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pharmacology > Ion channels and nerves > Flashcards

Ion channels and nerves Flashcards

1
Q

function of cell body ?

A

contains the nucleus and it is this that stores the genetic information.

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2
Q

dendrites ?

A

extensions of the nerve cell and these receive impulses from other cells at the synapse.

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3
Q

axon ?

A

single long process that extends from the cell body to it’s target cell.

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4
Q

axon hillock ?

A

located at the end of the soma and it controls the firing of the neuron. It is located by the portion of axon closest to the cell body where the axon is joined. If the strength of the signal exceeds the threshold limit of the axon hillock then a signal will be fired ( action potential).

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5
Q

Schwann cells ?

A

line the axon and they myelinate the axon and insulate it which speeds up the conduction of electrical signals.

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6
Q

node of ranvier ?

A

is the gap in the myelin insulated Schwann cells which insulate the axon. This results in the axon being exposed to extracellular fluid and Na+ channels.

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7
Q

axon terminals ?

A

found at the end of the axon and they make synaptic connections with other nerve cells or with the effector cell and transmit information ( muscle or gland cell).

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8
Q

graded potential?

A

temporary changes in the membrane voltage that are passive , they are brought about my an external stimuli and neurotransmitters , no refractory period is associated with them.

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9
Q

describe how the nervous system is divided into ?

A

2 parts
• Central nervous system ( CNS) – this is composed of the brain and the spinal cord
• Periphery nervous system ( PNS) – this is composed of nerves that extend between the brain or spinal cord and muscles , glands and sense organs.

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10
Q

explain how the PNS can work in both directions ?

A

sensory division , afferent picks up sensory stimuli and sends impulses to your brain towards the CNS. While the motor , efferent division is what send impulses from your brain to muscles and glands away from the CNS.

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11
Q

what do neurotransmitters act on ?

A

receptors found at the dendritic spine

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12
Q

action potentials ?

A

The nerve impulse and these are rapid, large alterations in the membrane potential. Occurs if the stimulus is large enough a threshold is reached. The voltage gated Na+ channels open and depolarisation on a large scale occurs, this is “all of nothing” regenerative. The system restores with voltage gated K+ channels and Na+/K+ pump to return to the resting potential.

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13
Q

neurotransmitters the CNS will release ?

A

glutamate , GABA , seretonin , dopamine and noradrenaline

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14
Q

the PNS will release?

A

noradrenaline and acetylcholine

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15
Q

how do cells maintain an unequal concentration of ions ?

A

because the membrane is selectively permeable to ions

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16
Q

main chemical substances in the extracellular fluid ?

A

na+ and Cl- ions

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17
Q

main in intracellular ?

A

potassium and organic anions like DNA

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18
Q

what is the membrane more permeable to and what does this mean?

A

more permeable to K+ ions than Na+ ions and this means a membrane potential develops.

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19
Q

what does the concentration , chemical gradient cause ?

A

K+ to flow out of the cell and Na2+ ions to flow into the cell as they move down their concentration gradient

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20
Q

electrical force cause ?

A

causes K+ ions and Na+ ions to flow into a cell

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21
Q

what is the membrane potential ?

A

the difference in charge and it is measured in mV normally

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22
Q

what is the resting membrane potential?

A

our cells are -70mV. and the inside of our cells are negatively charged while the outside is positively charged. This results in the cell being polarised.

23
Q

what maintains the membrane potential ?

A

Na+/K+ pump maintains the membrane potential as for every 3Na+ ions it pumps out a cell it pumps 2K+ into the cell. This causes an electrochemical gradient.

24
Q

why is the Nernst equation used ?

A

calculate the equilibrium potential (Ex) for an ion knowing the concentrations of the ion. (at 37OC):

25
Q

Ex ?

A

potential (i.e. the equilibrium potential) in millivolts generated by ion X.

26
Q

Z ?

A

(sometimes called n) is the charge on the ion: Na+ and K+ = 1; Ca2+ =2 and Cl- =-1

27
Q

In ?

A

natural logarithm

28
Q

Xo] and [Xi]

A

the concentration of the ion on the outside and inside of the membrane respective

29
Q

what is the membrane impermeable to ?

A

Pr- the Nernst equation does not apply to these ions.

30
Q

describe leak channels ?

A

opened most of the time and examples include K+ leak channels that regulate membrane potential and the Na+ leak channels that generate unstable membrane potentials.

31
Q

gated channels ?

A

closed most of the time and they are opened upon appropriate activation.

32
Q

voltage activated channels

A

open and close in response to changes in the membrane potential.Examples include Na+, K+ Ca2+ and Cl- channels

33
Q

ligand activated channels ?

A

open and close in response to the binding of a chemical (agonist/cAMP/cGMP/ H+). Examples include nicotinic cholinergic receptor opens when two molecules of acetylcholine bind. Also transient receptor potential channels (TRP channels – also voltage and stretch). As well as hyperpolarization-activated cyclic nucleotide-gated channels.

34
Q

describe mechanically activated channels ?

A

open and close due to a mechanical stimuls. An example includes sensory receptors that respond to pressure or stretch.

35
Q

how do Na+ ion channels open and close ?

A

open quickly and shut slowly

36
Q

when are they closed and open?

A

closed at the resting potential and open in response to a nerve impulse as there is an influx of Na+ that enters the cell.

37
Q

why do local potentials occur ?

A

net gain of Na+ ions , they are small and confined to a localised small region of membrane.

38
Q

what occurs at the local potential ?

A

potential dissipates (the charge leaks away from the membrane and the ions are diluted down by the bulk of the intracellular fluid and K+ moves out to restore the resting membrane potential.

39
Q

what is it’s size dependent on ?

A

upon the strength of the stimulus (hence graded)

40
Q

what causes depolarisation ?

A

influx of sodium ions

41
Q

what cause re-polarisation ?

A

efflux of K+ ion

42
Q

what is the inactivation gate for ?

A

breaks the positive feedback loop

43
Q

what occurs during the rising phase ?

A

depolarisation occurs as there is a Na+ influx via voltage gated Na+ channels. This depolarisation occurs as the stimulus has reached the threshold.

44
Q

what occurs action potential ?

A

reached at 40mV and this is when an impulse is fired.

45
Q

re polarisation ?

A

occurs as the K+ ions efflux via voltage gated K+ ions and the Na+ channels shut.

46
Q

refractory period?

A

there is no response to the stimuli , after this there resting state is restored.

47
Q

describe propagation of a nerve impulse ?

A

as the depolarisation occurs , the spot behind repolarises

48
Q

stages in transmission across a synapse

A
  • Membrane potential
  • Local potential
  • Action potential
  • Propagation along the neuron
  • Transmission across the synapse
49
Q

how do local anaesthetic work ?

A

they prevent Na+ gated channels from opening and the neurotransmission is decreased.

50
Q

anticholinesterase drugs work ?

A

cause neurotransmission to be increased , they are potassium channel blockers.

51
Q

neuromuscular blockers work ?

A

they compete with acetylcholine and D-Tubocurare is a competitive drug.

52
Q

what does strychnine poisoning lead to ?

A

– Tremors
– Twitching
– Rigor in face and limbs
– Convulsions

53
Q

what does strychine compete with ?

A

glycine – an inhibitory neurotransmitter

pharmacology (21 decks)

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