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Cardiovascular System > Cardiac muscle > Flashcards

Cardiac muscle Flashcards

1
Q

What are the three types of cardiac muscle?

A

Excitatory cells
Conducive muscle fibers
Myocardium

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2
Q

What are the properties of the cardiac muscle?

A

Striations
Actin and myosin filaments in the myofibrils
Dark bands called intercalated discs - forming gap junctions
Cell membrane that separates cardiac muscle cells
Syncytium (multinucleated)

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3
Q

Define syncytium

A

An arrangement of multinucleated muscle fibres in which the fibers fuse to form an interconnected mass of fibers

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4
Q

Name the sycytiums in the heart (heart divisions)

A

The heart is divided into atrial syncytium which is composed of atrial walls, and a ventricular scyncytium composed of ventricular walls

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5
Q

What separates the atria from the ventricles?

A

A fibrous tissue, and it does not allow for transmission of action potentials

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6
Q

What initiates action potentials in the heart?

A

Pacemaker (sinoatrial node)

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7
Q

What conducts Action potentials to the ventricles?

A

Atrioventricular bundle

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8
Q

What is the AV bundle composed of?

A

Conducive fibers

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9
Q

What is the myocardium resting potential?

A

-85 mV

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10
Q

What value is the membrane potential during depolarisation

A

+20 mV

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11
Q

Name the phases of cardiac action potential and give the term of what is happening at that phase.

A

Phase 0 – Depolarization
Phase 1 – Repolarization to plateau
Phase 2 – Plateau
Phase 3 – Repolarization
Phase 4 – Resting membrane potential

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12
Q

Explain what happens in each phase

A

Phase 0 - Rapid depolarization occurs when the cells reach threshold and fast sodium ion channels open.

Phase 1 - This phase is caused by closure of fast sodium ion channels, initiate repolarization and efflux of potassium ions through open potassium channels.

Phase 2 - The opening of voltage-gated, slow L-type calcium ion channels and potassium ion channels close.

Phase 3 - Voltage-gated slow L-type calcium ion channels close and opening potassium ion channels cause rapid repolarization.

Phase 4 - The resting membrane potential of these cells is restored, increase efflux of potassium ion.

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13
Q

Define cardiac cycle

A

A sequence of events the occur during one complete heartbeat.
It is spontaneously initiated by the SA node by the generation of action potentials

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14
Q

Differentiate between systole and diastole

A

Systole – contraction of cardiac muscle
Diastole – relaxation of cardiac muscle

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15
Q

How to calculate duration of cardiac cycle?

A

Duration=60sec/HR

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16
Q

What happens to the duration of each cardiac cycle when the HR decreases?

A

the duration of each cardiac cycle will increase

17
Q

Describe the phases of a cardiac cycle

A

Phase I: Period of Filling
Phase II: Period of Isovolumic Contraction
Phase III: Period of Ejection
Phase IV: Period of Isovolumic Relaxation

18
Q

What happens during late diastole?

A

Both sets of chambers are relaxed and ventricles fill passively

19
Q

What happens during Atrial systole?

A

Atrial contraction forces a small amount of additional blood into ventricle

20
Q

What happens during isovolumetric contraction?

A

The first phase of ventricular contraction pushes AV valves closed but does not create enough pressure to open semilunar valves.

21
Q

What happens during ventricular ejection?

A

As ventricular pressure rises and exceeds pressure in the arteries, the semilunar valves open and blood is ejected.

22
Q

Describe Isometric ventricular relaxation

A

As ventricles relax, pressure in the ventricles falls, blood flows beck into cusps of semilunar valves and snaps them closed.

23
Q

What is the term for Maximum blood volume in ventricles

A

End diastolic volume

24
Q

What is the minimum blood volume in ventricles?

A

End-systolic volume

25
Q

Describe the features of an ECG

A

P wave - Atrial depolarization
QRS complex - ventricular depolarization
T wave - ventricular repolarization

26
Q

What causes heart sounds?

A

Closing of heart valves

27
Q

What causes the Lub sound?

A

Closing of AV valves

28
Q

what causes the dub sound?

A

Closing of semilunar valves

29
Q

Name the 2 mechanisms that regulate heart pumping

A
  1. Volume of blood flowing into the heart (venous return)
  2. Autonomic nervous system
30
Q

How does venous return affect heart pumping?

A

The increase in venous return stretches the heart muscle
Increase in length of cardiac muscle stretch cause increased strength/force of cardiac contraction

Cardiovascular System (4 decks)

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