NBME Physiology Exam , Verified Exam Questions with 100% Correct Answers, All Graded A+, Latest Expert Premium Update()|>100% Guaranteed Success.

NBME Physiology Exam , Verified Exam Questions with 100% Correct Answers, All Graded A+, Latest Expert Premium Update()|>100% Guaranteed Success. Gap Junctions - ANSWER attachment between cells that permit intercellular communication (i.e. current flow and electrical coupling between myocytes) J= -PA (C1-C2) J= (1x10^-5)(100)[(20/100)-(10/100)] J= 1x10-4 mg/sec - ANSWER The urea conc. of blood is 10 mg/ 100mL the urea conc of proximal tubular fluid is 20 mg/ 100 mL. if the permeability to urea is 1x10^-5 cm/sec and the surface area is 100 cm^2 what is the magnitude and direction of the urea flux (diffusion)? 2 K+ for 3 Na+ Digitalis (cardiac glycoside drug) - ANSWER Na/K ATPase exchanges ___ K for ___ Na. Specific inhibitor of the Na/K ATPase? SERCA - ANSWER Ca++ ATPase in the sarcoplasmic and endoplasmic reticulum? Omeprazole (proton pump inhibitor) - ANSWER The H/K ATPase that pumps protons into the gastric lumen (against their conc. gradient) is inhibited by what drug? Osmosis - ANSWER Flow of water across a semipermeable membrane from a solution with low solute conc. to a solution with high solute conc. ? Increases - ANSWER Osmotic pressure ___________ when solute conc. increases. 1 M CaCl2 because the conc. of particles is higher. - ANSWER Which has a higher osmotic pressure: 1 M CaCl2 or 1 M KCl? Isotonic Hypertonic Hypotonic **Water flows from the hypotonic to the hypertonic solution. - ANSWER If two solutions have the same osmotic pressure, they are _________ If one solution has a higher osmotic pressure than the other, it is _____________ If one solution has a lower osmotic pressure than the other, it is __________ Reflection coefficient Rf= 1 means the solute is IMPERMEABLE (100% reflection) Rf= 0 means the solute is COMPLETELY PERMEABLE - ANSWER A number between zero and 1 that describes the ease with which a solute permeates a membrane? Rf= 1 Rf=0 - ANSWER reflection coefficient of serum albumin? (a large solute) Reflection coefficient of urea? (a small solute) Small Cations *will exclude large molecules and anions - ANSWER A small ion channel lined with negatively charged groups will be selective for? Equilibrium potential **At electrochemical equilibrium, the chemical and electrical driving forces that act on an ion are *equal and opposite*, and no more net diffusion of the ion occurs. - ANSWER Refers to the potential difference that would exactly balance (oppose) the tendency for diffusion down a concentration gradient? E Na= +65 mV E Ca= +120 mV E K= -85 mV E Cl= -85 mV - ANSWER Approximate equilibrium potentials in nerve and muscle? E Na= ? E Ca= ? E K= ? E Cl= ? Depolarization (cell interior becomes less negative) Repolarization (cell interior becomes more negative - ANSWER __________ makes the membrane potential less negative _________ makes the membrane potential more negative Inward current **depolarizes the cell - ANSWER Refers to the flow of positive charge into the cell? (current) outward current **hyperpolarizes the cell - ANSWER Refers to the flow of positive charge out of the cell? (current) NO: Action potentials are *all or nothing* - ANSWER Are action potentials different sizes dependent on different magnitudes of stimuli? Threshold - ANSWER The membrane potential at which an action potential is inevitable? -70 mV **A result of the high resting conductance to K+ which drives the membrane potential toward the K+ equilibrium potential (-85 mV) - ANSWER Normal resting membrane potential? 1. Inward current depolarizes the membrane potential to threshold 2. Depolarization causes opening of Na channels 3. Rapid depolarization occurs due to the increased conductance of Na (inward Na Current) **brief period where membrane potential is positive - ANSWER What causes the upstroke of the action potential? Repolarization is caused by an *OUTWARD* K+ current - ANSWER What causes repolarization of the action potential? Tetrodotoxin (TTX) Lidocaine - ANSWER Two drugs that block voltage gated Na channels, abolishing action potentials? Tetraethylammonium (TEA) - ANSWER Drug that blocks voltage gated K+ channels? Absolute refractory period (explanation: Na+ channels remain closed until repolarization occurs) - ANSWER Period where another action potential cannot be elicited? Relative refractory period **action potential can be elicited during this period, but only if a larger than usual inward current is provided. - ANSWER period that begins at the end of the absolute refractory period and ends when the membrane potential returns to resting levels? 1. *INCREASED fiber size*: increased diameter= decreased internal resistance= increased conduction velocity 2. *myelination*: allows for saltitiory conduction at nodes of Ranvier. - ANSWER What two things increase conduction velocity in nerves? 1. Action potential in presynaptic cell depolarizes the presynaptic terminal 2. *Ca++ enters the presynaptic terminal causing release of NT into the synaptic cleft* 3. NT diffuses and combines w/ receptors on the post-synaptic membrane - ANSWER How do action potentials allow for neuromuscular/ synaptic transmission (using NTs)? Hyperpolarize Depolarize - ANSWER Inhibitory NTs ________________ the postsynaptic membrane Excitatory NTs ____________ the postsynaptic membrane Acetylcholine (ACh) **Postsynaptic membrane contains a nicotinic receptor (Na/K ligand-gated channel) - ANSWER NT released from the presynaptic terminal at the neuromuscular junction? Acetyl-CoA and choline *Choline acetyltransferase* **ACh is stored in synaptic vesicles for later release - ANSWER Acetylcholine is generated from _________ and _________. Enzyme that catalyzes this reaction? Ca++ **Synaptic vesicles fuse with plasma membrane and empty their contents into the cleft by exocytosis. - ANSWER _________ Uptake causes release of Ach into the synaptic cleft? Acetylcholinesterase **Located on the muscle end plate. - ANSWER Acetylcholine is degraded to acetyl CoA and choline by? End Plate Potential (EPP) - ANSWER Depolarization of the muscle end plate; Not an action potential?