrio-ventricular node

Question 16

Where does the AV node occur?

Answer 16

Occurs at the lower end of the septum between the right atrium and left atrium

Question 17

What conducts impulses from the atria to the ventricles?

Answer 17

Bundles of His

Question 18

What is His?

Answer 18

Special muscle tissue

Question 19

Where does His occur?

Answer 19

Throughout the septum between the two ventricles

Question 20

What does the His do at the apex of the heart?

Answer 20

Branches Purkinje fibres

Question 21

What are Purkinje fibres?

Answer 21

The network of fibres which is the extension of the bundles of His

Question 22

Where do the Purkinje fibres occur?

Answer 22

Throughout the walls of the ventricles

Question 23

What do the Purkinje fibres do?

Answer 23

Conduct impulses faster and more effectively

Question 24

What is the route of the impulse and its effect during a cardiac cycle?

Answer 24

The contraction begins at the SA node and spreads across the two atria to the AV node
The two atria contract simultaneously
The impulse travels along the bundles of His between the two ventricles to the Purkinje fibres
This causes the ventricles to contract simultaneously from their lower ends

Question 25

What controls the heartbeat?

Answer 25

The nervous system | Hormones

Question 26

Which part of the nervous system controls the heartbeat?

Answer 26

The autonomic nervous system

Question 27

How does the autonomic nervous system control the heartbeat?

Answer 27

By conducting impulses via two types of nerve fibres

Question 28

What do types of nerve fibres conduct impulses to the heart?

Answer 28

Sympathetic | Parasympathetic

Question 29

Where do the impulses conducted by the autonomic nervous system come from?

Answer 29

From the brain | To the SA node

Question 30

What is the autonomic nervous system?

Answer 30

The part of the nervous system in vertebrates that controls the involuntary actions of smooth muscles, cardiac muscles and glands

Question 31

What kind of nerve impulses do the sympathetic nerve fibres conduct?

Answer 31

Impulses that accelerate the heartbeat

Question 32

What kind of nerve impulses do the parasympathetic fibres conduct?

Answer 32

Impulses that slow the heartbeat down to normal

Question 33

Which two hormones affect the heartbeat?

Answer 33

Adrenaline | Thyroxine

Question 34

What do adrenaline and thyroxine do?

Answer 34

Accelerate the heartbeat

Question 35

When is adrenaline released?

Answer 35

During times of stress

Question 36

Why does the heartbeat speed up in times of stress?

Answer 36

More oxygen is pumped to the brain and muscles, which improves the reactions of a person during stressful situations

Question 37

How does exercise affect the heartbeat?

Answer 37

It accelerates the heartbeat

Question 38

How many beats per minute can strenuous exercise increase the heartbeat to?

Answer 38

200 beats per minute

Question 39

Why does exercise increase the heartbeat?

Answer 39

``` Cells need more energy They perform more cellular respiration More CO2 is released More oxygen is needed Heart pumps faster to supply it ```

Question 40

How does the body know to increase the heartbeat during exercise?

Answer 40

Receptors in the carotid arteries detect the increase in CO2 It sends a message to the brain Sympathetic fibres conduct impulses to increase the heartbeat

Question 41

What is a pulse?

Answer 41

The regular contraction and relaxation of an artery, caused by blood pumped through the body

Question 42

Where can ones pulse be felt?

Answer 42

Where an artery lies close to the surface

Question 43

What is a pulse rate?

Answer 43

The number of heartbeats per minute

Question 44

Which fingers are used to take ones pulse?

Answer 44

Index and middle finger

Question 45

When a person exercises regularly, what happen to their pulse rate?

Answer 45

It decreases

Question 46

Why does a fitter person have a lower pulse rate?

Answer 46

The heart muscle is strengthened | It doesn't need to pump as many times to pump the same volume of blood