patho phys exam 1 Flashcards

Question

CHARACTERISTICS OF GRADED POTENTIALS

Answer 1

Graded potentials spread by passive current flow in all directions - so energy is not required because it is passive the potential exists because of the movement of ions, anytime you have ions crossing the membrane you have ion channels if there is a triggering event or stimulus, the channels will open and most often it'll be sodium channels 1 - unbalanced charges distrubuted across the plasma membrane that are repsosnbile for membrane potential 2 - triggering event opens ion channels, most commonly permitting net Na+ ENTRY 3 - RMP is -70mV but now becomes -65mV so a small depolarization is produced

Answer 2

B False because it is a passive

Answer 3

1 - current loss across the membrane 15mV potential has been created loss of charge means K+ leaves and not Na+ because the membrane is more permeable to K+ because there are more K+ leak channels numbers refer to the local potential in mV at various points along the membrane Graded potentials die out over short distances like ripples in the water

Answer 4

Graded potentials can undergo summation & initiate action potentials -50mV is the threshold potential, when the membrane potential reaches this potential of -50mV, an action potential will be generated The excitatory presynaptic inputs generate a depolarization The inhibitory presynaptic inputs generate a hyperpolarization graded potential can add onto each other to generate a bigger trigger no summation - the graded potential is too low to reach the -50mV threshold temporal summation (time summation) - spatial summation - a summation in space - two different neurons combine to create a threshold potential EPSP-IPSP cancellation - an excitatory stimulation is canceled out by the inhibitory stimulation graded potentials are needed because a small amount of urine generates a small graded potential, but when it is full it will cause an action potential and now we use the restroom

Answer 5

Brief, rapid, large changes in RMP: inside becomes more positive! - very brief DIFFERENT FROM GPs: - Magnitude & duration always same: 1msec - Do not die; serve as long-distance signals after the AP, there is a hyperpolarization then it goes back to the RMP which is -70mV

Answer 6

Arise due to changes in membrane permeability to ions due to conformational changes of voltage-gated sodium and potassium channels voltages gated ion channels can change their conformation (shape) to either open or close because of changes in the RMP VG Na+ channel - has two gates: activation and inactivation gate closed by capable of opening - *open (activated)* *closed and not capable of opening (inactivated)* VG K+ channel - has one gate: activation and inactivation gate closed - K+ cannot leave the cell *open (activated)* - when K+ can leave the cell

Answer 7

below threshold potential - Activation gates closed with action potential - Activation gate of VGSCs open - VGSCs activation gate closed, inactivation gate open at the top of the AP - The inactivation gate of VGSCs close - Activation gate of VGPCs open on the decline of the AP - VGSCs activation gate closed, inactivation gate open - Activation gate of VGPCs close - Na+-K+-ATPase restores balance +61mV know the conformation at the different parts of the AP trigger for AP - opening of the VGNa+ channels

Answer 8

Once initiated, AP is conducted throughout the axon Contiguous conduction in unmyelinated neurons the axon hillock has the most # of VGNa+ channels which is where the AP is generated activate area at peak of action potential the adjacent inactive area into which depolarization is spreading; will soon reach the threshold the remainder of the axon is still at resting potential the previous active area returned to resting potential; no longer active; in the refractory period

Answer 9

Action potentials are propagated in one direction only towards the axon terminal, always moving forward forward current flow excites new inactive area backward current flow does not reexcite previously active area because this area is in its refractory period forward current flow excites new inactive area

Answer 10

VGSCs are closed and not capable of opening the stage VGSCs are closed and capable of opening stage VGPCs are open absolute refractory period - relative refractory period - the VG Na+ is in a closed by capable... umm if at -70mV but what to get to -50mV, then you need a response of 25mV

Answer 11

1 - a depolarizing event brings the resting membrane potential (-70mV) up to the threshold of -50mV 2 - at this time, the voltage-gated sodium channels open 3 - Na+ moves down its electrochemical gradient into the cell making the cell more positive 4 - the inward movement of sodium leaves behind the negative charge with which the Na+ was paired. The membrane continues to depolarize as the inside of the cell becomes more and more positive and the outside more negative 5 - depolarization continues until 0mV is reached 6 - the inward movement of sodium reverses the potential and the inside continues to become more positive until the AP reaches the peak 7 - at the peak, the Na+ inactivation gates begin to close and the K+ gates begin to open 8 - K+ flows down its electrochemical gradient out of the cell making the cell less positive and outside more positive. This leaves behind the negative charges with which the positive charges were once paired inside the cell 9 - membrane potential drops to zero mV. Continual outward movement of K+ begins to restore the resting membrane potential 10 - at resting potential, the Na+ inactivation gates open and the activation gates close 11 - K+ continues to flow out and thus hyperpolarizes the membrane 12 - the K+ gates close and the cell returns to resting membrane potential of -70mV

Answer 12

- occur by passive current flow in all directions (unlike AP) - die out over short distances - proportional to the magnitude and duration of the stimulus - they are small changes in the RMP either in the positive direction (depolarization which decreases the potential) or in the negative direction (hyperpolarization which increases the potential - can undergo summation & initiate AP

Answer 13

no summation - both of the stimuli have little effect on the potential temporal summation - the stimuli stack on top of each other spatial summation - the stimuli are spaced out and are added together EPSP-IPSP - excitatory stimuli are canceled out by inhibitory stimuli

Answer 14

APs arise due to changes in membrane permeability to ions due to conformational changes in voltage-gated sodium and potassium channels - so because the ion channels change shape, the membrane gains permeability for the ions and allows for an action potential! APs are different from GPs because their magnitude and duration are always the same: 1msec - while GPs magnitude and duration depend on the stimulus! APs also do not die but serve as long-distance signals while GPs do die out over short distances

Answer 15

voltage-gated sodium channels - closed by capable of opening: the inactivation gate is moved out of the way from the inner cavity and the activation gate is closed - open (activated): the inactivation gate is moved out of the way from the inner cavity and the activation gate is open! This is a rapid opening triggered at the threshold :) so it is triggered when the threshold of -50mC is reached. So when the AP goes up from the RMP - closed and not capable of opening (inactivated): the inactivation gate is blocking the inner cavity and the activation gate is open Slow closing is triggered at the threshold, so when the AP comes back down voltage-gated potassium channels - closed: the inner cavity is closed - open: the inner cavity is open! Delayed opening triggered at the threshold An AP is triggered when the membrane has permeability for the ions due to the conformational changes ^^^ of the membrane

Answer 16

at RMP: - both of the sodium and the potassium activation gates are closed at -50mV which is the threshold :) - activation gated of the voltage-gated sodium channels open at the peak of the AP - inactivation gate of the voltage-gated sodium channels closed - activation gate of voltage-gated potassium channels open at the -50mV - voltage-gated sodium channel activation gate closes and its inactivation gate open at the RMP (-70mV) - the voltage-gated potassium channels activation gate close Na+/K+ ATPase restores balance

Answer 17

- once initiated, AP is conducted through the axon - continuous conduction in unmyelinated neurons - APs are propagated in one direction only (while the GPs are in all directions

Answer 18

voltage-gated sodium channels are closed and not capable of opening (the inactivation gate is blocking it but the cavity is open) voltage-gated sodium channels are closed and capable of the opening stage VGPCs are open absolute refractory period is where the AP is and also where the membrane has the permeability for Na+ relative refractory period is where the membrane has the permeability for K+

Answer 19

- Short range, released by electrical signals * Diffuse to act on target cells (gland/neuron/muscle)

Answer 20

Chemical messengers: lipid-soluble or water-soluble * Signal transduction process: → message (signal) is “transduced” inside the cell by “transducers” (convert one form of energy to another e.g., radio/phone) * Lipid soluble: cross membranes → affect gene transcription → affect activity of proteins * Water soluble: do not cross membranes, bind to receptors → transduce signal inside the cell – 1st Messenger-receptor binding → intracellular events: * By opening/closing ion channels allowing ions to move in/out * By transferring the signal to the intracellular 2nd messenger

Answer 21

The message is “relayed” inside the cell via 2nd messenger * 2nd messengers relay it further to other IC proteins * Signaling cascade amplifies the initial response * Major ones: – Cyclic AMP – Ca2+/DAG * Others exist! * Disturbances lead to disease

Answer 22

PM is polarized electrically = membrane potential – Separation of opposite charges across the membrane due to differences in the relative number of cations/anions