Use LEFT and RIGHT arrow keys to navigate between flashcards;
Use UP and DOWN arrow keys to flip the card;
H to show hint;
A reads text to speech;
40 Cards in this Set
- Front
- Back
What's a T-tubule and what's it good for?
|
An invagination of the sarcolemma; it allows depolarizations to reach all parts of the cell.
|
|
What's a thin filament made of?
|
F-actin + G-actin + tropomyosin + troponin. F-actin holds G-actin in a helix pattern; tropomyosin is entwined in the helix; and troponin attaches to tropomyosin and actin via subunits.
|
|
What causes a striated appearance?
|
Sarcomeres--the arrangement of thin and thick filaments. Within the sarcomere, the A and I bands are responsible for striations.
|
|
What is the "A" band?
|
Anisotropic band. It marks the length of the thick filament.
|
|
What's the "I" band?
|
Isotropic band. Marks the portion of thin filaments on either side of the sarcomere that are not overlapping with the thick filament.
|
|
What's the smallest functional unit of contraction?
|
The sarcomere.
|
|
What bounds the sides of the sarcomere?
|
The Z lines. "Zwischenscheibe."
|
|
What's a triad?
|
The meeting of a T-tubule and the sarcoplasmic reticulum. Located at the A-I junctions of the sarcomere in mammals.
|
|
Break muscular contraction down into 5 basic steps.
|
1) ACh is released and binds to receptors on sarcolemma.
2) AP propagates and reaches t-tubule. 3) SR releases Ca++. 4) Actin is unmasked and myosin binds to actin. 5) Contraction begins. |
|
Break relaxation down into 4 basic steps.
|
1) ACh is removed by acetylcholinesterase.
2) SR recaptures Ca++. 3) Active sites on actin are masked and myosin releases. 4) Contraction ends, relaxation occurs. |
|
What kind of sections of muscle show striations?
|
Longitudinal sections.
|
|
In a cross section of muscle fibers, where would you see the nucleus?
|
Peripherally.
|
|
Myofibrils are combined to form a:
|
Muscle fiber.
|
|
Muscle fibers are grouped into:
|
Fascicles.
|
|
Fascicles are surrounded by:
|
Perimysium.
|
|
Where do you find smooth muscle?
|
Walls of visceral organs, like the stomach, intestine, digestive tract, urinary bladder, uterus, and the walls of blood vessels.
|
|
What do smooth muscle cells look like?
|
They're elongated with attenuated tips.
|
|
What embryonic layer does smooth muscle come from?
|
Mesoderm. It comes directly from progenitor cells in the walls of visceral organs.
|
|
How are smooth muscle cells organized?
|
They are bundled and overlap. They're surrounded by, and separated by fine collagenous, reticular connective tissue.
|
|
What smooth muscle characteristic allow peristalsis?
|
Cells are arranged in bundles and have gap junctions. Layers of muscle run perpendicular to each other, allowing them to contract both laterally and longitudinally.
|
|
What layer is muscle derived from?
|
Mesoderm.
|
|
Where does muscle provide involuntary movement?
|
Visceral organs, heart.
|
|
What does it mean to say that muscle cells are "irritable"?
|
They contract when stimulated.
|
|
Size-wise, how do the three types of muscle fibers compare?
|
Skeletal is biggest, then cardiac, then smooth.
|
|
What role does fascia play in muscle?
|
Supports muscle fibers, supplies nerve endings, supplies nutrients.
|
|
Describe muscle cell development.
|
Skeletal muscle is derived from somites that give rise to myoblasts from the myotome portion. Myofibers are formed when myoblasts fuse, forming myotubules (these represent a syncytium, or multinucleate mass). Myotubules become mature myofibers with peripherally located nuclei and SR.
|
|
List the "layers" of muscle from inside (molecular) to outside (gross level).
|
Filament (actin/myosin), Fibril, Fiber, Fascicle, Gross.
|
|
What are the 3 CT wrappings in muscle and where are they?
|
Muscle fiber wrapped in endomysium; fascicle wrapped in perimysium; gross muscle wrapped in epimysium (superficial fascia).
|
|
What innervates cardiac muscle?
|
Autonomic nerves.
|
|
Are cardiac muscle fibers branched?
|
Yes.
|
|
What is an intercalated disc?
|
The junction between cardiac muscle fibers; contains gap junctions and adhering junctions (fascia adherens).
|
|
What is the purpose of adhering junctions in intercalated discs?
|
Holds cells together, enables efficient contraction.
|
|
What is the purpose of gap junctions in intercalated discs?
|
Allows communication--small molecules and ions pass from one cell to another; direct electrical connection is created. Lets APs pass rapidly and in a synchronized way.
|
|
What's the origin of cardiac muscle?
|
Cardiac mesoderm.
|
|
Where's the primary pacemaker and what does it do?
|
It's the SA node, located in wall of the right atrium near the entrance of superior vena cava. Cells of the SA node spontaneously depolarize resulting in regular contractions.
|
|
If the SA node fails, how does the heart keep pumping?
|
The AV node takes over. AKA the secondary pacemaker.
|
|
How can the autonomic nervous system affect pacemaking?
|
It can alter the pace established by the pacemaker cells.
|
|
What are Purkinje fibers?
|
Specialized myocardial fibers that conduct electrical impulses without synapses; enable heart to contract in a coordinated fashion.
|
|
Where are Purkinje fibers located?
|
In the inner ventricular walls of the heart, subjacent to the endocardium.
|
|
How do Purkinje fibers look on slides?
|
The stain distinct from other cardiac muscle cells. They look much bigger.
|