Cell Physiology Part 9 Flashcards
How many smooth muscle fibers are typically innervated by a single nerve fiber?
A number of smooth muscle fibers
How many neurons can innervate a single smooth muscle fiber?
More than one neuron
Can smooth muscle tension only increase, or can it also decrease?
Can be increased or decreased
Can a single neurotransmitter have the same effect on all types of smooth muscle tissue? (Yes/No)
No, a given neurotransmitter may produce opposite effects in different smooth muscle tissues.
What two factors determine the type of response elicited in smooth muscle by a neural or hormonal signal?
The type of response depends on chemical messenger and receptors.
Mechanism of Smooth Muscle Contraction
Uses cross-bridge movements to generate force. Calcium ions control cross-bridge activity, but unlike skeletal muscle, it does not involve troponin.
Difference Between Skeletal and Smooth Muscle Contraction
Smooth muscle lacks troponin, is regulated by phosphorylation of myosin, and involves calcium changes in thick filaments, not thin filaments.
ATPase Activity in Smooth Muscle
Smooth muscle has a low maximal rate of ATPase activity of myosin compared to skeletal muscle, leading to slower contractions.
Calcium Sources in Smooth Muscle Contraction
Calcium comes from both the sarcoplasmic reticulum and extracellular fluid via calcium channels. Skeletal muscle mainly uses SR calcium.
Effect of Calcium Concentration on Tension
Increased calcium leads to more cross-bridges activated and greater muscle tension.
Term: End Plate Potential
The depolarization of the skeletal muscle membrane caused by neurotransmitter binding to receptors on the motor end plate.
Cross-Bridge
A connection formed between actin and myosin filaments during muscle contraction.
Excitation-Contraction Coupling
The process that links the action potential in the sarcolemma to the activation of the myofilaments, resulting in contraction.
Active Tension
The force generated by the cross-bridges during contraction of a muscle fiber.
Isometric Contraction
contraction where muscle tension is developed without a change in muscle length.
Isotonic Contraction
A contraction where the muscle changes length while the tension remains constant.
Membrane Transport - Commons & Differences
Involves various ion channels and transporters; differences exist in how skeletal and smooth muscle regulate calcium and ion flow.
• How does the relationship of actin and myosin explain the length-tension curve of skeletal muscle?
The amount of tension a muscle can produce depends on the initial length of the sarcomere, which affects the number of actin-myosin interactions (cross-bridges). The length-tension curve shows this relationship, peaking at optimal overlap and dropping at lengths that are too short or too long.
• “Muscle is a machine for converting chemical into mechanical energy.” Analyze and discuss
this statement
How it works:
• Muscles use ATP for energy.
• ATP helps myosin heads grab and pull actin filaments, making the muscle contract.
• This process is called the cross-bridge cycle.
What we get from it:
• Muscle contraction creates movement, posture, and stability.
• After contracting, muscles need more ATP to relax and get ready to contract again.
Why it’s like a machine:
• Just like a machine uses fuel to do work, muscles use ATP to produce motion.
• Muscles are efficient, controlled, and repeatable in their actions—just like a well-designed machine.
