Neuroscience II

Question 1

What are Neurons?

Answer 1

Basic functional units of the NS

Question 2

What is the function of the Neuron?

Answer 2

Processes and trasmits info (electrical and chemical)

Question 3

How is the Structure of a Neuron?

Answer 3

1. Cell Body: contains organelles essential for survival
2. Short, highly branched dendrites: receive info from other neurons
3. Long, single axon: carries electric signal to target

Question 4

What is a Bipolar Neuron?

Answer 4

Has 2 processes separated by a cell body in the middle

Question 5

What is Unipolar Neuron?

Answer 5

Has 1 single elongated process with the cell body to the side

Question 6

What is a Multipolar Neuron?

Answer 6

Has more than 2 processes; a single axon and multiple dendrites

Question 7

What are Neuroglia?

Answer 7

Supporting neuronal function

Question 8

How many % of the total cell population in the NS are Neuroglia?

Answer 8

~50%

Question 9

What are the types of Neuroglia and their functions?

Answer 9

1. Astrocytes: regulate chemical content of the ESF
2. Myelinating Glia (Oligodendrocytes, Schwann Cells): Myelination of Neurons
3. Microglia: phagocytic role
4. Ependymal Cells: production of CSF

Question 10

What type of tissues are Nerves and Muscle Cells?

Answer 10

Excitable tissue (Produce electric signals when excited)

Question 11

Why are Electric Signals important for NS and MSK?

Answer 11

(NS) Receive, process, initiate and trasmit messages

(MSK) Initiate contraction

Question 12

What happens to the membrane potential during depolarisation and hyperpolarisation?

Answer 12

(Depolarisation) Less -ve

(Hyperpolarisation) More -ve

Question 13

What are the terms of Polarisation?

Answer 13

Polarisation: MP ≠ 0mV
Depolarisation: MP becomes less polarised than Resting Potential
Repolarisation: MP returns to RP
Hyperpolarisation: MP becomes more polarised than RP

Question 14

How are Electric Signals produced?

Answer 14

By changes in ion movement

Question 15

What is a triggering event?

Answer 15

An event that triggers a change in membrane potential, altering membrane permeability and thus, ion flow across membrane

Question 16

What types of Membrane Channels are there?

Answer 16

1. Leaky Channels

2. Gated Channels

Question 17

What are the types of Gated Channels?

Answer 17

1. Voltage gated
2. Chemically gated
3. Mechanically gated
4. Thermally gated

Question 18

What are Graded Potentials (GP)?

Answer 18

Local changes in MP occurring in varying grades

Question 19

How are GPs spread?

Answer 19

By passive current flow BUT they die out over short distances

Question 20

What is an Action Potential (AP)?

Answer 20

Brief, rapid, large changes in MP (100mV) when the inside of an excitable cell transiently becomes more than the outside

Question 21

What leads to an AP?

Answer 21

Marked changes in membrane permeability and ion movement

Question 22

What are the channels involved in AP?

Answer 22

Voltage-gated Na+ and K+ channels

Question 23

Which channel has an inactivation gate?

Answer 23

Na+ channel

Question 24

Describe how an AP is generated.

Answer 24

1. RP (-70mV): all channels closed
2. Threshold: Na+ channel OPEN
3. Excessive Depolarisation (+30mV): Na+ enters ICF (Rising phase of AP)
4. Peak of AP: Na+ channel INACTIVATED, K+ channel OPEN
5. Repolarisation (-70mV): K+ leaves ICF (Falling phase of AP)
6. Na+ channel resets to ‘closed but capable of opening’ state, ready to respond to triggering event
7. Hyperpolarisation (-90mV): Further outward movement of K+ out of ICF
8. K+ channel closes and MP = 70mV

Question 25

What does the Na+-K+ pump do?

Answer 25

Gradually restore [ ] gradients disrupted by AP

Question 26

From where to where are APs propagated?

Answer 26

From axon hillock to axon terminals

Question 27

What are the different zones in the Neuron?

Answer 27

1. Input zone 2. Trigger zone 3. Conducting zone 4. Output zone

Question 28

Where is and what is the function of the Input zone?

Answer 28

Dendrites; Receive incoming signals from other neurons

Question 29

Where is and what is the function of the Trigger zone?

Answer 29

Axon hillock; Initiates AP

Question 30

Where is and what is the function of the Conducting zone?

Answer 30

Axon; Conducts AP in undiminishing fashion, often over long distances

Question 31

Where is and what is the function of the Output zone?

Answer 31

Axon terminals; Releases neurotransmitter that influences other cells

Question 32

How long is a typical Axon?

Answer 32

1mm to more than 1m long

Question 33

What is a Refractory Period?

Answer 33

AP cannot be initiated in a region that has just undergone an AP due to inactivation of Na+ channels

Question 34

What is the purpose of a Refractory Period?

Answer 34

Ensures one-way propagation of AP and limits frequency

Question 35

In what fashion does AP occur?

Answer 35

"All-or-none" fashion due to discrimination of stimuli

Question 36

How is the strength of a stimulus coded?

Answer 36

By the frequency of AP (magnitude of each AP same)

Question 37

How does Myelination influence the AP?

Answer 37

Increases the speed of conduction of AP

Question 38

What does the fiber diameter influence?

Answer 38

Velocity of AP propagation

Question 39

What is Myelin?

Answer 39

Thick layer of lipids

Question 40

What is the function of Myelin?

Answer 40

Acts as an insulation to "electrical transmission" along the axon

Question 41

What is Contiguous conduction?

Answer 41

Local current flow that depolarises adjacent inactive area from RP to Threshold Potential (TP)

Question 42

What is Saltatory conduction?

Answer 42

Local current flow that depolarises adjacent inactive node from RP to TP

Question 43

What is a Synapse?

Answer 43

Junction between Neurons

Question 44

What are the types of Synapses?

Answer 44

1. Electrical synapses: neurons connected directly by gap junctions 2. Chemical synapses: chemical messenger transmits info one way across a space separating the 2 neurons

Question 45

How is the Anatomy of a Chemical Synapse?

Answer 45

1. Presynaptic Terminal 2. Synaptic Cleft 3. Postsynaptic Terminal

Question 46

How does Synaptic Transmission?

Answer 46

1. Depolarisation due to incoming AP from axon 2. Influx of Ca2+ due to opening of voltage-gated Ca2+ channels 3. Docking: Vesicles with neurotransmitter dock at protein 4. Release of neurotransmitter 5. Binding of neurotransmitter to receptor

Question 47

What does the neurotransmitter do?

Answer 47

Carries the signal across a synapse

Question 48

What are the different types of synapses based on its effects?

Answer 48

1. Excitatory: Generation of EPSP | 2. Inhibitory: Generation of IPSP

Question 49

What can modify synaptic transmission?

Answer 49

Drugs and diseases

Question 50

What are the types of pathways are neurons linked by?

Answer 50

1. Convergence: Given neuron has many other neurons synapsing on it 2. Divergence: Branching axon terminals so a single cell synapses and influences other cells

Question 51

What are some examples of neurotransmitters?

Answer 51

1. Acetylcholine 2. Dopamine 3. Glutamate 4. Gamma-aminobutaryic acid (GABA)

Question 52

What is the effect of Acetylcholine?

Answer 52

(PNS) Neuromuscular junctions, parasympathetic nerves | (CNS) Muscarinic and Ionotropic

Question 53

What is the effect of Dopamine?

Answer 53

Many pathways in CNS

Question 54

What is the effect of Glutamate?

Answer 54

EPSP in CNS

Question 55

What is the effect of GABA?

Answer 55

IPSP in CNS