50.5 Smooth and Cardiac Muscle Flashcards
1
Q
vertebrate cardiac muscle
A
only found in the heart
-striated-cells interlock at intercalated disks
2
Q
cardiac muscle vs
skeletal muscle
A
- CARDIAC: makes APs by itself (ion channels in the plasma membrane allow it to depolarise rhythmically)
- Aps last 20x longer than skeletal muscle
- SKELETAL: need motor neuron input (acetylcholine) to stimulate APs
3
Q
intercalated disks
A
where cardiac muscle cells interlock
-gap junctions there provide direct electric coupling between the cells
(Maps generated by cells in one part of heart reaches the entire heart)
4
Q
vertebrate smooth muscle
A
- walls of hollow organs (blood vessels and organs the digestive tract)
- unstriated
- can contract by signals from autonomic nervous system
- or can generate APs without neurons
- contract and relax slower than striated muscle
5
Q
why is smooth muscle unstriated
A
- the myosin and actin filaments are not regularly arrayed along the length of the cell (thick bodies in cytoplasm- thin attached to dense bodies on the plasma membrane)
6
Q
smooth vs
striated
A
SMOOTH: -contract and relax slower
- not troponin complex or T tubule- underdeveloped SR
- in AP, Ca2+ enters cytosol directly from membrane
- the Ca2+ cause contractions by binding to calmodulin (protein)
- calmodulin activates an enzyme that phosphorylates myosin head to make cross bridges
7
Q
muscles in invertebrates
A
- identical arthropod skeletal muscle
- flight muscles in insects can contract independently rhythmically
- thick filaments in clam shells (closed) has a protein that lets it remain closed for like a month