Zusammenfassung der Ressource
PSYC 318- Lecture #1
- Neurons
- rearrange elements to make different kinds of molecules in a cell
- hydrogen, oxygen, carbon
- 15% nucleic acids
- DNA, RNA
- 50% A.A
- proteins
- 10% lipids
- cell membrane
- 15% carbohydrates
- 10% organic molecules
- 20,000 protein encoding genes in our genome (humans)
- proteins characterized by function
- definition
- based on where cell body (soma) is located
- ex: hippocampal neuron
- cell body = hippocampus
- axons can be sent to other places in the body
- Protein Synthesis
- gene
- section of a chromosome encoding a specific protein
- gene reading
- when a gene is read it is transcribed to the nucleus
- by RNA polymerase in mRNA
- this mRNA leaves the nucleus and attaches itself to a ribosome where it is translated into a string of A.A. ( aka poteins)
- microtubules
- allow rapid transport of material in the neurone
- mitochondria
- extract energy from nutrient
- stored as ATP
- dendrites
- receive information from other cells and
sends to soma
- soma
- metabolic centre of neurone
- location of nuceuls
- nucleus contains DNA (chromosomes)
- axon hillock
- binary decision point
- should I fire or not?
- have we crossed threshold?
- cell membrane
- made of lipids
- cytoplasm
- axon terminal
- ending of the axon branch
- release NT after receiving an axon potential
- synapse
- how neurones connect to each other
- myelin sheath
- improves conduction velocity
- Synapses can form anywhere between axon terminals and....
- 4 types
- 2. dendritic spines
- 3. soma
- 1. dendrties
- 4. other axon terminals
- complicated one: see diagram in
notes
- presynaptic terminals transfrom
- electric signal into chemical signals
- term:
- Dendrites
- glutamate, gaba
- neurons have many different NT receptors ( they listen to many different kinds of molecules)
- but only release a few types of NT themselves
- Glutamate
- excitatory
- EPSCs (excitatory-post-synaptic potentials)
- causes depolarization of the post synaptic membrane
- drug
- agonist
- causes seizures
- antagonist
- dissociative anesthetics
- PCP, kedamine
- 99.9% of neurones use one of these two NT
- in addition to a NM (neuromodulator) or NP (neuropeptide)
- gas
- GABA
- inhibitory
- antagonist
- seizures
- agonist
- 1. anesthetic
- 2. anticonvulsant
- 3. muscle relaxants
- alcohol, barbiturates, benzodiazepines
- break
- IPSCs ( inhibitory post-synaptic currents )
- classical neurotransmitters
- Neural Integration
- interaction of excitatory and inhibitory synapse on a particular neurone called neural integration
- if several excitatory synapses are active at the same time
- EPSP cause axon to fire
- if several inhibitory synapses are active at the same time as the EPSP
- the IPSP will dec. the size of the EPSP
- the axon won't fire
- Neuromodulators
- NM are only produced in a small # of locations
- Midbrain,
Hindbrain
- but released widely
- receptors
- Called Neuromodulators b/c
- G-protein coupled receptors
- diffuse short distances
- influence activity of neighbouring neurons
- NOT ion channels
- glutamate & GABA
- point to point communication
- act locally
- ion channels?
- Chemical Transmission: Conventional Neurotransmitters
- Conventional Neurotransmitters
- includes
neuromodulators
- made in axon terminals (local synthesis)
- secreted from SSVs ( small secretory vesicles)
- dock close to site of Ca2+ entry in presynaptic terminals
- usually recaptured after
secretion
- usually bind to receptors directly across synapse
- even when NT diffuse they only act short distances
- receptors
- ligand gated ion channels
- NT
- G protein couple receptors
- NT & Glutamate & GABA
- Chemical Transmission: Neuropeptides (opioids)
- few A.A. joined w. peptide bonds
- small proteins
- secreted
- LDCV
- (large dense core vesicles)
- dock some distance from Ca2+ entry site
- synthesized
- cell soma & released once
- undergoes additional processing once it's transported down the axon
- no synaptic reuse of peptides or immediate precursors
- May diffuse some
distances
- only w. G-protein coupled receptor
- A.K.A. non-synaptic
communication
- Chemical Transmission: Lipid Based Signalling Molecules
- ex: cannabanoids
- secreted in non-vesicular manner from postsynaptic neurones
- synthesized & released on demand
- binds
- G-protein coupled receptors located on presynaptic axon terminal
- NT Receptors
- ionotrophic ( allows ions to flow in )
- 'fast'
- 1. NT binds to open channel
- 2. +/- ions flow through to change electrical potential of the cell
- metabatrophic (metabolic pathways)
- g-protein
- complicated
- 'slow'
- but can also mediate fast signals
- i.e. vision
- > 100 msec.
- NT binds, g protein activated, g protein subunits modulate ion channels, ions flow across membrane
- G-protein Signalling
- g-protein encodes the largest % of proteins in our genome
- when a ligand binds to a G-protein- linked receptor the effect is determined by
- the specific subtype of G protein & local effecters activated by it
- beta-noreepinephrine (beta- noradrenergic) receptors
- are coupled to the g-protein known as 'Gs'
- this activates the protein adenylate cyclase
- norepinephrine can activate receptors that produce opposite effects
- alpha-norepinephine ( alpha-noradrenergic) receptors activate 'Gi'
- inhibits adenylate cyclase protein
- can be activated by
- classical NT
- neuropeptides
- sensory inputs
- odors, light
- lipid based signalling
- Neural Plasticity
- learning mediated by the change in proteins at the synapse
- factors that change strength of synaptic connection
- postysnpatic
- effect of NT binding to the
postsynaptic
- presynaptic
- release of NT binding to the presynaptic
- a manifestation of brain plasticity is synaptic plasticity
- Complexity
- Nucleus Accumbens
- location
- forebrain
- reptilion brain
- ~ part of basal ganglia
- Prairie Voles vs. Mountain
Voles
- diff. amount of OXT receptor expressed in
NAc
- change how a species prioritizes pair bonding
- inc. OXT
- females find life time mate in a shorter period of time
- reason
- changes the value we place on social interactions
- naturally occurs
- sex, birth, parenting, lactation, social bonding
- reduces anxiety, inc. contentness
- OXT called 'bonding hormone'
- released into pituitary -> blood stream
- as a hormone
- genetic diff. in OXT receptors
- maladaptive social
- aggressive behaviour
- neural peptide
- produced
- hypothalamus
- released
- by axon projections from hypothalamus
- released into the brain
- blocking OXT receptor in NAc prevents pair bonding
- artificially deriving OXT receptors in NAc of non-monogamous vole causes them to become monogamous
- function
- transforms level of motivation into movement
- related to pleasure
- pleasure influences your future decision & level of work you put into it
- To use a conventional neurotransmitter a neuone needs
- key identifier
- vesicular transporter
- concentrates the transporter into a
vesicle
- often but not always present
- mech. for degradation of NT
- uptake transporter
- in plasma mebrane
- biosynthetic enzymes
- synthesize the NT