Lecture 4- Muscular Tissue Flashcards
What are the three types of muscle tissue?
- Skeletal- striated, voluntary, attached to skeleton
- Cardiac- striated, involuntary, heart
- Smooth- smooth, involuntary, bladder, organs, blood vessels
What does the term “muscle” mean?
Many muscles fibers (cells) surrounded by connective tissue
What is the endomysium?
Surrounding of the muscle fiber or cell
What is the perimysium?
Surrounds the muscle fascicle
What is the epimysium?
Surrounding of the entire muscle
Why is there more than one nucleus per muscle fiber?
The nucleus divided and the cell did not divide or myoblasts fused during development to form muscle fibers.
What are myofibrils and why is skeletal muscle striated?
Myofibrils are composed of Actin (thin) and Myosin (thick) filaments and are striated because of the orientation of these fibers
What is the Z-Disc made of?
A spider web of thin filaments including:
1. Alpha-Actinin
What is the role of titin?
Titin connects the thick filaments to the Z disk
What are the boundaries of the sarcomere?
Z-line to Z-line
What are the boundaries of the H Zone?
The central region between Z-lines containing the M line in the absolute center.
What is the I band (isotropic)?
The band containing the Z line, stained light
What is the A band (anisotropic)?
The band containing the thick filaments housing the H zone and the M line.
Do skeletal muscle fibers also have other organelles?
Yes, lots of mitochondria.
What is the main role of the sarcoplasmic (SR)?
Store calcium to release during contractions
How does Ca get released from the SR to cause contraction?
Excitation-contraction (E-C) coupling
What controls contraction of the skeletal muscle?
Somatic Nervous System
What is the neuropathway of contraction (E-C coupling)?
- Neurotransmitter (ACh) released from the neuron
- ACh binds to its receptor on the sarcolemma or muscle cell membrane
- Initiates a muscle or electrical impulse to spread along the sarcolemma
- Impulse travels down into the muscle cell via t-tubules
- triggers the release of Ca++ from the SR
What does the Ca++ do?
- Calcium binds to troponin C
2. Initiates contraction
What happens to the Z line, I band, A band, and sarcomere during contraction?
- Z lines narrow
- I band narrows
- Sarcomere shortens
- A band stays the same
What are the different types of muscle fibers?
- Slow twitch
- Intermediate twitch
- Fast twitch
What is the difference between cardiac muscle and skeletal muscle?
- Cardiac muscle contain nuclei in the center
- The cells are branched
- Cells have intercalated disks
What is the advantage of cell branching?
Branching helps organize the muscle in the heart chamber so it ejects more blood with each contraction.
What are the advantages of intercalated disks?
Intercalated disks bind cells firmly together. It helps with intercellular communication so the ventricles and atria can contract as one unit.
What structures in the intercalated disk helps bind cells firmly together?
- Desmosomes
2. Fascia adherens (resembles zonula adherens)
What structure helps the intercalated disk with intercellular communication?
Gap Junctions
What is the advantage of having the gap junctions?
Communication
What are the components of thin filaments?
- Actin
- Tropomyosin
- Troponin C, I, T
What type of organelles are found in cardiac cells?
Mitochondria
What is the terminal cisternae?
The endpoint of the sarcoplasmic reticulum. There is only one so it is a dyad.
How can you describe smooth muscle?
- few mitochondria
- no T tubules
- Actin & Myosin not organized in sarcomeres
- no striations
- cells are small and squished together
What is the function of dense bodies in smooth muscles?
They function as Z-discs as the attachment for:
- alpha actinin
- intermediate filaments
- thin filaments
What causes the corkscrew configuration in smooth muscle?
The configuration of smooth muscle during contraction.
Does smooth muscle contain desmosomes or gap junctions?
No, they don’t contain desmosomes, but they do contain gap junctions.
