Cardiac contractility lecture handout 1 per page

• To explain how force is produced in cardiac muscle, how it differs from skeletal muscle and how it can be influenced by the extrinsic sympathetic nerves.

troponin in cardiac muscle

the response to calcium is graded depending on the concentration this means if you vary concentration of Ca2+ you will vary activity of troponin and how many myosin actin cross-bridges will be available and therefore the force generated in each sarcomere's contraction this results in ‘’cardiac contractility’’ and allows us to control the force of each heart beat

troponin in skeletal muscle

is an all in one response and cannot be controlled on how much myosin/actin crossbridges appear and so the same force of contraction will always occur

describe the following process…

Action potential spreads across surface of cardiac muscle cell, down the T-tubules which causes L-TYPE dyhydropyradine receptors to open allowing an influx of calcium which actually causes calcium from the sarcoplasmic reticulum to be released (A HUGE amount) it is known as a Ca++ spark and this calcium then leads to an interaction with troponin (which is dependant on ca2+ concentration and variable by it which influences the contractile force generated by the signal)

• To relate the timings of the electrical activity of the heart to the resulting mechanical events of the cardiac cycle.

• To interpret cardiac volume/pressure diagrams and state how they differ between the left and right sides of the heart.

the ventricles, specifically the left ventricles generate the MOST pressure to push the blood OUT of the heart into the great vessels. the pressure actually contained by the atria themselves is higher than found in the ventricles and this allows for passive flow of blood from atria to ventricles

the volume of blood is the exact same on either side of the heart.