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PSYC 2012: Midterm 2
Ions critical to cell function (4)
|
Na+ (sodium)
K+ (potassium)
Ca++ (calcium)
Cl- (chloride) |
Phospholipid bilayer & what can cross it?
|
Cell membrane is a phospholipid bilayer that separates extracellular fluid from intracellular
-Small molecules (oxygen, co2), lipids, steroids
-Non-polar and hydrophobic |
Channel:
Gated channel:
Pump: |
Channel: Ions can cross through that are appropriately shaped
Gated channel: changes shape to allow passage
Pump: sodium/potassium |
3 products made in the nucleus
|
-Proteins for neuron functioning (receptors and enzymes)
-Genes/ intracellular proteins
-Neurotransmitters or building blocks for NTs |
Process of protein synthesis
|
-Part of DNA strand unwinds
-Gene serves as template
-Copy is made (mRNA) & leaves nucleus
-ER & ribosomes transform the mRNA into amino acids
-Amino acids make up polypeptide chains/ proteins |
Francis Crick
|
-Scientist credited with discover of DNA
-Used LSD to perceive the double helix shape |
Huntington's Disease |
-Genetic disorder
-Buildup of abnormal protein- huntington
-Development, memory
-Cell death in brain
Cortex & basal ganglia |
Epilepsy
|
-most common neurological disorder
-abnormal electrical activity: which spreads in the brain to initiate a seizure
-sensory overstimulation
-aura, abnormal movements, loss of consciousness |
Luigi Galvani
|
-Frog legs hanging on a wire twitched during a lightning storm
-Sparks of electricity activated the muscle
-Electrical current applied to a dissected nerve= muscle contraction |
Electrodes
|
-Touching the neurons with the tip of a charged electrode can cause a current flow through a neuron
Stimulus of the nucleus accumbens, amygdala
-Can be used to measure cellular or structural activity |
2 important influences for electrical activity in neurons
|
-Concentration gradient/diffusion: chemical pressure for separation
-Electrical/voltage gradient: like chargers repel |
Neuron is more ____ inside than ____
Resting potential? |
-inside
-outside
-70 mV |
Inside neuron vs outside at resting potential (A-, K+, Na+, Cl-)
|
Outside: very few A-, low K+, high Na+, high Cl-
Inside: Lots of A-, high K+, low Na+, low Cl- |
Driving forces during resting potential (K+, Na+, Cl-)
|
K+: moderate chemical force to LEAVE neuron
Na+: strong chemical and electrical force to ENTER neuron (strongest drive)
Cl-: very weak chemical pressure to ENTER |
Excitation vs Inhibition
|
-Excitation: signals make the inside of receiving neuron less negative- DEPOLARIZATION
-Inhibition: make the inside of the receiving neuron more negative (hyper polarization) |
EPSP |
-Excitatory post-synaptic potential
-Depolarization=less negative
-Glutamate |
IPSP |
-Inhibitory post-synaptic potential
-Result of an inhibitory neurotransmitter signaling the post-synaptic neuron
-Hyperpolarization
-GABA |
Single "graded-potential"
|
-slight changes in the charge of the membrane potential
-localized to that part of the neuron/dendrites
-temporary effect |
The Action Potential
|
-Small stimulation results in localized graded potential
-Action potential lasts about 1 ms
-membrane potential is reversed forming an electrical wave
-large, rapid influx of Na+ resulting in depolarization
-K+ channels open, K+ rushes out, re-polarizing the neural membrane |
Threshold |
-50 mV |
"All or none"
|
For a given neuron, an AP is always the same size, and either happens fully or doesn't
|
size of action potential is always the ___ only the rate varies with ___
|
same
stimulus intensity |
Voltage-sensitive ion channels
|
AKA: voltage-gated ion channels
-Open due to specific change in membrane potential
-Voltage sensitive Na+ and K+ channels: axon hillock and axon
-Voltage sensitive Ca++: axon terminals |
Saltatory Conduction
|
Myelin: made by glial cells
Node of Ranvier: gap between myelin cells, it enables saltatory cod
-The flow of the depolarization and repolarization wave |
Multiple Sclerosis
|
Disease that involves the deterioration of myelin sheaths on axons in brain, optic nerves, spinal cord
--Autoimmune disorder in which our immune system targets its own body in a way for damage to persist |
Electrical synapses
|
-contain gap junctions which allow for ions to flow from the presynaptic neuron to the postsynaptic neuron
-allows: ions, glucose, oxygen, amino acides |
|
|
A. axon
B. presynaptic terminal
C. presynaptic membrane
D. synaptic vesicles
E. synaptic cleft
F. postsynaptic membrane
E. dendrite spine |
4 steps of neurotransmission
|
1) synthesis and storage
2) release
3) binding
4) deactivation |
Synthesis and storage
|
-Neurotransmitters are derived in 2 general ways: axon terminal and cell body
|
Excitatory receptor actions (ionotropic and metabotropic)
|
ionotropic: allows + ions to flow into neurons
metabotropic: stimulate activity of nucleus (gene transcription), second messenger systems |
Binding
|
Neurotransmitter binds at receptor on target tissue
|
Deactivation |
Neurotransmitter is removed from the synapse so it does not signal forever
|
Inhibitory (ionotropic and metabotropic)
|
ionotropic: allow negative ions to flow into neuron
metabotropic: inhibit activity of nucleus, second messenger systems
|
Agonists vs antagonists
|
Agonists: drugs that increase, release or mimic a specific neurotransmitter
Antagonists: drugs that decrease the release, availability or block a specific neurotransmitter |
cfos |
-Recent neuronal & cellular activity in rodents
-immediate early gene |
Electricity
|
Flow of electrons from an area that contains a higher charge (more electrons) to a body that contains a lower charge (fewer electrons) |
Presynaptic vs postsynaptic
|
Pre: sending the signal into the synapse (site of communication)
Post: receiving in the synapse |
Summation (temporal or spatial)
|
Voting of excitatory and inhibitory potentials
Temporal: based on timing, when are these signals occurring in relation to each other
Spatial: based on where they are at |
Refractory periods
|
Absolute: no matter how much stimulation a neuron is getting the neuron cannot initiate another potential (during depolarization phase)
Relative: During hyper polarization, when another action potential can be generated it requires more energy than usual
|
Acetylcholine (ACh)
|
Excitatory (mostly)
muscle activity, Autonomic nervous system (body)
Excitatory for muscles, except heart
Attention functions (brain)
Wakefulness (brain)
Memory (brain)
Agonists: Nicotine, Alzheimer’s Disease
Schizophrenia? |
Dopamine (DA)
|
-Mostly excitatory
-Motor behavior, reward processing, attention, wakefulness, addiction
-Parkinson's Disease
-Agonists: amphetemines, cocain
-Antagonists: antipsychotics |
Serotonin (5-HT)
|
-Mostly excitatory
-Moods: anxiety, depression, wakefulness
Agonists: antidepressants, LSD, MDMA, 5-HTP
Antagonists: Atypical antipsychotics, reserpine |
Norepinephrine (NE)
|
-Mostly excitatory
-Stress stimulates NE release in forebrain, increases vigilance
-Agonists: SNRIs, ADHD meds
-Antagonists: ADHD meds, beta blockers, PTSD |
Glutamate |
-Main excitatory NT in brain
-Magnesium
-Hypoxia/ hypoglycemia
-Agonists: D-cycloserine
Antagonists: DXM, PCP, Ketamine |
GABA
|
-Main inhibitory NT in brain
-Withdrawal
-Agonists: Benzodiazephines, alcohol, barbituates
-Antagonists: uncommon, reversal drugs |