Phase 1 drive cardiovascular notes- heart Flashcards by Isobel Hutt

Describe cardiac muscle

Striated
Relatively small cells
Cells generally contain a single nucleus
Cells joined by intercalated discs

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What are intercalated discs?

Desmosomes + gap junctions

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What is the function of desmosomes between the cardiomyocytes?

Holds cells together

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What is the thick fimalment formed from?

Myosin

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Describe myosin

Two large polypeptide heavy chains
Two light chains
Two globular heads
Long tail formed from two intertwined heavy chains

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What are the binding sites on the myosin head for?

One for ATP

One for binding to actin

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What type of enzyme does the binding site for ATP act as on the myosin head?

ATPase

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What is the major component of the thin filament?

Actin

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Describe the core of the thin filament?

Two chains of actin intertwined

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How many binding sites are there for myosin on an actin monomer?

One

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What overlies the myosin binding sites on the actin?

Tropomyosin

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What does Ca2+ bind to in order for mysosin heads to be able to bind to actin?

Troponin

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What causes tropomysosin the change shape, exposing the mysosin binding sites on the actin?

Binding of Ca2+ to troponin

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What is the A band?

The region of the sarcomere that contains the myosin thick filaments

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What is the I band?

The region of the sarcomere occupied by thin filaments only

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What lines define the boundaries of a sarcomere?

Z lines

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What is the H-zone?

Contains thick filaments only

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Where is the M-line found?

In the centre of the H zone

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What helps keep the thick filaments in the middle of each sarcomere?

M-line linkage Wbetween thick filaments

Titin filaments

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How many H zones will you find in a single sarcomere?

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How many A bands will you find in a single sarcomere?

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Why is there a high Ca2+ concentration in the sarcoplasmic reticulum?

Ca2+ is actively transported into the sarcoplamsmic reticulum

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What do the action potentials travel down in order to reach the sarcoplasmic reticulum

t tubules

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Which arteries supply blood to the cardiomyocytes?

coronary arteries

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Where is the origin of the coronary arteries?

the aorta

What is the vein that most of the coronary arteries drain into called?

the coronary sinus

Where does the coronary sinus empty into?

the right atrium

What connects myocardial cells that allows the spread of action potentials?

gap junctions

Where is the sinoatrial node located?

the right atrium (near the entrance of the superior vena cava)

Which node normally determines heart rate?

SA node

What are the leaky Na+ channels in nodal cells referred to?

funny, F-type

What are the two types of Ca2+ channels in nodal cells ?

T-type and L-type

Rapid conduction from the SA node to the AV node occurs through which pathways?

Internodal pathways

Where is the AV node located?

The base of the right atrium

Why is the AV node and the bundle of His the only electrical connection between atria and ventricles?

Because the atria and ventricles are separated by a layer of non-conducting connective tissue

What does the bundle of His divide into?

left and right bundle branches

What are the fibres that distribute the impulse through the ventricles?

Purkinje fibres

Which nerve supplies parasympathetic innervation to the heart?

The vagus nerve (X)

What are the effects of parasympathetic innervation to the heart?

1. Decreased heart rate 2. Decreases force of contraction 3. Decreases cardiac output

What are the effects of sympathetic innervation to the heart?

1. Increased heart rate 2. Increased force of contraction 3. Increased cardiac outout

What does it mean if an effect is chronotropic?

Changes heart rate

What does it mean if an effect is negatively chronotropic?

Decreases heart rate

What does it mean if an effect is inotropic?

Effects force of contraction

What does it mean if an effect is positively inotropic?

Increases force of contraction

What does ECG stand for?

electrocardiogram

What is an ECG a measure of?

currents in the extracellular fluid

What is the p wave?

atrial depolarisation

Which lead is the p wave not present in?

aVR

What is the PR interval?

Time taken for atria to depolarise and electrical activation to get through AV node

What is the QRS complex?

Ventricular depolarisation

What is the ST segment?

Interval between depolarisation and repolarisation

What is the T wave?

Ventricular repolarisation

What is tachycardia?

Increased heart rate

What is the word for decreased heart rate?

bradycardia

What is the diagnosis when ST sgements are raised in anterior (V3-V4) and lateral (V5-V6) leads

acute aterolateral myocardial infarction

What is the diagnosis when ST segments are raised in inferior leads?

acute inferior MI

Why is atrial repolarisation usually not evident on an ECG?

Hidden by the QRS complex

What does an impulse look like on an ECG if it is moving towards the electrode?

Big

What are the standard limb leads?

I, II and III

Where are the standard limb leads placed?

Wrists and left leg

What does the RR interval represent?

Time between two QRS complexes

What are leads V1-V6 referred to?

The precordial leads

On an ECG, how long is each small square across?

40ms

On an ECG, how long is each big square across?

0.2s

Where are the precordial leads placed?

On the chest

Apart from aVR, what does a T wave look like on a normal ECG?

positive

What are the augmented leads called?

aVR, aVL and aVF

How long does a typical cardiac cycle last?

0.8 seconds

How long is a normal diastole?

0.5 seconds

What is stroke volume?

Volume of blood pumped from the left ventricle per beat

What is the cardiac output?

Volume of blood pumped by the heart per unit time

What time of vasculature contributes the most to total peripheral resistance?

Arterioles

What is total peripheral resistance?

the total resistance to flow in systemic blood vessels from the beginning of the aorta to the vena cava

What is preload?

volume of blood in the left ventricle before left ventricular contraction

How does vein dilation effect preload?

Dilation of veins decreases pre load as venous return is decreased

What is afterload?

The pressure the left ventricle must overcome to eject blood during contraction

What is elasticity?

Myocardial ability to recover after systolic stress

What is diastolic dispensibility?

The pressure required to fill the ventricles to the same diastolic volume

What is compliance?

How easily the heart chamber expands when filled with blood

Phase 1 drive cardiovascular notes- heart Flashcards

(79 cards)