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4. BIOL257 > Receptors, graded potentials > Flashcards

Receptors, graded potentials Flashcards

1
Q

define excitable cells:

A

cells which experience momentary change in membrane potential

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2
Q

membrane potential symbol:

A

Vm

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3
Q

change in Vm represents:

A

electrical signal

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4
Q

where is electrical signals used:

A

directly - electrical synapse

indirectly - chemical synapse

  • communicating w other cells
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5
Q

change in membrane potential process:

A

polarisation - depolarisation - repolarisation - hyperpolarisation

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6
Q

Vm: polarisation

A

anytime Vm not at 0mV, change separation exists

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7
Q

Vm: depolarisation

A

change in Vm making it less polarised (less -ve) than at RMP

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8
Q

Vm: repolarisation

A

Vm returns to RMP after depolarised

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9
Q

Vm: hyperpolarisation

A

change in Vm makes membrane more polarised (more -ve) than at RMP

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10
Q

RMP: generated by

A

uneven distribution of +ve and -ve charges across cell membrane (semi permeable)

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11
Q

RMP: governed by

A
  • concentrations of mostly K+ and Na+ in ICF and ECF

- relative permeability (P) of membrane to K and Na

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12
Q
  • any change in relative permeability will have dramatic effect on:
A

Vm as electrical forces generated by movement of few charged ions DOMINATES chemical forces

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13
Q

how does permeability of membrane change? and effects Vm

A

when ion channels open and close

  • cause Vm more -ve (hyperpolarise) or +ve (depolarise)
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14
Q

list types of gated channels:

A
  • ligand gated
  • mechanically gated
  • thermally
  • voltage-gated
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15
Q

neurotransmitter released by: and thus

A

pre-synaptic cell

  • activates ligand gated ion channels of post-synpatic cell -> open
  • ions move across post-synaptic cell (change to Vm)
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16
Q

electrical signals: graded potentials

A
  • small (few mV) rapid changes in membrane potential
  • excitatory (depolarising) or inhibitory (hyperpolarising)
  • spreads rapidly away from site of generation
  • dissipates quickly, short distances
17
Q

electrical signals: action potentials

A
  • triggered by EXCITATORY (depolarising) graded potentials -> reach threshold potential (typically -55mV)
  • fixed and large (100mV) dynamic change in Vm
  • regenerative, travels far without decrement (decreasing size)
  • spreads slower
18
Q

electrical signals: polarity of Vm depends on

A
  • type of cell
  • type of stimulus
  • type of ion channel that opens/closes in response to stimulus
19
Q

electrical signals: graded potential- hyperpolarisation (Y)

A
  • ligand binds to K ion channel and opens it

- K flow out of cell DOWN electrochemical gradient = Y

20
Q

electrical signals: graded potential- depolarisation (Z)

A
  • ligand binds to Na ion channel and opens it

- Na flows into cell DOWN electrochemical gradient = Z

21
Q

define electronic spread:

A

graded potentials spread out from origin (or active area) by passive flow of charges

22
Q

flow of charges aka

A

current

23
Q

graded potential magnitude:

A
  • proportional to stimulus strength
  • stronger stimulus = more ion channels open = more charged ions move across membrane
  • can also add up if overlaps and becomes stronger
24
Q

summation: (integration) most excitable cells receive stimulation from

A

more than one source:

  • multiple synaptic inputs
  • multiple membrane channels
  • repetitive stimulation
25
Q

graded potentials induced by these stimuli are summated (combined) within the cell:

A
  • spatially (A + B)

- temporally (time wise- repetitive)

26
Q

axon hilock importance:

A
  • specialised region of ‘spiking’ neuron

- important for generating action potentials (long term)

27
Q

EPSP:

A

excitatory post-synaptic potential

28
Q

IPSP:

A

inhibitory post-synaptic potential

29
Q

electrical response: eg. photoreceptors

A

stimulus - graded potential - neurotransmitter release

30
Q

electrical response: eg. motor neurons

A

stimulus - graded potential - action potential - neurotransmitter release

31
Q

cells that don’t generate action potentials eg.

A
  • photoreceptors
  • horizontal cells
  • bipolar cells in retina
  • hair cells in ear
32
Q

graded potential: function spread

A
  • spread electronically over short distances and:
  • change rate of release of neurotransmitters at chemical synapses
  • pass into other cells via electrical synapses (gap junctions)
33
Q

cells that generate action potentials: function

A
  • magnitude of combined (summed) graded potentials determines whether level of depolarisation of cell membrane will be sufficient for it to reach threshold -> generate action potential

4. BIOL257 (18 decks)

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