Synapses

The basics of biological psychology is the neuron. Nerves are collections of neurons and the brain is an accumulation of millions of neurons.

Note to self: Please put more here!

 

NOTES

Synapses

• At Neuron Terminal
• Depolarization
  • Cause calcium gates open
  • Calcium flows into terminal
  • NT is released within 1-2 milliseconds
• Thousands of synapses along neuron
• Three types of many
  • Axon-soma
  • Axon-dendrite
  • Axon-axon
• Axon-Soma (axosomatic)
  • Usually inhibitory
• Axon-Dendrite
  • Chemical

4 Stages

1. Release the chemical

• Pre-synapse
• Release & Diffusion
• release of NT thru membrane
• Exocytosis: lasts 1-2 ms
• Cross 20 to 30 nanometers
• About 0.01 ms
• Opposite of endocytosis
• Cells absorb protein molecules
• Most release only 1 NT
• If 2-3, always the same combo (typically)

2. Float across synapse

• Diffusion

3. Bind with receptors

• Not just anyone
• Matching key
• Nicotinic receptors
• Activated by nicotine
• Blocked by curare

4. Clean up gap

• Destroy leftovers
• (deactivation)
• Recycle (reuptake)
• After action potential
• After exciting or inhibiting
• Inactivation
  • broken down by an enzyme
  • Acetylcholine broken down by
  • acetylcholinesterase
• Reuptake
  • detach from the receptor
  • taken back by presynaptic cell
• Transporters
• Serotonin is reuptaken

Relative Size

• Sheet of paper  100k nm
• Hair                     40knm
• Red blood cell       7k nm
• Bacteria                5k nm
• Virus                      30-50 nm
• Ultraviolet light   40 nm
• Synapses              40 nm
• Cell membrane   10 nm
• DNA                         2.5 nm

Fill the gap with chemicals

Gap junction

• 10x closer than synapse
• 4nm
• .0004 milimeter

ionotropic effects

• quick start (10 ms)
• short duration (30 ms)
• Quick events
• visual stimulation
• muscle movements
• localized effect on membrane
• opens gates for ions
• e.g., acetylcholine
• Most common NT
• glutamate (excitatory)
• GABA (inhibitory)

Metabotropic Effects

• slow start (30 m)
• can last for hours
• has broad impact
• Can affect most of cell
• Opens-closes ion channels
• change protein production
• activate chromosomes
• Activated G-protein
• inside membrane
• G-protein activates 2nd message
• G-proteins: Little protein sits close to receptor
• coupled to GTP (guanosine triphosphate)
• energy-storing molecule
• Changing cell potential
• G-protein to change shape
• Part of G breaks off
• binds to an ion channel
• G-proteins
• Can also activate enzymes
• Enzymes cause production of second messenger

Summation (integration)

• neuron can receive input from 1000+ cells
• each input either excites or inhibits
• interaction between incoming
• EPSP’s (excitation)
• IPSP’s (inhibition)
• Two types of summation
• Spatial
• Temporal summation

Other

• acetylcholine & acetylcholinesterase
• inhibitory effect
•             axon-dendrite
•             axon-soma (axosomatic)
• binding
• endocytosis & exocytosis
• GABAa & GABAb
•             a = ionotrophic
•             b = metabotropic
• glutamate-glutamine cycle
• GABA-glutamine cycle
• too many GABA transporters
• G-protein work
• EPSP (excitation)
• ATP
•             Used as an enzyme
•             (adenosine triphosphate)
• cascade of reactions
• catecholamines
• Ionotropic effects
• Metabotropic effects
• Charles Sherrington = reflexes require integrated activation & reciprocal innervation of muscles
• nicotinic receptor
•             Chem $: receptor protein
•             Muscular contraction
•             acetylcholine
•             nicotine
• reflex arc
• What happens if reuptake occurs too quickly?
• What happens if binding lasts too long?
• How does spatial summation compare to temporal summation?

Developmentaldisorder

• Diagnosed 1-3 years old
• Symptoms by 18 months
• Seek help ~24 months
• Generally
•             Vary from moderate to severe
•             Not startle at loud noises
•             Heightened response to sounds
•             Miss language milestones:
•                         Babbling by 12 months
•                         Wave bye-bye by 12 months
•                         Say single words by 16 months
•                         2-word phrases by 24 months (not just echoing)
•             Boys more than girls
• Symptoms
•             Overly sensitive to $
•             Refuse to wear “itchy” clothes
•             Distress if routines changed
•             Repeated body movements
•             Unusual attachment to objects
•             Difficulty with pretend play
•             Lack of empathy
• Causes
•             Unknown
•             Genetics
•                         identical twins are much more likely than fraternal twins
•                         Relatives more like to have:
•                                     Language abnormalities
•                                     Chromosomal abnormalities
•             Diet?
•                         Some parents try:
•                                     Gluten-free diet
•                                     Casein-free diet (milk-cheese)
•             Mercury poisoning?
•             Inability to properly use vitamins and minerals?
•             Vaccines are not the cause
•                         Single-dose forms
•                         Don’t contain added mercury
•             Mirror Neurons in Autism
•                         No empathy
• Types
•             Asperger’s (good language skills)
•             Rett syndome (for girls)
•             Generally includes:
•                         Childhood disintegrative disorder
•                         Learn and then lose skills
•             Atypical (misc.)

 

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