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level: membrane potentials & APs

Questions and Answers List

level questions: membrane potentials & APs

Question	Answer
charged particles moving along the electrical gradient	definition of electrical potential
-calculates nernst potential for univalent ion -electromotive force that will balance concentration gradient so that it reaches equilibrium -> ratio, > tendency for ion to diffuse, > Nernst potential	Nernst Equation
FALSE	T/F: there is more Na+ inside the cell than outside.
TRUE	T/F: there is more K+ inside the cell than outside.
-94mV	what is K+ Nernst equilibrium potential?
+61mV	what is Na+ Nernst equilibrium potential?
K+ -leak channels favor K+, only a little Na+ comes through	which is more of a main player in resting membrane potential: K+ or Na+?
-70mV	RMP for normal cell=
-90mV	RMP for large nerve cell=
few -K+ ions diffuse in and out ALOT though - few Na+ flow into cell-> voltage-gated Na+ channels	during RMP are there lots/few K+ channels open?
1. @ RMP (polarization) 2. sudden change to RMP to more + value (depolarization) 3. Na+ gates quickly close & cell becomes more - (repolarization) 4. return to RMP	process of a nerve AP (4 steps)
demyelination	multiple sclerosis is a ______ disease.
1. simple mechanical disturbance of membrane (some pair & sensory fibers) 2. chemical effects (NTs bind to receptors, open Na+ channels) 3. electricity passes through membrane (heart & intestinal cells=gap junctions)	elicitation of an AP (3)
opening of voltage-gated Na+ channels moves membrane potential to more + value which opens adjacent cells Na+ channels in both directions -domino effect in getting AP to spread	positive feedback circle of an AP
-covers axons & made of schwann cells -decreases ion conduction -gaps in myelin speeds AP up tremendously -AP does NOT occur in these sections	myelin sheath
-gaps in schwann cells -ions can flow b/w axon and ECF - AP ONLY occurs here -Na+ channel activation occurs here	nodes of ranvier
-jumping of AP from node to node -Na+ channel activation occurs -ions flow b/w axons and ECF -DECREASES time and energy spent -INCREASES speed	saltatory conduction
attaches end of actin & attaches to myosin during contraction	z-disc
area where actin and myosin overlap	a-band
ONLY myosin NO actin	h-band
ONLY actin NO myosin	i-band
attachment of myosin	m-band
postion of myofibril b/w 2 z-discs -functional unit of skeletal m	sarcomere
1. z-discs become closer-> actin slide towards each other 2.i-band changes 3. a-band does NOT change 4. h-band changes	changes in bands and discs as skeletal m contracts
-stores Ca2+ -borders either side of t-tubule -has Ca2+ pumps	sarcoplasmic reticulum
-invagination of cell membrane -extension of plasma membrane -holes along membrane lead to t-tubules inside-> ECF allowed inside cell	transverse-tubules
1. innervation by nerve triggers AP in muscle plasma membrane 2. AP travels down t-tubule and reaches SR 3. SR opens Ca2+ channels; Ca2+ rushes out into cytosol where muscle filaments are	process of opening SR Ca2+ channels (3 steps)
thin	actin filaments are thick/thin.
thick	myosin filaments are thick/thin.
1. troponin 2. tropomyosin -AREN'T actin itself, just associated with it and control myosin head binding	proteins associated with actin (2)
long string-looking that wraps around actin and covers binding heads when resting	function of tropomyosin
1 TnT= binds to tropomyosin 2. TnC= binds to Ca2+ 3. TnI= binds to actin & inhibits contraction	components of troponin complex (3)
1. head 2. hinge 3. tail	regions of a myosin chain (3):
1. alkali= stabilizes head region 2. regulatory light chain= regulates ATPase activity of myosin	name/purpose of the four light chains on the myosin head
NO; hurts cell for next time it wants to contract -store in SR instead	does a cell want to remove ALL Ca2+ after a contraction?
1. pumps pump some Ca2+ from cell 2. Ca2+ mainly pumped back into SR 3. once in SR Ca2+ is binded to calquestrin and calreticulin	termination of contraction (Ca2+)
1. # of fibers 2. frequency of fibers	strength of skeletal m contraction depends on _____ and _____ of stimulation.
initiate 2nd AP before 1st is over--> frequency - b/c muscle twitch exceeds duration of AP	temporal summation
not allowing muscle to relax at ALL -stimulated SO much -NO fine motor control BUT maximum contraction	tetanus
# of fibers at the same time - multiple stimulated for increased contraction - activate individual muscle units asynchronously so some units developing tension, other relaxing	spatial summation
1. directly link cytoplasm of adjacent cells 2. junctions b/w cells made of [connexon channels] = allow small ions and molc to pass through w/ little delay b/w cells 3. alot of these in heart muscle	electrical synapses
synapse	cells communicate with muscles at a _______.
1. electrical 2. chemical	two types of synapses
1. neurotransmitters packaged in vesicles 2. AP received at pre synaptic terminal-> signals Ca2+ to rush into cell 3. Ca2+ in presynapse signals vesicles to go bind to membrane & release contents into synaptic cleft 4. neurotransmitter diffuse to muscle cell & bind to ligand gated channels allowing more ions into muscle cell 5. triggers AP in muscle cell	process of chemical synapses (5 steps):