Neuroscience

Question 1

Learn the structure of a neuron

Answer 1

cell body
nucleus
dendrite
axon hillock
Myelin sheath
axon
node on ranvier
axon terminals

Question 2

How many neurons does the brain contain?

Answer 2

About 86 billion

Question 3

What is the average number of connections a neuron makes?

Answer 3

1000

Question 4

What does the property ‘excitability’ of neuronal cells refer to?

Answer 4

The ability to respond to stimuli

Question 5

What does the property ‘conductivity’ of neuronal cells refer to?

Answer 5

Ability to generate and propagate electrical signals known as action potentials

Question 6

What does the property ‘secretion’ of neuronal cells refer to?

Answer 6

When chemical neurotransmitters are used to bridge gaps at synapses between neurons

Question 7

What is the resting charge across a membrane?

Answer 7

Approximately -70mV
(maintained as a result of balance between chemical and electrical gradient)

Question 8

What is the permeability like of a resting neuron membrane?

Answer 8

Membrane itself is relatively impermeable to ions

Question 9

What do Na+/K+ ATPase membrane protein pumps do to maintain resting potential?

Answer 9

Pumps out 3 Na+ for every 2 K+ it brings in
Works continuously in presence of ATP

Question 10

What are ion channels?

Answer 10

Proteins found in membranes that selectively control the permeability to cations (Na+, K+) and some anions (Cl-)

Question 11

Describe the charge inside and out a membrane during resting potential?

Answer 11

The inside of the membrane has a negative charge with respect to the outside

Question 12

What is the equilibrium potential of an ion?

Answer 12

The point at which there would be no net movement of the ion across the membrane

Question 13

What is the resting equilibrium potential for Potassium (Ek)?

Answer 13

approximately -80mV

Question 14

What is the resting equilibrium potential for Sodium (ENa)?

Answer 14

approximately +60mV

Question 15

What is the membrane more permeable to at rest?

Answer 15

K+ (this is what gives membrane resting potential of -70mV in neurons)

Question 16

What is the membrane state during rest?

Answer 16

membrane potential of -70mV
Votage gated Na and K channels closed
Intracellular - high [K+]
Extracellular - high [Na+]

Question 17

What is local potential?

Answer 17

Where membrane potential rises - Eg in respond to a ligand gated ion channel

Question 18

What happens to local potential if it doesn’t reach threshold?

Answer 18

Potential will diminish without causing action potential

Question 19

What happens when membrane reaches threshold?

Answer 19

Depolarisation
Voltage gated Na open
K channels remain closed
Sodium moves into cell - membrane potential rises rapidly

Question 20

What happens when membrane potential peaks at approximately 35mV?

Answer 20

Repolarisation
Voltage gated Na channels inactivated (not closed)
Voltage gated K channels open
K+ ions move out of cell
Membrane potential falls back towards resting

Question 21

What is absolute refractory period?

Answer 21

When it is impossible to fire another action potential
Lasts about 1ms
K channels closing, Na channels inactivated
Potential drops below resting

Question 22

What is relative refractory period?

Answer 22

When it is possible to fire an action potential but a larger stimulus is required
Lasts several milliseconds
Potassium channels closing, sodium channels de-inactivated
Sodium/potassium pump restores ion balance

Question 23

What ae action potential generated in and what by?

Answer 23

In the trigger zone
By graded potentials of sufficient size (when a certain voltage threshold is reached)

Question 24

Are action potentials graded?

Answer 24

No!
All or none response

Question 25

Are action potentials decremental?

Answer 25

No They do not decrease in size with distance from initial stimulus (non-decremental)

Question 26

How do action potentials carry sensory or motor information?

Answer 26

They propagate along axons to the appropriate location

Question 27

What is myelinination?

Answer 27

Where the neuron axon is insulated This allows for more rapid conduction of the action potential

Question 28

Are all neurons myelinated?

Answer 28

No, different types of neurons may be myelinated or unmyelinated

Question 29

What is the progress along an unmyelinated axon called?

Answer 29

Continuous propagation

Question 30

What is the progress along a myelinated axon called?

Answer 30

Saltatory propagation

Question 31

What are areas without myelin called?

Answer 31

Nodes of Ranvier

Question 32

How do action potentials pass the nodes of Ranvier?

Answer 32

The action potential jumps along these nodes, allowing for much faster propagation

Question 33

How does axon diameter affect the speed of action potentials across it?

Answer 33

The greater the diameter, the faster the action potential can travel (max up to 120m/s)

Question 34

What myelinates the peripheral axons?

Answer 34

Schwann cells

Question 35

What myelinates CNS axons?

Answer 35

Oligodendrocytes

Question 36

What is axoplasm?

Answer 36

cytoplasm of axon

Question 37

What is axolemma?

Answer 37

cell membrane of an axon

Question 38

What is neurilemma?

Answer 38

Sheath surrounding nerve axon, including the myelin sheath

Question 39

What is multiple sclerosis (MS)?

Answer 39

Autoimmune disorder when myelination of central nerves is targeted

Question 40

What is Guillain-Barre syndrome?

Answer 40

An autoimmune disorder when myelination of peripheral nerves is targeted

Question 41

Where do neurons communicate with one another?

Answer 41

At synapses

Question 42

What are the 2 types of synaptic transmission?

Answer 42

Electrical and Chemical

Question 43

Which type of synapse is rare in the adult brain?

Answer 43

Electrical synapse

Question 44

What is the synaptic cleft?

Answer 44

A gap at a chemical synapse between the pre and post synaptic elements

Question 45

What is the first step in synaptic transmission?

Answer 45

An action potential opens voltage-gated Ca2+ channels in presynaptic membrane Entry of Ca2+ triggers release of ACh from vesicles The ACh diffuses across synaptic cleft

Question 46

What is step 2 in synaptic transmission after ACh diffuses across synaptic cleft?

Answer 46

ACh interacts with ACh receptors (Na+ channels) which trigger an influx of Na+ ions

Question 47

What produces an excitatory postsynaptic potential?

Answer 47

Influx of Na+

Question 48

When is an action potential triggered in the postsynaptic neuron?

Answer 48

When the excitatory postsynaptic potential reaches -55mV

Question 49

What is reffered to as the language of the nervous system?

Answer 49

Neurotransmitters along with electrical signals (means of communication between neurons)

Question 50

Name 3 additional neurotransmitters

Answer 50

1. Acetylcholine (ACh) 2. Adrenaline 3. Noradrenaline

Question 51

3 amino acid neurotransmitter examples

Answer 51

1. glutamate 2. GABA 3. glycine

Question 52

What ere monoamine neurotransmitters derived from? Example?

Answer 52

Derived from amino acids Eg. Serotonin

Question 53

3 catecholamine neurotransmitter exaples

Answer 53

- Dopamine - Epinephrine - Norepinephrine (Also monoamines)

Question 54

2 Peptide neurotransmitters examples

Answer 54

Substance P Endorphins

Question 55

Slide 32

Answer 55

Neurotransmitter examples

Question 56

What are the 5 important processes in regulating different transmitter systems?

Answer 56

1. Synthesis 2. Storage 3. Release 4. Receptor binding 5. Inactivation/Reuptake

Question 57

Synthesis of acetylcholine

Answer 57

Choline acetyltransferase is not saturated. The substrate's (choline's) availability is the rate determining step Supplementing/restricting choline can increase/decrease acetylcholine production

Question 58

Synthesis of dopamine

Answer 58

L-Tyrosine--->L-Dopa (catalysed by tyrosine hydroxylase) - rate determining step as normally saturated by substrate. L-Dopa--->Dopamine (catalysed by dopa decarboxylase DDC) - enzyme has high activity and is non-specific

Question 59

Give an example of a treatment targeting synthesis

Answer 59

L-Dopa for Parkinson's Disease Provides additional substrate for substrate production

Question 60

Storage: what is glutamate?

Answer 60

Glutamate is a neurotransmitter packaged in vesicles in the presynaptic terminal

Question 61

How are transmitter systems relaeased?

Answer 61

- Action potential reaches the presynaptic terminal - Voltage gated Ca2+ ion channels open - Influx of calcium ions - This causes vesicle to bind with presynaptic membrane - Contents of vesicle is released into synaptic cleft by exocytosis

Question 62

What is a receptor?

Answer 62

Protein target which initiates a cellular response when activated

Question 63

What are the 2 main categories of receptors?

Answer 63

1. Inotropic (eg. nicotinic Ach receptor and NMDA receptor) 2. Metabotropic (eg.muscarinic Ach receptor and mGluR)

Question 64

Where can receptors be located?

Answer 64

On both the presynaptic and postsynaptic membrane

Question 65

What are excitatory postsynaptic potentials (EPSPs) caused by?

Answer 65

Excitatory neurotransmitter receptors to transmitters. These include: -glutamate -acetylcholine -noradrenaline

Question 66

What are inhibitatory post synaptic potentials (IPSPs) caused by?

Answer 66

Inhibitatory neurotransmitters such as: -GABA -Glycine -Noradrenaline

Question 67

See slide 43 onwards