OCB03-2003

Question 1

What are neurofilaments? Describe their structure.

Answer 1

Intermediate filaments found in neurons that maintain cell structure

Coiled coil of polypeptides

Question 2

Where is the action potential generated?

Answer 2

Axon hillock

Question 3

What are other terms used for a neuron cell body?

Answer 3

Soma or perikaryon

Question 4

What makes up the axon?

Answer 4

Axon hillock

Axolemma

Axoplasm

Question 5

What are Nissl bodies?

Answer 5

RER

Question 6

What is a multipolar neuron? Give an example.

Answer 6

Multiple processes leaving cell body

Motor neurons in ventral horn

Question 7

What is a bipolar neuron? Give an example.

Answer 7

Two processes leaving cell body, one with dendrites and the other with terminals

Bipolar neurons of retina

Question 8

What is a unipolar neuron?

Answer 8

One axon extends from cell body with a dendritic tree in the middle of it

Question 9

In what kinds of organisms are unipolar neurons common?

Answer 9

Insects

Question 10

What is a pseudounipolar neuron? Give an example.

Answer 10

One branch leaves the cell body and splits into two

Primary somatosensory neurons in dorsal root ganglia

Question 11

What cells myelinate axons in the periphery?

Answer 11

Schwann cells

Question 12

What cells myelinate axons in the CNS?

Answer 12

Oligodendrocytes

Question 13

What are the gaps of non-myelinated axon called?

Answer 13

Nodes of Ranvier

Question 14

What factors will maximise the speed of action potential conduction?

Answer 14

Large diameter

Myelination

(Increased temperature)

Question 15

Which conducts impulses fastest: Aδ or C fibres?

Answer 15

Aδ fibres

Question 16

What is the difference in nomenclature for fibres which are sensory/motor and sensory only?

Answer 16

Sensory/motor = capital letters (and sometimes a following Greek letter)

Sensory = Roman numerals (and sometimes a following lowercase letter)

Question 17

What is the fastest sensory/motor nerve fibre type?

Answer 17

Aα fibres (eg α-motoneurons)

Question 18

Are pain neurons myelinated?

Answer 18

Typically lightly or not myelinated

Question 19

Is the nucleolus of a neuron prominent? Why?

Answer 19

Yes as neurons are transcriptionally and translationally active

Question 20

What are the monomers of microtubules?

Answer 20

α and β tubulin

Question 21

Which part of the cytoskeleton is associated with axonal transport?

Answer 21

Microtubules

Question 22

In which direction does anterograde transport describe?

Answer 22

Towards plus ends (terminals)

Question 23

In which direction does retrograde transport describe?

Answer 23

Towards minus ends (soma)

Question 24

What molecular motor is used in anterograde transport?

Answer 24

Kinesins

Question 25

What molecular motor is used in retrograde transport?

Answer 25

Dyneins

Question 26

Describe the polarity of microtubules.

Answer 26

Plus end = terminals Minus end = soma

Question 27

How does kinesin move?

Answer 27

Two "heads" of the complex detach and reattach sequentially in an ATP-dependent manner "Walking"

Question 28

How does dynein move?

Answer 28

ATP-dependent "sliding" movement

Question 29

Describe the properties of anterograde movement.

Answer 29

Fast via kinesins, 100-400mm/day to move mitochondria and vesicles to terminals Slow via unknown mechanism, 0.5-10mm/day to move structural and metabolic elements

Question 30

Describe the properties of retrograde movement.

Answer 30

Fast via dyneins, 50-250mm/day to move aging mitochondria and vesicles

Question 31

What is the importance of retrograde transport?

Answer 31

Only way for soma to know if there is any damage to the nerve terminal (to change gene expression and start repair) Also enables pathogens/viruses to spread easily along nerve pathways from the skin

Question 32

Which type of axonal transport is generally faster?

Answer 32

Anterograde

Question 33

What is Diffusion Tensor Imaging (DTI)?

Answer 33

Type of MRI Allows visualisation of water movement in axons using "seed points" and "voxels"

Question 34

What is convergence?

Answer 34

Many presynaptic neurons ending on a single postsynaptic neuron

Question 35

What is divergence?

Answer 35

One presynaptic axon dividing into many branches to end on many postsynaptic neurons

Question 36

How many inputs does the average CNS neuron receive?

Answer 36

10,000

Question 37

How many inputs does a Purkinje cell of the cerebellum typically receive?

Answer 37

~300,000

Question 38

What is the significance of convergence and divergence in the CNS?

Answer 38

Many multiple ways of getting from one point to another in the brain Each with their own neural consequences Brain is like a super computer!

Question 39

What is the ratio of neuroglia to neurons?

Answer 39

10:1

Question 40

What are the two types of astrocytes?

Answer 40

Fibrous Protoplasmic

Question 41

What are the functions of astrocytes?

Answer 41

Homeostatic: - regulate ionic environment (esp K+) and water - take up neurotransmitter (esp glutamate) and convert to glutamine - glycogen energy reserve for brain - regulate blood-brain barrier (glia limitans) Structural: - bond axons together to give strength and stability - inhibit axon regeneration - myelination

Question 42

Which compound do astrocytes use to inhibit axon regeneration?

Answer 42

Chondroitin sulphate glycoprotein

Question 43

Which type of astrocyte clusters around synapses?

Answer 43

Protoplasmic

Question 44

Describe a protoplasmic astrocyte.

Answer 44

Greater number of shorter extensions Largely confined to grey matter

Question 45

Describe a fibrous astrocyte.

Answer 45

Fewer number of longer extensions Largely confined to white matter (for stability and support)

Question 46

How many axons can an oligodendrocyte myelinate?

Answer 46

Up to 40-50

Question 47

What functions do oligodendrocytes have?

Answer 47

Myelination Inhibiting axon regeneration

Question 48

What is the function of the microglia?

Answer 48

Main cell responsible for removal of cellular debris and immune defence

Question 49

What prevents normal immune surveillance of the brain?

Answer 49

Blood-brain barrier

Question 50

How do microglia detect damage and react?

Answer 50

Normally have multiple processes expressing ATP receptors ATP from damage or inflammation binds P2Y class of receptors causing a conformational change Processes retract and the microglia becomes phagocytic

Question 51

What are the three types of ependymal cell?

Answer 51

Ependymocytes Tanycytes Choroid plexus cells

Question 52

Which type of ependymal cell is most abundant?

Answer 52

Ependymocytes

Question 53

What is the function of ependymocytes?

Answer 53

Form epithelial lining Have cilia to circulate CSF and microvilli for absorption

Question 54

Describe a tanycyte and its function.

Answer 54

Elongated cell mainly associated with third ventricle Acts as a sensor for secreted hormones (hypothalamus) and other small molecules in CSF

Question 55

Describe choroid plexus cells and their function.

Answer 55

Specialised cuboidal epithelial cells CSF production in all ventricles of brain

Question 56

How many axons can a Schwann cell myelinate?

Answer 56

1

Question 57

What are the functions of Schwann cells?

Answer 57

Myelination Promote axon regeneration

Question 58

How do Schwann cells promote axon regeneration?

Answer 58

Upregulation of permissive ECM components Rapid removal of myelin debris by phagocytosis

Question 59

What is the function of satellite cells?

Answer 59

Structural support, homeostatic and metabolic support to neurons (similar role to astrocytes)

Question 60

What are satellite cells associated with?

Answer 60

Sensory neurons in dorsal root ganglia Sympathetic ganglia