lecture 11 study guide Flashcards
anatomy
what is smooth muscle tissue? where is it found in the body? What are its unique features?
- walls of hollow organs
- stomach, bladder, arteries
- involuntary
- spindle-shaped
- not striated
- uninucleate
what is skeletal muscle tissue? where is it found in the body? What are its unique features?
- attached to bones
- contracts rapidly and powerfully but tires easily
- longest muscle fiber
- visible striations
what is cardiac muscle tissue? where is it found in the body? What are its unique features?
- forms the bulk of heart walls
- involuntary
- short, bifurcated cells
- striated
- uni or nucleated
what is a sarcomere?
the basic contractile unit of muscle fibers
why is a sarcomere considered the fundamental unit of muscle contraction?
Sarcomeres contain a motor protein called myosin, which powers the muscle to contract by “grabbing” onto another protein called actin and “flexing.”
how does a sarcomeres structure contribute to its function?
Each sarcomere is composed of two main protein filaments—actin and myosin—which are the active structures responsible for muscular contraction
identify the organelle within muscle cells that stores calcium ions.
sarcoplasmic reticulum
Describe the process by which calcium ions are released from their storage site within the muscle cellWhat initiates this release, and why is it important for muscle
contraction
The action potential invades T-tubules and causes calcium channels to open, which in turn causes receptors in the SR to open and release calcium, which stimulates contraction.
Describe the two primary contractile proteins in muscle fibers and their roles in muscle
contraction
myosin, the principal component of thick myofilaments, and actin, which is the principal component of thin myofilaments.
why are myosin and actin essential for the process of muscle movement?
the binding of myosin to actin filaments, allowing myosin to function as a motor that drives filament sliding.
Explain the role of troponin in regulating muscle contraction.
On binding Ca2+ Tn transmits information via structural changes throughout the actin-tropomyosin filaments, activating myosin ATPase activity and muscle contraction.
how does troponin contribute to the control of myosin binding sites on actin?
calcium ions bind to troponin, causing conformational changes in troponin that allow tropomyosin to move away from the myosin-binding sites on actin
Explain the role of calcium ions in muscle contraction.
calcium causes a shift in the position of the troponin complex on actin filaments, which exposes myosin-binding sites
What effect do calcium ions have
on actin filaments, and how does their presence enable the contraction process?
calcium ions bind to troponin, causing conformational changes in troponin that allow tropomyosin to move away from the myosin-binding sites on actin
how does ATP interact with myosin and actin during contraction and relaxation phases.
ATP binding causes myosin to release actin, allowing actin and myosin to detach from each other.
