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Psychology - CN > Lecture 3 - fMRI > Flashcards

Lecture 3 - fMRI Flashcards

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1
Q

fMRI relies on the fact that…

A

deoxygenated haemoglobin disrupts the homogeneity of the magnetic field

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2
Q

EPSPs cause a neuron to become…

A

depolarized

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3
Q

The influx of the following ion is critical for neurotransmitter release…

A

calcium

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4
Q

The resting membrane potential of a neuron is approximately…

A

-60/65 mV

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5
Q

Which voltage-gated ion channel opens at the onset of an action potential?

A

Sodium channels open first
Resulting in a flood of Na+ ions
= rising phase

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6
Q

What two forces drive the movement of ions?

A

Diffusion and electrical

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7
Q

What does the sodium potassium pump do?

A

Takes 3 sodium ions from inside cell to outside
Takes 2 potassium ions from outside to inside
This pump is responsible for resting state potential (-60mv)

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8
Q

What energy molecule does the sodium potassium pump require?

A

ATP

Adenosine Triphosphate

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9
Q

What is hyperpolarization?

A

More negative

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10
Q

What is depolarization?

A

More positive

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11
Q

What is the threshold for triggering action potential?

A

-50mv

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12
Q

Do actions potentials vary in size?

A

Obvs not

“All or nothing principle”

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13
Q

Which forces pull Na+ into the cell once sodium channels open?

A

Electrical and diffusion

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14
Q

What happens at maximum positivity?

A

Sodium channels close

Potassium channels open and potassium leaves cell

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15
Q

What happens when potassium channels open?

A

Neuron becomes negative

= hyperpolarization

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16
Q

What is an EPSP?

A

Graded potential which causes depolarization

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17
Q

What is an IPSP?

A

Graded potential which causes hyperpolarization

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18
Q

Action potential time course

A
  1. EPSP add up
  2. Voltage gated sodium channels open (trigger each other)
    - Sodium comes into cell
    - Depolarization (reaches threshold)
    - Continued depolarization (peaks at +40mv)
  3. Sodium channels close (inactivated state)
  4. Potassium leaves cell through leak channels because of diffusion and electrical force
  5. Potassium also leaves through voltage gated potassium channels
    - Falling phase/undershoot
  6. Voltage gated potassium channels close (slowly)
  7. Absolute Refractory period
    - cannot trigger another action potential
  8. Relative Refractory period
    - difficult to trigger another action potential
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19
Q

EPSP at the synapse

A

AP travels down axon

AP depolarizes pre-synaptic membrane causing voltage-dependent Ca2+ ion channels to open

Ca2+ influx = vesicles to fuse with pre-synaptic membrane

Neurotransmitter e.g. glutamate released into synapse

Neurotransmitter binds with receptors on post-synaptic ion channels which opens them

Ions (e.g. Na+) flow into post-synaptic cell

= EPSP/ depolarization

20
Q

IPSP at the synapse

A

AP travels down axon

AP depolarizes pre-synaptic membrane causing voltage-dependent Ca2+ ion channels to open

Ca2+ influx = vesicles to fuse with pre-synaptic membrane

Neurotransmitter e.g. GABA released into synapse

Neurotransmitter binds with receptors on post-synaptic ion channels which opens them

Ion movement causes resting state potential of post-synaptic membrane to become more negative (i.e. further away from threshold)
- This may occur due to e.g. influx of Cl- or efflux of K+

= IPSP

21
Q

What are axons insulated by?

Why is this good?

A

Myelin sheath

Without Myelin, conduction of APs 100 times slower

22
Q

What do APs jump between?

A

Nodes of ranvier

23
Q

What happens to the neurotransmitter released into synaptic cleft?

A

It is either broken down by an enzyme or ‘re-uptake’ occurs

24
Q

what is an agonist?

A

Enhances (some prevent re-uptake)

25
Q

what is an antagonist?

A

Blocks

26
Q

Two types of summation

A

Temporal and spatial

27
Q

What is ATP?

A

Currency of energy

28
Q

How much energy does PSPs use?

A

37.5%

29
Q

How much energy do APs use?

A

15.8%

30
Q

How much energy is needed for resting potential?

A

15%

31
Q

Energy use for housekeeping?

A

25%

32
Q

Energy for presynaptic transmitter release

A

3.8%

33
Q

What carries blood to body?

A

Arteries

34
Q

What carries blood to heart?

A

Veins

35
Q

What are capillaries?

A

The function of capillaries is to allow food and oxygen to diffuse to cells while waste is diffused from cells.

Capillaries have thin walls

36
Q

What is the relationship between neural activity and blood flow?

A

Active neurons release vasoactive substance which diffuses through extracellular space to reach nearby blood vessels
= dilation
= reduced resistance
= increased blood flow

37
Q

If you increase diameter of vessels by 2…

A

you increase flow by 16

proportional to the power of 4

38
Q

Positron Emission Tomography

A

Measures blood flow

  1. Inject PS with radioactive molecule e.g. glucose
  2. When task is undertaken, radioactive material (e.g. fluorine 18) goes to active area
  3. Fluorine 18 decays and releases positron
  4. Positron releases two gamma rays
  5. PET measures these gamma rays and locates the intersection
39
Q

Magnetic properties of HbO and HbO

A

Hb = paramagnetic = inhomogeneity to nearby magnetic field

HbO= dimagnetic = little effect on magnetic field

40
Q

Effect of Hb on MRI signal

A

more Hb = rapid dephasing in transverse plane (T2) = drop in T2 signal
Therefore
Big difference in T2 decay between active and inactive brain area

41
Q

What is the haemodynamic delay?

A

Time between AP and BOLD signal

42
Q

At rest, there is more Na+ inside or outside the neuron?

A

Outside!

43
Q

After Na+ has entered the neuron, K+ leaves the

neuron, because…

A

the outside is negative with a

lower concentration of K+

44
Q

What structures in the neuronal membrane allow
selective movement of ions along their electrical
and chemical gradients?

A

Ion channels

45
Q

transmitter recycling

A

3%

Psychology - CN (9 decks)

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