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Psychobiology PS121 > Lecture 4 > Flashcards

Lecture 4 Flashcards

The Neurone 1

1
Q

why do more complex organisms need a NS

A
  • cells on the inside of the body are not in direct contact with the outside world
  • cells live in diff environments
  • cells have become specialised
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2
Q

what do the cells need to do for the organisms to function ?

A

coordinate

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3
Q

endocrine system do what ?

A

specialised to secrete chemicals ( hormones ) into bloodstream

slow

long term

not specific

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4
Q

nervous system

A

specialised to transmit electrical impulses between 2+ cells

fast

precise co-ordination + communication

specific

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5
Q

neural impulses

A

basis for constant and rapid communication between cells

( constant and rapid control and adjustment of ongoing cell activities)

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6
Q

what do neurones do

A
  • generate and transmit electrical impulses over great distances
  • rapidly
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7
Q

where do electrical impulses reach

A

specific target cells
- modifies the activity of this cell

  • allows selective control of specific target structures
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8
Q

how does the NS have a structured communication system

A

combination and integration of signals from diff sources
- structured communication
- input used to adjust output

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9
Q

special requirements of neurone - to do with energy

A

no possibility to store energy
so glucose ( sugar ) and oxygen must be constantly supplied

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10
Q

without glucose being provided for the neurone, what happens

A

it stops working within seconds
dies within minutes

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11
Q

where do neurones come from

A

neural stem cells ( they do not divide )

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12
Q

neurogenesis

A

generation of new neurones - 5 months after conception : after this, dead neurones usually replaced

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13
Q

how many neurones die during maturation

A

20-80%

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14
Q

Glia cells

A

provide protected environment for neurones to survive
develop like neurones - from neural stem cells
- as many glia as neurones in brain ( but 10th of a size of neurone )

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15
Q

Astrocytes

A

star shaped

physical, nutritional support for neurone ( blood brain barrier )
transport nutrients from blood vessels to neurones

waste products away from neurones

hold neurones in place

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16
Q

Microglia

A

small

mobile for defensive function

produce chemicals that aid repair of damaged neurones

digest dead neurones ( phagocytosis )

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17
Q

Oliogendrogia

A

large

flat branches

wrap around axons

fatty substance ( myelin sheath ) insulating axon

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18
Q

draw parts of neurone - look at diagram

A

dendrites
main input area
axon hillock
axon terminals
axon collaterals ( axon split into many branches )

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19
Q

resting potential

A

ion conc differ between inside and outside of cell

if membrane was non-permeable, electrical potential would remain static

protein channels in cell membrane allow ions to enter / leave cell

if membrane channels were just passive ‘holes’, membrane would depolarise ( electrical potential dissapears )

-70mV

20
Q

sodium potassium pump + membrane potential - resting potential

A

active channels work against equilibrium

neurone need energy to maintain their resting potential

3 Na+ out
2 K+ in

21
Q

conc gradient + electrical gradient try to push in our push out K+ ( resting potential )

A

concentration gradient : push out

electrical gradient : push in

22
Q

conc gradient + electrical gradient try to push in our push out Na+ and Cl- ( resting potential )

A

Na+
conc grad = pull in
electrical grad = pull in

Cl-
conc grad = pull in
electrical grad = push out

23
Q

ion specific channels can do what? and when ?

A

open - by chance or response to stimulus

24
Q

depolarisation happens when

A

if + ions enter ( or - ions leave ), membrane depolarises
- inside less negative than usual

25
Q

membrane hyperpolarisation when

A

if negative ions enter ( positive leave )

inside more negative than usual

26
Q

electronic transmission happens where

A

soma and dendrites

27
Q

electronic transmission

A

electrical and concentration gradients sweep ions along the membrane

passive and graded ( of diff magnitude - strength )
–> some ions get lost on their way eg. drift out of membrane so signal decays

28
Q

action potential - explain what is

A

electrical and concentration gradients push/pull ions across membrane

active and not graded ( always same magnitude / strength of signal)

self-replicating (signal replicates itself to same strength )

constant magnitude
so no decay

29
Q

action potential process

A

sodium channels open or close in response to electrical changes at membrane

membrane depolarises ( more negative )

sodium channels open if threshold reached ( -50mV)

sodium ions enter cell

membrane depolarises further

all nearby sodium channels open

membrane fully depolarises total sodium permeability

enough positive ions enter that it becomes more positive inside than outside ( complete depolarisation)

sodium channels close, no more sodium ions enter

potassium channels open

potassium ions rush OUT

30
Q

threshold potential is also called

A

Hodgkin-Huxley cycle

31
Q

Hodgkin-huxley cycle

A

IF membrane potential at axon hillock remains below -50mV = resting potential returns + signal decays

IF membrane potential at axon hillock depolarises above -50mV
- all sodium channels open
- action potential generated

32
Q

repolarisation

A

enough positive ions enter that it becomes more positive inside than outside ( complete depolarisation)

sodium channels close, no more sodium ions enter

potassium channels open

potassium ions rush OUT

membrane repolarises

33
Q

hyper polarisation

A

potassium channels close when resting potential is restored

fewer potassium ions inside than out cell = membrane hyper polarises

34
Q

conduction of action potential

A

starts from axon hillock and goes down axon

each burst of depolarisation triggers sodium channels in adjacent sections of the membrane of the axon to open

35
Q

why does AP not travel backwards ?

A

during hyperpolarisation - (after AP has just passed through) the membrane is difficult to depolarise
BUT
membrane in front of AP is still at resting potential and so more easy to depolarise

36
Q

properties of AP

A

doesn’t decay during transmission

always strong enough to depolarise next area of membrane

all-or-nothing phenomenon : either generated or not ( and at same intensities )

cannot be produced continuously - minimum Time of 2-5 ms between each AP

fast

37
Q

all-or-nothing phenomenon

A

either generated or not ( and at same intensities ) but can be diff frequencies

38
Q

can an AP be produced continuously ?

A

no

2-5 ms between each AP

39
Q

In mammals, how do the signals travel so fast ?

A

because sensory and motor neurones are myelinated

40
Q

what does myelin prevent ?

A

inflow and outflow of ions because it electrically insulates

electrical charges are transported inside the axon - without need to produce AP

41
Q

nodes of ranvier

A

every 1-2mm, myelin sheath has gaps called nodes of ranvier

42
Q

what happens at the nodes ?

A

new AP is generated - action potential jumps from node to node ( saltatory conduction )

43
Q

qualitative - types of info coded how

A

place in brain where signal received

44
Q

quantitative - how strong a stimulus is how detected ?

A

firing rate
- how many AP’s within given time

a strong input will cause neurone to send out signals more quickly

45
Q

weak stimulus

A

low frequency of AP

46
Q

strong stimulus

A

higher frequency of AP’s

Psychobiology PS121 (5 decks)

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