Lecture 4: Structure & Function Of Cardiac, Smooth, And Skeletal Muscles Flashcards
What are the several types of muscle? How do they differ?
- Skeletal, Cardiac, Smooth.
- They differ in structure, function, and location.
What is the function and characteristics of the skeletal muscle?
- For bone movement & maintaining posture.
~ Some muscles in the core/limbs are constantly active.
- Striated appearance (horizontal fibres), multinucleated.
~ Horizontal fibres –> formed by the fusion of many individual cells.
- Voluntary.
State the characteristics of cardiac muscles.
- Found only in the heart.
- Striated appearance, intercalated discs.
- Involuntary.
What are intercalated discs?
Gap junctions that link the cells together and define their borders (appear as dense vertical lines).
~ Not fully fused, don’t share cytoplasm.
They are the major portal for cardiac cell-to-cell communication, which is required for coordinated muscle contraction and maintenance of circulation.
What is the difference between skeletal and cardiac muscle cells?
Cardiac muscle cells don’t fuse together.
What is the function and the characteristics of smooth muscle cells?
- Walls of blood vessels & the lining of hollow organs.
~ Controls the volume of the container that it is lining (function varies depending on the organ).
- Not striated, single central nucleus.
~ Has a different way of contracting. Cells don’t connect to one another, spindle shaped.
- Involuntary.
How and why are the nuclei positioned differently in skeletal/cardiac muscle cells compared to smooth muscle cells?
Nuclei tends to be squished towards the edge of the cell for skeletal/cardiac muscles, because the cell is packed with contractile machinery.
Smooth muscle cells have a different way of contracting.
What is a myocyte?
A muscle cell.
State what is connective tissue crucial for.
It is important to hold the muscle together and distribute the force.
What is a tendon?
Attachment between muscle and bone matrix.
What is a fascicle?
A bundle of skeletal muscle fibres surrounded by perimysium, a type of connective tissue.
What is sarcolemma?
The cell membrane of a myocyte.
What is a muscle fibre (cell)?
Bundles of interconnected protein filaments of striated muscles.
State the differences between epimysium, perimysium, and endomysium.
- Epimysium – connective tissue surrounding entre muscle.
- Perimysium – connective tissue around muscle fascicles.
- Endomysium – connective tissue around muscle cells/fibres.
What does the prefix sarco- mean?
Regarding muscles.
What are the characteristics of the muscle fibre?
- Comprises of myofibrils.
- Mitochondria for energy.
- Surrounded by sarcolemma.
- Degree of overlap determines contractile state of the muscle.
~ More overlap -> shorter, contraction.
~ Less overlap –> longer, relaxation.
What is a myofibril?
Elongated contractile threads found in striated muscle cells.
- Made up of myofilaments (actin & myosin).
- Actin forms the thin filament (I band, doesn’t contain overlap).
- Myosin forms the thick filament (A band, contains overlap).
- Contractile unit is the sarcomere (Z line to Z line).
What are myofilaments?
Contractile proteins (actin & myosin).
What is the I & A band, Z disc, H zone, and M line?
- Z disc – where all the connective proteins of thin filaments lie. Attachment site for thin filaments.
- I (isotopic) bands – light bands that contain only the thin filaments (actin) and are located between the two thick filaments.
- A (anisotropic) bands – contains the entire length of a single thick filament. The anisotropic band contains both thick and thin filaments.
- H zone – the zone of the thick filaments that has no actin.
- M line – attachement site for thick filaments, centre of A band and sarcomere.
