A Beta Axon Function
Responds to touch.
A Delta Axon Function
Responds to first pain and temperature.
C Axon
Responds to second pain and temperature.
Conduction Velocity of A Beta Axons
35-75 m/s
Conduction Velocity of A Delta Axons
5-30 m/s
Conduction Velocity of C Axons
0.5-2 m/s
Width of A Beta Axons
6-12 microns
Width of A Delta Axons
1-5 microns
Width of C Axons
0.2-1.5 microns
Width of Synaptic Cleft
20-40 nm
Diameter of the Cell Body
100 microns
CNS
Central Nervous System: all parts of the nervous system within bone.
PNS
Peripheral Nervous System: all parts of the nervous system not within bone.
CSF
Cerebrospinal Fluid: surrounds neurons and contains sodium, potassium, chloride, and other ions.
TTX
Tetrodotoxin: found in pufferfish and causes death by paralysis of respiratory muscles.
STX
Saxitoxin: found in shellfish and causes paresthesia, numbness, paresis, and respiratory difficulty.
AHP
Afterhyperpolarization: phase of action potential where the cell's membrane potential falls below the normal resting potential, causing undershoot.
EPSP
Excitatory Postsynaptic Potential: makes the postsynaptic neuron more likely to fire an action potential.
IPSP
Inhibitory Postsynaptic Potential: makes a postsynaptic neuron less likely to fire an action potential.
GABA
Gamma-Aminobutyric Acid: the most common inhibitory neurotransmitter in the cerebral cortex.
VPL
Ventral Posterior Lateral Nucleus: receives sensory information from the body.
VPM
Ventral Posterior Medial Nucleus: receives sensory information from the head and face.
cGMP
Cyclic Guanosine Monophosphate: regulates calcium homeostasis and phototransduction.
Rostral
Towards the nose.
Caudal
Towards the tail.
Dorsal
Towards the back.
Ventral
Towards the stomach.
Superior.
Above.
Posterior.
Behind.
Inferior
Below.
Anterior.
In front of.
Midline
Line separating left and right.
Ipsilateral
Same side.
Contralateral
Opposite side.
Decussate
To cross midline.
Proximal
Close to point of reference.
Distal
Far from point of reference.
Efferent
Projecting away from reference.
Afferent
Projecting towards reference.
Medial
Near midline.
Lateral
Far from midline.
Coronal
Plane of section cutting in a [] way.
Sagittal
Plane of section cutting in a | way.
Horizontal
Plane of section cutting in a - way.
Symmetry
Neuroscience rule which states that the left and the right side are mirror images of each other.
Localization of Function
Neuroscience rule which states that different functions tend to be localized in different parts of the nervous system.
Contralaterality
Neuroscience rule which states that whatever is happening on one side of the world is sensed by the opposite side of the brain.
Topography
Neuroscience rule which states that each part of the body maps onto a particular part of the brain that can move that part of the body.
Lobes of the Brain
Frontal
Parietal
Occipital
Temporal
Why is the Resting Potential Negative?
The potassium concentration is greater inside than outside the neuron because of the sodium/potassium pump.
The neuron is primarily permeable to potassium because the membrane contains potassium leak ion channels, which only potassium ions can go through.
So, K+ diffuses out of the cell, making the inside negative.
Electrochemical Equilibrium
The potential at which the net flow of an ion would be 0.
Equilibrium
The potential is stable and negative.
What Establishes Equilibrium Potential?
Diffusion: when something is concentrated highly in one spot, it will naturally go where its concentration is lower.
Electrostatic Force: if the forces are opposite, it's a force of attraction; if the forces are the same, it's a force of repulsion.
Coulomb Force Law
F is proportional to (q1)(q2) / (r^2)
Nernst Equation
Ex = (58 / z)log(Xout / Xin)
Goldman-Hodgkin-Katz (GHK) Equation
Vm = 58log[(PKout + PNaout) / (PKin + PNain)]
Length Constant
Vx = (V0)e^(-x / sqrt(rm/ra))
Time Constant
Vt = (V0)e^(-t / (rm)(cm))
Driving Force Equation
Ix = gx(Vm - Ex)
Snell’s Law
(n1)Sin(theta1) = (n2)Sin(theta2)
How the Driving Force Equation can Determine the Direction of an Ion’s Flow Across the Membrane
If the answer is positive, the flow will be outward.
If the answer is negative, the flow will be inward.
Negative Current
When the cell gains positive charge or loses negative charge.
Positive Current
When the cell loses positive charge or gains negative charge.
Ion Channel Events that Occur During the Action Potential
Rising Phase: Na channels open and Na enters.
End of Rising Phase: Na channels inactivate and Na stops entering.
Falling Phase: K channels open and K leaves.
Absolute Refractory Period
The period of time where a second action potential cannot be initiated at all.
All-or-None
If the stimulus passes the threshold, it will always fire an action potential.
Regenerative
Action potentials self-regenerate every so often.
Saltatory Conduction
Action potentials traveling down the axon jump from node to node in between the myelin, which allows them to travel faster.
Unidirectional
Once an action potential starts, it can only occur in one direction.
Local Anesthetics
Gets into open channels and plugs them, stopping sodium from coming in and ultimately preventing an action potential, which prevents pain from being felt.
Myelin’s Effect on Action Potentials
Speeds up action potentials by…
Reducing Membrane Resistance: plugs the leak channels so ions cant flow through.
Reducing Membrane Capacitance: increases the distance between ions on the inside and the outside, making the force of attraction smaller.
Oligodendrocyte
A type of glial cell found in the central nervous system.
Schwann Cell
A type of glial cell found in the peripheral nervous system.
Multiple Sclerosis
Antibodies attack myelin in the CNS, causing it to break down and messing up the conduction of action potentials.
Guillain Barre Syndrome
Antibodies attack myelin in the PNS, causing it to break down and messing up the conduction of action potentials.
18
…
Otto Loewi
Did an experiment demonstrating chemical transmission by stimulating the vagus nerve to show how it slows down the heart.
20, 21, 22
Resting Potential of a Typical Neuron
-65 mV
Action Potential Threshold
-50 mV
Which ion has a Higher Concentration Inside than Outside the Cell?
Potassium
25, 26, 27, 28, 29, 30-49
50
Retino-Geniculo-Cortical Pathway (Pathway from Retina to Thalamus to Cortex)
Retina.
Optic nerve.
Optic chiasm.
Optic tract.
Lateral geniculate nucleus (LGN).
Optic radiation.
Primary visual cortex, striate cortex.
Right Monocular Blindness
Visual field deficit where left eye is seeing, right eye is blind.
Results from lesion to right optic nerve.
Bitemporal Hemianopsia
Visual field deficit where nasal half of eyes are seeing, temporal half of eyes are blind.
Results from lesion to optic chiasm.
Left Homonymous Hemianopsia
Visual field deficit where nasal half of left eye and temporal half of right eye are seeing, temporal half of left eye and nasal half of right eye are blind.
Results from lesion to right optic tract.
Left Homonymous Hemianopsia with Foveal Sparing
Visual field deficit where there’s a tiny bit in the center that can still see even in the blind areas.
Results from lesion to bottom of optic radiation.
Left Superior Quadrantanopsia
Visual field deficit where top temporal quarter of left eye and top nasal of right eye are blind, and the rest of the eyes are seeing.
Results from lesion to top of optic radiation.
Optic Nerves
The axons from one eye, before they reach the optic chiasm.
Optic Tracts
The axons from both eyes, after they’ve reached the optic chiasm.
53, 54, 55
V4
Involved in detecting colour vision.
V5 / MT
Involved in detecting motion of the entire visual field.
Ossicles
Malleus
Incus
Stapes
58, 59
Inner Hair Cells
We have more of them.
Responsible for acoustic transduction.
Outer Hair Cells
We have less of them.
Responsible for assisting the transduction done by the inner hair cells.
Conductive Hearing Loss and its Causes
Occurs when vibration is prevented from reaching the inner ear, due to…
Wax.
Otitis media.
Otosclerosis.
Sensorineural Hearing Loss and its Causes
Occurs when neural processing is compromised, due to…
Occupational deafness.
Presbycusis.
Antibiotic ototoxicity
Acoustic neuroma.