Major proteins in Thin filaments?
Actin, Troponin, Tropomyosin
Which thin filament protein has 3 components? What are they?
Troponin; C, T, & I
Which troponin subunit binds to tropomyosin?
Which troponin subunit binds to calcium?
C subunit. Think C for Cockkkk...i mean calcium
Troponin subunit I. Whats its purpose?
keeps troponin complex in a position so that without calcium, tropomyosin will cover myosin binding site on actin
Describe structure and purpose of actin?
Fibrous helical chains that has a high affinity binding site for the myosin head (of thick filament)
Tropomyosin is a fibrous protein that extends along ____ (thick or thin) filament to cover _____ binding sites on ____?
thin filament, myosin, actin
Thick filament component?
Where is the cell bodies of skeletal muscle motorneurons found?
Ventral horn of spinal cord
Relationship b/t muscle fibers and motor neurons?
Each muscle fiber receives innervation from only one motorneuron
Clicker question. Motor neuron acts as the final common pathway for motor unit activation b/c ___?
It integrates excitatory and inhibitory inputs
T/F. Muscle fibers within a motor unit produce an all or none contraction?
Specific type of receptor found on motor end plate of skeletal muscle? Activated via what neurotransmitter?
Nicotinic M receptor, activated via Ach
Nicotonic M receptors in motor end plate of skeletal muscle are what type of channel? Importance of this?
Monovalent cation channels, activatation of these channels will generate a GRADED depolarization. A sufficient # of receptors must be activated in order to bring the surrounding membrane above threshold for an action potential, activating the voltage gated Na+ channel that reside in the surrounding membrane
Release of Ach into NMJ requires what cation?
Ca2+ mediated Ach release. Action potential comes down axon, triggers influx of calcium, which will cause Ach vesicles to fuse, releasing Ach into NMJ
Depolarization of T-tubule membrane to the release of Ca2+ from sarcoplasmic reticulum. Walk me through it.
- Depolarization of T-tuble membrane causes a conformational change in dihydropyridine receptor
- This change activates ryanodine receptor (a Ca2+ channel) in the SR, releasing Ca2+ out of the SR
Once cell membrane repolarizes, walk me through Ca2+ path
Following repolarization of cell membrane, the dihydropyridine receptor returns to its resting confirmation, and the ryanadine receptor closes. Then Ca2+ is pumped back into SR via Ca2+ channel (active transport)
If someone's ryanodine receptors remained open (as a result of a poison), what muscle feature would occur?
Muscle cramps, if chronic exposure, person will die. bc diaphragm will stop working. diaphragm it be a muscle. crazy. i know right. we should do this more often. send us your email. name that movie
Ans to "name that movie"
hypothyroidism and its effects on calcium?
Slows calcium uptake by SR, causing slow muscle relaxation
Clicker question. Myosin cross bridge cycling occurs when ____ binds to ____ and causes _____ to move?
Troponin C binds to Ca2+ and causes tropomyosin to move
The power stroke occurs when (ADP or ATP) is solely bound to myosin head?
At optimum length, the passive tension of a muscle is what?
nearly zero. Main purpose of passive tension is to ensure that muscle operates at an optimal length
Comparing 2 motor units, if one reaches peak isometric twitch tension faster, you know this is a ?
fast motor unit. speed at which a motor unit reaches peak isometric twitch tension is indicative of the type of motor unit it is (fast or slow)
Name the 2 ways to produce more force by a muscle (graded contraction)?
1. Recruit more motor units
2. Increase the frequency of motor unit contraction
If slow motor units aren't producing enough force, what will occur? Relate this to frequency
If slow motor units aren't producing enough force, fast motor units will be recruited. However, the slow motor units are contracting at a greater frequency (essentially theyre maxed out. thats why fast motor units had to come help out)
Don't forget the 2 ways to increase force of contraction
1. Increase the frequency of motor unit contraction (which the slow motor unit did)
2. Recruit more motor units (which is why the fast ones showed up)
Twitch vs tetany. Which occurs first
Twitch = 1st contraction that occurs.
Tetany = contraction at which muscle is producing maximal force. cant work anymore.
Fast motor units have (more or less fibers)? The diameter of these fibers is (smaller or larger)?
Fast motor units = more fibers at larger diameters
Slow twitch vs fast twitch. Which has more mitochondria?
Slow twitch vs fast twitch. Which has more blood vessels?
Slow twitch, need to deliver O2 to mitochondria (via dablood)
Slow twitch vs fast twitch. Which has greater myosin ATPase activity?
Fast twitch. Myosin heads split ATP more quickly, thus faster contraction
Oxidative Phosphorylation. Slow or fast twitch?
Glycogen as source of energy. Slow or fast twitch?
Order of muscle use (slow oxidative vs fast oxidative/glycogenolytic vs fast glycogenolytic)
1st - slow oxidative
2nd - fast oxidative/glycogenolytic
3rd - fast glycogenolytic