electrical activity of the heart Flashcards
what are electrical properties of the heart
Excitation contraction coupling Ionic basis of the non-pacemaker action potential Ionic basis of the pacemaker potential Modulators of electrical activity The special conducting system The electrocardiogram
do skeletal muscle and cardiac muscle exhibit tetanus
skeletal does, cardiac doesn’t
in extraction-contraction coupling, how is cardiac muscle formed into a functional syncytium
electrically connected via gap junctions
physically connected by desmosomes
these form the intercalated discs
does cardiac muscle have a long or short action potential
long
why cant cardiac muscle exhibit tetanic contraction
long refractory period
what regulates the contraction?
calcium
what happens to pk and pca in non pacemaker when its a resting membrane potential?
high resting pk
what happens to pk and pca and pna in non pacemaker when its a initial depolarisation
increase in PNa+
what happens to pk and pca and pna in non pacemaker when its plateau
increase in PCa2+(L-type), and decrease in PK+
what happens to pk and pca and pna in non pacemaker when its Repolarisation
decrease in PCa2+, and increase in PK+
what happens to pk and pca and pna in pacemaker when its action potential?
increase in PCa2+ (L-type)
what happens to pk and pca and pna in pacemaker when its pacemaker potential?
gradual decrease in PK+
early increase in PNa+ (= PF)
late increase in PCa2+ (T-type)
what are the modulators of electrical activity?
Sympathetic & parasympathetic systems – see later Drugs Temperature Hyperkalemia Hypokalemia Hypercalcemia Hypocalcemia
what drugs modulate electical activity
Ca2+-channel blockers – decrease force of contraction
cardiac glycocides – increase force of contraction
in what way does temperature effect electrical activity?
increases ~10 beats/min/ºC
in what way does Hyperkalemia effect electrical activity?
(high plasma K+)
fibrillation & heart block
in what way does Hypokalemia effect electrical activity?
(low plasma K+)
fibrillation & heart block (anomalous)
in what way does Hypercalcemia effect electrical activity?
(high plasma Ca2+)
increased HR & force of contraction
in what way does Hypocalcemia effect electrical activity?
(low plasma Ca2+)
decreased HR & force of contraction
is annulus fibrosis conducting
no
whats in the Sinoatrial node and how quickly does it conduct
pacemaker
~ 0.5 m/sec
whats in the Atrioventricular node
and how quickly does it conduct?
delay box
~ 0.05 m/sec
whats in the Purkinje fibres
and how quickly does it conduct
rapid conduction system
~ 5 m/sec
whats the order of the conducting system?
arterial excitation, ventricular excitation, ventricular relaxation
