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Biomedical Physiology > Physiology of Nerve cells (W4) > Flashcards

Physiology of Nerve cells (W4) Flashcards

1
Q

Describe how the Purkinje fibres were discovered and by who

A

Jan Purkinje
- found cells in the cerebullum in 1863

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2
Q

What 2 theories were suggested upon the discovery of the Purkinje cells

A
  1. Reticular theory - nerve cells form a syncytium in which the nerve cells are interconnected
    via protoplasmic bridges
  2. Cell theory - nerve cells are independant units
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3
Q

How did Camillo Golgi further investigate to discover the nature of the brain cells

A

worked on chemical staining of brain smaples out of his kitchen
- stained different cell types to see if they had indiviudal nuclei

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4
Q

What did Cajal discover about the brain tissue

A
  • identified dendritic tree and axons
  • developed the Golgi staining
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5
Q

Who won the Nobel prize in 1906 for physiology and why was it controversial

A

Cajal and Golgi
- Golgi supported the reticular theory
- Cajal supported cellular theory

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6
Q

What are glial cells

A

supportive cells
- structural and metabollic

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7
Q

Describe the function
- Astrocytes
- Oligodendrocytes
- Microglia

A
  1. maintain chemical environemnt around the neuron allowing them to function
  2. from myelin shetah increase rate of conduction
  3. immune system of NS - proptect brain against pathogen
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8
Q

Describe how we can measure membrane potential

A

saline bath and microelectrode
- cell is bathed in saline bath
- reference and recording electrode are placed into the bath
- difference between the 2 of the membrane potential

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9
Q

What is ion behaviour based on

A

diffusion and electric field

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10
Q

How does changing the concentration of solution change the membrane potential

A

causes ion to flow from high to low concentration
- Cl- ions can’t flow which will generate a volatge across the selectvely permebale membrane
- K+ ions flow until they are replused by an electrical difference
- elecve motive force estbalished

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11
Q

What is the Bernstein hypothesis

A

The resting potential of a potsaaium in arises aross a membrane
- ion selective membraner is only permebale to postasium

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12
Q

What EK (equilibrium potential for potassium)

A

difference in potassium ions

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13
Q

How did Bernstein hypothesis get tested

A

giant squid axon

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14
Q

What were the results of the giant squid axons

A
  • the measured and calulated values difered therfore his hypothesis couldn’t fully explain resting potential
  • it suggests other ions are contributing to resting potential
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15
Q

Explain the discovery of the unequal permeability in a membrane

A
  • sodium ions have +ve equlibrium
  • if memebrane is only permebale to sodium the membrane potenial would be +ve value
  • if membrane iequally permebale to th soidum and otassium membrane would be sum of 2 (it isn’t)
  • therefore there is unequal permeabilty
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16
Q

What determines membrane permeability

A
  • leak channels
  • passage of actions through the channels
  • membrane ion channels
17
Q

What are leak channels

A

ion channel ions when the cell is in rest state

18
Q

What contribute to the resting membrane potential

A

sodium and potassium pumps

19
Q

How is the membrane potential maintained
- indirectly
- directly

A

Indirectly - Ma/ pumps maintain equal concentrations of Na/K ions across membrane
Directly - electrogenic (pumping 3 Na+ ions to and 2 K+ ions in

20
Q

What is an action potential

A
  • a change in membrane potential due to change in ion movement
  • all or nothing principle
21
Q

How ddid Hodgkins & Huxley sure an action potential

A
  • placed and electrode inside the giant squid axon
  • reference in the extracellular medium
  • neurone stimulated with a stimulator
  • measure AP
22
Q

Why is an AP “all or nothing”

A

a certain threshold must be met -55mv to fully allow the ion channels to open and stimulate an AP

23
Q

Why does the membrane go into hyper polarisation

A

the neurone overshoots causing the membrane potential to go below -70mV was the K+ ion channels are too slow to close

24
Q

How did Overtons theory the Na matters get tested

A
  • 6 variables and found out that the depolarisation phase id due to the increae membrane permeability to Na
25
Q

What’s the ionic basis of the axon potential

A
  1. An increase in pNa+
  2. Increase in pK+ & decrease in pNa+
  3. Return to resting state permeability
26
Q

How is a difference in membrane permeability achieved

A

volate gated ion channels

27
Q

What is the refractory period

A

a time where no new action potential can be generated
- ensures unidirectional AP
- prevents “bounce back” from the axon terminal
- prevent “super AP” occurring

28
Q

How does propagation of AP occur

A
  • a current flows through an activated patch of membrane depolarised the adjacent patch
  • repolarized patch is refractory so AP travels in 1 direction
29
Q

How does myelination affect an action potential

A

increase velocity of Ap propagation without increasing axon diameter by “jumping” the AP between the Nodes of Ranvier

30
Q

How do electrical synapses ad an AP

A
  • allow rapid propagation of AP between neurons using gap junctions
31
Q

How do chemical synapses aid an AP

A

release chemicals (neurotransmitters) that bind to specific post-synaptic receptors

32
Q

Explain how a neurotransmitter gets released

A
  1. AP arise at post-synaptic terminal depolarising the axon terminal
  2. Voltage-gatedCa2+ ion channels open allowing an influx of in which move the presynaptic vesicles towards the membrane
  3. The vesicles fuse with the membrane and neurotransmitters to be released
  4. They ends to specific receptors on post-synaptic axon terminal causing an influx of Na+ ions triggering the AP on a new neurone
33
Q

What do
- excitatory
- inhibitory neurotransmitter do and give and example

A

Excitatory - increase the changes of depolarisation occurring
- triggers EPSP (excitatory post-synoptic potential) e..g Acetylcholine and Glutamate
Inhibitory - increase the chance of hyper-polarisation occurring
- triggers IPSP (inhibitory post-synaptic potential) e.g. GABA & Glycine

34
Q

What is
- Temporal summation
- Spatial summation

A

Temporal summation - releasing neurones many times over a period of time
- can cause EPSP and reach a higher membrane potential
Spatial summation - multiple synapses firing towards the same target to increase the chances of threshold being met

Biomedical Physiology (5 decks)

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