PSY260 - 2. Neuroanatomy/Neurotransmission Flashcards
Tolman’s Maze
rat explores maze at will, eventually will follow route without error
will find a different route if preferred route blocked
Tolman’s Maze
rat retains cognitive map to make it nonrandom search if changed
retains info it doesn’t know it’s going to need
blank slate isn’t blank, holds info that isn’t perceivable
NEUROBIOLOGY
Hodgkin and Huxley (1939, 1945)
look inside neurons
organisms made up of cells + nervous systems made up of neurons
NEUROBIOLOGY
Hodgkin and Huxley (1939, 1945)
putting wires on axons of squids
first measured action potential in neuron
action potential forms basis of neuronal activity
MOLECULAR BIOLOGY Watson and Crick (1953) Franklin (1953)
DNA model
Santiago Ramon y Cajal neuron theory
anatomist
notion of units in brain that formed structure
active participants in learning, but no knowledge of how they work
How do neurons transmit and store information?
billions of neurons working
learning relies on coordinated action of multiple neurons
Neuron
dendrite receives info ⇒ nucleus - integrates into single signal ⇒ axon - action potential ⇒ released to terminal buttons
in diff configurations - multiple connections to other neurons
Mechanisms of Neurons
A: Creating + maintaining potential difference across the cell membrane (membrane potential, Vm)
B: Generating a signal down axon(action potential)
C: Receiving an input signal
D: Transmitting the signal to a target
E: Synaptic plasticity
axon model
cell membrane made of lipid bilayer: porous tube separating inside of cell
diff ions can be accumulated creating diff environ than outside
structural protein makes it stronger
ion selective channels for K + Na
Simple diffusion
probability of moving across based on concentration of ion inside compared to outside
inside + outside will equilibrate
2 ions work independently if only diffusion is working
Axons - Action Potential
ions have charge
channels made differentially permeable
reds can move more easily, then more likely to move to balance negative charge out
built on propensity to diffuse
Pumps
pumps increase diff inside
pressure to move based on differential permeability maintains gradient difference
works to change differential permeability
at rest, lots of K inside, pressure to move out
positive pressure of Na to move inside
Membrane Current
demonstrates electrical potential that can be measured
potassium can’t come out if there’s an electrical force keeping it in
electrical forces in the cell that keep sodium outside
ion concentrations
- Membrane separates molecules inside from outside with the exception of small ion-specific pores.
- Negatively charged molecules inside (only) balanced by positively charged ions
ion concentrations
- Potassium moves more easily, so is concentrated inside
- Sodium is kept out by electrostatic charge.
- Sodium-potassium pump maintains the gradients.
Nernst Equation
V at equilibrium = potential to move out - potential to move in
C = concentration
balanced by electrical charges on right side
Goldman-Hodgkin-Katz Equation
integrates diff pressures of multiple ions
will equal total membrane pressures
potassium bigger on inside, Na bigger on outside
Na wants to move in, but opposed by electrostatic charges
Action Potential
Action potential form because the ion channels are sensitive to voltage.
At rest, most ion channels closed except K channel - leak current at negative membrane potentials: membrane potential will remain strongly negative
potential less negative = other channels may open
actions don’t actually have to move, just be there to push out
Action Potential
membrane potential rises to about -40 mV, sodium channels open: providing an inward potential
positive feedback effect + rapid depolarization
Simple action potentials
first open Na channels - potential to move in increases ⇒ depolarized - positive inside ⇒ Na close, open K channels to repolarize - outside positive, inside negative
pumps return Na outside + K inside during refractory period
Simple action potentials
Near the peak of the action potential, other voltage dependent potassium channels open and contribute to further outward currents. At the same time sodium channels close + membrane returns to its negative potential
Action potential propagation
- Na potential increase causing nearby channels to do same
Nearby affected + next region is affected
Schwann cells: insulator around axons - directs currents along axon rather than through adjacent regions
accelerates transmission of the signal down axon
Action potential propagation
now negative outside causes depolarization to propagate along axis
Loss of myelin results in slower transmission speed + poor regulation of transmission timing = disorganized brain activity and loss of control ⇒ multiple sclerosis
synapse
gap, where chem signals dropped into
neuronal communication: Ca causes movements of synaptic vesicles containing neurotransmitters
neurotransmitters moves to synapse + interacts with postsynaptic receptors
Synaptic function
regulatory site: allows signals to be regulated
allows for modification in treatment of action potentials by sensitizing
General principles of neuronal organization in the brain
- Neuronal activity similar in all cells
* Neuron structure reflects its functional role in info processing
General principles of neuronal organization in the brain
- Synaptic contacts - sites for regulation + integration
* Modifications of synapse # + strength (growth + retraction of neurites) = plasticity, neural correlate of memory
General principles of neuronal organization in the brain
- Learning ⇒ relatively permanent changes in synaptic connectivity underlying memory
- Flexibility, capacity, + capability increase with # of neuron
- Folding increases density of neurons in brains
General principles of neuronal organization in the brain
•Distance counts: Brain regions specialized into centres with defined functions.
Regional activity accompanied by changes in blood flow
closer regions can communicate faster with one another
conservative design to neurons, fastest possible way to get signal transmtted
General principles of neuronal organization in the brain
•Timing critical to learning + plastic changes
some cells have lots of connections + integrate a mass of input
not everything causes synapse to change same way
Computed tomography [CT]
scan from multiple x-ray images at multiple angles ⇒ computer integrate, generating images that look like cross-sections through body
Magnetic resonance imaging [MRI]
changes in magnetic fields generate images of internal structure
•Powerful magnets
radio waves broadcast, disturb atoms⇒Generate tiny electrical currents
•radio waves stop, return to stable align state
•Computer collects all signals and use them to generate images
Primary motor cortex [M1]
generates coordinated movements - frontal lobe, adjacent to S1 in parietal lobe
•sends output to brainstem ⇒ send instructions down spinal cord to activate motor fibers that control muscles
•input from frontal lobe - high-level plans based on present situation, past experience + future goals
•Complex motor movements requires choreographed interactions betw frontal lobe, basal ganglia + brainstem + muscles
Neuropsychology
deals with relation betw brain functions + behavior, examining functioning of patients with specific types of brain damage
Engram
supposed physical change in brain that forms basis of a memory
Theory of equipotentiality
memories not stored in one area of the brain, rather brain operates as a whole to store memories
Positron a mission tomography [PET]
measures brain activity by detecting radiation from emission of subatomic particles called positrons, associated with brains use of glucose from the blood
Functional magnetic resonance imaging [fMRI]
oxygenated blood produces slightly diff signals betw deoxygenated blood, fluctuations in signal received from areas of the brain that undergo change in activity level
•Tend to emphasize associations between specific brain regions and particular functions
•Both are comparatively slow
Electroencephalography [EEG]
technique for measuring electrical activity in brain
•Electrodes record changes in electrical activity, measure combined tiny electrical charges of lots of neurons in brain
•Event related potential: average across many repetitions of the same event
oSimple and cheap way to monitor changes in brain activity, can detect rapid changes in brain with more precision, signal show activity over a wide swath of the brain (not location precise)
