Lecture 12: Nerve and muscle Flashcards
(24 cards)
What are the two broad classes of muscle?
Tissue and isolated cells.
What tissue muscles are there?
Skeletal, cardiac, smooth.
What isolated cells are there?
Myoepithelial, myofibroblasts, pericytes.
Describe skeletal muscle cells.
It attaches to bone, and commonly stretches the length of the muscle. Can be up to 100um in diameter and is multinucleate.
Peripheral nuclei on both cross and longitudinal section stain. Striated.
Describe cardiac muscle cells.
Same physiology as skeletal muscle cells, but no longer elongated and stretched. Single cells instead, and have intrinsic contracting properties.
Central nuclei on both cross and longitudinal stain. Branched and striated.
What is the cytoskeleton predominantly made of? How is it organised?
Actin-myosin, triggered by AP. Organised into myofibrils with repeating sarcomeres. The sarcomeres are basically repeating actin myosin.
True or false? Myofibrils are organelles.
False, they don’t have membranes around them.
What helps to anchor myosin? Is myosin thin or thick?
Z discs. Thick.
Describe the sarcoplasmic reticulum and its functions.
It is a network of tubules rich in calcium ATPases that pump calcium back into its lumen for storage. During an action potential, it triggers the release of calcium through T-tubules which surround each myofibril. Note that there are mitochondria lying between myofibrils.
T-tubules are a continuation of the surface membrane.
How many T-tubules are there per myofibril?
2.
Cardiac muscle are joined by what?
Intercalated discs. But more specifically, each myofibril are joined by fascia adherentes, with desmosomes to help reinforce it.
What is found longitudinally between cardiac muscles cells.
Gap junctions that help to electrically couple cells and coordinate APs.
True or false? Smooth muscle cells have nuclei centrally.
False, they have them on the periphery, otherwise known as perinuclear organelles.
What’s different about smooth muscle cells?
They have no myofibrils, sarcomeres or t-tubules.
Skeletal muscles can be broken up into 3 types, what are they? List their colour, speed, fatigue levels, tension, and mitochondria number.
Type 1: Red in colour, slow twitch, does not fatigue, low tension and many mitochondria.
Type 2a: Pink, fast twitch, fatigue resistant, high tension, few mitochondria.
Type 2b: White, fast twitch, fatigue prone, high tension, few mitochondria.
PAS stain glycogen, so therefore will darken which type of skeletal muscle most?
Type 2.
Succinate dehydrogenase found in mitochondria can be stained, so which skeletal muscle will darken most with this stain?
Type 1.
What cells are responsible for muscle regeneration?
Satellite cells.
True or false? All muscle cells have the ability to regenerate.
False, heart muscle cells cannot, but smooth can. This can still result in atherosclerosis.
How are myofibroblasts formed?
From fibroblasts that have had to change to pull scar tissue together.
What are pericytes?
They are contractile cells that contain actin/myosin and wrap around capillaries to control vasoconstriction.
In regards to peripheral nerves, motor arise from ___ and sensory arise from ___.
CNS + autonomic NS ganglia. Dorsal root ganglion.
What are the three layers in the wrapping of nerves?
Epineurium, perineurium, endoneurium. They wrap whole neve, fascicles and individual axons respectively.
True or false? Myelinated axons are not visible with H&E.
True.
