Muscle Flashcards
Muscle surrounded by dense connective tissue.
Epimysium
What are muscle fiber bundles (fascicles) surrounded by?
Perimysium
Muscle fiber bundles consist of what?
Multinucleated muscle fibers that are 10-100um wide and up to 30 cm long.
What is endomysium made up of?
Basal lamina and reticular.
Where the shit do nuclei lie in muscle fibers?
Just beneath the sarcolemma.
Satellite cells found where?
Between sarcolemma and basal lamina.
When do cells proliferate from satellite cells?
After trauma.
List the order of muscle divisions from largest to smallest.
Muscle-> Fascicle-> Fiber->Myofibril->Myofilaments
What is the function unit of contraction!
Sarcomere
If I fold in a piece of the sarcolemma (plasma membrane) what do I call that?
T-tubule
What is the specialized endoplasmic reticulum called in muscle cells?
Sarcoplasmic reticulum
A T-tubule sandwiched between two portions of sarcoplasmic reticulum is called what?
A triad.
Where are triads found?
A and I band junctions.
What innervates muscle cells?
Motor end plate at the myoneural junction.
True or false? Axons going to muscle cells lose their myelin but are still covered by Schwann Cells?
True.
What name did people rename Schwann Cells that reach the motor end plate?
Teloglia
Acetylcholine crosses what to get from axon terminals to muscle receptors?
Synaptic cleft
What is the place acetylcholine receptors are located called?
Junctional folds (subneural clefts) of the sarcolemma
How many muscle fibers can a single nerve innervate? And what is this unit called?
One or more. Whatever an axon innervates is referred to as the motor unit
Where does Botulism bind to block Acetylcholine (Ach)?
Presynaptic membrane of axon. (Remember it like how botters are goddamn lazy so they don’t bother to go across synaptic cleft)
Where does Curare block Ach?
Ach receptor across synaptic cleft. (Remember how “Cur” like a villain will take your shit (receptors).
How does Myasthenia Gravis block Ach?
It’s an autoantibody so it attacks the Ach receptor itself. (Remember it as “My” (from Myasthenia) stupid body is attacking itself.)
How is action potential brought into the cell?
Via the transverse T tubule system and continuous with the sarcolemma.
If I depolarize the cell what will I release and from where?
Ca++ and from the terminal cisternae of the sarcoplasmic reticulum.
Describe Red Fiber muscles to me.
Known as type 1 slow twitch, they have high myoglobin, lots of mitochondria, and fatigue resistant.
Now do White Fibers.
Type 2, fast twitch, low myoglobin, more stored glycogen, more atpase activity.
If I decide to play Frankenstein and start switchin nerves that innervate red and white fibers what will happen?
I can change a red fiber to a white fiber or vice versa.
Where do muscle spindles run?
Parallel with the main muscle fibers.
And what do the muscle spindles do while we’re at it?
They sense changes in muscles length.
Intrafusal muscle fibers are skeletal muscle fibers that serve as specialized sensory organs (proprioceptors) inside muscle spindles that detect the amount and rate of change in length of a muscle. They constitute the muscle spindle and are innervated by two axons, one sensory and one motor.
I wasn’t asking anything, it was just something from the notes annoying me.
If a sensory nerve is stretched what will happen to the nerve discharge rate?
That shit’ll go up.
Actually, back to intrafusal fibers for a second what are the two types them?
Nuclear bag and nuclear chain.
What are the three types of afferent nerve fibers that spindle muscles will recieve?
Annulospiral (spiral), flower spray (cluster), and y-efferents (fusimotor).
What’s Rigor Mortis and how does it happen?
Ca++ helps myosin and actin attach. And ATP pumps the Ca++ out. But here’s the problem once a person dies they run out of ATP to pump the Ca++ out and cell become even more permeable to the Ca. So the muscles stay stuck together.
What happens in muscle atrophy?
Muscle fiber size is reduced, the number of fibers itself doesn’t change.
Can I see myofilaments in a light microscope?
No. Go get an electron microscope.
List the four main proteins of myofilaments.
Actin, tropomyosin, troponin, and myosin.
What’s titin do?
Connects mysoin to Z disk and keeps myosin filaments in sarcomere. (Remember that myosin is the thick filament and titin is the only “Titan” that can hold it in place)
Nebulin does what?
Inelastic protein attached to z disk, runs parallel to actin. (Remember it as it’s like a nebulla in space. It doesn’t really do anything.)
Myomesin is what?
Myosin binding protein, holds myosin filaments in register at M-line.
C protein?
Myosin binding protein - functions similar to myomesin
a- actinin?
Bundles actin filaments into parallel arrays and anchors them to the z disk.
Desmin: Intermediate filament that helps bind myofibrils to each other. Also encircles Z-disk and is linked to each other by plectin protein.
I fucked up and put definition in first box so there ya go.
Dystrophin?
Actin binding protein- absent in Duchenne muscular dystrophy patients.
Difference between F-actin and G-actin?
F-actin is made out of globular actin.
What regulates polymerization of actin?
thymosin B4
How large is tropomyosin? And where is it?
35K m.w. Lies in the grooves of the actin helix.
What three molecules of troponin does tropomyosin bind?
Tn-T, Tn-I, and Tn-C
What does each do?
Tn-T: binds the Tn complex to tropomyosin
Tn-I: inhibits the binding of actin to myosin
Tn-C: Ca binds here and stops Tn-I from inhibiting the binding.
aB-crystallin protects what?
Desmin from stress induced damage
How many myosin molecules do thick myofilaments consist of?
300-400
How many chains is each myosin molecule made up into?
2 heavy chains and 2 light chains.
During proteolytic digestion the heavy chain cleaves and produces what?
Globular head termed heavy meromyosin and rodlike a-helical tail called light meromyosin.
How many light chains does each mysoin head bind?
2
In striated muscle what does myosin form?
bipolar filaments
Where is the actin and ATP binding region located?
Heavy meromyosin on the head
Where is the nucleus located in cardiac cells?
More centrally than in skeletal muscle.
How many nuclei are there per cardiac cell?
1
What joins the cardiac cells into a cardiac muscle fiber?
Intercalcated dics.
What does the intercalcated disc transverse portion contain?
Fasciae adherens (which is an actin filament anchor site) and macula adherens (desmosomes)
The lateral portion of intercalcated discs have?
Gap junctions
Cardiac muscle has more of what than skeletal muscle?
Mitochondria and extrafibrillar sarcoplasm
How are the T-tubules different between cardiac and skeletal?
They are larger in cardiac muscle and located at the Z-disk.
Cardiac v. Skeletal triads?
Triads less common in cardiac, diad arrangement where it’s at.
What is smooth muscle under the control of?
Sympathetic or parasympathetic nervous system.
What shape are smooth muscle cells?
Spindle shaped.
How many nuclei for SM?
1 located in the center with 1 or more nucleoli.
What do the gap junctions do for smooth muscle cells?
They facilitate electrical conduction.
Where are myoepithelial cells of ectodermal origin (single smooth muscle cells) found?
Sweat, salivary, lacrimal, and mammary glands.
Mesodermal origin SM cells found?
Respiratory, circulatory, digestive, and reproductive tracts.
Ectodermal origin of SM?
Iris and ciliary body of the eye,
Does smooth muscle contain sarcomeres?
No.
Function equivalent of Z disk in smooth muscle?
Membrane associated and cytoplasmic dense bodies containing a-actinin
Smooth muscle cytoplasm contains actin and tropomyosin but is missing what?
troponin
SMooth muscle myosin has how many heavy and light chains?
2 heavy 4 light
When is SM completely soluble?
When SM myosin is dephosphorylated.
In SM what does Ca complex with?
Calmodulin
What does the Ca-calmodulin complex activate?
Myosin light chain kinase which phosphorylates myosin
What is the effect of cAMP on SM?
It can activate myosin light chain kinase thereby also allowing myosin to interact with actin.
Estrogen effect on cAMP?
Increase
Progesterone effect on cAMP?
Decrease
