Medical Physics Final Flashcards
Electricity-Neurons-Heart
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| 392131341 | What are 4 Characteristics of an Action Potential? | 1) All-or-none Respone 2) Propagation without attenuation 3) Constant amplitude of discharge (for given neuron) 3) Refractory period = 2-5msec | |
| 392131342 | What's the normal refractory period for cardiac muscle? | 250msec! | |
| 392131343 | How does the membrane act like a capacitor? (2 traits) | 1) Stores charge 2) Supports a strong electric field within the membrane | |
| 392131344 | What is the charge of the solution outside a membrane? (charge, etc) | Outside membrane 1) Electric field = 0 2) Solution is ELECTRICALLY NEUTRAL | |
| 392131345 | What does the Na/K pump do? | -CREATES CONC. GRADIENT - Active process Na+ = Pumped OUT K+ = Pumped IN | |
| 392131346 | What parameter is needed for the NERST equation to work and thus define the membrane potential of a cell? | -Only ONE ion species can have appreciable permeability "If only one ion species has appreciable permeability, the membrane potential is given by the NERST equation." | |
| 392131347 | What does the membrane potential depend on if MULTIPLE IONS can permeate the cell? (x2) | 1) The permeability of the membrane to each ION 2) The [Conc] Gradients of each ION across the membrane. | |
| 392131348 | In the Goldman-Hodgkin-Katz equation for multiple ions within the neuron (Na, K, Cl), what does RT/F equal? | RT/F = 61.5mV R= ideal gas constant; F=Faraday's constant; T= 37C | |
| 392131349 | What are the equilibrium potentials of each ion AND where does it concentrate when concerning a neuron: 1) K+ 2) Na+ 3) Cl- | 1) K+ = -90mV (conc's inside) 2) Na+ = +60mV (conc's outside) 3) Cl- = -70mV (conc's outside) | |
| 392131350 | What are the concentrations of Na+ and K+ governed by? | Na+ / K+ PUMP! | |
| 392131351 | In a resting neuron, which ion has greater permeability, AND, which ion passively adjusts to the membrane potential? | Resting Neuron... K+ Permeability ==> MUCH GREATER than Na+ Permeability Cl- [conc] ==> Adjusts passively to Vm | |
| 392131352 | What is the resting membrane potential in a a typical neuron?!? | -70mV | |
| 392131353 | Concerning Neurons... How does lethal injection work? | Neurons = very sensitive to EXTRACELLULAR Potassium! Inject High [conc] of Potassium ==> membrane potential abolished | |
| 392131354 | -- What equation predicts the Vm x [K+] relationship during lethal injection? -- Graphically depict the relationship as [K+] increases... | -- Goldman equation predicts the Vm x [K+] relationship | |
| 392131355 | Define an Action Potential. | Action Potential is a self-propagating depolarization-repolarization wave of the axon (not the dendrites). | |
| 392131356 | What is depolarization caused by? | Opening Na+ Channels ==> Na+ IN Closing of K+ Channels ==> K+ IN (prevents repolarization) | |
| 392131357 | Depict an Action Potential. Include a time-scale, charges inside and out, and repolarization of the axon. | ... | |
| 392131358 | What can alter membrane permeability (just one). | Changes in Membrane Potential! | |
| 392131359 | Voltage-gated channels | ... | |
| 392131360 | Will a Na+ Channel Protein be closed or open at -65mV? What about -40mV? | Na+ channel @ -65mV ==> CLOSED Na+ channel @ -40mV ==> OPEN | |
| 392131361 | "An Action Potential is a complex, non-linear phenomenon" ==> -- It ALTERS membrane Permeability -- TRIGGERS Na+ influx ==> further alters membrane potential ==> further alters membrane permeability, etc, etc | ... | |
| 392131362 | When does a neuron generate an AP? | When the AXON HILLOCK has reached a potential that EXCEEDS a well-defined threshold level | |
| 392131363 | What can account for referred pain or masking of pain? | Convergent inputs of neurons into other neurons | |
| 392131364 | What are 2 differences between a dendritic current and an AP? | 1) Dendritic signals can be graded ==> Have variable amplitude AND 2) Can be Excitatory (depolarizing) or Inhibitory (hyperpolarizing) | |
| 392131365 | What do local anesthetics effect on a neuron? | Local anesthetics INHIBIT changes in permeability | |
| 392131366 | What equation is used for the Electrical model of a Neuron? | Neuronal Electrical Model = Cable Equation N.E.M. = Cable | |
| 392131367 | What's the transmission rate of a 1) myelinated neuron and 2) an unmylenated neuron? | Myelinated = 20-100 m/sec Unlmyelinated = 2-5 m/sec | |
| 392131368 | M.S. Disease (x4) | 1) age = 20-40 2) Leading cause of major disability in working age adults 3) Autoimmune 4) attack and remission cycle | |
| 392131369 | Synaptic Transmission being two steps... | 1) Electrical = AP 2) Chemical = synaptic transmission | |
| 392131370 | Synaptic transmission properties (x3) | 1) Neurotransmitters alter perability ==> inject current into dendrite 2) 1-way transmission ==> Axon->Dendrite 3) Graded input (variable amplitude) & Excitatory or Inhibitory | |
| 392131371 | What are Body Surface Potentials and what are they do to? | EEG & ECG = Body Surface Potentials Body surface potentials are due to widespread IONIC CURRENT FLOW in a RESISTIVE MEDIUM ==> governance by OHM'S LAW | |
| 392131372 | 2 ways to describe Body Surface Potentials ==> 1) Nerve and muscle cells act like tiny current sources 2) Body is like a bag of conducting solution with appreciable sensitivity | ... | |
| 392131373 | What are EEGs recording from a neuron? | Record signals that arise from DENDRITIC ACTIVITY | |
| 392131374 | Alpha-wave EEG | 8-12 Hz ==> Relaxed wakefulness ((approx. 100 uV in amplitude)) most posterior scalp | |
| 392131375 | Delta-wave EEG | <4 Hz (pathological) | |
| 392131376 | Theta-wave EEG | 4-7 Hz ==> Drowsiness | |
| 392131377 | Beta--wave EEG | >13, alert wakefulness (PFC) | |
| 392131378 | Sharp spike EEGs may be indicative of ... (x2) | Epilepsy and/or Seizure disorders | |
| 392131379 | Large, slow waves may be indicative of ... (x4 -- LISI) | Lesion, Injury, Stroke, Infection | |
| 392131380 | NREM Sleep | 4 stages with distinctive EEG for each stage --> EEG slows with deeper (delta wave) sleep | |
| 392131381 | Electrocardiography (ECG) measurement | Heart depolarization produces current flow and differences in potential outside the heart. ECG records DIFFERENCES IN POTENTIALS | |
| 392131382 | Describe how a 3-Lead ECG works | --Location of 3 leads ==> Left Arm (LA), Right Arm (RA), and Left Leg (LG) -- ECG measure the difference in potential between electrodes due to current flow along the direction of the leads. I = V(LA)-V(RA) II = V(LL)-V(RA) III= V(LL)-V(LA) | |
| 392131383 | What are the 3 components of the Cardiac cycle and what electrical component do they correspond to? | P-Wave ==> Atria Depolarization QRS-Complex ==> Ventricular Depolarization T-Wave ==> Ventricular Repolarization | |
| 392131384 | What is the SA node and where is it located? What is it responsible for? | Sinoatrial Node = SA-Node --Primary pacemaker ==> initiates Heartbeat --silent on an ECG --depolarize the atria (P-WAVE) | |
| 392131385 | The amplitude of the ECG is on the order of 1 mV | ... | |
| 392131386 | Describe the timing of the electrical and mechanical events of a heartbeat. | 1) SA node fires 2) Atria Depolarize & Fill 3) AV node slowly conducts impulse ((receive signal from SA)) 4) Ventricles Fill 5) Purkinje fibers conduct rapid impulse throughout the ventricles 6) Ventricular contraction | |
| 392131387 | QRS-complex | --Ventricular depolarization & atria repolarization (masked by vent. depol) | |
| 392131388 | T-wave | Ventricular repolarization | |
| 392131389 | What do the P-wave and QRS-complex initiate and precede? | Atrial AND Ventricular Contraction | |
| 392131390 | What are Impulses formed by? | Pacemaker cells! Leaky ion channels ==> Spontaneous cell depolarization | |
| 392131391 | AV Node DOES fire if SA node fails | ... | |
| 392131392 | What are 3 types of arrythmias | 1 -- Abnormal impulse formation and conduction 2 -- Abnormal conduction due to block at AV node (like an open circuit) 3 -- Abnormal conduction due to Extraneous Atrioventricular Connection ("Short Circuit") | |
| 392131393 | What's an example of "Abnormal impulse formation and conduction" arrythmia? | Ventricular Fibrillation= V-FIB ==> Chaotic, ineffective beating - cause of death & secondary to heart attacks --due to multiple ECTOPIC FOCI THROUGHOUT (ischemic) HEART or abnormal conduction pattern that does not die out ==> Treated by applying a large Depol. to heart | |
| 392131394 | When is a pacemaker used? | In the case of a Complete/3rd Degree AV Blockage ==> Impulse is BLOCKED at AV-NODE ==> causes Ventricular rate to be lower than atrial rate --Pacemaker fixes problem --Congenital | |
| 392131395 | What is Reentrant supraventricular tachycardia (SVT)? | SVT is an example of of extraneous atrioventricular connections that cause abnormal conduction --abnormal "accessory" pathway (AP) between atria and ventricles -- Fixed via ablation of accessory pathway in cardiac-cath lab | |
| 392131396 | What is ectopic focus in terms of heart impulses? | Ectopic focus = Injured and/or irritated cells fire ==> Abnormal pacemaker |