Exam 2 Flashcards
How did Loewi’s experiment show chemical communication across a synapse?
He electrically stimulated a heart in one container and transferred the fluid in that container to a heart in another container and observed that both hearts reacted the same way; one reacting to the electrical impulse and one reacting to nothing more than fluid.
What is a neurotransmitter?
chemical with an excitatory or inhibitory effect when released by a neuron onto a target
What are the criteria for determining a neurotransmitter?
- Must be synthesized in the neuron or otherwise be present in it
- When the neuron is active, the transmitter must be released and produce a response in some target
- The same response must be obtained when the transmitter is experimentally placed on the target
- A mechanism must exist for removing the transmitter from its site of action after its work is done
What are the parts of a synapse?
Microtubule - transport structure that carries substances to the axon terminal
Mitochondrion - organelle that provides the cell with energy
Synaptic vesicle - round granule that contains neurotransmitters
Storage granule - large compartment that holds synaptic vesicles
Postsynaptic receptor - site to which a neurotransmitter molecule binds
Post synaptic membrane - contains receptor molecules that receive chemical signals
Synaptic cleft - small space separating presynaptic terminal and postsynaptic dendritic spine
Presynaptic membrane - encloses molecules that transmit chemical messages
What are the five steps of neurotransmitter transmission?
- Synthesis - neurotransmitters are created from precursor modules
- Packaging and Storing - neurotransmitters are moved into vesicles and await the arrival of an action potential
- Release - in response to an action potential, the transmitter is released across the membrane by exocytosis
- Receptor Action - the transmitter crosses the synaptic cleft and binds to a receptor
- Inactivation - the transmitter either diffuses away, is enzymatically broken down, is taken into the neuron terminal, or is taken by an astrocyte
What is the role of autoreceptors?
Part of the negative feedback loop, helps the neuron to manage output
What is the role of electrical synapses?
To provide faster information processing
What is the role of chemical synapses?
Show plasticity; they can amplify or diminish a signal sent from one neuron to the next; plays a role in learning
What are the types of chemical synapses?
Dendrodendritic - dendrites to dendrites
Axodendritic - axon terminal to dendritic spine
Axoextracellular - terminal with no specific target; release outside cell
Axosomatic - axon terminal to cell body
Axosynaptic - axon terminal to another terminal
Axoaxonic - axon terminal to another axon
Axosecretory - axon terminal to tine blood vessel
Excitatory vs Inhibitory synapse?
Excitatory - dense material on membranes, round vesicles, wide cleft, large active zone
Inhibitory - sparse material on membranes, flat vesicles, narrow cleft, small active zone
Describe a Renshaw Loop?
The main motor axon projects to a muscle and its axon collateral remains in the spinal cord to synapse with. The Renshaw interneuron contains the inhibitory transmitter glycine which acts to prevent motor neuron overexcitation. Both the main motor axon and its collateral terminals contain ACh.
How is ACh formed?
Acetyl CoA and ChAT bind choline and acetate
How is ACh degraded?
AChE detaches acetate from choline in the synaptic cleft
How are amine neurotransmitters formed?
Tyrosine hydroxylase changes tyrosine into L-DOPA which is then made into dopamine (DA), norepinephrine (NE), and epinephrine (EP)
What is a rate-limiting factor?
any chemical in low supply that restricts the pace at which another chemical can be synthesized
What disease can L-Dopa be used to help treat?
Parkinsons
What are two amino acid transmitters?
glutamate, gamma-aminobutyric acid (GABA)
How are peptide neurotransmitters created?
From mRNA in the neurons nucleus
Where are peptide neurotransmitters created?
Some in the axon terminal but most on the ribosome
Which amino acid neurotransmitter is the main inhibitory NT?
GABA
Which amino acid neurotransmitter is the main excitatory NT?
glutamate
What are the lipid neurotransmitters?
Endocannabinoids
What are the neurotransmitter gasses?
NO, CO, H2S
How do ionotropic receptors work?
When activated, embedded transmitter proteins bring about direct, rapid changes in membrane voltage
How do metabotropic receptors work?
When activated, embedded membrane receptor proteins trigger associated G proteins, exerting indirect effects (A) on nearby ion channels or (B) in the cell’s metabolic activity
What is a secondary messenger?
chemical that initiates a biochemical process when activated by a NT (first messenger)
What is an advantage to metabotropic receptors?
Amplification cascade
What is the main neurotransmitter for the PNS?
ACh
What are the main neurotransmitter for the SNS?
ACh and NE
What are some important facts for the Cholinergic system?
Active in maintaining attention, death of these neurons and decrease of ACh in neocortex thought to be linked to alzheimers
What are some important facts for the dopaminergic system?
active in maintaining normal motor behavior, loss of dopamine is related to Parkinson’s, thought to be most linked to addictive drugs and behavioral addictions, increases in dopamine activity linked to Schizophrenia, decreases may be linked to ADHD
What are some important facts for the noradrenergic system?
active in maintaining emotional tone, decreases thought to be linked to depression, increases thought to be linked to mania, decreases thought to be linked to ADHD
What are some important facts for the noradrenergic system?
changes are thought to be linked to OCD, tics, and Schizophrenia, decreases are linked to depression, abnormalities in brainstem 5-HT neurons linked to sleep apnea and SIDS
What is habituation?
learned behavior in which the response to a stimulus weakens with repeated presentations
What is sensitization?
learned behavior in which the response to a stimulus strengthens with repeated presentations
Where is the blood brain barrier not as secure?
The brainstem area postrema and the pineal gland to induce vomiting in exposure to toxic substances and for enabling hormones to regulate the day-night cycles, respectively
Where are the 6 points for drugs to affect synaptic function?
Synthesis, Packaging and storing, release, receptor interaction, reuptake, degradation
What is an agonist?
Substance than enhances neurotransmitter function
What is an antagonist?
substance that blocks neurotransmitter function
What are some ACh agonists?
choline-rich diet (diet based increase), black widow spider venom (release), nicotine (receptors)
What are some ACh antagonists?
botulin toxin, curare
What are the 3 main types of tolerance?
Metabolic tolerance - number of enzymes needed to break down increase
Cellular tolerance - brain cell activities adjust to minimize effects
Learned tolerance - people learn to cope with the effects
What is drug sensitization?
increased responsiveness to successive equal doses
What drug affects the Adenosinergic system?
caffeine
What drug affects the cholinergic system?
nicotine
What drug affects GABAnergic system?
alcohol
What drug affects the glutamatergic system?
PCP or ketamine
What drug affects the dopaminergic system?
cocaine, meth
What drug affects the serotonergic system?
LSD, psilocybin
What drug affects the opiodergic system?
opium, morphine, heroine
What drug affects the cannabinergic system?
THC
What are the different dose level affects for GABAnergic agonists?
Low - reduce anxiety
Medium - sedate
High - anesthetize or induce coma
Why is it dangerous to drink alcohol and take GABAnergic agonists?
They affect the channel at different locations and can drastically increase the flow
How do dopamine agonists affect the synapse?
They prevent reuptake
How do dopamine antagonists work for treating schizophrenia?
They decrease the amount of dopamine that can bind to the receptor sites and thus decrease the amount of dopamine the brain is exposed to
How do serotonergic drugs affect the synapse?
They block the transporter protein and prevent reuptake
What is disinhibition theory?
explanation holding that alcohol has a selective depressant effect on the frontal cortex, while sparing subcortical structures responsible for more instinctual behaviors
What is behavioral myopia?
“nearsighted” behavior displayed under the effects of alcohol, wherein local and immediate cues become prominent; remote cues and consequences are ignored
What is the fast acting stress hormone?
Epinephrine
What is the slow acting stress hormone?
Cortisol
What are place cells?
neurons maximally responsive to specific locations in the world
What does an EEG measure?
electrical activity of the cortex
What did we learn from EEGs?
- EEGs changes as behavior changes
- An EEG recorded from the cortex displays an array of patterns, some rhythmical
- The living brain’s electrical activity is never silent
What is a CT?
X-ray technique that produces a static 3D image of the brain in cross-section
What is an MRI?
technique that produces a static 3D image by passing a strong magnetic field through the brain followed by a radio wave to see how it affected the hydrogen atoms
What is an fMRI?
MRI technique that measures brain activity indirectly by measuring blood flow during cognitive testing or at rest
What is a PET scan?
imaging technique that detects changes in blood flow by measuring changes in the uptake of compounds such as glucose or oxygen; used to measure metabolic activity of neurons
What are the advantages to each scan?
EEG - short time periods
EEG and optical tomography - only examine cortical structures
Others - resolve deep brain structures
What is microdialysis?
technique used to determine the chemical constituents of extracellular fluid in freely moving animals
Why is BDNF important?
plays important role in brain plasticity, Met allele has an 11% hippocampal volume reduction and poor episodic memory, Val allele shows higher rates of neuroticism and anxiety
What are three perspectives on the relationship between brain development and behavioral development?
- Predicting behavior from structure
- Guessing what neural structures will have matured based on behavioral changes
- Study of factors affecting both behavior and neural structures
What are the two types of neural cells?
Interneuron and Pyramidal neuron
What are the two types of glial cells?
Oligodendroglia and Astrocyte
What are neurotrophic factors?
chemical compound that supports growth and differentiation in developing neurons and may act to keep certain neurons alive in adulthood
What are tropic molecules?
molecules that help guide cells during migration
What are the 7 stages of Brain Development?
- Cell birth
- Neural migration
- Cell differentiation
- Neural migration
- Synaptogenesis
- Cell death and synaptic pruning
- Myelogenesis
What is a radial glial cell?
path-making cell that a migrating neuron follows to its appropriate destination
Cortex normally thins between ages 5 and 20 but the major language area increases in gray matter
Simpler brain areas mature faster than more complex ones
What are unique aspects of Frontal Lobe development?
The frontal lobe is particularly sensitive to epigenetic influences
The trajectory of the frontal lobe development correlates with adult intelligence (reduction in cortical thickness and the increase in connectivity between the medial regions of the frontal lobe)
Why is grasping important in neuroscience research?
a group of axons from the motor cortex myelinate around the same time the grasping motion appears
When in more enriching environments neural connections are more abundant
Adolescence shows a critical period most likely due to the gonadal hormones and connections are increased and improved and cortical thickness is decreased
Sex differences can be seen in the brain due to different amounts of receptors for the respective hormones in different areas
The worst time for injury is during the last half of the intrauterine period and the first couple of months after birth
What is anencephaly and what disease is correlated with?
failure of the forebrain to develop, Spina Bifida
Other abnormalities
Schizophrenia - abnormal connections in hippocampus
Autism - poor neural pruning
Retardation and abnormal synaptic development
