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Abi Biology 2017 > Mechanisms Controlling The Heartbeat > Flashcards

Mechanisms Controlling The Heartbeat Flashcards

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1
Q

What important property does the heart have?

A

Automatism

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2
Q

What does the automatism of the heart mean?

A

It can contract and relax without any external stimuli

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3
Q

Where do the contractions of the heart begin?

A

In the muscle cells of the heart

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4
Q

What is a heartbeat?

A

The sound that results from each cardiac cycle

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5
Q

What instrument allows the heartbeat to be heard?

A

Stethoscope

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6
Q

What sound does the heart make?

A

Lub-dub

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7
Q

Which heartbeat sound is louder?

A

Lub

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8
Q

What causes the heart to beat?

A

An electrical impulse

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9
Q

What initiates the electrical impulse of the heart?

A

The SA node

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10
Q

What does the SA node stand for?

A

sino-atrial node

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11
Q

What is the SA node?

A

A group of specialised muscle cells

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12
Q

Where does the SA node occur?

A

In the wall of the right atrium

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13
Q

What is the SA node known as?

A

The pacemaker of the heart

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14
Q

What is the AV node?

A

Another group of specialised conducting cells

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15
Q

What does the AV node stand for?

A

Atrio-ventricular node

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16
Q

Where does the AV node occur?

A

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

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17
Q

What conducts impulses from the atria to the ventricles?

A

Bundles of His

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18
Q

What is His?

A

Special muscle tissue

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19
Q

Where does His occur?

A

Throughout the septum between the two ventricles

20
Q

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

A

Branches Purkinje fibres

21
Q

What are Purkinje fibres?

A

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

22
Q

Where do the Purkinje fibres occur?

A

Throughout the walls of the ventricles

23
Q

What do the Purkinje fibres do?

A

Conduct impulses faster and more effectively

24
Q

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

A

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

25
Q

What controls the heartbeat?

A

The nervous system

Hormones

26
Q

Which part of the nervous system controls the heartbeat?

A

The autonomic nervous system

27
Q

How does the autonomic nervous system control the heartbeat?

A

By conducting impulses via two types of nerve fibres

28
Q

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

A

Sympathetic

Parasympathetic

29
Q

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

A

From the brain

To the SA node

30
Q

What is the autonomic nervous system?

A

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

31
Q

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

A

Impulses that accelerate the heartbeat

32
Q

What kind of nerve impulses do the parasympathetic fibres conduct?

A

Impulses that slow the heartbeat down to normal

33
Q

Which two hormones affect the heartbeat?

A

Adrenaline

Thyroxine

34
Q

What do adrenaline and thyroxine do?

A

Accelerate the heartbeat

35
Q

When is adrenaline released?

A

During times of stress

36
Q

Why does the heartbeat speed up in times of stress?

A

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

37
Q

How does exercise affect the heartbeat?

A

It accelerates the heartbeat

38
Q

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

A

200 beats per minute

39
Q

Why does exercise increase the heartbeat?

A 
Cells need more energy
They perform more cellular respiration
More CO2 is released
More oxygen is needed
Heart pumps faster to supply it
40
Q

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

A

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

41
Q

What is a pulse?

A

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

42
Q

Where can ones pulse be felt?

A

Where an artery lies close to the surface

43
Q

What is a pulse rate?

A

The number of heartbeats per minute

44
Q

Which fingers are used to take ones pulse?

A

Index and middle finger

45
Q

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

A

It decreases

46
Q

Why does a fitter person have a lower pulse rate?

A

The heart muscle is strengthened

It doesn’t need to pump as many times to pump the same volume of blood

Abi Biology 2017 (57 decks)

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