Neural Anatomy

Error creating thumbnail: File missing

Harris Website

The Size of Dendrites

adapted from Sheng and Hoogenraad (2007) ^FIG: {{#info

Error creating thumbnail: File missing{{{2}}} CLICK AWAY FROM IMAGE TO CLOSE }}

• Dendrite: 1–10 spines per 10 μm
  
• Spines: 0.5–2 μm in length
  
• PSD: 100 - 300 nm diameter
  
• PSD95: within 12 nm of surface
  

adapted from Harris ^FIG: {{#info

{{{2}}} CLICK AWAY FROM IMAGE TO CLOSE }}

• proximal dendrite diameter: 1 - 3 µm
• distal dendrite diameter: 0.2 - 2 µm
• dendrite length: 2000 - 9000 µm
• dendrite tip to soma: 100 - 200 µm
• dendrites at soma: 1 - 5
• dendrite branches (granual): 10 - 30
• dendrite branches (purkinje): 400-500

Particle Counts

adapted from Sheng and Hoogenraad (2007) ^FIG: {{#info

Error creating thumbnail: File missing{{{2}}} CLICK AWAY FROM IMAGE TO CLOSE }}

• PSD: 10,000 proteins (or 100 copies of 100 proteins)
  
• CaMKIIα: 7.4%
  
• CaMKIIβ: 1.3%
  
• SynGap: 2.1 pmol/20 μg
  
• NMDAR: 20 proteins
  
• AMPAR: 15 proteins
  
• GluR: 60 subunits, 15 tetramers, 80% or 12 GluR1/GluR2 heteromers
  
• PSD95: within 12 nm of surface
  

Diffusion Rates

from Choquet 2010 ^FIG: {{#info

{{{2}}} CLICK AWAY FROM IMAGE TO CLOSE }}

• extrasynaptic: 0.1 µm²⁄s
• synaptic: 0.05 µm²⁄s
• synaptic after glu/gly: 0.01 µm²⁄s

Images

From Sheng and Hoogenraad 2007

• Spine morphology ^FIG: {{#info: Error creating thumbnail: File missing{{{2}}} CLICK AWAY FROM IMAGE TO CLOSE }}

From Harris KM and Weinberg 2012

• Spine morphology ^FIG: {{#info: 3D reconstruction of a proximal CA3 pyramidal cell dendrite (blue) and a large mossy fiber bouton (translucent yellow). The cut-away in C2 shows synapses (red) onto multiple dendritic spines, some of which are highly branched. The bouton also forms nonsynaptic cell adhesion junctions (fuchsia). CLICK AWAY FROM IMAGE TO CLOSE }}
• Hippocampal dendrite ^FIG: {{#info: {{{2}}} CLICK AWAY FROM IMAGE TO CLOSE }}

Choquet 2007 Real Time Receptor Diffusion

{{{2}}}

Choquet 2007 Real Time Receptor Diffusion Analysis

• The video represents a 10µm × 10µm section scaled to a 535px × 535px video.
  • 1_µm : 53.5_px
• The analysis below documents one instance of Qdot diffusion, between the 6s-7s time points.
• This instance was chosen because of the clarity of motion and no Qdot flicker.
• The Qdot (center) moves from pixel location (X:291, Y:302) at 6.78s to (X:319, Y346) at 6.98s
  • That is a distance of 52.2px in 200ms
  • Qdot velocity: Q_v ≈ 1_µm ⁄ 200_ms
  • Note this diffusion rate of 5µm/s is 10-fold higher than the median diffusion rate reported above.
  • An upper bound of 5µm/s means that receptors can move between synapses in fractions of a second.

Figures:

^FIG: {{#info: {{{2}}} CLICK AWAY FROM IMAGE TO CLOSE }}

^FIG: {{#info: {{{2}}} CLICK AWAY FROM IMAGE TO CLOSE }}

^FIG: {{#info: {{{2}}} CLICK AWAY FROM IMAGE TO CLOSE }}

^FIG: {{#info: {{{2}}} CLICK AWAY FROM IMAGE TO CLOSE }}

Quick Facts

• There are ~90 billion neurons in the adult human brain
• Neurons usually form 1,000 to 10,000 synaptic connections (on average, heavily depending on neuron type/region)
• 1mm³ of gray matter contains ~30k neurons, each having ~6k synapses, for a grand total of 300mil synapses per mm³
• neurons fire at a rate of x
• GABAA receptors diffuse at a rate of: .01 - .05 µm²/s ^FIG: {{#info: Choquet 2010 CLICK AWAY FROM IMAGE TO CLOSE }}

Malinow

Molecular Methods

Quantum Dots

Choquet

AMPAR