Chapter 5 Midterm 2 Flashcards
What was a historical controversy in neuroscience?
Whether communication in the brain was electrical or chemical
What experiment did Otto Loewi perform?
Loewi put a frogs heart in a saline bath, then electrically stimulated the vagus nerve, at the same time he transferred the fluid in this container to another where a heart was immersed but not electrically stimulated. He then recorded both heart rates and found the heart rate of the electrically stimulated heart slowed after stimulation and the heart that wasn’t electrically stimulated also slowed after fluid transfer, proving that neurotransmission was chemical in nature as a chemical (acetylcholine) released from the vagus nerve into the fluid caused the second heart to slow down. Did the reverse experiment to conclude noradrenaline speeds up the heart
What three findings have helped researchers understand parkinsons neural basis?
- That the substania nigra is a small midbrain nucleus that degenerates and in the brain of a patient who had parkison symptoms on one side of the body, the opposite side had the SN degrading
- Chemical examination of the brain of ppl w parkinsons showed that disease symptoms appear when dopamine levels had a 90% loss in the basal ganglia, today is aroudn 80%
- we found that injecting a neurotoxin called 6-hydroxydopamine into rats destroyed dopamine containing neurons and produced symptoms of Parkinson’s disease.
When parkinsons is diagnosed what percent of neural damage is done?
60-70%
How did joy smell parkinsons?
because parkinsons has a chemical signal
When a neuron dies it is not replaced except where?
the dentate gyrus of hippocampus and in the striatum next to the ventricle
How was parkinsons tried to be cured?
Treat parkinson’s with juvenile cells that were destined to be dopaminergic but the source of cells were aborted fetuses, was abandoned and didn’t work as the disease just kills the neurons
What were the frozen addicts?
Addicts that went to sweden for surgery, got fetal tissue and had a benefit. They didn’t have parkisnosn but they took a drug that killed the dopaminergic neurons, got new neruons and it relieved symptoms
what are the parts of a synapse ?
There’s a postsynpactic neuron and presynaptic terminal which leads into a cell body. The cell body contains a presynaptic membrane which has protein mlcls that transmit chemical messages. Past the membrane you have a mitochondrion, and then a synaptic vesicle which contains neurotransmitters, these vesicles can be stored in bunches in storage granules. The vesicles release neurotransmitters onto the synaptic cleft where they enter neurotransmitter channels on the postsynaptic receptor where they bind, the postsynaptic membrane contains protein mcls that receive chemical messages.
What is the tripartite synapse?
The presynaptic membrane, post synaptic membrane, and glial cell (usually surrounding astrocytes)
What does anterograde mean?
That the information flows from presynaptic to postsynaptic
What are the five steps synaptic transmission takes place?
- Synthesis- have to make neurotranmitter from precursor modules
2- pack transmitter into vesicle and store it there
3- then the neurotransmitter is released through exocytosisin response to an action potential
4- The transmitter crosses the cleft and interacts with the receptor, which effects the post synaptic cell
5- Inactivation- The transmitter diffuses away, is degraded, taken into the neuron terminal, or taken by an astrocyte
What are receptors?
proteins
Why would plants make substances that have drug effects?
It’s a form of reproduction for plants seeds to move, we found out how to synthesize and make large quantities of it
Why do drugs work?
Because we have receptors for opiates, because you make neurotransmitters called opiodes which the mlcls from these plants can fit into these receptors and work.
What two receptors do we have that allow cannabis to work?
CB1 and CB2, which correspond to molecules anandamide and 2 AG
What drug does not work by receptors?
alcohol
How are neurotransmitters released?
When an action potential reaches the terminal it open calcium channels,
the incoming calcium ions bind to proteins forming a complex, this complex binds to vesicles releasing some from filaments and inducing others to bind to the presynaptic membrane and empty their content by exocytosis onto the postsynaptic receptor sites
What is an omega body?
Is when the fusion pore widens, membrane of synaptic vesicle fuses with presynaptic membrane
How is the neurotransmitter released from the presynaptic cell bodyafers its at the presynaptic membrane?
the vesicle binds to the presynaptic membrane by calcium opening a fusion pore, the fusion pore widens and the membranes of the synaptic vesicles fuses with presynaptic membrane, the proteins on the initial vesicle get removed, and the neurotransmitters get released from the presynapse
What are the four types of inactivating a neurotransmitter?
1: Diffusion- neurotransmitter simply diffuses
away from the synaptic cleft and is no longer available to
bind to receptors
2: Degradation: Enzymes in the synaptic cleft break down the neurotransmitter: these pieces are usually recycled/reused
3: Reuptake: the transmitter is brought back into the presynaptic axon terminal is degraded by enzymes, and then used again by being taken into the terminal
4: Astrocyte uptake: nearby astrocytes take up the transmitter, also stores them for re-export to the axon terminal- reason why the tripartite synapse is so important.
What are the 7 variety of synapses?
Dendrodendritic, Axodendritic, Axoextracellular, Axosomatic, Axosynaptic, Axoaxonic, axosecretory
What is a Dendrodendritic synapse?
Two different dendrites come in close contact and communicate
Whats axoextracellular synapse?
The end of an axon doesn’t make a synpatic connection but just releases it’s neurotransmitters and it floats around and interacts with receptors it bumps into.
Whats axosomatic synapse?
When axon terminal makes contact on the cell body, usually inhibtory
What’s axosynaptic?
The axon terminal makes synaptic contact to another synaptic terminal
What’s axoaxonic?
rare, axon terminal ends on another axon
What’s Axosecretory?
axon terminal end son tiny blood vessel and secretes transmitter directly into blood
What’s the difference between hormones and neurotransmitters?
Just the distance it travels, hormones travel longer distance before it interacts with it’s receptor, hormones have to travel several feet to an internal organ its hormone, if it travels 200 angstroms is a neurotransmitter
What proteins mediate electrical synapses?
Gap junctions
What are electrical synapses?
Two membranes come so close together that hemichannels go through both membranes and substances cross from one cell to another, fluid can travel between them, allow action potentials to pass from one nueron to the next directly
How do electrical synapses differ from chemical?
They’re very fast (flies have them), but less plastic so you can’t learn new info (can’t really teach fly something new)
How do chemicals synapses effect us?
Make us plastic, can learn
What are features of inhibitory synapses?
Typically located on cell
body- very close to initial segment
– Flat vesicles
– Sparse material on
membranes
– Narrow cleft
– Small active zone
What are features of excitatory synapse?
Typically located on
dendrites
– Round vesicles
– Dense material on
membranes
– Wide cleft
– Large active zone
Which synapse is more likely to fail? excitatory or inhibitory?
excitatory, as it’s mor eplastic, breaks more important so inhibtory don’t fail
What is the four criteria for a neurotransmitter?
1: Transmitter must be synthesized or present in a neuron
2: When released, the transmitter must produce a response in the target cell
3: The same receptor action must happen if you squirt it on the receptor experimentally
4: There must be a mechanism for removal after the transmitters work is done
All motor neurons leaving the spinal cord use what as a neurotransmitter?
acetylcholine
What is the renshaw loop?
Each motor axon has a main axon projecting to a muscle (leaving spinal cord) and has an axon collateral within the spinal cord that synapses on a nearby CNS (renshaw) interneuron releasing acetylcholine, the interneuron contains the inhibitory transmitter glycine which stops motor neuron excitation as it in turn synapses on the motor neurons cell body creating a loop