Electron microscopy

Question 1

Advantages

Answer 1

Can see much smaller structures than with LM.

Question 2

Disadvantage

Answer 2

Magnification is restricted by the limit of resolution - the minimum separation of two points that is needed to allow them to be distinguished.

Question 3

Resolution of EM

Answer 3

<1nm

Question 4

What can you see on EM?

Answer 4

Plasma membrane and other membranes (7-8nm thick), mitochondria(100-500nm), ribosomes(23nm), synaptic vesicles(40-50nm), synaptic cleft (10-20nm) and postsynaptic density

Question 5

Asymmetrical synapses

Answer 5

Are excitatory

Question 6

Symmetrical synapses

Answer 6

Are inhibitory

Question 7

Types of EM

Answer 7

Transmission EM (electron beam passez through section of tissue), scanning EM ( used to reveal surfaces), freeze fracture ( form of TEM used to study membranes)

Question 8

Main components of TEM

Answer 8

Source of electrons- electron gun
Vacuum
Lenses - electromagnets
Method for capturing images - flouroscreen, digital camera, photographic plates.

Question 9

5 step tissue prep for TEM

Answer 9

1. Fixation using aldehydes
2. Post-fixation (osmium tetroxide)
3. Dehydration ( graded alcohol series)
4. Embedding (resin)
5. Sectioning and staining

Question 10

Staining for TEM

Answer 10

Uranyl acetate
Lead citrate
V. Non specific compared with LM stains