Physiology - Part 1 Flashcards
what is the muscle membrane called?
sarcolemma
what is the name for the invaginations made by the sarcolemma?
T-tubules
what do the T-tubules interact with?
sarcoplasmic reticulum
what is a syncitium?
a single cell containing several nuclei, formed by fusion of cells
do cardiac cells form a true syncitium?
no, only functionally
what is an intercalated disc?
an arrangement of a desmosome and a gap junction
which of desmosomes or gap junctions provides the electrical connection?
gap junctions
which of desmosomes or gap junctions provides the physical connection?
desmosomes
roughly how long does a cardiac action potential last?
200-250 ms
can cardiac muscles exhibit tetanus?
no
is the refractory period in cardiac muscle long or short?
long
why can’t cardiac muscle exhibit tetanus?
due to the long refractory period
how long is the action potential in skeletal muscle?
2 ms
aside from preventing tetanus, why does cardiac muscle have a long action potential?
Ca entry from outside the cell can regulate contraction as it does not saturate the troponin
in non-pacemaker cardiac cells, what causes the resting membrane potential?
high resting permeability to K+
in non-pacemaker cardiac cells, what causes high resting permeability to K+?
leaky K+ channels
in non-pacemaker cardiac cells, what causes the initial depolarisation?
increase in permeability to Na+
in non-pacemaker cardiac cells, is the part of the action potential attributed to Na+ influx short or long?
short
in non-pacemaker cardiac cells, what causes the action potential to plateau?
increase in PCa2+ (L-type) and decrease in PK+
in non-pacemaker cardiac cells, what causes repolarisation of the cell?
decrease in PCa2+ (L-type) and increase in PK+
in cardiac pacemaker cells, what causes the majority of the action potential?
increase in PCa2+ (L-type)
in cardiac pacemaker cells, which three other events cause the pre potential?
decrease in PK+
increase in PNa+ (PF)
increase in PCa2+ (T-type)
in cardiac pacemaker cells, what causes an increase in PF (funny sodium channels)?
previous action potential repolarising and coming back to baseline
do calcium channel blockers increase or decrease the force of contraction of the cardiac muscles?
decrease
do cardiac glycosides increase or decrease the force of contraction of the cardiac muscles?
increase
does an increase in temperature affect the heart?
yes
what happens to the heart when the temperature increases by 1°C?
increase by ~10 beats per minute
what can happen to the heart in hyperkalemia?
fibrillation and heart block
what can happen to the heart in hypokalemia?
fibrillation and heart block
what can happen to the heart in hypercalcemia?
increased heart rate and increased force of contraction
what can happen to the heart in hypocalcemia?
decreased heart rate and force of contraction
how fast does depolarisation travel over the atria?
~0.5m/s
why doesn’t depolarisation immediately spread straight down through the atria into the ventricles?
it hits the annulus fibrosus, non conducting part
how does depolarisation travel from the atria to the ventricles?
through the atrioventricular node
how fast does depolarisation travel through the atrioventricular node?
~0.05m/s
how fast does depolarisation travel through the bundle of His and Purkinje fibres?
~5m/s
