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Muscle Physiology -

Pharmacology Test

What attaches muscle to a bone? Tendons
What is the bundle of cells in each muscle fiber called? Myofibrils
What is the role of the myofibril? It carries contractions along muscle fiber
The _____________ are cylindrical structures within the myofibrils. Sarcomere
What is the specialized plasma membrane of the muscle cell? Sarcolemma
What is the name given to the sections of sarcoma that separates the sarcomeres? T-tubules (aka transverse tubules)
True or False: Nerve impulses travel through the sarcolemma and to the individual sarcomeres. True
What are the bands that border the sarcomere called? Z-lines
The band that marks the sarcomere's middle is called what? The M-line or "M Disc"
The lightest area (under microscope) of the sarcomere is what? Thin filaments
What contractile protein is found on the THIN filaments? Actin
What inhibitory proteins are found on the thin filament? Troponin and Tropomysin.
What contractile protein is on the THICK filaments? Myosin (think Mike Tyson?)
Do the thick and thin filaments overlap? Yes
There are 2 sets of THIN filaments in each sarcomere. What is the distance between the ends of the thin filaments know as and what happens to this area during muscle contraction? The "H" zone. It shortens during muscle contraction.
The space between the THICK filament of one sarcomere and the THICK filament of another sarcomere is called? The "I Band". These also shorten during muscle contraction.
What is the length of the THICK filament called? What happens to it during muscle contraction? It is called the "A" band and it does not shorten during contraction.
Describe the "Sliding Filament Theory" During contraction, the thin filament Actin slides towards the "M line" of the sarcomere along the thick filament Myosin. (the M Line is straight down the middle of the sarcomere)
Describe the process of muscle contraction from neuron to contraction. 1. CNS sends action potential down its axon. 2. This AP causes Ca+ influx through voltage-gated Ca+ channels. 3. This causes vesicles to release ACH into extracellular space between motor neuron terminal and NMJ.
Process Continued 4. ACH binds to nACHr on the NMJ causing sodium to rush in and potassium to trickle out. This causes the muscle fiber membrane to become more positive and triggers an AP. 5. Muscle fiber is depolarized.
Process Continued 6. sarcoplasmic reticulum releases calcium which bind to the troponin which then modulates the tropomysin, uncovering binding site for myosin. 7. Myosin binds to thin filament. 8. Contraction occurs.
What happens after muscle contraction on a cellular level? Na+ channels close. ACH is broken down by ACH-E. Pump moves 3na out and 2k in to the cell which restores its RESTING MEMBRANE POTENTIAL
What is a muscle cell's Resting Membrane Potential? -90mv
What changes a muscle cell's RMP causing depolarization? Na+ influx which make the intracellular charge more positive (aka less negative)
What is the significance of the Synaptic vesicles in the axon? It contains the neurotransmitter ACH
Where are nicotinic receptors found? the motor end plate junctional folds. (on the shoulders)
What causes the cessation of muscle depolarization? When plasma cholinesterase breaks down ACH, it stops the depolarization from sodium entering the muscle cell, letting the muscle cell charge to re-polarize back to its RMP of -90mv
Where does skeletal muscle receive innervation from? The Motor Nerve (motor neuron)
Where does the motor neuron arise from? The cell body of the ventral horn of the spinal grey matter.
What is ACH made of and where do these components come from? the nerve terminal manufactures ACH from acetate and choline. The acetate is supplied by acetyl-coA (mitochondria) and choline is derived from dietary intake and the liver.
What enzyme combines acetate and choline to form ACH? Where is ACH stored? acetyl-transferase. ACH is stored in quanta at the nerve terminal.
Nicotinic cholinergic receptors (nAChR) are found where? the folds of the motor end plates called gyri.
Each vesicle contains how many molecules of ACH? 5,000-10,000
How many vesicles of ACh are released with each depolarization? 200-400
How large is the synaptic cleft? 20-50nm (very small!)
During depolarization, sodium changes the RMP of -90 to a charge of approximately what? -45mv this is called threshold potential
What part of the nAChR does ACh bind to? the alpha subunits (2 of them)
Is release of ACh dependent upon Na or Ca? Calcium
What does Cyclic-AMP do? opens Ca channels, causing synaptic vesicles to fuse with the nerve membrane to release Ach.
What drugs affect the release of ACh? Aminophyllin and high dose lasix INCREASE ACh, and CCB and low dose lasix DECREASE ACh
What is the binding site for NMB drugs? the 2 alpha subunits of the Nicotinic Acetylcholine receptors
Describe the nAChR. Contains Ligated ion channels. Contains 5 protein sub-units: B (beta), Delta, epsilon, and 2 alpha.
Prejunctional receptors: Contain 3 alpha subunits and 2 beta. They resemble more neuronal type of ACh found elsewhere. Stimulation facilitates the release of ACh. This is thought to be the mechanism of action of post-tetanic facilitation. It also explains "fade phenomenon".
Extrajunctional Receptors: Are present only when there has been nerve injury. DON'T GIVE SUCC
Created by: itrevorj