W1: What is Cognitive Neuroscience: Information Processing in the Brain

Question 1

Brain is made up of

Answer 1

neurons

Question 2

What are neurons composed of? (3)

Answer 2

1. Cell body
2. Axon
3. Dendrites

Question 3

Diagram of a neuron

Answer 3

Question 4

What are nerve cells or neurons specialised to do?

Answer 4

are specialized to generate and propagate electrical signals

Question 5

What does a neuron’s cell body contain? (2)

Answer 5

• contains nucleus
• contains organelles (e.g., endoplasmic reticulum, ribosomes, Golgi apparatus, mitochondria)

Question 6

Neurons long extension from the cell body is called a

Answer 6

axon

Question 7

Neurons’s short branches extending from the cell body is called

Answer 7

dendrites

Question 8

What is the purpose of a neuron’s axon?

Answer 8

carries nerve impulses (sends info) away from the cell body

Question 9

What is the purpose of dendrites?

Answer 9

Dendrites receive information from
the axonal endings arising from other nerve cells.

Question 10

There are proteins in the neuronal membrane known as

Answer 10

ion pumps & ion channels

Question 11

Diagram of ion channels and pumps:

Answer 11

Question 12

Ion channel and ion pumps support

Answer 12

action potential propgation down the axon of the neuron

Question 13

The ion channel and ion pump control

Answer 13

the movement of ions (charged atoms) from the inside of the neuron (intracellular) to the outside of the neuron (extracelluar).

Question 14

Cell membrane is a lipid bilayer that surrouds the neuron and keeps stuff

Answer 14

separate from outside to the inside

Question 15

Action potentials (those electrical impulses that send signals around your body) are nothing more than a temporary shift (from negative to positive) in the

Answer 15

neuron’s membrane potential caused by ions suddenly flowing in and out of the neuron.

Question 16

Diffusion

Ion channels allow

Answer 16

specific ions to move through the neuronal membrane

Question 17

There are 2 forces that determine the movement of ions inside and out of the cell (2)

Answer 17

1. concentration/diffusion (high to low concen grad)
2. electrical (negative <–> positive; pos goes to neg, neg goes to pos)

Question 18

The fluid inside and outside of the neuron contains different types of ions such as (4)

Answer 18

1. Sodium (Na+)
2. Potassium (K+)
3. Chloride (Cl-)
4. Large negative ions (A-)

Question 19

Diffusion

Whats happening in A? (10)

Answer 19

• In A we put equal amount of K+ (orange) and Cl- (Green) in a solution which becomes KCL
• We put equal amount of KCL in chamber 1 and in chamber 2
• Purple membrane which allows movement of K+ allows to move through
• K+ ions moves from chamber 1 to chamber 2
• It makes chamber 2 more positive as K+ carries its charge
• K+ then drawn to chamber 1 since chamber 2 more positive than chamber 1
• There is a diffusion gradient pushing back to chamber 1
• There is electrical force pushing back to chamber 1 as chamber 2 is positive and chamber 2 is negative so things are positive attract to things are negative
• It re-establishes the equilibrium
• Some K+ ions move to chamber 1 and some move to chamber 2 based on electrical forces and diffusion until molecules are evenly spaced out

Question 20

What is diffusion?

Answer 20

the random movement of particles towards a state of equilibrium

Question 21

When does a diffusion concentration gradient occur? (2)

Answer 21

A concentration gradient occurs when the concentration of particles is higher in one area than another.

In passive transport, particles will diffuse down a concentration gradient, from areas of higher concentration to areas of lower concentration, until they are evenly spaced.

Question 22

Neurons, like all living cells, are surrounded by a plasma membrane that is

Answer 22

imperable to ions.

Question 23

Neuron’s imperable membranr property allows to

Answer 23

maintain different concentration of ions between the inside and outside of the cell by preventing the passive diffusion of ions from regions of high to low concentration:

Question 24

In a typical neuron at rest, there is a large difference in the concentration of ions such as

Answer 24

sodium and potassium between the intracellular and extracellular environments

Question 25

The plasma membrane is composed of a

Answer 25

lipid bilayer

Question 26

The hydrophobic interior of the lipid bilayer of the cell membrane prevents

Answer 26

the movement of ions across the membrane:

Question 27

The only way ions can diffuse across plasma membrane is by passing through

Answer 27

specialized channels that permit the movement of ions while excluding others (ion channels)

Question 28

The ion channels can be in a ___ or ___ state

Answer 28

These channels can be in an open or closed state

Question 29

When the neuron is at rest, most ion channels are closed. However, a few potassium

Answer 29

channels are open, and potassium ions are therefore free to diffuse out of the cell into the extracellular environment

Question 30

Note: channels can be highly selective; the potassium channels do not permit the passage of

Answer 30

sodium ions.

Question 31

Since only a few sodium channels are open at rest, very few sodium ions flow into

Answer 31

the interior of the neuron.

Question 32

How can Electrical Potential Across Membranes be Measured? (2)

Answer 32

The electrical potential across the membrane can be measured using a pair of electrodes

An oscilloscope is used to continuously display the potential difference between the reference and recording electrode:

Question 33

If we consider only potassium ions, which are relatively free to cross the membrane, we notice the intracellular concentration remains higher than the extracellular concentration at rest

This is because K+ ions pulled by 2 different and opposing forces (2)

Answer 33

1. First, a diffusion force acts to pull potassium ions down their concentration gradient toward the exterior of the cell. The movement of potassium ions out of the cell results in a depletion of the internal positive charges causing the potential to become increasingly negative.
2. An electrical force, produced by K+ ions toward the negative cell interior generates an electrical gradient that brings potassium back to the interior of the cell.

Question 34

The diffusion and electrical forces come to balance where

Answer 34

electrical gradient is balanced by diffusion gradient -this is electrochemical equilibrium

Question 35

For K+ at electrochemical equilibrium there is no

Answer 35

net movement of potassium ions

Question 36

W

When both electrodes are in the bath outside of the cell,

Answer 36

no difference in potential in potential is measured between them and the display registers 0 mV.

Question 37

However, when the recording electrode enters the cell, the display records a membrane potential of about

Answer 37

60mV –> this value represents the resting membrane potential of the neuron

Question 38

Resting MP is the difference in

Answer 38

in electrical potential acrss the membrane during an inactive period.

Question 39

When the concentration of K+ ions in KCl solution is same in chamber 1 and chamber 2 then

Answer 39

no electrical potential will be meausred across the membrane (V = 0)

Question 40

If the concentration of K+ ions is not the same on chamber 1 and chamber 2

Answer 40

then electrical potential will be generated (-58 mV) as K+ flow down concentration gradient (diff) to cham 1 to cham 2 and electrical force moving K+ to cham 2 and 1

Question 41

What is the purpose of the sodium-potassium pump?

Answer 41

Helps to maintain a higher concentration of Na+ ions outside the cell and higher concentration of K+ ions inside the cell (at resting)

Question 42

Proposed mechanism of Na+ and K+ (6)

Answer 42

1. The cycle begins with the pump open to the inside of the cell – in this forum the pump has a relatively high affinity for sodium ions which bind to the pump:
2. When bound by sodium, the pump is a substrate for phosphorylation (addition of phosphoryl group to a mole) by the high-energy molecule, ATP. The energy requirement in this step is estimated to account for 20-40 percent of the brain’s energy consumption:
3. The phosphorylation triggers a conformational change in the pump. In the new conformation, the pump has a low affinity for sodium which it releases outside of the cell.
4. The pump now has a relatively high affinity for potassium which binds to the pump:
5. Potassium binding triggers the dephosphorylation of the pump. Without the phosphate group, the pump returns to its original conformation:
6. Back in its original conformation, the pump has a relatively low affinity for potassium, which it releases into the cell:

Question 43

In sodium-potassium pump, For every three sodium ions that are taken out of the cell, the pump transports

Answer 43

2 potassium ions into the cell.

Question 44

Why is sodium-potassium pump said to be electrogenic? (2)

Answer 44

Fore every 3 Na+ out of cell, pump takes 2 K+ into cell

net loss of one positively charged ion for each round of pumping results in a very small electrical current.

Question 45

At rest a neuron is

Answer 45

negatively charged (~-65mV)

Question 46

What is a recording electrode?

Answer 46

one to record membrane voltage

Question 47

What is stimulating electrode?

Answer 47

it inject current that can be used to push the membrane voltage toward more positive (depolarizing) or more negative (hyperpolarizing) voltages.

Question 48

If the stimulus is sufficient to push the membrane potential past the firing threshold for neurons, then

Answer 48

action potential is generated.

Question 49

Action potentials are a all-or-none event meaning:

Answer 49

amplitude of an action potential is independent of the EPSP that is used to generate it.

Question 50

APs are all or nothing event
However,

Answer 50

if the amplitude or duration of the EPSP is increased the number of action potentials propagated per second increase (known as spiking rate)

Question 51

Each AP lasts for

Answer 51

1 millisecond

Question 52

Any suprathreshold stimuli will produce

Answer 52

produce an action potential of similar amplitude and duration:

Question 53

If negative current is injected in neuron then

Answer 53

an inhibitory post-synaptic potential (IPSP) occurs because the neuron becomes less likely to fire an action potential (hyperpolarized)

Question 54

If a positive current is injected in a neuron then

Answer 54

an excitatory post-synaptic potential (EPSP) occurs because the neuron becomes more likely to fire an action potential (depolarized)

Question 55

If the EPSP exceeds threshold (~-50mV) an

Answer 55

action potential occurs

Question 56

Voltage-gated or voltage-sensitive ion channels play an important role in

Answer 56

generating action potentials.

Question 57

There are 2 types of voltage-gated channel (2)

Answer 57

Na+ and K+

Question 58

When EPSP’s amplitude or duration increased then you don’t get bigger AP but

Answer 58

more APs

Question 59

Voltage-gated channels open when

Answer 59

membrane becomes depolarised above threshold due to EPSPs

Question 60

Na+ channel open and close faster than

Answer 60

the slower K+ channels

Question 61

Action potential generation (8)

Answer 61

1. Resting potential: When a neuron is at rest, only the so-called “leak” potassium channels are open, establishing the resting potential
2. Rising phase: During this phase, the increasingly positive shift in MP is driven by the opening of progressively more and more voltage-gated Na+ channels and the entry of Na+ ions into the neuron. This inward Na+ current depolarizes the membrane voltage
3. 3. Overshoot phase: The membrane potential is now at its most positive state, it has overshot 0mV. At this positive potential, two processes are occurring simultaneously. a. First, the voltage-gated Na+ channels that initially activated during the rising phase begin to close. As a result, Na+ conductance starts to decline.
      b. Potassium channels begin to open driving the MP back toward the equilibrium potential for potassium. These voltage gated potassium channels differ from leak potassium channels in that they are normally closed at resting potential but open in response to depolarization (thus the term voltage-gated)
      i. Now the AP is in its repolarizing phase which means the MP is rapidly returning to the resting potential.
4. Falling phase: During this phase, activation of voltage-gated K+ channels is at max and the number of open Na+ channels is dramatically reduced. The AP repolarizes beyond the MP.
5. Undershoot phase: The undershoot occurs because most voltage-gated K+ channels are still open such that total K+ conductance of the neuron is greater than when the membrane is at its steady state
6. Recovery: During this phase, the MP returns to the original steady-state MP. This occurs as the delayed K+ channels that were opened during AP now close. The MP is now determined by the other channels normally open at resting MP.

Question 62

Voltage-gated channels are present at the

Answer 62

axon hillock.

Question 63

When an action potential is generated it moves down

Answer 63

the axon.

Question 64

Voltage-gated channels are present at the Nodes of Ranvier where the

Answer 64

action potential is regenerated.

Question 65

The axons of many neurons is surrounded by a myelin sheath. This helps the

Answer 65

conduction of the action potential

Question 66

Multiple sclerosis is a

Answer 66

disease of myelin

Question 67

Communication between neurons occur at specialized junctions called

Answer 67

synapses

Question 68

The most common type of synapse is the

Answer 68

chemical synapse

Question 69

Puffer fish contains tetrodoxin that blocks

Answer 69

voltage-gated Na+ channels and will die

Question 70

The arrival of an action potential at a presynaptic axon terminal sets off a

Answer 70

cascade that results in the release of neurotransmitter molecules into the synapse

Question 71

Synaptic vesicles are either binded to the or… (2)

Answer 71

cytoskeleton in reserve pool or free in the cytoplasm.

Question 72

Steps of synaptic transmission

Answer 72

1. When the axon terminal of is depolarized, voltage-gated calcium channels open and Ca+ ions rush into axon terminal.
2. Some Ca+ ions bind to a protein on synaptic vesicle membrane, called synaptotagmin, nearest to the active zone which makes synaptic vesicles draw even closer to the presynaptic membrane
3. The vesicles fuse with the axon terminal membrane and release their neurotransmitter which diffuses across the synaptic cleft
4. Some of the NT molecules bind to the special receptor molecules in the postsynaptic membrane

Question 73

5. The response of the post-synaptic cell (either excitation or inhibition) depends on specific

Answer 73

NT and receptor combination

Question 74

Example of that the response of the post-synaptic cell (either excitation or inhibition) depends on specific NT and receptor combination

Answer 74

For NT acetlycholine that binds to specific receptor it generates an excitatory post-synaptic response (EPSP)

Question 75

6. Eventually, NT are inactivated or removed rapidly from the synaptic cleft so that transmission is

Answer 75

brief and accurately follows pre-synaptic signal

Question 76

How is acetlycholine removed from synaptic cleft?

Answer 76

an enzyme in syanptic cleft called acetlycholinesterase breaks down acetylcholine into choline and acetate.

Question 77

Not all NT are broken down by enzymes in synaptic cleft but many NTs are (3)

Answer 77

taken up into presynaptic terminal by special proteins called transporters (on pre-synaptic terminal

This process is known as reuptake.

Reuptake not only cuts off synaptic activity prompty, but also allows the pre-synaptic terminal to recycle NT molecules.

Question 78

Neurotransmitter receptors are membrane proteins in postsynaptic cell that have a region for

Answer 78

binding neurotransmitter and an ion channel

Question 79

What happens to the ions when an appropriate NT binds to this neurotransmitter receptor - (2)

Answer 79

causes the opening of the ion channel component

Ions flow through the ion channel changing the electrical potential of the post-synaptic cell

Question 80

Glutamate in synapse is terminated as it is taken up by

Answer 80

glial cells, where it is recycled and used again.

Question 81

If NT does not get taken away or recycled (reuptake) than there is a more than normal

Answer 81

effect of NT

Question 82

Agonist vs antagonists drugs - (2)

Answer 82

An agonist is a drug that binds to the receptor, producing a similar response to the intended chemical and receptor (mimics actions of NT)

Whereas an antagonist is a drug that binds to the receptor either on the primary site, or on another site, which all together stops the receptor from producing a response (stops NT from binding to NT receptor)

Question 83

Prozac prevents reuptake of

Answer 83

serotonin making effect of serotonin stronger

Question 84

The correct balance of excitatory and inhibitory signals is necessary for the

Answer 84

proper working of the nervous system.

Question 85

Excitatory and inhibitory postsynaptic potentials (EPSP & IPSP) are integrated by neurons. If the neuron is sufficiently excited, an action potential is ……The action potential is then….. - (2)

Answer 85

generated at the axon hillock.

propagated down the axon.

Question 86

The post-synaptic potentials that are caused by NT chemicals can be either depolarizing, often (but not always) resulting in an - (2)

Answer 86

excitatory post-synaptic potential (EPSP)

or hyperpolarizing resulting in an inhbitatory post-synaptic potential (IPSP).

Question 87

2 EPSPs give rise to +
2 EPSPs + 1 IPSPs stops - (2)

Answer 87

AP
stops AP from happening (incorrect balance of EPSPs and IPSPs for AP to occur)

Question 88

Epilsey is disturbance between

Answer 88

excitatory and inhbitatory inputs in brain - EPSP and IPSP

Question 89

Post-synaptic potentials generally move passively along the dendritic membrane gradually becoming

Answer 89

smaller as they spread.

Question 90

Since post-synaptic potentials become smaller as they spread
post-synaptic potentials from distant synapses will decay more than

Answer 90

PSPs from synapses closer to the integration zone at the axon hillock

Question 91

What is the axon hillock?

Answer 91

inputs from other neighboring neurons combined at soma in axon hillock which controls the firing of an AP down the axon

Question 92

The postsynaptic APs produced at most synapses are usually well below the

Answer 92

the threshold for generating postsynaptic APs