Case 4 Sem 2 Flashcards
Right heart pumps blood into
Lungs
Left heart pumps blood into
Peripheral organs
Atrium
Weak primer pump for ventricle (moves blood into ventricle)
Ventricles
Main pumping force propelling blood
Right ventricle
Pulmonary circulation
Left ventricle
Peripheral circulation
Atrial muscle
Contracts strongly like skeletal
Longer contraction than skeletal
Ventricular muscle
Contacts strongly like skeletal
Longer contraction than skeletal
Specialised excitatory and conductive muscle fibres
Contract weakly because few contractile fibrils
Exhibit autonomic rhythmical electrical discharge in form of action potentials or conduction of action potentials through the heart
(Excitatory system that controls rhythmical beating of the heart)
Syncytium
Single cell/cytoplasmic mass containing several nuclei formed by fusion of cells/division of nuclei
Intercalated discs
Cell membranes that separate individual cardiac muscle cells (cardiomyocytes)
Cardiac muscle fibres
Many individual cells connected in series, parallel to each other
Gap junctions
At each intercalated disc
Permeable communicating junctions that form where cell membranes of different cardiomyocytes fuse
Gap junctions and free diffusion of ions
Gap junctions allow total free diffusion of ions therefore ions move with ease in intercellular fluid along longitudinal axis of cardiac muscle fibres, so action potential can travel from one cardiac muscle cell to the next past the intercalated disc
So when one of the cardiac cells are excited, action potential spreads to all of them, spreading from cell to cell through latticework interconnections
Sodium potassium pump
Pumps out 3 sodium ions for ever 2 potassium ions it pumps in with aid of ATP
sodium ions diffuse in through membrane
And potassium ions diffuse out of the neuron (potassium ions diffuse more rapidly than sodium ions going in - electrochemical gradient)
M gate
Positive voltage sensor detects voltage of positive ions on outside of neuron membrane
As potassium ions diffuse out, Increase in positive voltage (presence of K and Na) on outside of neuron detected by m gate
Once reached a certain voltage, m gate rapidly opens, allowing for influx of positive ions for generation of action potential
When m gate open, channel is activated
Depolarisation
Ion selectivity filter selects sodium ions, leading to influx of sodium ions
Depolarisation causes slow closing of h gate and channel becomes inactivated
Repolaristaion
M gate detects decrease in positive voltage on outside of membrane (decreased sodium ions)
M gate opens again, this time potassium ions selected by ion selectivity filter, so outflow of potassium ions from inside the neuron
ATP driven sodium potassium pump brings about resting potential, h gate ions and channel reactivated
Voltage gated ion channels
6 alpha helical transmembrane proteins
S4
Positive voltage sensor (m gate)
S5-S6 loop
Pore forming loop allows for selectivity of specific ions
Action potential
The change in electrical potential associated with passage of an impulse along membrane of a muscle /nerve cell
Action potential in ventricular muscle cell fibre
105 millivolts
Intracellular potential rises from negative value (-85 millivolts) between beets to slightly positive value (+20 millivolts) during each beat
After initial spike, membrane remains depolarised for 0.2-0.3 seconds (plateau)
At end of plateau, membrane depolarises abruptlly
Presence of plateau in action potential causes ventricular contraction to last longer in cardiac muscle than skeletal
