PHYS Electrical Activity of the Heart

Question 1

Part of the heart = pulse

Answer 1

Contraction of left ventricle.

Question 2

Process of electrical activity spread through the heart.

Answer 2

SA node (internodal pathway) -> Bachmann’s bundle -> AV node -> Bundle of His -> Left & Right branches via septum -> Purkinje fibres.

Question 3

How is conduction slowed btw SA - AV node?

Answer 3

Less gap junctions in the intercalated discs - primary purpose is to enable conduction to spread to right atrium so that atria contract before ventricles.

Question 4

Most negative point of nodal APs =

Answer 4

Max diastolic potential (MDP)

Question 5

Describe ionic movements during a ventricular AP

Answer 5

Na+ moves into the cell via voltage-sensitive Na+ channels during depolarisation (the upstroke)
Ca2+ moves into the cell via voltage-sensitive Ca2+ channels during depolarisation when membrane potential = -40mV (the plateau)
K+ moves out of the cell via voltage-sensitive K+ channels (repolarisation).

Question 6

Explain ANS regulation of the SA node in pacemaking

Answer 6

Para. - vagus nerves w ACh hormones acting on M receptors.
Symp. - thoracic spinal nerves w NA hormones acting on B receptors.