Cell Physiology Part 8 Flashcards
What is preload?
Preload is the force on the muscle prior to contraction
What of the muscle does preload set?
Initial length
What is Afterload?
The force during contraction
What does the rate of ATP splitting determine?
shortening velocity
Types of Summation
- Multiple fiber summation: : involves the recruitment of more motor units and follows the size principle.
- Frequency summation: involves increasing the frequency of stimulation, leading to incomplete tetanus and eventually complete tetanus.
What does Summation do?
Regulates the intensity of contraction rapidly by;
Increasing frequency of contraction (frequency summation)
Increasing number of motor units(multiple fiber summation)
Characteristics of smooth muscle
•Lack the cross-striated banding pattern
•The nerves are derived from the autonomic division of the nervous system rather than the somatic division
• Smooth muscle is not normally under direct voluntary control.
How many smooth muscle cells contain nuclei?
A single nucleus
What cellular process is smooth muscle capable of throughout an individual’s life?
Division
Compared to other muscle types, are there typically more or fewer thick (myosin-containing) filaments in smooth muscle?
Fewer
Are there more or fewer thin (actin-containing) filaments compared to thick filaments in smooth muscle ?
More
What structure are dense bodies in smooth muscle similar to?
Z lines
Are sarcomeres present in smooth muscle tissue? (Yes/No)
No
Describe the nature of smooth muscle contraction in terms of speed and extent.
Slow but wide (or Contract slowly but widely)
What type of mechanical connection is present in smooth muscle?
Dense band
What type of electrical coupling is present in smooth muscle, allowing for coordinated contraction?
Gap junction
Single unit smooth muscle is also known as?
Visceral smooth muscle
Characteristics of smooth muscle
Found in intestinal tract, uterus and small-diameter blood vessels
• Synchronous activity: electrical & mechanical
• Link to adjacent fibers by gap junctions
• A few of them are pace maker cells (autorhythmicity)
• Altered by nerves, hormones and local factors
• A contractile response can often be induced by stretching the muscle.
Characteristics ofMulti -unit smooth muscle
Found in Ciliary muscle, iridic muscle, erector muscle, smooth muscle in the large airways and aorta
• On or few gap junctions
• Responds independently of its neighbors
• The contractile response of the whole muscle depends on the number of muscle fibers that are activated and on the frequency of nerve stimulation.
95
What can occur in smooth muscle in the absence of neural input?
Spontaneous electrical activity
What are the key electrical events observed in the spontaneous activity of smooth muscle?
Repolarization, depolarization, tonic stage of contractile activity
Where are pacemaker cells typically found in relation to the smooth muscle of the gastrointestinal tract?
Pacemaker cells are found throughout the gastrointestinal tract.
What types of factors can alter smooth muscle tension?
Neural, hormonal and local factors
What type of autonomic nervous system regulation do most smooth muscles (excluding arteriolar smooth muscle) receive?
Sympathetic and parasympathetic neurons regulation
Do smooth muscle fibers possess a specialized motor end-plate region like skeletal muscle? (Yes/No)
No
What is the structural basis for neural control of smooth muscle?
Synapsis (varicosity)
