PSYC 318- Lecture #1

Neurons
1. rearrange elements to make different kinds of molecules in a cell
  1. hydrogen, oxygen, carbon
2. 15% nucleic acids
  1. DNA, RNA
3. 50% A.A
  1. proteins
4. 10% lipids
  1. cell membrane
5. 15% carbohydrates
6. 10% organic molecules
7. 20,000 protein encoding genes in our genome (humans)
8. proteins characterized by function
9. definition
  1. based on where cell body (soma) is located
    1. ex: hippocampal neuron
      1. cell body = hippocampus
        axons can be sent to other places in the body
Protein Synthesis
1. gene
  1. section of a chromosome encoding a specific protein
2. gene reading
  1. when a gene is read it is transcribed to the nucleus
    1. by RNA polymerase in mRNA
      1. this mRNA leaves the nucleus and attaches itself to a ribosome where it is translated into a string of A.A. ( aka poteins)
3. microtubules
  1. allow rapid transport of material in the neurone
4. mitochondria
  1. extract energy from nutrient
    1. stored as ATP
5. dendrites
  1. receive information from other cells and sends to soma
6. soma
  1. metabolic centre of neurone
  2. location of nuceuls
    1. nucleus contains DNA (chromosomes)
7. axon hillock
  1. binary decision point
    1. should I fire or not?
    2. have we crossed threshold?
8. cell membrane
  1. made of lipids
9. cytoplasm
10. axon terminal
  1. ending of the axon branch
  2. release NT after receiving an axon potential
11. synapse
  1. how neurones connect to each other
12. myelin sheath
  1. improves conduction velocity
Synapses can form anywhere between axon terminals and....
1. 4 types
  1. 2. dendritic spines
  2. 3. soma
  3. 1. dendrties
  4. 4. other axon terminals
    1. complicated one: see diagram in notes
2. presynaptic terminals transfrom
  1. electric signal into chemical signals
    1. term:
Dendrites
1. glutamate, gaba
2. neurons have many different NT receptors ( they listen to many different kinds of molecules)
  1. but only release a few types of NT themselves
Glutamate
1. excitatory
  1. EPSCs (excitatory-post-synaptic potentials)
    1. causes depolarization of the post synaptic membrane
2. drug
  1. agonist
    1. causes seizures
  2. antagonist
    1. dissociative anesthetics
      1. PCP, kedamine
3. 99.9% of neurones use one of these two NT
  1. in addition to a NM (neuromodulator) or NP (neuropeptide)
4. gas
GABA
1. inhibitory
2. antagonist
  1. seizures
3. agonist
  1. 1. anesthetic
  2. 2. anticonvulsant
  3. 3. muscle relaxants
    1. alcohol, barbiturates, benzodiazepines
4. break
5. IPSCs ( inhibitory post-synaptic currents )
6. classical neurotransmitters
Neural Integration
1. interaction of excitatory and inhibitory synapse on a particular neurone called neural integration
2. if several excitatory synapses are active at the same time
  1. EPSP cause axon to fire
3. if several inhibitory synapses are active at the same time as the EPSP
  1. the IPSP will dec. the size of the EPSP
    1. the axon won't fire
Neuromodulators
1. NM are only produced in a small # of locations
  1. Midbrain, Hindbrain
  2. but released widely
2. receptors
  1. Called Neuromodulators b/c
    1. G-protein coupled receptors
      1. diffuse short distances
        influence activity of neighbouring neurons
      2. NOT ion channels
  2. glutamate & GABA
    1. point to point communication
      1. act locally
    2. ion channels?
Chemical Transmission: Conventional Neurotransmitters
1. Conventional Neurotransmitters
  1. includes neuromodulators
2. made in axon terminals (local synthesis)
3. secreted from SSVs ( small secretory vesicles)
  1. dock close to site of Ca2+ entry in presynaptic terminals
4. usually recaptured after secretion
5. usually bind to receptors directly across synapse
  1. even when NT diffuse they only act short distances
6. receptors
  1. ligand gated ion channels
    1. NT
  2. G protein couple receptors
    1. NT & Glutamate & GABA
Chemical Transmission: Neuropeptides (opioids)
1. few A.A. joined w. peptide bonds
  1. small proteins
2. secreted
  1. LDCV
    1. (large dense core vesicles)
    2. dock some distance from Ca2+ entry site
3. synthesized
  1. cell soma & released once
    1. undergoes additional processing once it's transported down the axon
4. no synaptic reuse of peptides or immediate precursors
5. May diffuse some distances
  1. only w. G-protein coupled receptor
  2. A.K.A. non-synaptic communication
Chemical Transmission: Lipid Based Signalling Molecules
1. ex: cannabanoids
2. secreted in non-vesicular manner from postsynaptic neurones
3. synthesized & released on demand
4. binds
  1. G-protein coupled receptors located on presynaptic axon terminal
NT Receptors
1. ionotrophic ( allows ions to flow in )
  1. 'fast'
  2. 1. NT binds to open channel
    1. 2. +/- ions flow through to change electrical potential of the cell
2. metabatrophic (metabolic pathways)
  1. g-protein
    1. complicated
  2. 'slow'
    1. but can also mediate fast signals
      1. i.e. vision
    2. > 100 msec.
  3. NT binds, g protein activated, g protein subunits modulate ion channels, ions flow across membrane
G-protein Signalling
1. g-protein encodes the largest % of proteins in our genome
2. when a ligand binds to a G-protein- linked receptor the effect is determined by
  1. the specific subtype of G protein & local effecters activated by it
    1. beta-noreepinephrine (beta- noradrenergic) receptors
      1. are coupled to the g-protein known as 'Gs'
        this activates the protein adenylate cyclase
        norepinephrine can activate receptors that produce opposite effects
    2. alpha-norepinephine ( alpha-noradrenergic) receptors activate 'Gi'
      1. inhibits adenylate cyclase protein
3. can be activated by
  1. classical NT
  2. neuropeptides
  3. sensory inputs
    1. odors, light
  4. lipid based signalling
Neural Plasticity
1. learning mediated by the change in proteins at the synapse
2. factors that change strength of synaptic connection
  1. postysnpatic
    1. effect of NT binding to the postsynaptic
  2. presynaptic
    1. release of NT binding to the presynaptic
3. a manifestation of brain plasticity is synaptic plasticity
Complexity
Nucleus Accumbens
1. location
  1. forebrain
    1. reptilion brain
  2. ~ part of basal ganglia
2. Prairie Voles vs. Mountain Voles
  1. diff. amount of OXT receptor expressed in NAc
    1. change how a species prioritizes pair bonding
  2. inc. OXT
    1. females find life time mate in a shorter period of time
      1. reason
        changes the value we place on social interactions
    2. naturally occurs
      1. sex, birth, parenting, lactation, social bonding
    3. reduces anxiety, inc. contentness
    4. OXT called 'bonding hormone'
    5. released into pituitary -> blood stream
      1. as a hormone
    6. genetic diff. in OXT receptors
      1. maladaptive social
        aggressive behaviour
  3. neural peptide
    1. produced
      1. hypothalamus
        released
        by axon projections from hypothalamus
    2. released into the brain
  4. blocking OXT receptor in NAc prevents pair bonding
  5. artificially deriving OXT receptors in NAc of non-monogamous vole causes them to become monogamous
3. function
  1. transforms level of motivation into movement
4. related to pleasure
  1. pleasure influences your future decision & level of work you put into it
To use a conventional neurotransmitter a neuone needs
1. key identifier
  1. vesicular transporter
    1. concentrates the transporter into a vesicle
2. often but not always present
  1. mech. for degradation of NT
  2. uptake transporter
    1. in plasma mebrane
  3. biosynthetic enzymes
    1. synthesize the NT

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PSYC 318- Lecture #1

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	Created by Pascale Bockelmann almost 8 years ago