what does cardiac and skeletal muscle look like?
striated - good for contractibility
what are the darker bands on cardiac cells
intercalated discs - gap junctions
what are the characteristics of cardiac muscle cells?
uninucleate, striated and non-fatiguing, involuntary high power
what proteins are within the gap junctions?
regulatory proteins - stop contractions
explain the sliding filament theory
when the muscle contracts they slide into each other. the shortening of the striated cells is by thick filaments pulling thin filaments towards the centre of the sarcomere
Ca2+ dependent
describe the neuromuscular junction
- Voltage -sensitive Ca2+ channels open
- Ca2+ enters the cell
- Vesicle fusion – Ach exocytosis
- Ach diffusion in the synaptic cleft
- Ach-sensitive cation channels open
- 3Na+ out and 2K+ in
- End -plate membrane depolarises
- Generation of action potential
describe the structure of actin filaments?
tiny actin molecules wrapped around each other like string. A few troponin molecules placed and tropomyosin wrapping around whole filament to keep it together
describe the structure of myosin filament
wider filament- thin stripe texture with myosin molecules attached.
what does T Tubules and sarcoplasmic reticulum do?
creates a network to oversee electrical conductivity
what is functional syncytium?
network where cells work cohesively with adjacent cells to undergo excitation
what is the function of gap junctions?
- Allows cellular communication through connexons
- Small ions can move freely through pores
what are connexons?
transmembrane protein channels
why is there a plateau stage of cardiomyocyte action potential?
time while AVN briefly pauses to allow for signal to be fully ready to go down septum to ventricles
what is the absolute refractory period?
time where there is no firing/ no AP generated as the ions are in the wrong place
describe the route of the action potenial
SAN is depolarised and conduction spreads across the atria and reaches AVN. Brief pause then fast conduction through Bundle of His and spreads across ventricles to ensure simultaneous contraction.
what are the two different inputs to CV centre in medulla within autonomic NS?
- From higher- cerebral cortex, limbic (emotion), hypothalamus
- From sensory- proprioception (movements), chemoreceptors (pH), baroreceptors (pressure)
what are the outputs from CV to heart within autonomic NS?
- Increased rate of spontaneous depolarisation in SAN/ AVN increases heart rate
- Increases contractility of atria and ventricles – increases stroke volume
- Decreased rate of spontaneous depolarisation in SA node/ AVN – decreases heart rate
what is vagal tone?
reduces Hr by hyperpolarising san cells and decreasing slope of pacemaker potentials
what is sympathetic tone?
keeps Hr up by increasing slope of pacemaker potentials
