lecture 18 Flashcards
The cardiac muscle cells
- myocytes:
- force producing cells
- striated muscle fibers
- can generate and action potential - pacemaker cells
- they are autorythmic
- they self excite
- generate spontaneous muscle action potential
- have lots of voltage gated ion channels
why in this case are they called cells and not fibres
they are not long and cylindrical
intercalated disks
- muscle cells are connected at these regions
- the provide physical coupling so they’re structural they keep 1 muscle cell attached to its neighbour and this is made possible by desmosones
-bthey provide functional coupling made possible by gap junctions so when 1 cell excites all cell excites because we want heart to function has a whole
Cardiac muscle cells vs. skeletal muscle fibers
- called cells because they are not long cylindrical cells that resulted from a fusion event
- they are smaller and have 1 or 2 nucleus
- they irregular shaped (branch or y shape)
- have intercalated disks
- skeletal muscle have larger t-tubules
- smaller sarcoplasmic reticulum
- have lots of mitochondria
excitation-contraction coupling in cardiac myocytes
- Action potential started from a pacemaker cell arrive and enters from adjacent cell (gap junction)
- that wave of excitation will cause voltage gated K+ and Na+ channels to open
- Action potential moves along plasma membrane of our cardio myocytes
- Action potential will travel down the t-tubule
- which will activate “L type Ca2+ channels”
- calcium will move from ECF to in and bind to the “RyR Ca2+ channel” in the SR
- RyR channel is ligand gated
- in cardiac muscle calcium from ECF is critical - RyR channels open and now we get a bulk of Ca2+ release from SR
- this is call “calcium induced calcium release” - we get a Ca2+ spark that leads to Ca2+ signal
- Ca2+ signal
- Ca2+ binds to troponin which pulls tropomyosin our of the way and tropomyosin is no longer blocking myosin binding sites
- we get high force cross bridge and crossbridge cycling and heart will contract
What is the ration of calcium from ECF and SR
90% from SR
10% from ECF
Mechanism of myocyte relaxation
Relaxation occurs when Ca2+ is put away of kicked out
Put away: SERCA is a pump that requires energy that moves calcium back into SR
Kicked out: NCX
- sodium-calcium exchanger
- secondary active transport because Na+ move down its electrochemical and using that energy to remove Ca2+
3 key differences between skeletal and cardiac excitation-contraction coupling
- Calcium induced calcium release
- NCX
- Lack of summation in cardiac muscle. They contract then relax rather than entering a fused or unfused tetanus
arteries take blood ________ from the heart
away
veins bring blood _______ to the heart
back
pericardium
minimizes friction
The coronary artery
- branch right off the aorta that comes right back to the heart and feeds the heart muscle
- provides a blood supply for the heart
- related to cardiovascular diseases
The 4 major blood vessels
- Pulmonary veins: bring back oxygenated rich blood from the lungs to heart.
- Pulmonary arteries: carrying oxygen poor blood from the heart to the lungs
- Aorta: carries oxygen rich blood from the heart to the circulatory system
- Vena cava (inferior/superior): entry point, both drain into right atrium
Valves open and close to
prevent back flow
Valves between the atria and ventricles are called
Atrioventricular valves
1. Tricuspid valve (RA to RV)
2. Bicuspid (mitral) valve (LA to LV)
