13.2 Nervous System

Question 0

Neurobiological reserach on nervous system made on…

Answer 0

Giant squid (axon up to 1mm in diameter)

Question 1

The function of the nervous system is to?

Answer 1

Produce behaviour

Question 2

3 tasks performed by nervous system?

Answer 2

1. Detection and analysis of sensory signals
2. Decision making
3. Generation of coordinated motor output

Question 3

Nervous system in…
A) Sea anemone?
B) Earthworm + squid?
C) Human?

Answer 3

A) Nerve net
B) Ganglia + nerves
C) CNS + PNS

Question 4

Nervous systems consist of nerve cells and….

Answer 4

Glia (electrical isolation or nerve cells + blood-brain barrier + uptake of transmitter)

Question 5

Role of neurons?

Answer 5

Generate and transmit electrical signals

Question 6

Role of glial cells?

Answer 6

Provide nutrients, oxygen, maintain extracellular environment, make the bloodbrain barrier, fight infections, insulate neurons

Question 7

Which is more present - neurons or glial cells?

Answer 7

Glial cells (5-10x)

Question 8

How do neurons work?

Answer 8

Electrochemically

Question 9

What prevents the free movement of ions?

Answer 9

Lipid biulayer

Question 10

What control the ion flux across the membrane?

Answer 10

Ion channels and ion transporter proteins

Question 11

Typical ion concentration - intracellular?

Answer 11

A lot of K+, a medium amount of Na+, a bit of Cl-, a lot of A-

Question 12

Typical ion concentration - extracellular?

Answer 12

Little K+, lots of Na+, lots of Cl-, no A-

Question 13

What is the membrane potential?

Answer 13

The electrical potential difference across membrane

Question 14

What is the resting potential?

Answer 14

-65 mV

Question 15

The interaction of …. determines membrane potential

Answer 15

Two forces

1. Diffusion: favours net movement of ions down their concentration gradient (intra–>extracellular)
2. Electromagnetic force: favours net movement of ions according to potential difference (extra–>intracellular)

Question 16

What is equilibrium potential?

Answer 16

When the diffusion force and the electromagnetic force are balanced for a given ion

Question 17

What ion shows sizable leak current at rest?

Answer 17

K+

Question 18

Resting membrane potential is dominated by ….. equilibrium potential

Answer 18

K+

Question 19

What happens when channels open?

Answer 19

Ions follow their electrochemical gradient, which moves the membrane potential towards the equilibrium potential of that ion

Question 20

How are ion channels gated?

Answer 20

• Voltage-gated
• Mechanically-gated
• Chemically-gated

Question 21

Use of energy by ion channels?

Answer 21

None

Question 22

At resting potential - what happens to voltage-gated Na+ channels?

Answer 22

They are closed

Question 23

When membrane is depolarized, what happens to voltage-gated Na+ channels?

Answer 23

They open

Question 24

What happens during the depolarization phase?

Answer 24

Na+ flows into the cell

Question 25

What happens during the repolarization phase?

Answer 25

K+ flows out of the cell

Question 26

What happens when threshold level of depolarization reached at - 50mv?

Answer 26

Depolarization becomes regenerative: action potential

Question 27

What happens after repolarization?

Answer 27

Membrane is briefly hyperpolarized, but then returns to resting potential with only K+ leak channels open

Question 28

The ion flux during a single spike ........ the concentration gradients.

Answer 28

Barely changes. (Neurons can fire many spikes before concentration gradients are lost)

Question 29

How are cocnentration gradients of ions maintained in the long run?

Answer 29

``` By active (energetically expensive) processes - Na+/K+ pump moves 3 Na+ out for every 2 K+ it moves in - requires ATP ```

Question 30

Action potentials are ...... events

Answer 30

- All-or-none events - they do not decay with distance along the axon (they get "regenerated" along the axon)

Question 31

What are graded potential?

Answer 31

- Strength and temporal pattern of input determines membrane potential - Decays with distance along nerve fiber - Only works over short distances

Question 32

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Answer 32

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