The physiology of cardiac function L8 Flashcards
what is special about cardiac muscle
intercalated discs
functional muscle cells
myocyte
what is a sarcomere between
2 Z lines
what is a sarcomere made up of
overlapping contractile proteins myosin and actin
what is the thin filament made up off
actin
what is the thick filament made up off
myosin
H zone=
just myosin
I band=
just actin
A band=
actin and myosin
Myosin molecule structure=
long molecule, 2 heads containing ATPase, alpha helix chain with a hinge region
what is needed for cross bridge formation
hydrolysis of ATP
Troponin C=
binding site for Ca2+ ions
Troponin I=
inhibits actin and myosin coupling
Troponin T
attaches to tropomyosin
3 parts of troponin complex
TnT
TnC
TnI
what transmitter is released at SA and AV nodes during sympathetic stimulation
noradrenaline
what does noradrenaline bind to at SA and AV nodes
B1 receptors
what types of protein do B1 receptors trigger
G protein
what is the overall result of sympathetic stimulation on the SA and AV nodes
Ca2+ channels open and increase speed and force of contraction
relaxation is also called
lusitropy
what does an increase in returning to resting level more quickly
allows contractile machinery to relax faster more time for ventricle filling
what modulates Ca2+ binding to Tnc
PKA phosphoylation (increased dissociation)
where does parasympathetic control come from
cardioinhibitory center cardioacceleratory
what transmitter is used in parasympathetic control
acetyl choline
What does acetyl choline bind to
muscarinic M2 cholinergic receptors
what effect does acetyl choline have
hyperpolarising the cell decreasing muscle contraction
inotropy=
contraction of myocardium
lusitropy=
relaxation of myocardium
chromotropy=
firing of sinoatrial nerve
dromotropy=
conduction velocity of atrioventricular node
cardiac output calculation
heart rate x stroke volume
cardiac output=
volume of blood pumped from one ventricle each minute
ejection fraction=
fraction of end diastolic volume (EDV) ejected out by each ventricle/ beat
EDV=
end diastolic volume
ESV=
end systolic volume
stroke volume can be calculated by
EDV- ESV
ejection fraction calculation
stroke volume/ EDV
normal ejection fraction=
55%-75%
2 types of action potential in the heart
fast response
slow response
where is the fast response
cell to cell depolarisation in cardiac myocytes
where is the slow response
SA and AV nodes
what is the trigger for SA and AV nodes depolarisation
Calcium
