SM01 Mini3 Flashcards Preview

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Flashcards in SM01 Mini3 Deck (37):
1

excitable cells

neurons & muscle cells (skeletal, heart, & smooth)

2

rule of electroneutrality

number of postive & negative are equal w/in each compartment

BUT composition is different

3

ways to modify an ion's membrane permeability

membrane voltage

ligands

mechanical stimuli

4

K+ concentrations

extracellular: 5mM

intracellular: 150mM

equilibrium potential= -90mV

electrical & chemical gradient push ions out of cell via leak

5

Na+ concentrations

extracellular: 150mM

intracellular: 15mM

equilibrium potential= +60mV

electrical & chemical gradient push ions into cell via leak

6

Ca2+ concentrations

extracellular: 1.8mM

intracellular: 70nM≈ 10-7 to 10-5M

equilibrium potential= +130mV

7

Cl- concentrations

extracellular: 110mM

intracellular: 10mM

equilibrium potential= -65mV

8

concentration force

chemical work for particular ion= RT*ln ([x]i/[x]o)

at equilibrium

 

9

electrical force

electrical work of particular ion= -VmZxF

@ equilibrium

Vm= membrane potential

Zx= valence for ion

F= Faraday constant

10

Nernst Equation

@ equilibrium

Vm= - (RT/zxF) ln ([x]i/[x]o)

simplified for @ 1atm & T=37ºC

Vm= - (61/zx) log10([x]i/[x]o)

**permeability is NOT considered**

11

simplified method for Nernst equation

  1. divide bigger concentration by smaller
  2. log10
  3. *61/zx
  4. determine +/- value relative to intracellular membrane potential, does it become more + or - with movement of ion?

12

resting membrane potential

summation of equilibrium potentials for all ions acting on membrane

influencing factors: ion permeability & concentration differences

much closer to K+ equilibrium potential b/c membrane  is more permeable to K+

= -70mV

13

Na+/K+ pump

primary active transport

uses 2/3 ATP/day to maintain elctrochemical gradient across membrane

3 Na+ out for 2 K+ in

NOT part of action potentials, just there to compensate for leakage of ions

14

inward positive current causes

membrane depolarization

15

outward positive current causes

membrane hyperpolerization

16

depolarization

membrane potential becomes less negative than resting membrane potential

17

hyperpolarization

membrane potential becomes more negative than resting membrane potential

18

action potential

rapid alteration of membrane potential

usually lasts 1ms

may change 100mV (-70mV to +30mV)

19

regenerative depolarizaion phase

after passing threshold, action potential is propogated by increasing permeability of Na+ via opening of voltage gated Na+ channels

20

overshoot

action potential above 0mV

21

repolarization

return to resting membrane potential after depolarization

factors: closing of inactivation gate of Na+ channels & increase of K+ permeability

 

22

after hyperpolarization

rebound phase when potential is more negative than resting

caused by reduces ratio of Na+:K+ permeability compared to resting

23

threshold potential

minimum a stimulus must depolarize a cell to propagate an action potential

for most excitable cells= 15mV less negative than resting

if less than 15mV, called subthreshold potential

24

absolute refractory period

period when all Na+ channels activation gates are open & inactivation gates are closed

action potential cannot be produced b/c Na+ channels need activation gate to be closed in order to be excited

prevents propagation of action potentials in the wrong direction

25

relative refractory period

some Na+ activation gates have closed and can be excited, but not all

therefore, second smaller action potential can be created

threshold level is also higher

26

graded potentials

changes in membrane potential in small region of membrane

depolarizing or hyperpolarizing

variable amplitude dependent on magnitude of stimulus

types: receptor, synaptic, end-plate, & pace-maker

27

temporal summation

successive graded potentials in same location that sum to larger potential

28

spatial summation

sum of graded potentials at different locations on membrane 

29

membrane resistance to current flow

great resistance→ smaller decline in voltage amplitude with distance

reason why long axons are myelinate to increase their membrane resistance

30

axon inside resistance

smaller inside resisitance to current flow→ less voltage amplitude decline with distance

decline of amplitude in larger diameter axons is less than in smaller diameter axons

31

factors influencing propagation velocity of action potentials

increases with increasing membrane resistance & axon diameter

32

continuous conduction

unmyelinated axons

larger diameter & thick plasma membrane have higher velocity of propagation than smaller nerve fibers w/thinner membranes

33

saltatory conduction

in myelinated axons

increased velocity of action potential propagation via increased membrane resistance

new potential at each node of Ranvier

34

postsynaptic potential

graded potential change produced in postynaptic neuron in response to release of neurotransmitter at presynaptic terminal

EPSP (excitatory postsynaptic potential) or IPSP (inhibitory)

35

Aalpha fiber type

primary afferent fibers from muscle spindles, motoric fibers to skeletal muscles

avg diameter: 15micrometers

avg conducting velocity: 100m/s

36

C type nerve fibers

skin afferent fibers from nociceptors & sympathetic postganglionic efferent fibers

avg diameter: 1micrometers

avg conducting velocity: 1m/s

37

pacemaker potential

spntaneously occurring graded peotential

only occurs in sertain specialized cells

ex. SA node, AV bode, bladder smooth muscle