cardiac muscle Flashcards
Describe the structure of the heart
left atrium
left ventricle
right atrium
right ventrical
aorta
what are the heart cells termed as
Ventricular muscle cells
What structures are located at the intercalated disc
desmosomes
gap junctions
describe the feature of desmosomes
prevents separation of cardiac muscle during contraction
describe the function of gap junctions
allows action potenital to be carried from one cell to the next
what to desmosomes and gap junctions allow the heart to do
allows coordination
Describe action potential within the heart
long
has a plateau phase as there is a presence of Ca
membrane potential depolarized throughout most of the twitch phase
Does summation/ tetanus occur within the ventricular myocute
No
unlikely
what are the three major phases of the Action potential in cardiac muscle cells
- Rapid depolarisation
- Plateau
- Repolarisation
Rapid depolarization
Fast opening of voltage gated NA channels
Plateau
Slow voltage voltage gated Ca channel
Depolarisation
Closing of Ca channels opening of K channels (influx of K outward)
What does the Ca influx cause
triggers the opening of Ca sensitive channels in the SR= burst of Ca
CALCIUM INDUCED CALCIUM RELEASE
What does Calcium cause the Cardiac muscle to do
CONTRACTION
What controls and regulates the Ca2+ back into the SR for a ventricular myocute
Na+/Ca+ exchanger
Ca2+ ATPase active pump
State the equation for cardiac regulation
CO= SV x HR
who is HR set by
set by the pacemaker in the sinoatrial node
Who affects the HR
Autonomic nerves releasing neurotransmitters
Describe the SA + AV node potential
unstable membrane potential
Depolarisation due to relatively slow Ca2+ current
Vagus nerve
Parasympathetic
decreases HR releases Ach
slows down depolarisation & hyperpolarises the resting membrane potential
Sympathetic cardiac nerve
increases heart rate
and force of contraction
releases noradrenaline
increases rate of depolarisation
what is stroke volume
tension developed by the cardiac muscle fibres
what increases stroke volume
increased HR
increases stretch of the ventricles
neurotransmitters (noradrenaline)
Increasing Heart rate causes what to stroke volume
increases stroke volume as their is less time for Ca2+ to be released from the cell
Describe the length tension relationship within ventricular myocyte
- increased stretch
= increase volume
= increase contraction
What does increased noradrenaline cause
leads to increased cytosol calcium
therefore there in increased output
increased inotropy and heart rate
