The downward slope - Conduction of the heart - SAN-Generation of the signal

6 important questions on The downward slope - Conduction of the heart - SAN-Generation of the signal

How is the signal that is generated at the SAN travel to the cardiomyocytes of the atria?

The cells of the SAN are connected to the cardiomyocytes of the atria through gap junctions- therefore allows the passage of the impulse through to the cardiomyocyte.

What is the role of the SAN?

The SAN is responsible for generating the electrical impulse- it is not involved in contraction.

What is the resting membrane potential of the SAN?

-55 to -60mv.
-85 to -90mv in ventricular muscle fibre.
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Which channels are involved in the generation of the impulse at the SAN?

1. HCN/funny channels allow hyperpolarisation of the SAN- -65mV: allow the influx of Na+. Causes depolarisation.
2. @ -40mv: Ca2+ ions move into the cell through the T-type VGCC and L-channels
3. @+15mv: the K+ voltage-gated channels fully open. K+ flows in and causes repolarisation.

Where do the SAN fibres connect?

They connect to the atrial muscle fibres- this ensures that the action potential is transmitted immediately to the atria.

Where is the SAN located?

Inferior and slightly lateral to the opening of the superior vena cava

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