Lecture 1 + Assignment 1 Flashcards by Sophie Cournoyer

Transduction

physical stimuli transformed to neural processing

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How many neurons in the human brain

1 x 10^11

100 billion

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Size of a typical neuron

10 um (micrometer aka microns)

1 um = 10^(-6) m

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How much of our brain do we use

all of it

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Brain’s power (watts) vs. body power

20 W

entire body 100 watts

uses 20% = energy intensive

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Most common neurotransmitter

glutamate

also most important

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Voltage inside neuron at rest + ions in neuro-electric activity

-65 mV

Na, K, Ca, Cl

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Central nervous system

+ examples

all parts of the nervous system within bone

spinal cord, brainstem, thalamus, cortex, etc.

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Peripheral nervous system

all parts not within bone = peripheral nerves

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3 components of the brainstem

midbrain
pons
medulla

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Spinal cord sections / dermatomes

Cervical
Thoracic
Lumbar
Sacral

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Similarities between neurons and other cells

Enclosure
- lipid bilayer membrane

Organelles
- nucleus
- mitochondria
- etc.

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Differences between neurons and other cells

Morphology
- dendrites
- axons

Electrically excitable
- action potentials

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Function of dendrites and axons

Dendrites
- receive signals from other neurons (input)
- many or no dendrites

Axons
- send signals to other neurons (output)
- have ONLY ONE (branches like a tree)

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Morphological variation - cortical pyramidal vs cerebellar purkinje cells

Cortical pyramidal cells
- most popular excitatory neurons
- dendrite and axon ratio pretty similar
- one major dendrite branch

Cerebellar Purkinje cells
- in cerebellum
- tons of dendrites

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Cortical pyramidal vs stellate cells

Cortical pyramidal cells
- look like a tadpole
- one main dendrite

Cortical stellate cells
- look like an explosion
- many dendrites

Glial cell types (3)

function + appearance

Astrocytes
- maintain ionic environment
- many dendrites spreading far
KEEP UP

Oligodendrocytes
- myelinate neurons
- less dendrites spreading a medium amount
SPEED UP

Microglia
- scavenge cellular debris
- many dendrites not spreading far
CLEAN UP

Nissl stains - procedure

slice coronal (vertical) slice
tissue fixed using paraffin using paraffin
stain ER with cresyl violet to reveal cell bodies

Nissl stains - result

only stains cell bodies

Golgi stain

1870s-1880s
- stains entire neurons but only some of them
- uses silver

Brodmann’s areas

+ examples

used Nissl stain found different area areas of the cerebral cortex with distinct cytoarchitectural appearances
52 areas differ based on appearances

ex.
3, 1, 2 = primary somatosensory
4 = primary motor cortex
17 = primary visual cortex
41, 42 = primary auditory cortex

Why is the resting potential negative

Potassium electrochemical equilibrium

3 Na+ are pumped out of the cell for every 2 K+ that enter

Cerebrospinal fluid (CSF)

aqueous saline solution
contains Na, K, CL and other ions
lipid bilayer (neuronal membrane) impermeable to the movement of ions

Transport through the neuronal membrane

2 things

Active ion transporters
- actively move selected ions against the concentration gradient
- create ion concentration gradients
(active transport pumps)

Ion channels
- move selected ions with the concentration gradient
- selectively permeable to certain ions
(leak channels)

Electrochemical equilibrium

- K concentration greater inside than outside neuron due to sodium potassium pump - neuron primarily permeable to K due to leak channels - electrochemical equilibrium when K leaves and returns at the same rate

Equilibrium potential | Depends on what 2 things

- net flow of an ion is zero Depends on: 1. Diffusion K diffuses down its concentration gradient 2. Electrostatic force As K diffuses out, the inside becomes progressively more negative Makes K attracted to the inside again (opposites attract)

The Nernst Equation

Ex = (58/z)log([X]out/[X]in)

General position terms

- rostral (front) - caudal (behind) - dorsal (back) - ventral (stomach) midline = line separating left and right ipsilateral = same side contralateral = opposite side decussate = 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

Planes of the brain

horizontal = x-axis sagittal = a plane with the midline coronal (frontal) = perpendicular to sagittal

Neuroscience rules

- symmetry - localization of function - contralaterality - topography

Symmetry

brain is bilaterally symmetric across the midline so coronal sections you can't tell if they're from the top or bottom

Localization of function | lobes

- four lobes 1. frontal lobe (cognition + language + movement) 2. parietal lobe (touch + vision) 3. occipital lobe (vision) 4. temporal lobe (language + hearing + vision) central sulcus = between frontal and parietal lateral / sylvian fissure = between frontal and parietal

Contralaterality

opposite sides control each other to move right hand activate the left side to move left hand activate the right side

Topography

neighbouring neurons control neighbouring parts of the body ex. motor homunculus, somatosensory homunculus which are coronal

Neuron growth rate

Pt = Po(1+R)^t

Why does it make sense that the valence, z, is in the denominator of the Nernst equation?

- all ions have the same concentration gradient - same tendency to diffuse and same attraction to keep them from leaving Coulombs law - to create the same force of attraction, the inside of X++ needs to be just half as negative as that of X+ F = (qin)(qion)/r^2 qx++ = 2qx+