Podcast
Questions and Answers
What is the contractile or functional unit of the myocyte?
What is the contractile or functional unit of the myocyte?
What is the purpose of the Z-line in the sarcomere?
What is the purpose of the Z-line in the sarcomere?
What is the function of tropomyosin in muscle contraction?
What is the function of tropomyosin in muscle contraction?
What is the result of the actin filament sliding over the myosin filament during muscle contraction?
What is the result of the actin filament sliding over the myosin filament during muscle contraction?
Signup and view all the answers
What is the function of desmin in the myofibril?
What is the function of desmin in the myofibril?
Signup and view all the answers
What is the result of the summation of all sarcomeres shortening?
What is the result of the summation of all sarcomeres shortening?
Signup and view all the answers
What is the term for cardiac cells also referred to as?
What is the term for cardiac cells also referred to as?
Signup and view all the answers
What is the primary function of smooth muscle in the urinary bladder and uterus?
What is the primary function of smooth muscle in the urinary bladder and uterus?
Signup and view all the answers
What is the characteristic color of conductile cardiac muscle cells?
What is the characteristic color of conductile cardiac muscle cells?
Signup and view all the answers
What is the main characteristic of Purkinje cells?
What is the main characteristic of Purkinje cells?
Signup and view all the answers
What type of muscle cells have an ectodermal origin and contain actin and myosin?
What type of muscle cells have an ectodermal origin and contain actin and myosin?
Signup and view all the answers
What is the function of modified cardiac muscle cells?
What is the function of modified cardiac muscle cells?
Signup and view all the answers
What is the function of dense bodies in smooth muscle cells?
What is the function of dense bodies in smooth muscle cells?
Signup and view all the answers
What is the shape of smooth muscle cells?
What is the shape of smooth muscle cells?
Signup and view all the answers
What is the percentage of shortening of smooth muscle cells when contracted?
What is the percentage of shortening of smooth muscle cells when contracted?
Signup and view all the answers
How do smooth muscle cells communicate in single-unit smooth muscle?
How do smooth muscle cells communicate in single-unit smooth muscle?
Signup and view all the answers
Where are multi-unit smooth muscle cells typically found?
Where are multi-unit smooth muscle cells typically found?
Signup and view all the answers
What type of cells are involved in wound contraction?
What type of cells are involved in wound contraction?
Signup and view all the answers
What is the maximum length of smooth muscle cells in the uterus?
What is the maximum length of smooth muscle cells in the uterus?
Signup and view all the answers
What is the unique shape of myoepithelial cells?
What is the unique shape of myoepithelial cells?
Signup and view all the answers
What type of muscle cells lack the ability to regenerate?
What type of muscle cells lack the ability to regenerate?
Signup and view all the answers
What is the primary function of the T-tubules in skeletal muscle cells?
What is the primary function of the T-tubules in skeletal muscle cells?
Signup and view all the answers
What is the location of satellite cells in skeletal muscle?
What is the location of satellite cells in skeletal muscle?
Signup and view all the answers
What is the primary function of fibroblasts in muscle repair?
What is the primary function of fibroblasts in muscle repair?
Signup and view all the answers
What is the term for the dense irregular connective tissue that surrounds muscles?
What is the term for the dense irregular connective tissue that surrounds muscles?
Signup and view all the answers
What is the primary function of intercalated discs in cardiac muscle cells?
What is the primary function of intercalated discs in cardiac muscle cells?
Signup and view all the answers
Which type of skeletal muscle fiber is characterized by fast contraction and fast fatiguing?
Which type of skeletal muscle fiber is characterized by fast contraction and fast fatiguing?
Signup and view all the answers
What is the term for the contractile elements within skeletal muscle cells?
What is the term for the contractile elements within skeletal muscle cells?
Signup and view all the answers
What is the primary function of the perimysium in skeletal muscle?
What is the primary function of the perimysium in skeletal muscle?
Signup and view all the answers
What is the primary function of longitudinal elements in intercalated discs?
What is the primary function of longitudinal elements in intercalated discs?
Signup and view all the answers
What is the percentage of cellular volume occupied by mitochondria in cardiac muscle cells?
What is the percentage of cellular volume occupied by mitochondria in cardiac muscle cells?
Signup and view all the answers
What is the characteristic of Type 1 skeletal muscle fibers?
What is the characteristic of Type 1 skeletal muscle fibers?
Signup and view all the answers
What is the term for a multinucleated cell, such as a skeletal muscle cell?
What is the term for a multinucleated cell, such as a skeletal muscle cell?
Signup and view all the answers
What is the function of desmosomes as a transverse element for intercalated discs?
What is the function of desmosomes as a transverse element for intercalated discs?
Signup and view all the answers
What is the size of a cardiac muscle cell?
What is the size of a cardiac muscle cell?
Signup and view all the answers
What is the number 1 referring to?
What is the number 1 referring to?
Signup and view all the answers
What is the number 2 referring to?
What is the number 2 referring to?
Signup and view all the answers
What is the number 3 referring to?
What is the number 3 referring to?
Signup and view all the answers
What is the number 4 referring to?
What is the number 4 referring to?
Signup and view all the answers
What does "A" refer to?
What does "A" refer to?
Signup and view all the answers
What does "B" refer to?
What does "B" refer to?
Signup and view all the answers
What does "C" refer to?
What does "C" refer to?
Signup and view all the answers
Which cell type is the arrow pointing to?
Which cell type is the arrow pointing to?
Signup and view all the answers
What cell type is "A" (the green outline) referring to?
What cell type is "A" (the green outline) referring to?
Signup and view all the answers
What cell type is "C" (the yellow outline) referring to?
What cell type is "C" (the yellow outline) referring to?
Signup and view all the answers
What is depicted in this image?
What is depicted in this image?
Signup and view all the answers
What is depicted in this image?
What is depicted in this image?
Signup and view all the answers
Study Notes
Skeletal Muscle Structure
- Thick and thin myofilaments give skeletal myocytes a striated appearance, with A bands (dark) composed of actin and myosin, and I bands (light) composed of actin
- I bands are bisected by the Z-line, which actin filaments are anchored to
- One sarcomere is located from one Z-line to the next Z-line
- Actin and myosin are contractile proteins, while tropomyosin is a regulatory protein
- Myofilaments can only be seen with an electron microscope
- Individual myocytes are surrounded by reticular fibers forming the endomysium
- The sarcomere is the contractile or functional unit of the myocyte
Skeletal Muscle Contraction
- Motion is mediated by muscle cells and is based on the conversion of chemical energy (ATP) into mechanical energy
- Myofibrils are composed of repeating assemblies of thick and thin filaments constituting dark A and pale I segments
- During muscle contractions, the actin filament slides over the myosin filament, resulting in a shortening of the I band
- Actin and myosin are held in position in the myofibril by other proteins such as desmin, tropomyosin, and troponin
- The summation of all sarcomeres shortening produces contractions of a muscle cell
- The sliding filament model: step 1: each sarcomere shortens, while the myofilament length is constant; step 2: the I band shortens and almost disappears; step 3: the thin (actin) filaments slide past the thick (myosin) filaments
Skeletal Muscle Development
- Myotubes are multinucleated tubes formed due to mesenchymal cells (myoblasts) aligning and fusing together
- Myotubes differentiate, forming functional myofilaments, and the nuclei are displaced against the plasma membrane
- Satellite cells are mesenchymal stem cells that function in muscle repair
- Satellite cells are positioned between the basal lamina and sarcolemma of the muscle cell
- They retain mitotic potential, which allows them to accomplish some repair
- Fibroblasts also form connective tissue (scars) as part of the repair process
Skeletal Muscle Organization
- The epimysium (fascia) is a layer of dense irregular connective tissue that surrounds the muscles
- Multiple bundles of fascicles make up a whole muscle
- Perimysium is a dense connective tissue that surrounds each fascicle
- Each fascicle is made up of many muscle cells
- Myofibers contain cylindrical bundles of myofibrils
- Myofibrils contain many smaller bundles of myofilaments
- Myofibrils are the contractile element within skeletal muscle cells, as they are composed of actin (thin) and myosin (thick) myofilaments
Skeletal Muscle Fiber Types
- Type 1 (slow) fibers compose red muscle, which have a slow twitch, use aerobic metabolism, and are fatigue resistant
- Type 2 fibers compose white muscle that uses anaerobic metabolism and can be further divided into type 2A and 2B
- Type 2A (intermediate) uses mixed oxidative-glycolytic metabolism and is slow fatiguing
- Type 2B (fast) is fast contracting, fast fatiguing, and uses glycolytic metabolism
Cardiac Muscle
- Cardiac muscle cells are arranged into fibers, with each cell only containing one central nucleus
- Cardiac cells are cross-striated and has intercalated discs that contain gap junctions and desmosomes
- Intercalated discs attach cardiac muscle cells to each other, providing strength and the ability to function as a syncytium
- Cardiac muscle cells have a sarcoplasmic reticulum, mitochondria, and the mitochondria make up 20% of the cellular volume
Smooth Muscle
- Smooth muscle cells have a fusiform spindle shape, and they are surrounded by a basal lamina and reticular fibers
- Smooth muscle cells have a single central nucleus
- Smooth muscle cells have parasympathetic and sympathetic innervation, causing them to have involuntary contractions
- Smooth muscle cells can act as a single unit or multi-unit
- Single-unit smooth muscle cells are found in visceral organs and have sparse innervation, yet cells communicate via multiple gap junctions
- Multi-unit smooth muscle cells are found in the iris of eyes and have precise contractions
- Smooth muscle functions include peristalsis, vascular dynamics, propulsion, and secretion
Contractile Non-Muscle Cells
- Myoepithelial cells have an ectodermal origin and contain actin and myosin
- They can be stimulated by hormones such as those produced by the mammary gland
- They are basket-like shaped and are known as "basket cells"
- Myoepithelial cells are located in salivary, mammary, and lacrimal glands
- They are enclosed in clusters of glandular cells
- Myofibroblasts are from the mesoderm and are involved in wound contraction
Studying That Suits You
Use AI to generate personalized quizzes and flashcards to suit your learning preferences.
Related Documents
Description
Learn about the structure and function of skeletal muscles, including the composition of A-bands and I-bands, and the role of actin and myosin. Understand the importance of Z-lines in muscle contraction.
