Compare cardic and skeletal muscle in view of
1. Structure
2. Action potential
3. Ability for Tetanization
Answer
1. Structure
|
Skeletal muscle
|
Cardiac muscle
|
Attachment
|
Attach to tendon
|
Does not attach to tendon( found in heart )
|
Muscle fiber diame
| Large (100 µm ) | Small (10 µm )
|
Muscle fiber shape
|
Cylindrical
|
Branched
|
Myofibrils
|
Regular
|
Regular
|
Mitochondira
|
Few
|
Many
|
Syncitium
|
None
|
Functional
|
Nucleus
|
Multiple
|
Single
|
Gap junction
|
No
|
Present ( intercalated disc )
|
T tubules
|
Wider and few
|
Narrow and many
|
Muscle fiber length
|
Long (200mm)
|
Short (50µm)
|
2. Action potential
- In skeletal muscle Duration of action potential short (2- 5 mS) whereas in cardiac muscle it is long 200-400ms.
- In cardiac muscle there is plateau phase but not in skeletal muscle
3. Ability for Tetanization
Skeletal muscle fiber is electrically refractory only during rising phase and part of the falling phase of the action potential (short refractory period). During this time muscle fiber start to contract by the first stimuli. If new stimulus given to muscle fiber after this refractory period new action potential develop and result contraction of muscle before relaxation as contractile mechanism have no refractory period . This new contraction added to already present contraction (summation of contractions). Repeated stimulation without any relaxation of muscle result continues contraction muscle this is known as tetanus.
In cardiac muscle absolute refractory period span from phase 0 to half of phase 3 and it remain relatively refractory until phase 4. During this time, cardiac muscle cannot contract .therefore tetanization can not seen in cardiac muscle.
Labels: Excitable tissue, Excitable tissue MCQs, Excitable tissue SEQs, Physiology SEQ