Psych 110 Exam 1

brain

* most complex structure
* composed of 100 billion neurons
* each has about 15,000 connections
* total connections 1,500 trillion
* each neuron can perform about 50 calculations a second
* massively parallel (neuronal calculations are performed simultaneously)

central nervous system (cns)

brain and spinal cord

peripheral nervous system (pns)

cranial nerves and spinal nerves

cranial nerves

connect directly from the base of the brain with various motor and sensory structures

sensory

input

motor

output

spinal nerves

connect directly with the spinal cord

dorsal spinal nerves

receive sensory input from the body (touch, pain, temperature, kinesthetic information)

ventral spinal nerves

carry motor commands to the muscles

somatic nervous system

voluntary control

autonomic nervous system

* involuntary control
* sympathetic nervous system
* parasympathetic nervous system

sympathetic nervous system

* fight, fright, flight, fornication
* arouses the body, mobilizing its energy in stressful situations

parasympathetic nervous system

* opposes the sympathetic nervous system
* calms the body, conserving its energy

anterior/rostral

in front of

posterior/caudal

behind/back

superior/dorsal

above/top

inferior/ventral

bottom/below

lizard brain

* brain stem
* this ancient brain is all about survival
* when danger appears, it decides whether to fight or flee

mouse brain

* an extra layer of brain provides more memory and a wider range of emotions
* allows mammals to do things like learn from their experiences and anticipate danger, rather than merely reacting to it

brain surface

* frontal lobe
* parietal lobe
* occipital lobe
* temporal lobe
* cerebellum

frontal lobe

* decision making
* motor control

parietal lobe

sensorimotor associations

occipital lobe

vision

temporal lobe

* vision
* auditory
* memory

cerebellum

* little brain
* motor control

cortical localization

* different functions are located or localized in different areas of the brain
* established that an area of the left frontal lobe was necessary for the production of language
* damage to back of the brain produced visual impairments and blindness

proliferation of brain areas

modern neuroscience has mapped many functions to specific regions of the brain

comparative brain anatomy

the cortex becomes progressively more wrinkly, which allows more cortex to fit inside the skull

sulci (sulcus)

* shallow grooves separating the gri
* divides the cerebral hemispheres into lobes

gyri (gyrus)

ridges between sulci

gray matter

consists of cell bodies of the neurons, and is where the brain’s computations occur

white matter

* consists of the “wires” connecting the neurons together
* these wires are insulated with fat, giving it the ___ appearance

korbinian brodmann

identified 52 distinct regions in the human brain, and in a variety of different mammals (___ areas)

flow of information

cell body → dendrites → axon → axon terminals

golgi stain

* potassium dichromate and silver nitrate, that randomly stained individual neurons, enabling them to pop-out against the background of other neurons
* reveals how neurons are organized in the hippocampus

santiago ramon y cajal

* used the golgi stain to postulate the neuron doctrine
* insisted that although neurons came very close to one another there were tiny gaps that kept them separate and that they were individual cells

brainbow (jeff lichtman)

* individual cells can be visualized offering a way to describe where each neuron sends its processes and how it interconnects with other neurons, by engineering mice to produce fluorescent (RGB) proteins


* different neurons express different amounts of protein

clarity (karl diesseroth)

* by removing the lipid around cells (washing the brain in detergent), while using a hydrogel to maintain support for the cell components, diesseroth was able to make the brain transparent
* this technique can be combined with brainbow techniques to allow us to visualize individual neurons throughout the brain

tract tracing

* determines where a neuron is receiving communication from and where it is communicating to
* a staining substance is injected into one region of an animal’s brain
* the neurons transport that substance along their length
* the animal is euthanized and the brain is sectioned showing the wiring of the neurons

afferent projection

arriving signals, input

efferent projection

exiting signals, output

anterograde labeling

* where a neuron is communicating to
* tracer taken up by cell body and transported to terminals

retrograde labeling

* where a neuron receives communication from
* tracer taken up by terminals and transported to cell bodies

diffusion tensor imaging (dti)

* water, which can be picked up on mri scans, tends to diffuse down paths of least resistance, as well as the strength of those connections
* this is a non-invasive method, that can be used in humans, but the resolution is only sufficient for the largest pathways

connectomics

aims to map out every connection in the brain

resting potential

neurons at rest have a resting membrane between -50 and -80 mV

membrane ion channels

* protein structures that span the lipid membrane of the cell
* little doors that allow charged particles to enter/exit

diffusion

* ___ of solutes across membranes
* large concentration in one place and very little in another place, it’ll follow from high concentration to low concentration

electrostatic forces

* like charges repel
* unlike charges attract

sodium-potassium pump

* energy costly mechanism that contributes to maintaining/restoring the resting potential, by moving Na+ ions out of the neuron and K+ ions in
* the pump is an active process that requires energy (about 40% of the brains energy usage is devoted to maintaining this potential)
* in the resting state the membrane is 100 times more permeable to K+ than Na+

hyperpolarizing the neuron

* making the interior of the neuron more negative (or less positive)
* decays rapidly--the further away from the source of the charge, the smaller the potential recorded in the neuron
* passive

depolarizing the neuron

* making the interior of the neuron more positive (or less negative)
* when it reaches threshold (\~ -40 mV) an action potential is generated
* response is an all-or-none spike
* the return overshoots producing an afterpotential (hyperpolarization)
* active

patch-clamp recording

* technique used to monitor the activity of ion channels in a membrane
* involves the formation of a tight seal between the tip of a glass electrode and a small region of cell membrane, and manipulation of the membrane potential by varying the concentrations of ions in the electrode

voltage-gated ion channels

a specialized ion channel that opens or closed in response to changes in membrane potential

voltage-gated na+ channels

* monitors axon polarity and at threshold channel changes it shape to open the pore
* has a timing device that ensures the pore only remains open for

first sequence of events underlying an action potential

open k+ channels create the resting potential

second sequence of events underlying an action potential

some na+ channels open, depolarizing the cell to threshold

third sequence of events underlying an action potential

at threshold, additional voltage-gated na+ channels open, causing a rapid change of polarity--the action potential

fourth sequence of events underlying an action potential

* na+ channels are inactivated
* gated k+ channels open, re-polarizing and even hyperpolarizing the cell (undershoot phase)

fifth sequence of events underlying an action potential

all gated channels close, the cell returns to its resting potential

the rate law

neurons must code information by changing the number of action potentials they fire because the size and shape of an action potential is fixed

absolute refractory period

* neuron won’t fire no matter how strong the stimulus
* arises because the na+ channel won’t open again for a short while after being open

relative refractory period

* stronger stimulus than normal needed to make the neuron fire
* corresponds to the period of hyperpolarization

neuronal conduction

* the ___ of the action potential down the neuron is an active process
* as the distance from the stimulating electrode to the recording electrode increases, the latency of the recorded action potential increases, but not its amplitude
* the refractory period prevents the action potential from traveling in the wrong direction
* ___ speed is dependent on the diameter of the axon, with faster speeds in larger axons; range 1 - 20 m/s

saltatory conduction

* describes the way an electrical impulse skips from node to node down the full length of an axon, speeding the arrival of the impulse at the nerve terminal in comparison with the slower continuous progression of depolarization spreading down an unmyelinated axon
* unique to vertebrates
* giant axon of squid is 0.5mm diameter and has a ___ velocity of about 20 m/s
* to maintain ___ velocities without myelin would require a brain 10x larger than its current size
* multiple sclerosis is an autoimmune disease in which myelin is destroyed

axodentritic (synapse)

presynaptic neuron synapses on a postsynaptic neuron’s dendrite

axosomatic (synapse)

presynaptic neuron synapses on a postsynaptic neuron’s cell body

axoaxonic (synapse)

presynaptic neuron synapses on a postsynaptic neuron’s axon terminal

ionotropic receptors

* an ion channel with a receptor protein site that is opened in response to a ligand binding to the receptor
* an ion channel whose opening is controlled by a chemical
* the nature of receptors at a synapse determine the neurotransmitter’s actions (excitatory or inhibitory)

endogenous ligands

* a receptor can be activated by neurotransmitters and hormones made by the body
* agonist


* e.g., ACh

exogenous ligands

* a receptor can be activated by drugs and toxins made outside of the body
* agonist
* e.g., nicotine which also activates the ACh receptor

metabotropic receptor

* a receptor protein that does not contain an ion channel but may, when activated, use a G protein system to open a nearby ion channel
* linked to the ion channel through biochemical reactions

agonist

binds and activates the receptor

antagonist

bind the receptor but fail to activate it; block agonists

short term habituation

* if the siphon repeatedly stimulated over the course of an hour the animal gradually stops contracting its gill
* arises due to a decrease in the release of neurotransmitter from the sensory neuron

long term habituation

* if the animal undergoes habituation sessions the habituation takes place more and more rapidly
* arises due to structural changes in the synapse
* decrease in the number of active zones per synapse
* decrease in the total number of synapses per neuron and the extent of axonal branching

short-term memories rely on

changes in the effectiveness of processes involved in neurotransmitter release

long-term memories rely on

structural changes

hebbian synapse and associative learning

neurons that fire together wire together

cause of long-term potentiation (ltp)

* seems to require some sort of additive effect
* the same number of bursts delivered over a longer period of time will not produce ___
* when the postsynaptic neuron is in a depolarized state when it receives neurotransmitter, which occurs in a rapid train due to summation

nmda receptor

long-term potentiation arises due to the properties of a glutamate receptor called the ___

ampa receptor

* sodium/na+ floods in when glutamate binds to ___
* mediates fast synaptic transmission and synaptic strength

otto loewi

* termed the unknown chemical “vagusstoff”
* known as aceltylcholine
* stimulated the heart of a frog with electrical impulses and had it pump a small amount of nutrient solution
* when the fluid was transferred to another heart, it operated in a similar way
* provided proof that chemical substances convey nerve signals to organs

receptors can be activated by both

* endogenous ligands (neurotransmitters and hormones made by the body, i.e., ACH)
* exogenous ligands (drugs/toxins made outside of the body, i.e., nicotine on nicotine ACh receptors)

up-regulation of receptors

increase the number of receptors on membrane

down-regulation of receptors

decrease in the number of receptors on membrane

mechanism by which the action potential is conducted down the axon

* voltage gated channels in the axon initial segment open, and sodium pours into the axon
* sodium/na+ spreads to the “next” part of the axon, causing voltage gated ion channels to open there, bringing in sodium/na+ and so on down the axon

how does myelin allow the action potential to be conducted faster?

* prevents the sodium/na+ from leaving by blocking the voltage gated channels on the axon
* saltatory conduction: so-called because the signal jumps from node to node, and ion gates don’t have to open which takes time, the signal propagates faster

leak ion channels

* “holes” in the cell membrane that let ions pass through
* they cause sodium/na+ ions to move into the cell and potassium/k+ out of the cell at rest
* always open
* potassium--a lot of channels open at rest
* sodium--a few channels open at rest

ion pumps

* takes 3 sodium (na+) from inside the cell and brings 2 potassium (k+) ions from outside of the cell
* results in a decrease in voltage since it is moving 1 net positive ion outside of the neuron
* pumps continuously

why the resting state of a neuron has a negative voltage

* sodium-potassium pump: pumps out positive ions
* potassium ion channels: k+ leaves due to gradient created by pump
* negatively charged proteins inside the cell

information transmitted through dorsal root ganglion

sensory information from periphery

information transmitted through ventral root ganglion

motor commands

brodmann’s regions were identified using what anatomical features?

number and thickness of layers

forms of tract tracing

* retrograde
* anterograde

epsp (excitatory postsynaptic potential)

* a depolarizing potential in the postsynaptic neuron that is caused by excitatory connections
* brings the neuron’s potential closer to its firing threshold
* increases the probability that the postsynaptic neuron will fire an axon potential

ipsp (inhibitory postsynaptic potential)

* a hyperpolarizing potential in the postsynaptic neuron that is caused by inhibitory connections
* change the charge across the membrane to be further from the firing threshold
* decrease the probability that the postsynaptic neuron will fire an action potential

paul broca

studied stroke patients and established that an area of the left frontal lobe was necessary for production of language

alan hodgkin + andrew huxley

* studied the giant squid axon (0.5 mm in diameter, \~1000x bigger than mammalian axons)
* motor neuron responsible for escape response
* dissected neuron can survive in sea water for up to 2 days

erwin neher + bert sakmann

in order to understand how ion channels work, wanted to be able to record how not just from a single neuron but from a single ion channel