Cardiac Muscle Structure & Function Flashcards
1
Q
What are the specialized features of cardiac muscles?
A
- Striated
- Not under direct neural control
- Shorter, narrower, richer in mitochondria than skeletal muscles
- ATPase activity of cardiac myosin slower than skeletal muscle but faster than SM
- Ca++ binds to troponin => regulates actin-myosin interaction
2
Q
Describe myosin
A
a
3
Q
Describe actin
A
a
4
Q
Describe troponin C
A
- Contains 1 Ca++ binding site
5
Q
Describe troponin I
A
- Contains 2 PKA phosphorylation sites (critical for adrenergic response)
- Interacts with TnC but released with phosphorylation
6
Q
Describe troponin T
A
- Binds tropomyosin
- Regulates isoform expression
7
Q
Describe tropomyosin
A
- Only alpha isoform in heart
8
Q
Describe the basic contraction-relaxation cycle
A
- AP leads to Ca++ release
- Ca++ binds to TnC
- Tn complex undergoes conformation change => moves tropomyosin out of way
- Myosin binds actin and cross bridge moves
- Ca++ is released from TnC => tropomyosin reblocks binding site => relaxation
9
Q
Describe the mechanisms of altering cross-bridge cycling in cardiac muscle
A
- many ways to regulate Ca++ flow
- Depolarization opens L-type calcium channels => calcium influx
- Calcium influx triggers more Ca++ release from SR via RyR2
- Ca++
10
Q
Describe the length-tension relationship (Frank-Starling) in cardiac muscle
A
a
11
Q
Identify sarcomeric changes associated with heart failure
A
a
