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Difference in electrical charge between inside and outside cell
is....
Membrane potential
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What are 2 factors contributing to even distribution of ions?
- Random motion
- Electrostatic pressure
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Particles tend to move down their concentration gradient
Which type of motion is this?
Random Motion
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Like repelslike, opposites attract. Is which type of pressure?
Electrostatic pressure
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Selective permeability to certain ions & sodium-potassium pumps are factors contributing to what?
uneven ditribution of ions
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The neuron at rest:
Ions move in & out through......
Ion specific channels
- K+ & CL- pass readily
- Little movement of NA+
- A- dont move at all, trapped inside
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The neuron at rest:
The potential at which there is no net movement of an ion- the potential it will move to achieve when allowed to move freely is.....
Equilibrium potential
- Ex; NA+ = 12-mV
- K+=90mV
- Cl-=-70mV(same as resting potential)
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Na+ is driven in by both......
Electrostatic pressure (repelling) & its concentration gradient (random motion)
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K+ is driven in by _____ & out by _______
- Electrostatic forces
- Its concentration gradient
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Neurotransmitters bind at.....
Postsynaptic receptors
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These chemical messengers bind & cause electrical changes...
- Depolarizations ( making the membrane potential less negative)
- Hyperpolarizations ( making the membrane potential more negative)
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Postsynaptic depolarizations = ?
An excitatory PSP (EPSP)
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postsynaptic hyperpolarization= ?
An inhibitory PSP (IPSP)
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______ Make it more likely a neuron will fire, _____ Make it less likely
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_____ are graded potentials- their size varies
PSPs
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What is being described?
- travel passively from their site of origination
-Duration varies but transmitted at great speed
- Decremental- They get smaller as they travel
EPSPs & IPSPs
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One EPSP will not suffice to cause a neuron to " fire" & release neurotransmitters, which is needed?
summation
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What is needed to generate an AP ( or fire)
The threshold of activation must be reached near the axon hillock
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Integration of IPSPs & EPSPs must result in....
A potential of about -65mV in order to generate an AP
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Adding or combining a # of individual signals into one overall signal is...
Integration
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Integration of events happening at differnt times is....
Temporal summation
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Integration of events happening at differnt places is.....
Spatial summation
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All or none- when threshold is reached the neuron " fires" & the action potential occurs
- When the threshold is reached, voltage- activated ion channels are opened
This is...
Action potential
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What are the differences of APs and PSPs?
- EPSPs/IPSPs:
- -Decremental
- -Fast
- -Passive(energy is not used)
- APs:
- Nondecremental
- Conducted more slowly than PSPs
- Passive & active
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Refactory periods:
Absolute:
Relative:
- Prevent the backwards movement of APs & limit the rate of firing
- - Impossible to initiate another action potential
- -Harder to initiate another action potential
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What is the conduction like in myelinated axons?
- Passive conduction( instant & decremental) along each myelin segment to next node of ranviee
- - new action potential generated at each node
- - Instant condution along myelin segments results in faster conduction than in unmyelinated axons
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What are the different types of synaptic conncetions?
- Most common:
- Axodendritic- axons on dendrites
- Axosomatic- axons on cell bodies
- Dendrodendritic- capable of transmission in either direction
- Axoaxonic- May be involved in presynaptic inhibition
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What are the 2 main types of NT molecules?
- Small- synthesized in the terminal button & packaged in synaptic vesicles
- Large- Assembled in the cell body, packaged in vesicles, & then transported to the axon terminal
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What is the main type of Neuropeptides molecules?
- Large
- Ex: endorphines "endogenous opioids"
- Produce analgesia ( pain suppression)
- Receptors were identified before the natural ligand was
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What are the small NTs types?
- Amino acids- building blocks of proteins
- Monoamines-All synthesized from a single amino acid
- Acetylcholine(Ach)- activity terminated by enzymatic degration
- Unconventional neurotransmitters-soluble gases & endacannabinoids
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found at fast acting directed synapses in the CNS
Glutamate- Most prevalent excitatory neurotransmitter in the CNS
GABA- synthesized from glutamte
Most prevalent inhibitory NT in the CNS
Aspartate & glycine
are all part of which small NT
Amino acid
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Effects tend to be diffuse
Catecholamines- synthesized from tyrosine
dopamine
norepinephrine
epinephrine(adrenaline)
-Indolamines-synthesized from tryptophan
serotonin
Are all part of which small NT?
Monoamines
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Production of NTs at the terminal
- The arrival of an AP at the terminal opens voltage-activated Ca2+ channels,
- The entry of Ca2+ causes vesicles to fuse with the terminal membrane & release their contents
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The process of NT release is...
Exocytosis
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A molecule that binds to another is a ?
Ligand
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What is associated with ligand- activated ion channels?
Ionotrophic receptors
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What is associated with signal proteins & G proteins ( molecular switches- active/inactive)?
Metabotrophic receptors
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These describe what?
-NT binds & an associated ion channel opens or closes, causing a PSP
-If NA+ channels are opened, for ex: an EPSP occurs
If K+ channels are opened, an IPSP occurs
Ionotropic receptors
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This describes what?
Effects are slower, longer-lasting, more diffuse & more varied
They opperate in the following sequence
1-NT 1st messenger binds
2-G protein subunit breaks away
3- ion channel opened/closed OR a 2nd messenger is synthesized. 3- 2nd messengers may have a wide variety of effects
Metabotropic receptors
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What are 2 ways of recycling NTs?
- Reuptake- scoop up & recycling NT
- Enzymatic- degration-a NT is broken down by enzymes
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Increase or facilitate activity is.....
Agonists
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Decrease or inhibit activity is
antagonists
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Two examples of agonists are
- Cocaine (fight or flight)
- Benzodiazepines- (sedative, anti anxiety- GABA agonists
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What are two examples of antagonists?
- Atropine- Ach , high does disrupt memory
- Curare- causes paralysis
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Describe an NT cycle
- 1-NT molecules are synthesized from precursors under the influence of enzymes
- 2-NT molecules are stored in vesicles
- 3- NT molecules that leak from vesicles are destroyed by enzymes
- 4-APs cause vesicles to fuse w/the presynaptic membrane & release their NT molecules into the synapse
- 5- released NTs molecules bind w/autoreceptors & inhibit subsequent NT release
- 6- released NTs molecules bind to postsynaptic receptors
- 7-released NTs molecules are deactivated, by either reuptake or enzymatic degradation
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What is this?
Inject a substance into a brain structure to increase the contrast w/surrounding
- Angiography inject dye into artery
Contrast x-rays
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what is this?
2-D x-ray images are combined to create a 3-d image
CT
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What is this?
Place head into powerful magnetic field, which aligns hydrogen atoms ( present in water). Then pulse the field w/brief radio waves, which knocks atoms out of aligment. Detect energy released (megnetic field) as they wobble back into place
MRI
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what is this?
Relies on increased glucose consumption in active brain areas during particular kinds of info precessing
- to track glucose, participants are given a mildly radioactive form of glucose
- The brain is then scanned to detect the positrons
PET
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How does a PET work?
- Seeing- activates visual areas in the occipital lobe
- Listening- activates the temporal lobes of both hemispheres
- Speaking- activates portions of the motor cortex, the insular cortex, the middle cerebellum
- Gererating- words trigger complex activations inclduing the left frontal cortex, the anterior cingulate, posterior temporal lobe, & the right cerebellum
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What are the advantages of fmri over PET?
- - nothing injected
- - provides both structual & functional info in one image
- - better spatial resolution
- - Can create 3-D images of activity over the entire brain
- Both use subtraction technique
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what is this?
Is a non invasive technique that stimulates the brain using magnetic fields. It induces an electric field in the neurons of the cortex below the coil to produce brain activity
TMS
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What is this?
Measures changes in megnetic field
Provides higher temporal resolution of brain activity changes than fMRI
MEG
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What is this?
A measure of the average electrical activity of the brain
- EEG
- ( some EEG wave forms assicated with: specific states of consciousness, cerebral pathology( such as epilepsy)
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Sensory evoked potentials are triggered by sensory stimuation, is an example of...
ERPs
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what is used to position experimental devices w/in the brain
Stereotaxic surgery
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what is a point on the top of the skull ofter used as a reference point?
Bregma
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Lesion- Remove, damage, or destroy a part of the brain to observe impact on behavior
name and define the four different types...
- Aspiration-suction cortical tissue
- Radio- frequency lesions- heat destroy tissue
- Knife cuts- may damage surrounding area
- Cryogenic blockage- reversible lesion
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Name and define the four different types of Electrophysiological recording....
- Intracelluar unit recording- detects graded changes in membrane potential of a neuron
- Extracellular unit recording- detects firing of a neuron
- Multiple unit recording-firing of many neurons
- Invasive EEG recording
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Measuring chemical activity of the brain:
2-deoxyglucose
cerebral dialysis
- - inject animal w/radioactive 2-DG & allow it to engage in behavior of interest
- -use autoradiography to see where radioactivity accumulates in brain slices
Measures extracellular concentration of specific chemicals in live animals
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locating NTs & receptors: dye or radioactive labels used to visualize the protein of interest-uses ligands of the molecule
Define
immunocytochemistry
In situ Hybridization
- - based on the binding of labeled protein specific antibodies
- -immune response-antibodies created that bind & remove/destroy antigens( foreign proteins)
Uses artificial ( & labeled) RNA that is complementary to mRNA corresponding to protein of interest
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removing a gene is called
knockout
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This allows for development of gene but blocks its expression
Antisense drugs
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Inserting pathological human genes in mice is...
Gene replacement
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What is the adv. of a single test?
Used to defferentiate brain damage from functional causes
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What is the adv. of standardized test?
same as single test
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What is the adv. of customized test battery?
- now predominant
- charaterizes nature of psychological deficits
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What is the WAIS test?
- Wechsler adult intelligence scale
- an iq test
- often fails to detect memory deficits
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What is the language lateralization test?
used to identify language dominant hemisphere
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What is the WCST ?
- Wisconsin card sorting test
- Patient must learn the sorting rule
- Frontal lobe damage leads to repetitive guessing & failure to learn a new rule
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What are some common tests with rats?
- open field test- general activity
- Colony intruder paradigm- aggression & defensive behavior
- Elevated plus maze- anxiety
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What are some common conditioning tests with rats?
- Pavlovian- pairing an unconditional stimuls w/ a conditioned stimulus
- Operant- reinforcement & punishment
- self stimulation- animal works with electrical stimulus
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seminatural learning
name and define
Morris water maze
conditioned defensive burying
Tests spatial abilities-rats must find hidden platform in an opaque pool
- - following a single aversion stimulus delivered from an object, rats will spray bedding at the object
- - antianxiety drug decreases the amount of burying behavior
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What are the three layers of embryonic cells?
- Ectoderm (outermost, forms CNS)
- Mesoderm (middle, forms circulatory system, bones and sex organs)
- Endoderm (innermost, forms lungs and digestive system)
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what is this ?
earliest cells have the ability to become any type of body cell
Totipotent cell
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What is this?
with development, neural plate cells are limited to becoming one of the range of mature nervous system cells
Multipotent cell
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A structure dorsal to the neural tube and formed from neural tube cells
Develops into the cells of the peripheral nervous system
Cells migrate long distances
This is the....
neural crest
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radial migration and tangential migration
are 2 types of what?
neural migration
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Aid both migration and aggregation
CAMs recognize and adhere to molecules
What is this?
Cell adhesion molecules
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Prevalent in brain development
May play a role in aggregation and other processes
What is this?
Gap junctions
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what is the first to travel a route, interact with guidance molecules
After that, other developing axons follow the established path
pioneer growth cones
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what are presumed to guide connections across structures while maintaining the same layout
Topographic gradient hypthesis
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Formation of new synapses
Depends on the presence of glial cells – especially astrocytes which supply the high levels of cholesterol needed
Chemical signal exchange between pre- and postsynaptic neurons is also needed
is known as
Synaptogenesis
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promote growth and survival, guide axons, stimulate synaptogenesis
Nerve growth factor (NGF)
is known as...
Neurotrophines
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Both passive cell death (necrosis) and active cell death (apoptosis)
Apoptosis is safer than necrosis – “cleaner”
.
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whole brain volume....
Increases until about 16 years, then decreases
71 - 80 years were smaller than 2 years
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gra/white matter ration.........
- Decreases rapidly from 19 months to 50 years
- Then decreases slowly
- Due to decrease in gray matter and increase in white matter
- At 4 yrs, we have 3x more gray matter than white matter. At 50 yrs we have 1.6x more gray matter than white matter
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neutogenesis in adults....
- Mature brain changes and adapts
- Neurogenesis (growth of new neurons) seen in olfactory bulbs and hippocampuses of adult mammals – adult neural stem cells created in the ependymal layer lining in ventricles and adjacent tissues
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interactions betwn experience & brain development
- Tinnitus (ringing in the ears) – produces major reorganization of primary auditory cortex
- Adult musicians who play instruments fingered by left hand have an enlarged representation of the hand in the right somatosensory cortex
- Skill training leads to reorganization of motor cortex
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