Exam 1 Flashcards
describe the resting membrane potential (using K)
so… the RMP is determined when there is an electrical and a chemical gradient. The membrane has channels in it that allow K to leave the cell. However, the K in the cell is accompanied by a negative anion. So when the K leaves, its negative counterpart cannot leave (The K only leaves because there is wayyy more K inside the cell then outside, so it goes down its concentration gradient). So now the K is gone, but the inside becomes more negative, which will attract the K to come back into the cell. This is the electrical gradient pulling it back in. This then leads to the RMP of K to be -94mV
what is the RMP of K
-94mV
RMP of Na and a how it works
So, the Na has a much higher concentration outside the cell then inside. The Na will enter the cell, causing a more (-) environment outside of the cell, and more (+) inside the cell. The (+) inside of the cell repels further Na from entering, which leaves the RMP of Na to be +61mV.
What has a very large impact on the resting membrane potential?
passive diffusion (channels about 90%) and only about 10% from the Na/K ATPase pump.
which ion is the membrane more permeable to (K or Na)
K+
Describe the active transport of both K and Na
There is much more K inside the cell then outside. The Na is higher on the outside then the inside. So, the pump will send 3Na out of the cell, and bring 2 K into the cell. This uses ATP. The break down of ATP will cause a conformational change that brings the Na out and the K inside.
Where is there more K
inside the cell
where is there more Na
outside of the cell
where does the K get pumped
from out to in (against its concentration gradient)
Where does the Na get pumped
from inside to outside
ratio of K in to Na out
every 3Na out there is 2 K pumped in
why is the Vm closer to that of K then Na
the membrane is far more permeable to K then it is to Na, therefore the the RMP is closer to the -94mV (-70 to -90mV)
the resting membrane potential will be closest to the ion with the ____ permeability
greatest
How does the Dr. Death thing work
Dr. Death administered KCl to patients who wanted to die. This increased the K concentration outside of the cell. Since there is more K inside the cell then out, it usually wants to leave the cell. However, when K is higher on the outside, there is less of a drive for K to leave. If K does not want to leave, no RMP. No RMP means that there is no excitability for cells, can’t breath or heart stops and that is death.
What are the 5 ion channels at the cleft
- Voltage gated Ca channels, which cause Ca to rush into the axon, and release the NT ACh.
- ACh goes across synaptic cleft, and then binds to nicotinic receptors (causes a conformational change and Na influx)
- Then the local depolarization causes voltage gated Na channels to open for more depolarization and AP
- At the T-tubule, the DHPR opens and Ca is released.
- The Ryanodine receptors (RyR) open on the SR and Ca is released into the cytoplasm.
Botulinum toxin
Blocks the ACh release from the nerve terminal. Doesn’t go across and open the Na channels which will open the Na voltage gated channels and cause the AP to release the Ca. NO CONTRACTION
Curare
Competes with the ACh (pushes ACh away and prevents binding)
Tetrodotoxin
puffer fish, inhibits Ca
Neostigmine
AChEsterase inhibitor. ACh has more time in the cleft to be picked up by nicotinic receptors. For a contraction
what does neostigmine help treat
myasthenia gravis (this is when your body makes antibodies against ACh receptors, so there aren’t as many receipts to bind the ACh to. there is a normal amount of ACh but not enough receptors. So the neostigmine helps to keep the ACh in the cleft so more can be picked up by the remaining receptors
Hemicholinium
blocks the choline re-uptake (need choline to make ACh, so when this is blocked, don’t make as much ACh, which depletes stores, which will mean not enough for sufficient contractions, and therefore tired fatigue much MUCH quicker.
how can you increase the conduction velocity of a nerve firing
by increasing the fiber size (increase diameter to decrease resistance)
also by myelinating.
Describe how MS has anything to do with myelin
the MS prevents the production of myelin, so the impulses top traveling down the axon.
why does propagation of a nerve fiber only happen in one direction?
the refractory periods prevent the AP from traveling in reverse down an axon.
What is ACh made of, and what catalysis this reaction
ACh is made from acetyl CoA and choline, catalyses by choline acetyltransferase
EPSP vs IPSP
the EPSP causes depolarization, by opening the Na and K channels. Depolarization brings it closer to the threshold for an AP. IPSP hyperpolarizes it, bringing it away from threshold, like opening of Cl channels.
Examples of EPSP and IPSP
the EPSP are norepinephrine, ACh, epi, dopamine, serotonin, glutamate.
IPSP’s are GABA and glycine.
what causes relaxation of a skeletal muscle contraction
the re-uptake of Ca from interacellular back into the SR via SERCA.
What causes tetanus
increased intracellular Ca
passive tension
the tension of the muscle when it is stretched
total tension
tension under the muscle when it is contracted (at different lengths)
active tension
difference between total and passive tension
where is tension maximum
when there are maximum overlaps between the actin and myosin
tension and cross bridge
overstretched, not enough cross bridge, not as much tension, same applies to too short, too much overlap and bands hit into each other.
when after load increases (the load against which the muscle must contract), the velocity of shortening ____
decreases.
as you increase the load, you ____ the velocity
decrease
fast twitch vs slow twitch fibers
the fast twitch are anaerobic (Type II). These have a high glycolytic enzyme amount, and few mitochondria’s, and decreased capillary density and a decrease myoglobin. These are for the smaller movements of things like the eye, because they have rapid movement
slow twitch are aerobic, (Type I), so they have a lot of myoglobin, mitochondria and a high capillary density, but a low glycolytic enzyme count. They are responsible for the increased court movements like postural movements.
Motor unit
all muscle fibers innervated by a single nerve
small motor units
fast things, like precise movements like the eye. very precise
large motor units
slower, course movements, like the quad.
how do we get tetanus
strength of contraction increases because there is an increase in the firing rate, not the size of the stimulus.
Treppe
this is the phenomenon that when you increase the amount of Ca in the intracellular, by not picking it all the way up after the first stimulus, there is more Ca available to bind to sites, which leads to a stronger contraction. Not picked up in time, not that it can’t be picked up
hypertrophy vs hyperplasia vs atrophy
hypertrophy is when you get an increase in the size of the fiber, more sarcomeres arranged in parallel. Lifting weights
Hyperplasia is when you increase the number of muscle fibers, which s cray hard
Atrophy at first is a decrease in size, then a decrease in the number of fibers (from disuse)
what does hyperplasia and hypertrophy do to Vmax and force production
they increase force production but nothing happens to Vmax.
lengthening and Vmax and force production
force production remains the same, but the velocity increases.
what is special about actin in terms of movements
they can cause cell locomotion by breaking a piece off and shifting it to the end of the actin molecule
why is titin important
it allows the molecules to bounce back after being stretched. holds the shape of the sarcomere.
lidocaine
blocks the Na channels and therefore blocks an AP
the heads and tails of a membrane
tails are hydrophobic, and made of fatty acids. Heads are POLAR
how do lipid and water soluble things get through the membrane
the lipid soluble can pass right through because they dissolve. The water soluble need channels, pores, etc.
benefit of an unsaturated hydrocarbon
the unsaturated hydrocarbon has a kink in it, which leaves more space between heads and flows things to diffuse in more easily
the thicker the membrane, and ____ the diffusion
harder
Hypertonic solution
the hypertonic solution means there is more solute outside of the cell. So, water will leave the cell and travels out, causing the cell to shrink.
what three things increase permeability
decreasing the membrane thickness
decrease the size (radius) of the solute
increasing the oil/water perm coefficient
osmolarity and osmotic pressure of water
osmolarity is 282mOsm/L and the osmotic pressure is 5400mmHg.
