Nerve impulse process action potential term 2 Flashcards

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1
Q

Describe and explain what a nerve impulse is and it’s function

A

electrochemical change that travels along a nerve fibre
-transmitted quickly
-make it possible for body to respond rapidly to any change in the internal/external environment

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2
Q

What is contained in intercellular vs extracellular fluid following dissolving in water

A

intracellular- low conc of sodium ions and chloride ions
main positive ions are K
extracellular- has high

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3
Q

What occurs due to difference in concentration of ions in outer/inner cell fluid? What is this called?

A

There is a potential between the inside and outside of cell membrane =membrane potential

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4
Q

Explain what the resting membrane potential is and it’s value? What does it mean?

A

-70mV
the charge difference across plasma membrane of an unstimulated nerve cell

-means the potential of the inside of the membrane is 70mV less than outside

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5
Q

Describe differences between the concs of Na and K in relevance to neuron

A

Na
-conc is 10x higher outside neuron than in. the cell membrane is only slightly permeable to Na ions due to limited number of sodium leakage channels=limited facilitated diffusion of Na ions

K
-conc is 30x larger inside neuron than out. cell is highly permeable to K due to large number of K leakage channels=more K ions able to diffuse than sodium ions

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6
Q

Define difference between leakage channel and voltage gated

A

leakage-protein channel that is always open
voltage-protein channel that is opened by an electrical stimulus to nerve

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7
Q

Describe how sodium-potassium pump works following hyperpolarisation

A

Needed to maintain RMP. Pump moves 2xK into cell for every 3xNa removed=net reduction of positive ions inside cell

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8
Q

How is net flow of positive ions out of cell established?

A

-the location of ions
-permeability of membrane (channels)
-sodium-potassium pump

and presence of negative organic ions

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9
Q

Define polarised

A

the situation when the inside of the membrane of a nerve cell has a negative electrical charge compared with the outside

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10
Q

Define action potential. How does it occur? (shorter summary)

A

rapid depolarisation and repolarisation of the membrane
=opening/closing of voltage-gated channels caused by sufficient stimulus, passing a signal along the neuron

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11
Q

Describe the process of depolarisation

A
  1. RMP is -70mV
  2. ligand gated channels open when stimulus transmitted by neurotransmitter to neuron
  3. membrane permeable to Na allowing entrance of some Na increases potential difference (inner more positive)
  4. if increases to -55mV threshold, voltage gated channels open
  5. influx of Na ions into cell that proceeds independently of stimulus =all or nothing
  6. original polarity of membrane increases as inside more positive than outside=depolarised membrane
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12
Q

Describe the process of repolarisation.
How does hyperpolarisation occur
Use diagram to display

A
  1. Na voltage gated channels close simultaneously to K voltage channels open
    -increases diffusion of K out of cell
  2. inside membrane become negatively charged in comparison to out, decreasing the membrane potential to RMP (-70mV)
  3. channels open longer than needed=lower membrane potential due to too much k rushing out=hyperpolarised membrane
  4. k gate will close
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13
Q

Explain and give the significance of the refractory period

A

short period following stimulus to RMP
-nerve cell cannot be re-stimulated/action potential cannot occur
-once Na channels opened they quickly become inactive=unresponsive to stimulus

-prevent nerve impulse moving backwards due to inability of another action potential being generated at that point

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14
Q

Describe transmission along unmyelinated fibres
(revise over diagram either book or worksheet)
How does this continue down an axon

A

-positive out and neg inside (-70mV RMP)
-stimulus causes open of ligand gated, and if higher than -55mV threshold, voltage gate open
-influx of Na into membrane=depolarised
-stimulates movement of Na+ into adjacent area
-movement stimulates opening of voltage gated channels in next part of membrane, initiating action potential
-mention repol and hyperpol
-slower response

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15
Q

Describe transmission along myelinated fibres
(revise over diagram either book or worksheet)
Describe “saltatory conduction”

A

-positive out and neg inside (-70mV RMP)
-stimulus causes open of ligand gated, and if higher than -55mV threshold, voltage gate open
-influx of Na into membrane=depolarised node
-triggers open of next sodium gate in node of ranvier
-impulse moves bwn uninsulated gaps = nodes of Ranvier that exist between each Schwann cell.
-called saltatory conduction
-mention repolarisation and hyperpolarisation
-Sodium-Potassium pump restores the concentration of the sodium and potassium ions during this period.
-allows faster impulse

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16
Q

How is the strength of a stimuli determined

A

-strong stimulus causes depol. of more nerve fibres than weak
-strong stimulus produces more nerve impulses in a given time than weak

17
Q

Draw, annotate and label a diagram to describe transmission across a synapse
including axon terminal, presynaptic and postsynaptic[tic terminal, synaptic vesicles, neurotransmitters, receptors, voltage gated calcium channels, synaptic cleft

A

1.When impulse reaches the axon pre-synaptic terminal of receptor, it activates voltage-gated Ca ion channels to open
-increasing Ca uptake into cell at the pre-synaptic terminal
2. Vesicles move toward axon surface. Release of neurotransmitters via exocytosis
3. Transmitter diffuses across synapse and binds to receptor on post-synaptic terminal on dendrite of other neuron
4. This stimulates ligand-gated protein channels to open, allowing original impulse through the next neuron

18
Q

How is a neurotransmitter removed from a synapse

A

-being reabsorbed by the presynaptic membrane
-degraded by enzymes
-moving away through diffusion

19
Q

Explain the all-or-none response

A

if potential increases to -55mV threshold, voltage-gated Na channels open
this produces movement of Na ions into cell that proceeds independently of stimulus i.e. size of response is not related to strength of stimulus

20
Q

Define and describe the role of a “neurotransmitter”

A

molecule that carries a nerve impulse across the small gap between branches of adjacent nerve cells

21
Q

Describe the structure and function of a synapse

A

junction between branches of adjacent neurons