Nissl Stain - ️️Nissl used basic died to stain the endoplasmic reticulum (RNA),
thereby revealing cell bodies. Using the nissl stain, Brodmann found that different areas
of the cerebral cortex had distinct cytoarchitectonic appearances. He identified 52
cortical areas, now called Broadmann's...
PNB 2XB3 - Neuroanatomy &
Neurophysiology
Nissl Stain - ✔️✔️Nissl used basic died to stain the endoplasmic reticulum (RNA),
thereby revealing cell bodies. Using the nissl stain, Brodmann found that different areas
of the cerebral cortex had distinct cytoarchitectonic appearances. He identified 52
cortical areas, now called Broadmann's areas
contralaterality - ✔️✔️right brain controls left, left brain controls right. most functions
are contralateral
What is the size of a typical neuron? - ✔️✔️10 um (cell body diameter)
What is the most common neurotransmitter? - ✔️✔️Glutamate
What is the voltage of a neuron at rest? - ✔️✔️-65mV
What is the name of the neuro-electrical impulse? - ✔️✔️Action potential
What ions are involved in neuro-electrical activity? - ✔️✔️Sodium (Na+), Potassium
(K+) and Chloride (Cl-)
What is the CNS? - ✔️✔️Everything within bone, spinal cord, brainstem, thalamus,
cortex etc.
How many neurons are in the human brain? - ✔️✔️about 100 billion
What is the PNS? - ✔️✔️All parts not within bone, peripheral nerves
Rostral - ✔️✔️towards the nose, top of the neuraxis
Caudal - ✔️✔️towards the tail, end of the neuraxis
,dorsal - ✔️✔️towards the back
What percentage of the brain do we use? - ✔️✔️100%
ventral - ✔️✔️towards the front/stomach
anterior - ✔️✔️in the front
posterior - ✔️✔️behind
inferior - ✔️✔️below
superior - ✔️✔️above
midline - ✔️✔️line seperating right and left
ipsilateral - ✔️✔️same side
contralateral - ✔️✔️opposite side
decussate - ✔️✔️cross the midline
proximal - ✔️✔️close to the point of reference
distal - ✔️✔️far away from the point of reference
efferent - ✔️✔️projecting away from reference
afferent - ✔️✔️projecting towards reference
medial - ✔️✔️near midline
lateral - ✔️✔️far from midline
Neuroscience rules - ✔️✔️symmetry, localization of function, contralaterality,
topography
topography - ✔️✔️like a map onto the surface of the nervous system
.
,cerebrospinal fluid (CSF) - ✔️✔️plasma-like clear fluid circulating in and around the
brain and spinal cord. saline solution. Contains sodium (Na+), potassium (K+), and
chloride (Cl-) and other ions. this is why resting potential is negative.
2 things that establish equilibrium potential - ✔️✔️Diffusion, electrostatic force
(coloumb force law)
Coloumb force law - ✔️✔️((q1)(q2))/(r^2)
Time from stimulus to perception (Close to brain vs. farther from brain) - ✔️✔️Close to
brain - perception occurs with little delay
Farther from brain - perception occurs with longer delay
Conduction speed of 30-70ms
Threshold of an action potential - ✔️✔️-50mV
The Goldman-Hodgkin-Katz Equation - ✔️✔️Vm =
58log((Pk[k]out+PNa[Na]out)/(Pk[k]in+PNa[Na]in))
2 Feedback loops in an action potential - ✔️✔️Fast positive feedback loop, slow
negative feedback loop
Fast Positive Feedback loop - ✔️✔️Depolarize membrane potential - voltage gated
Na+ channels open - Na+ rushes in - Depolarization occurs
Slow Negative Feedback Loop - ✔️✔️Depolarize membrane potential - Voltage gated
K+ channels open - K+ rushes out - Hyperpolarization occurs
3 States of the voltage gated sodium channel - ✔️✔️Closed, Open, Inactivated
Action Potential Summary - ✔️✔️1. Membrane is depolarized past threshold by a
receptor or synaptic potential
2. Voltage gated sodium channels open in a positive feedback loop, causing rise
3. The sodium channels inactivate, ending the rising phase and initiating the refractory
period
4. Voltage gated potassium channels open causing the falling phase and the
undershoot (afterhyperpolarization: AHP)
5. The sodium channels close, ending the refractory period
6. The potassium channels close, ending the undershoot and restoring the membrane
to it's resting potential
Refractory - ✔️✔️Inability to continue
, Benefits of the refractory period - ✔️✔️Ensures unidirectional action potential
conduction, away from the point of origin
Consequences of the refractory period - ✔️✔️places an upper limit on the firing rate of
a neuron (bad thing)
Unidirectional conduction - ✔️✔️- Action potentials only move one way on the axon
- this is not due to the intrinsic property of the axon it is due to the refractory period
Voltage Clamp - ✔️✔️injecting positive charge into the neuron is a downward refection.
they detected that when they put the cell into a depolarized state, they saw a current.
How do local anesthetics work? - ✔️✔️They block voltage gated Na+ channels
Tetradoxin - ✔️✔️Found in puffer fish, blocked Na+ channels forever
3 things that make an action potential move slowly - ✔️✔️1. The axon is leaky = low
membrane resistance (Rm)
2. The axon is sticky = high membrane capacitance (Cm)
3. The axon is thin = high axoplasmic resistance (Ra)
What causes a leaky membrane? - ✔️✔️Sodium comes down the axon and it
depolarizes the axon in both directions. Ions also push potassium with it (passive flow).
If it was fast, the AP will move faster. Slower movement is due to a leak channel.
What causes a sticky membrane? - ✔️✔️When positive charge comes, it can stick to
the membrane. The membrane is thin and therefore there is little distance between
charges.
What causes a thin membrane? - ✔️✔️Smaller diameter axon
Invertebrate axons - ✔️✔️Invertebrates evolved wide axons. Solution to the problem of
slow conduction and increases effectiveness.
ex. The giant squid axon
The Nodes of Ranvier - ✔️✔️The Nodes of Ranvier are the spaces between myelin
sheaths - the exposed regions of the axon. Voltage gated channels are still there. There
are about 2,000 channels per square micron at each node.
Myelination in the PNS - ✔️✔️-Schwann cells myelinate (wrap around) axons in the
PNS during fetal development
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