Cardiovascular Mechanics Flashcards
What ion produces a contractile event?
Calcium
What happen when you remove calcium from the extracellular space of cardiac tissue?
The cardiac tissue will not contract
What are T-Tubules?
Finger like invaginations from the cell surface that are spaced such that each T tubule lies alongside the Z line of every myofibril
What do T tubules do?
Allow the excitatory depolarisation event to travel deep into the cell
What is the lace like structure above the sarcomeres?
Sarcoplasmic reticulum
What is the function of the sarcoplasmic reticulum?
holds and stores calcium
What percentage of volume of cardiac cell does the sarcoplasmic reticulum occupy?
4%
What channels lie in the T tubule membrane?
L type calcium channels
What receptors lie above the L-type calcium channels
Ryanodine receptors
Where are ryanodine receptors found?
Embedded within the sarcoplasmic reticulum membrane
What are SR calcium release channels?
Ryanodine receptors
What structure is involved with detecting the action potential / depolarisation event?
The L type calcium channel
What first happens when a depolarisation event is detected?
Ca2+ ions from outside the cell enter through the calcium channels
What two things happen to the calcium which enter into the L-type Ca2+ channel?
Most binds to Ryanodine receptor but some goes to sarcomere for muscle contraction
What happen when the ryanodine receptor binds calcium?
Undergoes a conformation change, and allows stored calcium to be released from the sarcoplasmic reticulum into the cytoplasm
What happens to the stored calcium that is released from the sarcoplasmic reticulum?
Binds to the myofilaments to initiate muscle contraction
What is the calcium induced calcium release effect?
When calcium comes and binds to the ryanodine receptor, to trigger the release of more calcium from the sarcoplasmic reticulum
How is relaxation of the muscle brought about?
The calcium ions are taken back up into the sarcoplasmic reticulum by SR Ca2+ ATPase
What is the sodium calcium exchanger?
A protein embedded in the T tubule which allows calcium to leave into the extracellular space to trigger relaxation of the muscle
What is the balance between the amount of calcium entering into the cell, and leaving the cell?
They are equal
What does force production depend on?
The concentration of intracellular calcium
What is the relationship between force production and calcium concentration in the cytoplasm?
Sigmoidal relationship
What happens to the amount of force produced when you increase the stretch on the muscle?
The amount of force produced increases
What is passive force?
As you stretch a muscle fibre more, the elasticity this results in is called the passive force - like a recoil force
What happens to passive force as you stretch cardiac muscle more?
Passive force increases
What is meant by isometric contraction?
Contraction that produces forces without the muscle shortening
What is total force?
Active force + Passive force
Between cardiac and skeletal, which produces more passive force?
Cardiac muscle
Why does cardiac muscle have a larger passive force?
Cardiac muscle is more resistant to stretch, so when it does get stretched the passive elastic recoil force it can produce is greater