Exam #1: Skeletal Muscle Flashcards
What is the difference between the three main types of muscle?
- Skeletal & Cardiac are striated
- Smooth is non-striated
What type of muscle contains intercalated discs?
Cardiac
What is the functional unit of skeletal muscle?
Sarcomere
What is the definition of a sarcomere?
Z-disc to z-disc
What is the function of intercalated disc found in cardiac muscle?
- Mechanical connection
- Electrical connection
What is contained in intercalated discs that allows for electrical connection?
Gap junctions
What are the two types of smooth muscle?
Multiunit & Unitary
What is unitary smooth muscle?
Group of fibers that contract together as a single unit:
- Found in visceral smooth muscle
- Pacemaker cells make it spontaneously active
- Contains gap junctions that work as a functional syncytium
How is multiunit smooth muscle different from unitary smooth muscle?
Discrete smooth muscle fibers that contract independently
- Not spontaneously active
- Stimulated to contract by motor nerves
- Each cell has a synaptic connection with a varicosity
*Found in the eyes e.g. ciliary muscle & in piloerector muscle
What is a myofibril?
Myofibril= cylindrical structure made up of end-to-end chains of sarcomeres
What connective tissue element surrounds a bundle of myofibrils?
Endomysium
Define muscle cell.
Muscle fiber, a bundle of myofibrils surrounded in endomysium
What is a fascicle?
A bundle of muscle fibers
What connective tissue element en-sheaths fasciculi?
Perimysium
What connective tissue element en-sheaths bundles of fasciculi?
Epimysium i.e. the covering around the entire muscle
Where are the nuclei & mitochondria located in a muscle cell?
Sarcoplasm
Are skeletal muscle cells uninucelate or multinucleate?
Multinucleate
What is a T-Tubule?
Transverse Tubule, extensions of cell membrane into the muscle cell;
- Because these structures are an extension of the plasma membrane, they contain extracellular fluid
What is the function of the T-Tuble? What does the ionic composition of a T-tubule resemble?
Function= electromechanical coupling- conveys the action potential to the muscle
- ECF (high Na+)
What are thick filaments composed of?
Myosin filaments
What are thin filaments composed of?
Actin filaments