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Bio Psych > Lecture 2 - The neuron > Flashcards

Lecture 2 - The neuron Flashcards

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1
Q

Define neurons

A

Specialised cells that receive, assimilate and pass on info. They are electronically excitable and generate an electircal impulse

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2
Q

What are they 3 functional classess of neurons?

A

Afferent
Efferent
Interneurons

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3
Q

Define Afferent Neurons

A

Carry signals away from sensory organs, towards CNS

E.g. pain/ stretch receptors

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4
Q

Define efferent Neurons

A

Opposite to afferent, carry signals from CNS to muscles and glands in PNS

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5
Q

Define Interneurons

A

Only found in CNS, make up 99% of neurons, change signals, intergrate info and relay it

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6
Q

What are the 3 structural different neurons?

A

Unipolar, Bipolar and Multipolar

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7
Q

Describe a unipolar neuron

A
  • Dendrites dont come from soma, they’re on seperate branches
  • Transmits sensory info - touch/pain, temperature, pressure
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8
Q

Describe a bipolar neuron

A
  • Soma is in middle, no dendrites, but a receptor cell instead
  • transmits just auditory/ visual sensory info
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9
Q

Describe a multipolar neuron

A
  • Most common in cns
  • either motor or interneurons
  • Populate skeletal muscle
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10
Q

What are the 3 types of glial cells?

A

1) Astrocytes
2) Oligodendrocytes
3) microglia

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11
Q

Describe Astrocytes

A
  • clean up debris (like dead cells) via phagocytosis - engulf them
  • Regulate chemical composion of extracellular fluid
  • Provide Nourishemtn (lactate)
  • Form scar tissue - flood area of dead cells
  • Provide physical support - keep in place
  • Stop signals getting scrambled
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12
Q

Describe oligodenodroctyes/ schwann

A
  • Suppor axons, produce myelin sheath - fatty tissue wrapped around tightly
  • Electrical insulation to increase processing speed
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13
Q

Descibre Microglia

A
  • Act as phagocytes
  • Active immune system - protect brain from invadign mirco-organisms
  • Inflammatory reaction to brain damage
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14
Q

Whats the difference beteen schwan and oligo?

A
  • Olig - only in CNS, branch out to wrap multiple sections of different neurons - but at the end of these branches are cells like scwhann, but are still prat of oligo
  • Schwann - only in pns, wrap axon in its entirety, not connected to oligo, dont branch out
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15
Q

what is communication within cells?

A

Electircal (ions)

  • resting membran potential
  • graded potentials
  • AP
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16
Q

What is communication between neurons?

A

Biochemical

  • synapses
  • NT’s
  • Activation of post-synaptic cells
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17
Q

Described the cell membrane of a neuron

A

Its a lipid bi-layer

  • two layers of fat like molecules - act like a barrier
  • Inside is hydrophobic
  • outside is hydrophillic

Inside = intracellular fluid, outside = extracellular fluid

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18
Q

Describe the fluid environemtn

A

Contains different electrically charged ions

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19
Q

What are the 2 types of ions?

A

Cations - POSITIVE CHARGE (e.g. potassium/ sodium)

Anions - NEGATIVE CHARGE (e.g. chlorine)

20
Q

What causes electrical signals in cells to occur?

A

Movement of ions in/ out of the cell via channels or pumps

21
Q

What is the difference in ion concentrations inside and outside the cell?

A

Inside: RELATIVELY NEGATIVE - MORE K+

outside: RELATIVELY POSITIVE - MORE NA+ AND CL-

22
Q

what two reasons are there for ions to move?

A
  1. Diffusion - ions want to move from areas of high concentration to low
  2. Electrostatic pressure - ions want to move away from similar charged ions
23
Q

Where do K+ ions want to move and why?

A

They want to move outside, as they are usually inside - they want to go outside due to diffusion, as there is less oustide.

But then they want to move back in as the inside is negatively charged, and they are in a positive outside - so move back in due to electrostatic pressure.

This creates stability and a resting potential

24
Q

Where do Cl- and NA+ want to move and why?

A

Want to move inside where it is oppositely charged (opposites attract) but then want to move outside because of diffusion

This creates stability and a resting potential

25
Q

What is the resting membrane potential of neurons?

A

-70mv inside, 0mv outside

26
Q

What does the resting membrane potential prevent?

A

Ions moving freely

27
Q

When can Ions move freely?

A

When ion channels open - they can move over in alrge quantities

28
Q

What does the movement of ions cause?

A

Changes in the membrane potential

  • either depolarisation - inside loses its charge, becomes more positive
  • Hyperpolarisation - inside becomes more negative, further away from thresholdw
29
Q

What are the two terms for ions moving? not thre reasons why;

A

Influx - going in
Efflux - going out
Causes electrical signals

30
Q

What 2 electrical signals does influx/ efflux cause?

A
  1. Graded potentials

2. Action potentials (long distance)

31
Q

What inputs cause ions to move?

A

Sensory receptors or another neuron

32
Q

Define Graded potentials

A
  • Short distance signals
  • small changes in membrane charge
  • below threshold of excitation
  • Can be excitatory (causing small depolarisation)
  • Or inhibitory (causing small hyperpolarisation)
  • if put together, can cause an AP
33
Q

What are the two ways graded potentials are added toether to cause an AP?

A

SPATIAL SUMMATION - input to different locations on dendrites, close together in time
TEMPORAL SUMMATION - input from single neuron/ location in quick succession

34
Q

Define action potential

A
  • No signal decay
  • Rapid
  • Frequent - depends on stimulus
  • Larger change in charge than graded potentials
  • All or non phenomenon
35
Q

describe ion movement during an AP

A
  1. Na+ channels open - Na+ moves into cell, making it more positive and depolarising it towards AP
  2. K+ channels open - K+ moves outside, hyperpolarising neuron by making it less positive, and more negative (K efflux)
  3. Na+ channels close at peak
  4. K+ channels close at trough
36
Q

What is the point of ion channels during AP?

A
  • Allow lots of ions to move and cause rapid and significant change in membrane potential
37
Q

describe the refractory period

A
  • After Na+ close at peak, they only reset near -70mv - which is more negative than when it started
  • Extra K+ just diffuses away back into neuron - helps restore resting potential
  • The Na+/ K+ ATPase pump moves 3 NA+ OUT AND 2 K+ IN - over time making the inside more nevative
38
Q

What are the mechanisms behind the refractory period?

A

Pumps

39
Q

What can chemical signalling between neurons (via NT) be?

A
  • excitatory (e.g. serotonin/glutamate) increases chances of AP
  • Inhibitory (e.g. GABA) decreases chances
  • Both (eg. Acethylcholine) depends on binding site
40
Q

How is Ca2+ important in synapstic transmission?

A

When AP reaches axon terminal, voltage gated Ca2+ channels open - Ca2+ moves into neuron and causes vesicle to migrate + fuse with presynaptic membrane.

41
Q

Describe the lock and key mecahnism

A

NT = key, receptor =lock

  • Receprtors open specific ion channels - ions move in/ out
  • When the lock is opened, the ions it lets in rush in, changing membrean potential, causing an AP
42
Q

What happens in post-synaptic cell?

A

ion movement in/out causes depolarisation/ hyperpolarisation - these changes in membrane potentials are called POST-SYNAPTIC POTENTIALS - these can cause AP

signal is converted back to electrical btw

43
Q

what are the 2 types of post-synaptic membrane potential

A

Excitatory Post-Synaptic potential (EPSP)

  • if Ca2+ or Na+ open - and postive ions move in
  • Creates depolarisation and a likely AP

Inhibitory PSP (IPSP)

  • If cl- or K+ channels open, cl= enters, or K+ leaves
  • makes it more negative - causing stabilisation/ hyperpolarisation
  • AP = less likely
44
Q

Define synaptic intergration

A

Same as summation but for sum of all synaptic activity

If a neuron has mainly:

  • inhibitory signals - hyperpolarisation
  • equal - stabilisation
  • excitatory signals - depolarisation
45
Q

What is synpatic intergration influenced by?

A
  • number of synapses activie (strength)

- Balance of excitatory or inhibitory

46
Q

What are the 3 ways NT is removed from synapse?

A
  1. Reuptake - pumped into nearby astrocyte or into axon terminal that released it
  2. Removal - diffuses into surroundiing area, i.e. blood
  3. Deactivisation - NT destroyed by enzymes so it doesn’t fit its receptor.

Bio Psych (11 decks)

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