Cardiac muscle Flashcards
How does the heart beat (mechanism)
spontaneous depolarization and triggering of the action potential via pacemaker
Myocardium are broken down into
Nodal and contractile cells
Function of nodal cells
Set rhythm and pace for the beating
Contractile cell consist of
Tropomyosin, actin, myosin, troponin
The pathway of impulses in the heart
Sa nodes -> av nodes
How does the sa node impulse travel to the other side
Via backman bunder
Bundle of his separates into
Right and left bundle branches
The last bundle to receive an impulse is the
Purleinje fibers
Sa nodes are
The pace makers
What kind of wave are the impulses
Depolarisation waves
Why does the av nodes takes 0.1 second slower (delay)
Cause of the lesser gap junction and smaller diameter
What kind of cells can nodal cells send an impulse to
Other nodal or contractile cells
What are intercalacted disk
The junction between each cell (the gap junction between desmosome)
Desmosome function
Physically holding the cells together
Intrinsic cardiac contraction steps (from nodal cell)
- Na+ leak into the cells (-60 to -55)
- T-type Ca+ channel open due to the depolarization (-55 to -40)
- L-type Ca+ channel open which leads to excessive amount of Ca+ to flow in
- K+ channel opens to repolarize
Intrinsic cardiac contraction steps (contractile cells)
- Cations from nodal flows in (-90 to -70)
- Na+ voltage gated channel opens for Na+ to flow back in (reaches 10)
- Ca+ channel open for it to enter, K+ channel open for it to exit (reaches 0) And this continues until back to -90
Muscle contraction steps
- ca+ calmodulin attaches to RYR-2 receptor (R2)
- Ca+ then attaches to TnC to pull start the cross-bridge
Down /”rest” period for the heart beat
- Block Ca+ channel
- Ca+ at tnC flow back out into the sarcoplasmic reticulum
- Release Ca out of the cell
Open K+ channel to repolarize
Difference between cardiac and smooth muscles
Cardiac m. Has a longer refractory period (cool down since a tetanus cannot be achieved)
What is the frank starling law
Stretching of heart increases force of contraction (elastic energy contribution)
Concentric and eccentric
Con= force > resistance (better)
Ec = force < resistance
Extrinsic cardiac contraction (nodal / sym. Cells)
- Norepinephine /epinephrine stimulates b1-ar
- Activates Gs -> stimulate G protein
- Active adrenaline cyclase (ATP to be converted to cAMP)
- CAMp -> pKA
- PKA to open Ca+ channel and Ca+ flow in
- Contraction via depolarization
Extrinsic cardiac contraction (contractile/para. Cells)
- Sym nerves connects to b1-ar and activate Gs
- Activates acetyl-coa cyclase (convert to kPA)
- Open Ca+ channel for Ca to flow into SR and cell to connect with tnC
- Contraction via depolarization
What is used to increase the HR
Positive Chronotropic action
Positive inotropic causes
Increase in contractility
Negative inotropic causes
Decrease in contractility
What does the smooth muscle do not have
Sacromere
Types of smooth muscles
Single unit and mutliunits
Where are the mulitunit located
Iris
Where are the single unit located
GI tract
Function of single unit
Gross control
Function of multiunit
Large arteries or goosebumps
