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Biol 1412 > Topic 3 > Flashcards

Topic 3 Flashcards

1
Q

Neurons

A

when stimulated usually on cell body or dendrites an electrical impulse may be generated and propagated along the axon = nerve impulse

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2
Q

Electrical properties of cell is due to

A
  • ionic concentration differences across membrane

- permeability of cell membrane to ions

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3
Q

Important ions

A

K, Na, Cl, Ca, large negatively charged organic ions (org)

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4
Q

Large negatively charged organic ions are..

A

non diffusible proteins

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5
Q

Only ion that is higher on the inside of the cell

A

K

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6
Q

Na and K due to and maintained by..

A

activity of Na/K ATPase pump in cell membrane

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7
Q

Ca due to..

A

various transporters in cell endoplasmic reticulum membranes

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8
Q

Cl repelled by ..

A

org so is higher outside of the cell than inside

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9
Q

Org stay where..

A

inside the cell

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10
Q

Permeability of cell membrane to ions determined by..

A

ion channels - ions diffuse through them down conc. gradients

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11
Q

2 types of ion channels

A
  • gated

- non gated

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12
Q

Non gated ion channels

A

always open, more K than Na therefore cell membrane more permeable to K at rest (no stimulus).

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13
Q

What channels are import in establishing the resting membrane potential

A

non gated ion channels, especially K (more numerous)

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14
Q

Gated channels

A

not involved at rest, open in response to stimuli

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15
Q

4 types of gated channels and their stimuli

A
  • voltage gates: membrane voltage changes
  • chemical gates: chemicals, binding of hormone/nt
  • thermal gates: temperature
  • mechanical gates: mechanical deformation
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16
Q

Resting membrane potential (RMP)

A

at rest, MP= -70 mV (inside of cell is more -ve)

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17
Q

Membrane potential

A

a charge difference (potential difference) exists just across the cell membrane

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18
Q

Factors establishing RMP (-70 mV)

A
  • Na/K ATPase
  • Org inside cell can’t cross membrane
  • more non gated K channels than non gated Na channels (membrane more permeable to K than Na at rest, so K is major determinant of RMP)
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19
Q

K diffuses out of the cell down the concentration gradient therefore..

A

cell loses positive charge and inside becomes more negative

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20
Q

What increases due to increasing attraction to -‘ve cell interior

A

Na diffusion into cell

21
Q

Until -70 mV is reached..

A

positive out of the cell (K) is greater then positive in the cell (greater K permeability)

22
Q

Once at -70mV ..

A

amount of positive (k) moving out equals the amount of positive (Na) moving in because force on Na much higher than on K, therefor the net movement of charge (ions) is 0

23
Q

Electrically excitable cells are ONLY

A

muscle and nerve cells

24
Q

Electrically excitable cells are capable of producing..

A

departures from RMP in response to stimuli

25
Q

When a neuron is stimulated

A
  • gated ion channels open
  • MP changes = producing graded potential if the threshold is reached
  • triggers an action potential
26
Q

Graded potentials

A

stimulis causes a small change in RMP, usually on dendrite or cell body by opening gated channels (changed membrane permeability)

27
Q

Possible results from graded potentials

A
  • more positive than RMP = depolarization

- more negative than RMP = hyperpolarization

28
Q

In GP ions move ..

A

passivley (unlike charged attract) = current flow causing deplo. or hyperpol. on adjacent membrane

29
Q

GPs are..

A

short distance signals, die away quickly

30
Q

Magnitude and distance travelled by GP varies..

A

directly with the strength of the stimulus

31
Q

How do GPs summate

A

1st GP present when 2nd stimulus occurs, these add together to create the resulting GP

32
Q

After GP..

A

repolarization, return t the RMP after deplo. or hyperpol.

33
Q

GPs are essential to..

A

initiating a nerve impulse (AP)

34
Q

What leads to an action potential

A

GP that causes depolarization and is large enough

35
Q

Steps in a GP action potential

A
  • critical stimulus (summating stimuli)
  • GP reaching threshold
  • action potential
36
Q

Action potential

A

nerve impulse, large change in MP that propagates along an axon w/ no change in intensity

37
Q

Action potentials initiates at..

A

trigger zone

38
Q

Phases of action potential

A
  • depolarization
  • repolarization
  • after-hyperpolarization
39
Q

Depolarization phase

A

voltage gated Na channels respond to MP change and open. as gates open more Na diffuses in cause even more Na gates to open (positive feedback) Na diffuses in causing depolarization to 30 mV

40
Q

Repolarization phase

A

Na channels close, become inactivated and Na movement returns to resting levels, voltage gated K channels open therefore K diffuses out

41
Q

After-hyperpolarization phase

A

K channels are slow to close and remain open longer than necessary, Na channels are reactivated, can response to stimuli at this point

42
Q

Once K channels close..

A

MP returns to RMP

43
Q

Na/K ATPase always working ..

A

maintain gradients

44
Q

Takes ____ of APs to cause a…..

A

10 000; measurable change in ion in the cell

45
Q

Absolute refractory period prevents..

A

AP summation

46
Q

During the absolute refractory period no..

A

AP can be generated, regardless of stimulus size

47
Q

Absolute refractory period results from either..

A
  • all Na channels being open (region b)

- all Na channels being inactivated (can’t open until MP reaches RMP, region c)

48
Q

Relative refractory period

A

period when an AP can be generated but only by a greater than normal stimulus, Na channels are reactivated when MP passes RMP, they are closed but can be reopened if theresfolg reached

Biol 1412 (15 decks)

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