Lecture 1 - Introduction to neuronal cell biology

Question 1

What are some of the structures in the brain?

Answer 1

Don’t need to learn all, just familiarity

• Cerebral cortex (higher functions e.g. thinking, sense perception)
• Choroid plexus
• Hypothalamus (Control of visceral (ANS) and somatic functions e.g. temp)
• Thalamus (Sensory relay for cerebral cortex)
• Pituitary gland
• Spinal cord
• Medulla (controls breathing, swalling, digestion, heartbeat)
• Pons
• Cerebellum (little brain. Muscle tone, balance, voluntary movement, motor learning)
• Corpus callosum

Question 2

What is the hierarchy of brain complexity?

Answer 2

Brain regions and circuits
Neurons and Glia
Axon and Dendrites
Synapses
Post-translational modification

Question 3

How many neurons and glia are there in the brain?

Answer 3

Neurons = 8.8 x 10^9
Glia = 2-3 x number of neurons

Question 4

How many axons/dendrites per neuron?

Answer 4

1 Axon

Dendrites, many, varies between cell types

Question 5

How many synapses per neuron/in total?

Answer 5

around 10,000 average

10^15 total

Question 6

What is white matter?

Answer 6

consists of glial cells and myelinated axons that transmit signals from one region of the cerebrum to another and between the cerebrum and lower areas of the brain

Question 7

What is grey matter?

Answer 7

contains numerous cells bodies and non myelinated neurons

Question 8

How do white and grey matter differ in their water and lipid components?

Answer 8

White
70% water
19% lipid (higher because forms major myelinated connections between neurons)
Grey
83% water
7% lipid

Question 9

What is the funtion of neurons and how many types are there?

Answer 9

• receive and transmit impulses

- around 50 types

Question 10

What is the function of glia?

Answer 10

structural and metabolic support for neurons

Question 11

What is the history behind the Neuronal vs Reticular theory (organisation of the nervous system)?

Answer 11

reticular theory = network of interconnect cells
Neuron doctrine = nervous system made up of independent cells
-1871- originally the reticular theory (Gerlach)
-1873- Golgi then introduced the silver-chromate technique to stain brain tissue
-1888- followed by the neuron doctrine (Cajal) gaps between cells
-1891- Waldeyer coined term ‘neuron’. Golgi - defence of the physiological significance of the ‘diffuse nerve network’ theory
-1892- Laws of dynamic polarisation of neurons (Cajal)
-1897- Concept of synapse (Sherrington)
-1906- Nobel prize, Cajal and Golgi
-1921- Nobel prize, Sherrington - the integrative action of the nervous system, modern neurophysiology

Question 12

What are two features of neurons that make them different to normal body cells?

Answer 12

1) Polarity - develop from epithelial cells and share structural features
- basolateral (dendrites - input)
- apical (Axon - output)
2) high excitability

Question 13

Give an example of two different types of neurons and their features

Answer 13

Spiny Neurons
-critical in learning and memory
-have ‘spines’ along the dendrites (post synaptic receptors which detect glutamate(neurotransmitter, amino acid))
-excitatory
Non-spiny neurons
-release GABA (neurotransmitter, amino acid)
-inhibitory

Question 14

What are the different types of glia?

Answer 14

Astrocytes
Oligodendrocytes
Microglia

Question 15

What are some features of Astrocytes?

Answer 15

• most numerous of the glia
• star like shape (processes have end like feet)
• involved in the blood brain barrier
• take up neurotransmitter/K+ ions from synaptic cleft

Question 16

What are some features of the Oligodendrocytes?

Answer 16

• schwann cells in the parasympathetic nervous system (PNS)

- ensheath axons with myelin (up to 15/OD)

Question 17

What are some features of Microglia?

Answer 17

• during development arise from cells outside the CNS
• the macrophage of the CNS
• become activated during infection, injury and seizure

Question 18

What are the three major types of neuronal specific cytoskeletal proteins?

Answer 18

• microtubules (+MAPs, different in axons and dendrites)
• neurofilaments (intermediate filaments of the brain, ‘bones’ of the axon)
• microfilaments (Actin)

Question 19

How are microtubules different in the axons and dendrites?

Answer 19

Axon -long and continuous

Dendrites -in small chunks

Question 20

How was it found that neurons use active transport to move e.g. mitochondria from the cell body to the axon?

Answer 20

Took a cat syatic nerve and removed it
-tied it off
-observed that it began to ‘bunch up’, suggesting active transport
Second experiment
-took syatic nerve and cut it up
-enzyme activity (identified by markers) build up at the gaps, suggesting a movement of enzymes and active transport

Question 21

What is anterograde and retrograde transport?

Answer 21

Anterograde (away from cell body)

Retrograde (towards cell body)

Question 22

What proteins transport organelles from the cell body to the axon?

Answer 22

transport along microtubules mediated by dynesins and kinesins

Question 23

What are the two types of axonal transport?

Answer 23

Fast transport
-rate between 50 - 400 mm/day
Slow transport
-rate between 0.2-8 mm/day

Question 24

How is cargo e.g. mitochondria, deposited at its destination?

Answer 24

• Adapter protein Miro binds mitochondria to kinesin
• synaptic activity causes cytoplasmic Ca2+ to increase, recruiting mitochondria via Ca-dependent protein-protein interactions
• Ca2+ binding to Miro causes an uncoupling of the mitochondria from the kinesin motor

Question 25

What does the cytoskeleton of the neuron define?

Answer 25

neuronal shape and polatiry

Question 26

How is the problem of axon length overcome?

Answer 26

bi-directional fast and slow transport

Question 27

What did Ramon y Cajal do?

Answer 27

Used novel staining techniques to characterise the cell types of the CNS and develop neuronal theory

Question 28

What did Weiss and Hiscoe demonstrate?

Answer 28

the presence of axonal transport