Physiololgy, Anatomy and Neurochemistry of Brain Circuits Flashcards
What is Behavioral. Neurobioology?
Behavioral NeuralBiology- the understanding of the physiology, anatomy and neurochemistry of brain circuits that generate that behavior
Explain the pattern of generation behavior starting from the cell.
Pattern:
* Cell-> Network-> Circuit->Behavior
How the cell generates activity and how activity of cells are represented at neuronal network level. The activity at the network is generates throughout a circuit in the brain, whic h will generate behavior.
What is the oldest written piece of evidence of the word brain in the world?
First writing of words brain in Hieroglyphics (by Edwin Smith)
-dates back to about 3400 years ago
Discuss the brief history of neuroscience including the importance of Santiago Cajal and Camilio Golgi. What was the Neuron Doctrine and what did it entail?
Santiago Cajal - neuroscientist who used Golgi stain(invented in 1873) to stain only a small percent of neurons, which allowed Cajal and Golgi to begin documenting somas and processes of a neuron
-1890-1910, the strain of neuron and drawing provided evidence for Neuron Doctrine
-Neuron Doctrine- there are neural units that are specialized and there are nerve fibers called cell processes and a synapse that connects these neurons (opposed to reticular theory: protoplasmic system tubes and pumps moves arms and legs)
Cajal and Camilio Golgi won the Nobel Prize together in 1906 with the concept of CNS (central nervous system) being made of discrete units
Who is Lord Adrian and what discoveries did he make ? Who is Scherrinton and why was he important?
Lord Adrian- Electrophysiologist who studied the activity of individual neurons
He observed the idea of activating neurons and when some threshold was hit the neuron would respond with maximal amplitude potential and it would be same amplitude every time
- *All or None Law of Neuronal siganaling : either the cell was not firing or was firing action potentials
-Due to his electrical methods of studying nerve and Brain activity He won the Nobel Prize, 1932
Scherrington: 1890’s- 1920’s introduced the concept of the “Synapse” (important development that ended reticular theory debate)
he won the Nobel prize with Adrian 1932)
Had the idea of REFLEX ARC - reciprocal innervation of opposing muscle groups; idea that you needed excitatory and inhibitory input to activate opposing muscle
“idea that muscles are governed by excitatory and inhibitory impulses “
-he thought about “enchanting loom (strings and fibers) in brain; millions of flashings shuttles weaving a pattern” (how he envisioned brain working)
What are reflexes? Where do they occurr in the body?
Reflexes:
-fast, stereotypical, inborn, protective actions
-Occur at spinal cord or brainstem levels
-May be monosynaptic or polysynaptic
What are the requirements for reflexes? Discuss the example Patellar reflex and mechanism behind it.
All reflexes require:
-Stimulus at receptor
-Sensory information relay
-processing at CNS level
-activation of motor response
-response of peripheral effector
ex:
Patellar reflex: physician taps the patella ( knee bone) and you have stretch of quadriceps muscle. The stretch receptors in the quadriceps muscle sends an excitatory signal into spinal cord. some fibers form neurons activate alpha motor neurons in same muscle, causing quads to contract. At the same time, alpha motor neurons will activate inhibitory neuron to shut off opposing alpha motor neuron and relax opposing muscle for response (foot jerk up to patella tap)
Discuss the history behind the neurotransmitter, including scientists that were a part of its discovery. Explain who Sir Henry Dale, Otto Loewi, and Sir John Eccles were and their achievements
The neurotransmitter (chemical communication at a synapse)
-Sir Henry Dale: first Identified Acetycholine as a possible neurotransmitter in PNS (won Nobel Prize with Loewi in 1936)
“Dale’s Principle”- one neuron, one transmitter (thought neurons can be differentiated by transmitter release; ex GABA, ACh)
Dale and Loewi- pals who discussed whether the synaptic connections transmitted information across another, either chemical or electrical transmission
-Otto Loewi: 1921, “Vagusstuff experiment ( studied frog hearts and stimulated the vagus nerve which slowed heart in frog)
-theorized something came from vagus nerve that had to slow down heart . The stuff had to be chemical.
This experiment helped prove that synapses use chemical transmission to help communicate with neurons.
-won Nobel Prize with Dale in 1936.
-Sir John Eccles : Favored Electrical synaptic transmission in CNS
-He was a student of Scherrington
Did a series of experiments that proved synapse was an electrical connection (try and prove Dale and Loewi wrong)
-1951, critical experiment that confirmed Chemical transmission in CNS (and PNS)
(won Nobel Prize with Hodgkin iand Huxley, 1963)
Later found that there are specific proteins in synapse that form electrical conduits , so Eccles, Dale and Loewi were all right, since a synapse uses both chemical and electrical neural transmission
Discuss the scientists who discovered the action potential
The Action Potential
- Alan Hodgkin and Andrew Huxley (1952)
-they used squid giant axon that they stuck an electrode inside axon, and found interior is negative; When action potential occurs, it becomes very positive. After AP, it drops below original voltage and then recovers which corresponds to wave of activity of voltage moving down axon
-*Came up with Mathematical model that describes how action potentials in neurons are initiated and propagated
(Nobel Prize with Eccles 1963)
Who were the scientists that studied Neural coding and activity in different brain areas ? Motor and visual cortex? Anesthesized animals? Cerebellum?
Neural Coding (1950s)
Vernon Mountcastle- studied motor cortex in anesthetized monkeys (to understand when neurons fire in neuromotor cortex, how it generates movement and behavior.
-D Hubel and T Wiesel- studied Visual cortex, anesthesitized cats and monkeys( to figure how neurons represent visual stimuli around you)
-Ed Evarts- Motor cortex, awake monkeys
-Eccles, Ito, Szentagothai- Cerebellum (to understand how neurons do their magic)
-Thach and Llinas- Cerebellum
Discuss the electrophysiological Techniques that occurred in neuroscience and the scientists that came up with these ideas
Electrophysiological Techniques:
-Luigi Galvani (1737-1798) “animal electricity” :
-considered the Founder of of Electrophysiology;
Found that animal electricity generated muscle movement and behavior
Used frog body (Lower half) and exposed wires in experiment
Experiment (insert wire through vertebral canal in frog and touch body with lancet, causing legs to contract and sparks from electrical machine)
-EEG(electroencephalograph) - 1924, Hans Berger (from his son) wired up his son and recorded electrical activity in brain
“Brain generated constant activity”
-Field Potentials (localized recording, like Berger)
-Intracellular Recording (within brain )
1931, squid giant axon
-Intracellular Recording
1951, CNS neurons
-Extracellular Recording
-1950s
-Microiontophoresis (allowed us to deliver known quantities of transmitters or drugs onto neurons)
1967
-Patch Clamp (allows people to understand the current of individual channels or small groups)
1980s
-Optogenetics (manipulate neuronal activity with light being shone)
Describe what happens when an action potential is propagated. How does frequeny of spikes change with action potential?
Action potential:
-Influx of Na+
-Outflux of K+
-An action potential is a self-regenerating electrical pulse traveling along the axon (either unmyelinated or when hopping to node to. node of Ranvier when myelinated)
*The greater the action potential, the more spikes arre generated (> frequency of spikes are generated)
Process: initial segment at Node of Ranvier- large density of Na+ and K+ channels
when voltage reaches threshold (by concentration of Channels), Na+ channels open up and Na+ ions rush in, which drives membrane voltage into positive region. positive voltage drives K+ channel to open which causes K+ ions to rush outside cell and bring back membrane potential below initial membrane potential which then recovers
inside of a cell has a membrane potential of -68 mV
glutamate binds to receptor or GABA binds to receptor, they will generate excitatory post-synaptic potentials or inhibitory post-synaptic potentials( raise the voltage inside the cell or decrease the voltage)
What is the function of Patch Clamp Recording and how does it work?
Patch Clamp Recording - study the activity of Channels or receptors
- used to study Synaptic Inputs- EPSPs/IPSPs
-Drug responses (study responses of channels to drugs)
process: remove mouse brain, cut into slices and dissociate neurons of a slice. Then take a glass pipette (heat glass) and move it to edge of cell, where glass sticks to lipid membrane. Give suction to create seal between lipid and glass
Now do Cell-attached recording: allows you to record currents going across patch of membrane or inside cell)
can do whole cell recording, outside-out patch and inside out patch
What occurs in Intracellular Recording and why is it important
Intracellular Recording - Interrogate how the ENTIRE cell is processing information
- Active and passive membrane properties (channels, resistance capacitance)
-Excitability
-Channel properties
-Transmitter responses
Slice up brain, put it in chamber with artificial cerebrospinal fluid and sugar sucrose and O2 to keep it alive. Large electrode to puncture cell, and read voltage inside cell; inject electricity current into the cell. The way membrane responds below threshold helps you understand how excitable neurons are and how easily neurons discharge and drugs that affect it. Can increase electrical impulses and generate APs.
stimulate microeletrode to inject current
-record microelectromechanical to measure membrane potential
What is Extracellular Recording and how does it work ?
Extracellular Recording: Record activity of a single neuron or many neurons at once
Ex: take a platinum tungsten electrode that is covered in quartz glass (or resistive compound) and stick the electrode in brain cell to listen to action potentials.
Different types of electrodes
-Generate things that look like daggers with individual pad to record many cells at once in linear form
- bed of nails: hundreds of electrodes sticking up, take wafer and flip over and insert into brain to record neurons in plane form (ex :neurons encode information)
-tetrode form- record neurons from multiple pads or electrodes to , differentiate who is firing Action potential
