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Week 8
Cell Signaling
68
Biology
Graduate
09/28/2008

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Term
What is the difference between action potential in a skeletal muscle fiber versus a heart muscle fiber?
Definition
In a skeletal muscle the action potential is limited to one fiber, but since cardiac muscle produces rhythmic coordinations of contraction the action potential spreads to adjacent fibers through gap junctions of intercalated discs.
Term
True or False: The motor nerve contacts skeletal muscle cells at three point, at the beginning, middle, and end of the fiber.
Definition
False, it contacts it at one point and it is variable.
Term
Why are skeletal muscles multinucleated?
Definition
Because the form from the fusion of myoblasts.
Term
Briefly describe the process of muscle contraction starting with the motor neuron.
Definition
Ach is released, depolarizes end plate of muscle fiber and propagates the length of the fiber, depolarizes T-tubules, releases Ca in SR, Ca binds to troponin, tropomyosin has conformational change and shows binding sites on actin, energized myosin+ADP+Pi bind to actin, causing muscle contraction, myosin gets fresh ATP to release binding site and bind again.
Term
How is calcium taken back up into the sarcoplasmic reticulum?
Definition
An ATP dependent calcium pump.
Term
What is key to maintaining a muscle contraction in regards to calcium level in the muscle cell.
Definition
The contraction will stay maintained as long as internal calcium levels are elevated.
Term
What is the tool called that measures membrane permeability as a function of transmembrane voltage and time?
Definition
Voltage-clamp
Term
What is the difference between inward and outward current with respect to the membrane potential?
Definition
Inward- positive charge moving into the cell, outward- positive charge moves out
Term
The H&H blocker studies revealed that the early and late phases of membrane current after depolarization are due to what?
Definition
Na+ and K+ selective conductance through their respective independent pathways
Term
What does this equation describe in regards to membrance potential: I^ion=g^ion(Vm-E^ion)?
Definition
The relationship between the ionic current(I^ion), the conductance(g^ion), and driving force (Vm-E^ion, which is the voltage - equilibrium potential).
Term
True or False: the key discovery of membrane conductance was that upon depolarization there was a fast activation of Na+ conductance, fast deactivation of Na+, and a slow K+ activation.
Definition
True
Term
What do akrasia and teleological mean?
Definition
Acting against your better judgement; the philosophical study of design and purpose.
Term
What is the resting membrane potential of a cell and by how much does it change when it depolarizes?
Definition
-65mv, approx. 100mv towards positive voltage (+40mv)
Term
Since action potentials are all or none events and they propagate without decrement, how much change in voltage is necessary to cause depolarization?
Definition
At least 10-20mv.
Term
After an action potential there is a brief absolute refractory period during which another action potential can not be triggered, what is this period called?
Definition
Absolute refractory period, which limits firing frequency to 1000hz.
Term
True or False: The amplitude of the action potential can vary depending on the strength of the stimulus.
Definition
False, it is an all or none event.
Term
What is it that the Goldman-Hodgkin-Katz equation figures out in regards to membrane potential?
Definition
The resting membrane potential in Voltage factoring relative concentrations of 2 different ions.
Term
What is accommodation?
Definition
Slow depolarization of a membrane may not cause an AP because Na+ channels inactivate and K+ channels open.
Term
What are the differences between cardiac and skeletal muscle AP’s?
Definition
skeletal muscle AP triggers contraction while cardiac AP controls duration of contraction, cardiac AP’s are also much longer and have Ca+ channels contribute to the AP shape.
Term
True or False: All action potentials are the same.
Definition
False.
Term
True or False: action potential requires only active current flow.
Definition
False, both passive and active.
Term
Why is that there is faster conductance for thicker axons?
Definition
Internal resistance decreases.
Term
True or False: the difference in speed of signal conduction in myelinated versus unmyelinated axons is small but significant.
Definition
False, the difference is large and significant, 10m/s vs 150m/s
Term
What are the two types of synapses and what are their main features?
Definition
Electrical- AP current can flow freely between cells, in both directions, due to gap junctions, seen in heart cells; Chemical- calcium regulated neurotransmitters induce AP, seen in brain
Term
True or False: these are criteria for a neurotransmitter - stored in vesicles with molecular machinery, calcium-dependent, it has a receptor in postsynaptic cell, have enzymes or transporters to terminate their actions after release.
Definition
True
Term
What is the basic summary of the classic neuromuscular junction experiments?
Definition
Basically, Katz found that the chemical messengers were quantized and that you could create many subthreshold events happen at the junction without an AP response.
Term
With low frequency firing in chemical synapses, what is preferred as a signal molecule - small molecules or peptides?
Definition
Small molecules first, then as signaling becomes exhaustive then both released as internal concentration of Ca+ increases
Term
Which responds faster, a ligand gated ion channel or a G-protein coupled receptor?
Definition
Ligand gated channel, in about 1ms vs .1-1s
Term
Which ion are nicotinic channels permeable to, Na+ or K+?
Definition
Normally both, they are non-selective cationic channels, so its ability to hyper or depolarize depends on resting membrane potential
Term
True or False: Ligand gated ion channels are composed of these families - nicotinic, glutamate, and P2X.
Definition
True.
Term
What is the enzyme that degrades Ach in the postsynaptic membrane?
Definition
Acetylcholinesterase.
Term
In the Physician’s Charter, what are the 3 principles describes as fundamental, universal, and definitive?
Definition
Primacy of patient welfare, patient autonomy, social justice.
Term
In PBL case 1, Nikhil was diagnosed with B-thalassemia major, a disorder with malfunctioning Hb, what happened on day 2?
Definition
The mother went through IVF several times to get an embryo without the defect and a good HLA match so that they could use the cord blood for Nikhil. In real life the IVF was blocked by courts of England.
Term
In PBL case 2, baby bryce was exposed to Accutane by his dumb ass teenage mother, the ultrasound showed no abnormalities, what happened on day 2?
Definition
The retinoic acid severely disrupted normal brain formation causing extensive neurological and developmental problems.
Term
In PBL case 3, Herman was hospitalized after heat exposure, he had high levels of chloride in his sweat, and he had a long history of lung infections, what happened on day 2?
Definition
His genetic tests confirmed that he had CF but a mild version, his brother had extensive genetic testing for his wife and himself and found that their child was only a carrier of CF.
Term
In PBL case 4, Mr. Markov had extreme reactions to ricin poison, he soon died from the shock and coursing poison, what happened on day 2?
Definition
The doctors realized that there was nothing that they could do because there is no antidote, ricin blocks ribosomal translation of proteins, and the only option would to stabilize his symptoms.
Term
In PBL case 5, Ms. Collins returns from Haiti with odd, irregular mole formation, she has them biopsied and given a path report with bad news, what happens on day 2?
Definition
She goes on chemo to attempt to stop the metastasis of the carcinoma but it was too late and the cancer went to her brain, so she stopped chemo because of its limited bioavilability, she then died.
Term
In PBL case 6, Sam shows severe and multiple infections and isn’t responding to normal antibiotics and is found to have Nocardia, what happenes on Day 2?
Definition
He is diagnosed with CGD because his respiratory burst was negative, showing that his immune system could phagocytize pathogens but not kill them.
Term
In PBL case 7, dude had a bad, dry cough that kept getting worse, what happened on day 2?
Definition
He was diagnosed with Mycobacterial Tuberculosis, quarantined for a period and given an extensive therapy of antibiotics both in the hospital and to take home for six months.
Term
What is pharmacovigilance?
Definition
The science of understanding and preventing adverse effects of drugs.
Term
For pharmacovigilant rates of frequency, what is the prevalence in a population of adverse effects if it is deemed - very common, common, uncommon, rare, very rare?
Definition
1/10, 1/100, 1/1000, 1/10,000, >1/10,000
Term
What is iatrogenic?
Definition
Adverse effects from medical treatment or advice
Term
What is enzyme inhibition?
Definition
Two drugs competing for the same enzyme
Term
What changes the most with geriatric pharmacology and what should you do - absorption, distribution, metabolism, elimination?
Definition
Metabolism and elimination slow the most and so you should lower the dose.
Term
What is the difference between relative and absolute contraindication?
Definition
Relative refers to a condition which makes a particular treatment slightly inadvisable(X-rays) whereas absolute refers to a treatment that is completely inadvisable(aspirin).
Term
What is the difference between a primary resource and a secondary one?
Definition
Primary is creating a new data set and findings, secondary is summaries of primary studies like textbooks as meta-analysis.
Term
What is the difference between an observational study and an experimental study?
Definition
Observational is case series/control or cohort studies, experimental is clinical trials and they are the preferred method to answer clinical questions
Term
How many half lives does it take to reach 90% of steady state?
Definition
3.3 half lives
Term
What is the equation for bioavailability (F)?
Definition
(AUC parenteral/enteral dose)/AUC IV dose
Term
What is the equation of volume of distribution?
Definition
Vd=dose/plasma concentration(Cp)
Term
What is the equation for half-life?
Definition
.693/k
Term
What is the equation for clearance?
Definition
Cl=(rate of elimination/Cp)=.693*Vd/t(1/2)=k*Vd
Term
What is the equation for concentration at steady state(Css)?
Definition
Css=infusion rate/Cl
Term
What is the equation for loading dose?
Definition
Css*Vd
Term
What is the equation for maintenance dose?
Definition
Maintenance dose=Css*Cl*time interval
Term
Describe the structure of the sarcomere and what happens to the A bands and I bands upon contraction.
Definition
[image]
Term
Describe the relation of calcium to tropomyosin and the myosin head.
Definition
[image]
Term
Describe how movement of K+ ions in a cell are related to the balance of membrane potential and equilibrium potential for an ion.
Definition
[image]
Term
describe the overall structure of a muscle fiber and notice that the T-tube and the SR get close next to the A-I band junction.
Definition
[image]
Term
Understand the following image, including inactivation and time delays.
Definition
[image]
Term
Understand the following from the picture that follows: negative charges attract K+ to pore, the pore helix draws K+ to filter, backbone carbonyl oxygens help K+ shed its water, mutual repulsion between K+ ions moves them through selectivity filter.
Definition
[image]
Term
Review image: the reason saltatory conduction works is because it insulates leaky channels and allows the flow of action potentials to jump from node to node versus channel to channel.
Definition
[image]
Term
Image review: The key point of this is that repolarization is due to a decrease in Na+ and an increase in K+, and that during this time another AP cannot be generated because the h gates are closed.
Definition
[image]
Term
Understand the basics between the two synapses in the following image.
Definition
[image]
Term
Understand the details of the chemical synapse in this image.
Definition
[image]
Term
Know the difference between ligand-gated ion channels and G-protein coupled receptors, using this image.
Definition
[image]
Term
What does positive current refer to?
Definition
Positive charges moving out of the cell, negative charges move in.
Term
True or False: the Na/K ATPase plays a vital role in the action potential.
Definition
False, it plays no role.
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