Unit 1 Flashcards
What is trepanation?
a surgical intervention where a hole is drilled into the skull exposing the duramatter
- aka a craniotomy
What is a trepanation where the bone isn’t replaced?
craniectomy
What is a trepanation/craniotomy used for?
- used to relieve pressure and treat health problems -surgical access for intracranial pressure monitoring
- to treat epidural and subdural hematomas
What is a hematoma?
- a solid swelling of clotted blood
What is the brain made of?
network of neurons and glia
How do neurons communicate?
-electrical and chemical signals
What is the neuronal pulse called?
AP
What is aphasia?
partial or complete loss of language abilities
Which aphasia is known as fluent or sensory aphasia?
Wernicke’s Aphasia
What are the symptoms of Wernicke’s aphasia?
- fluent speech that makes no sense
- poor comprehension
Which aphasia is known as motor aphasia, non-fluent aphasia, or production aphasia?
Broca’s Aphasia
What are the symptoms of Broca’s aphasia?
- non-fluent speech, struggle to produce words
-telegraphic (agrammatical) - speech makes sense
- good comprehension
What do the different types of aphasia prove?
localization of function
What is localization of function?
- different areas of the brain control different functions
How does aphasia prove localization of function?
- damage in the different areas of the brain have different results
Where does wernicke’s aphasia occur?
- temporal lobe
Where does broca’s aphasia occur?
- frontal lobe
-cerebral cortex
What is a stroke?
- a rapid loss of brain functions due to a loss of blood supply
What are the types of strokes?
-ischemic
-hemorrhagic
What is an ischemic stroke?
- a blockage of blood supply
What is a hemorrhagic stroke?
blow out to blood supply
What are transient ischemic attacks (TIAs)
- mini strokes
What are the symptoms of a stroke?
-depends on the area of the brain it effects
What did Camillo Golgi do?
- developed the Golgi stain
- reticular theory
What did Ramon y Cajal do?
- grandfather of neuroscience
- neuron doctrine
- discovered the synaptic cleft
How wide is the synaptic cleft?
20 mm wide
What is the site of synaptic contacts?
dendritic spines
Are all axons milenated?
no, but most are
What does myelin do?
- increases speed at which AP travels down the axon
What are the non-neuronal cell types?
-mast cells
- microglia
-macroglia (everything below= micro)
- astrocytes
-oligodendrocytes
-radial glia
-Schwann cells
-satelite glial cells
What are astrocytes?
- chemical environment regulation
- buffer extracellular K+ levels
- modulate and control blood flow in the brain
- CNS
-sucks up K+
What are Mast cells?
- Immunoactive cells in the CNS
What are microglia?
- specialized macrophages
What are oligodendrocytes?
myelin
CNS
What are radial glia
-neuron progenators
-stem cells
- scaffolds
-highways
-CNS
What are Schwann cells?
-myelin in the PNS
What are neuronal circuts?
- a population of neurons interconnected by synapses and supported by non-neuron cells
What do neuronal circuits do?
- carry out specific functions when activated
-underlies all functions of the nervous system
-simple or complex
How do neuronal circuits work?
- input- processing- output
-afferent to efferent
What are examples of simple circuits?
- stretch reflex (knee jerk)
- leg withdrawal reflex
What do efferent signals do?
- carry nerve impulses away from the CNS
What do afferent signals do?
- carry nerve impulses from receptors/sense organs towards the CNS
What is a seizure?
-abnormal neuronal activity
What is epilepsy?
- chronic condition of repeated seizures
What is an EEG and what does it do?
-electroencephalography
- measures brain electrical signals
How does an EEG work?
- shows voltage fluctuations from ionic current flows by large groups of neurons
- displaying synchronous activity by many neurons in similar spatial orientation
What is an EMG and what does it do?
- electromyography
-measures muscle signals
What is an EKG and what does it do?
- electrocardiography
-measures heart signals
What is a current?
energy flow between one area and another
What are seizures caused by?
chronically overexcited neurons
- you can see them on an EEG even when they aren’t happening
What are the surgical treatments for epilepsy?
- remove the focal point
- remove the corpus callosum
What does removing the corpus callosum do for seizures?
- limits how seizures spread because the two sides can’t communicate
What do drugs do for epilepsy?
- cause a use-dependent increase in the inactivation time of voltage-dependent Na+ channels
-Enhance GABAergic inhibition
Does an axon’s membrane have a charge?
yes
What does a membrane’s charge do?
- allows for AP to be induced and for APs to travel down the axon without a loss of signal
What has to happen for signals to be transmitted across the axon’s membrane
-ions must cross the membrane
- membranes are too thick for ions to flow through so Ion channels are neccessary?
Do all ions flow in the same direction?
- no
-Different ions flow in different directions
What are the key characteristics of ion channels?
- they are specific for particular ions (element, not just charge)
-integral membrane potentials - they can open and close
- don’t physically ions, they move down a gradient
How do ions move through the ion channels?
- Move passively down a gradient
-Electrical and chemical gradients
-Different ions move in different directions across the membrane
-ions travel in the direction of the electrochemical gradients
What is membrane potential?
- the difference in electric potential between interior and exterior of the cell
-what you measure
What dictates the direction an ion flows?
- the driving force and the concentration/electrical gradients
If an ion is positively charged and the gates are open what would happen to the membrane potential?
- membrane potential would be more positive
If an ion is negatively charged and the gates are open what would happen to the membrane potential?
- would become more negative
What is Vm
membrane potential
What does more ions do to the driving force?
-more ions= stronger driving force
What is equilibrium potential?
- membrane potential where the ion is at electrochemical equilibrium
- for a single ion
-when concentration and electrical driving forces are equal and opposite
What is wrong with the Nerst equation?
- it doesn’t equate forpermeability
- Most neurons are permeable to more than 1 ion so Vm doesn’t normally match Eion
What is the typical mammalian membrane potential?
-40 - -90
How many ions move to generate membrane potential?
- very few ions move to generate membrane potential
- no immediate effect on the concentration gradient
- over a long time (especially in active neurons) Na+ and K+ can run down
Does the NaK+ Pump actively drive AP?
no
What drives AP
ion channels
What does the NaK+ pump do?
plays an important role in maintaining concentration gradients OVER TIME
What are ion transporters?
- integral membrane proteins
-selective for specific ions
-actively moves ions across the membrane - moves ions opposite to the concentration gradient
What cells regulate K+
- astrocytes buffer extracellular K+ levels
- they link together to widely regulate K+
How does astrocyte-neuron communication through Calcium and gliotransmitter signaling in the tripartite synapse work?
-gliotransmitters leave astrocyte through transporter and bond to their receptor on the neuron
- neurotransmitters leave the neuron and bind to gq proteins on astrocyte
- Inside the astrocyte PLC is coming through GQ protein
- pLC to PIP2 to IP3 to ER to Calcium
-glial cells can regulate extracellular milieu and buffer K+
What is AP controlled by?
-voltage-gated ion channels
-ion permeability and conductance
- current flow
-inactivation of voltage gated channels
What is ap conduction influenced by?
- passive and active components
-myelin
When does undershoot occur?
after repolarization
What is hyperpolarization?
-when the membrane doesn’t immediately return to resting potential bc voltage-gated channels are open
- K+ is flowing out through leak channels and since K+ is flowing out the positive ion is leaving the membrane becomes more negative
How does the membrane go back to normal after the undershoot?
leak channels
What is overshoot?
- When membrane potential reaches the positives
-doesn’t quite reach Na+ potential bc K+ channels kick in and the voltage channels overlap - Na channels close and K+ starts leaving
What is the rising phase?
- when Na+ and K+ channels are open
-Na+ flowing in is what makes the membrane less negative, depolarizing it
-once rising for a little while before it can start again
What is the falling phase?
- where re-polarization is happening
- K+ is flowing out of the cell
- K+ pumps have been on the entire time just too slow to cause a response until now
- Since K+ is slower it helps control AP and allows cell to be open longer
What are the phases of AP?
- Threshold: K+ going in and out at an equal rate
- Rising: K+ going out, Na+ going in
- Falling: K+ going out only
- Threshold
What mediates the rising phase?
- voltage-gated Na+ channels
- these are different from leak channels open at rest
What are the advantages of the voltage-gated channels?
-can open and close very fast
- has an ion-selective pore, a voltage-gated sensor that opens the pore via an activation gate in the pore and an inactivation gate separate from the voltage gate
- once it opens it can’t open again until it repolarizes to a negative voltage
What mediates the falling phase?
-voltage gated K+ channels
What are the ways to graph the changes during AP?
-membrane potential (vm)
- ionic permeability or conductance’s
V=IR
V=I(1/g)
1/g=R
What does depolarization do to K+ channels?
- Voltage-gated K+ channels are activated by depolarization but are much slower to open than Na+-gated channels
How many different types of voltage-gated K+ channels?
lots
Does K+ have an activation gate?
- yes activation gate
-some have deactivation gate
What is the AP positive feedback loop?
- AP is all or none
- depolarization
-opens voltage-gated Na+ channels - Na+ influx is greater than K+ efflux
-more depolarization
-threshold
What is threshold?
- membrane potential at which Na+ influx overcomes K+ efflux resulting in at least 1 AP
How does the brain slice technique work?
- take a thin slice out of a rats brain
- keep it as alive as possible in the petri dish
-typically studies caudut/putman area and nucleus accumbens
What does Putman area control?
- motor control
What does the nucleus accumbens control?
reward and motivation
What are the types of patch recordings?
-voltage clamp
-current clamp
- dynamic clamp
What does a voltage clamp measure?
current changes
What does a voltage clamp manipulate
voltage