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Cardio & Thoracic Biology > CTB3: Mechanical and electrical properties of the heart > Flashcards

CTB3: Mechanical and electrical properties of the heart Flashcards

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1
Q

What are the three types of cardiac muscle?

A

1) atrial
2) ventricle
3) specialised excitatory and conductive fibres

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2
Q

Cells that form cardiac muscle fibres are called _________.

A

cardiomyocytes

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3
Q

How are atrial and ventricular cardiomyocytes connected?

A

In parallel with one another so that they can contract in a synchronised manner

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4
Q

What do excitatory and conductive cardiomyocytes do?

A

They show weak contraction but can generate and conduct electrical impulses that control heartbeat

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5
Q

What distinguishes cardiomyocytes from other cell types?

A

Segmentation

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6
Q

What dimensions are cardiomyocytes?

A

100um by 15um

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7
Q

What are cardiomyocytes joined together by?

A

intercalated discs containing gap junctions

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8
Q

What is the purpose of gap junctions?

A

Allows fast exchange of ions between cells, important in the synchronisation of contraction.

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9
Q

What is the Plasma membrane of cardiomyocytes together with its glycocalyx is called?

A

Sarcolemma

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10
Q

What is the fundamental contractile unit of muscle cells?

A

Sarcomeres

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11
Q

What do protein fibres consist of?

A

actin and myosin

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12
Q

What are T-tubules?

A

Finger-like invaginations from the cell surface that reach deep into the cell, to sarcoplasmic reticulum

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13
Q

What are T-tubules for?

A

Carry surface depolarisation deep into the cell. T tubules lie in close proximity to Z-lines separating different myofibrils.

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14
Q

How do cardiomyocytes contract in such a synchronised way?

A

Rhythmic contraction and relaxation of cardiomyocytes depends on a process called excitation—contraction coupling.

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15
Q

What does excitation contraction coupling in cardiomyocytes rely on?

A

Sarcolemma depolarization and subsequent Ca2+ entry to trigger additional Ca2+ release from the sarcoplasmic reticulum.

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16
Q

What is an action potential?

A

Change in membrane voltage as a result of movement of K+, Na+ and Ca2+ across the membrane

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17
Q

Name the phases of an action potential

A

Phase 0: Depolarisation
Phase 1 - 3: Repolarisation cell returns to its oiginal
Phase 4: repolarisation complete

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18
Q

Calcium-activated calcium release and can be seen as _________ restricted Ca2+ spark.

A

spatio-temporally

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19
Q

What controls the duration of the heart contraction?

A

The duration of the action potential

20
Q

What systems are electrical activity of the heart coordinated by?

A
  • Intrinsic

- Extrinsic

21
Q

Does the heart act independently or dependently of the nervous system?

A

Independently

22
Q

What is the muscular wall in the septum of the heart called?

A

Bundle of His

23
Q

What are the two nodes in the heart called?

A
  • Sinoatrial node (SA node)

- Atrioventricular node (AV node)

24
Q

What are the nerves at the base of the ventricles called?

A

Purkinje fibers

25
Q

What are the four relay systems of the electro-chemical circuit system called?

A
  • Sinoatrial (SA) node
  • Atrial-Ventricular (AV) node
  • Bundle of HIS
  • Purkinje fibres
26
Q

What is the natural pace maker of the heart?

Where is it located?

A
  • sinoatrial (SA) node

- located in the upper part of the right atrium.

27
Q

Describe the route of the electrical signalling in the heart

A

From the SA node, the signal passes down to ventricles via the AV node, which controls the signal so that atria contract before the ventricles. The electrical signal then travels through the muscle of ventricles, so they contract at the same time, pumping blood to lungs and the rest of the body.

28
Q

Where does extrinsic control of the nervous system come from? What does it do?

A

Autonomic nervous system (ANS), which serves to modify and control the intrinsic beating established by the heart.

29
Q

What is heart rate controlled by?

A

ANS: sympathetic and parasympathetic nervous systems

30
Q

In what manner do the sympathetic and parasympathetic nervous systems act on the heart?

A

Sympathetic and parasympathetic neurons exert antagonistic effects on the heart.

31
Q

How does the sympathetic nervous system act on the heart?

A

It releases the hormones (catecholamines - epinephrine and norepinephrine) to accelerate the heart rate. To prepare the body for fight or flight.

32
Q

How does the parasympathetic nervous system act on the heart?

A

Most active under restful conditions. The parasympathetic counteracts the sympathetic system after a stressful event and restores the body to a restful state. The parasympathetic nervous system releases the hormone acetylcholine to slow the heart rate.

33
Q

What nerve relays information from brain to heart in the parasympathetic nervous system?

A

Vagus nerve

34
Q

What nerve relays information from brain to heart in the sympathetic nervous system?

A

Sympathetic cardiac nerves

35
Q

What is the cardiac cycle?

A

Sequence of events in one heartbeat: simultaneous contraction of both atria, followed a fraction of a second later by the simultaneous contraction of both ventricles.

36
Q

Name the two phases of the heart beat

A

1) Systole

2) Diastole

37
Q

Explain the two phases of the nervous system

A

1: Systole = ventricular contraction when blood is pumped into the arteries.
2: Diastole = ventricular relaxation during which the ventricles fill with blood.

38
Q

Describe the contraction of the heart in one word.

A

In a wave

39
Q

When the impulse reaches the septum, how long is the delay to allow the ventricles to fill?

A

0.2 seconds

40
Q

How is it ensured that the ventricles empty completely after each beat?

A

The ventricles then contract simultaneously, from the bottom upwards

41
Q

What is the average resting heart rate?

A

60-80bpm

42
Q

Heart rate when exercising?

A

150 for most people

200 for athletes

43
Q

What are the two functions of the heart?

A

Electrical

Mechanical

44
Q

What does it mean that the heart is controlled by intrinsic and extrinsic systems?

A

Intrinsic: From
Extrinsic: From the autonomous nervous system

45
Q

Ventricular contraction is called?

A

systole

46
Q

Ventricular relaxation is called?

A

Diastole

Cardio & Thoracic Biology (11 decks)

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