Neuro

A Beta Axon Function

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

1. Frontal

2. Parietal

3. Occipital

4. 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?

1. Diffusion: when something is concentrated highly in one spot, it will naturally go where its concentration is lower.

2. 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

1. Rising Phase: Na channels open and Na enters.

2. End of Rising Phase: Na channels inactivate and Na stops entering.

3. 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…

1. Reducing Membrane Resistance: plugs the leak channels so ions cant flow through.

2. 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)

1. Retina.

2. Optic nerve.

3. Optic chiasm.

4. Optic tract.

5. Lateral geniculate nucleus (LGN).

6. Optic radiation.

7. 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

1. Malleus

2. Incus

3. 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.