CH18 W4B Electrophysiology

This cardiac muscle cell feature allows cells to connect to each other electrically:

Intercalated Discs

Cardiac myocytes use what kind of respiration?

Aerobic respiration (have many mitochondria)

Where is the pacemaker of the heart? (Where does the heartbeat start?)

Sino-atrial node (SA node)

In which atrial structure is the SA node located?

Crista terminalis of Right Atrium

Compared to a skeletal muscle cell action potential , the cardiac action potential is:

Longer (300 msec) 

What makes pacemaker myocytes different to contractile myocytes?

They don’t have a steady RMP. Instead, the RMP drifts back to the threshold automatically, called the pacemaker potential.

When neurons of the parasympathetic nervous system fire at the pacemaker, more of which ion channels open? 

K+

When neurons of the parasympathetic nervous system fire at the pacemaker, resting membrane potential becomes

more negative

When neurons of the parasympathetic nervous system fire at the pacemaker, the heart rate

slows down

When the neurons of the sympathetic nervous system fire at the pacemaker, more of which ion channels open?

Na+

When the neurons of the sympathetic nervous system fire at the pacemaker, resting membrane potential becomes

more positive

When the neurons of the sympathetic nervous system fire at the pacemaker, the heart rate 

speeds up