Lecture 1 + Assignment 1 Flashcards
Transduction
physical stimuli transformed to neural processing
How many neurons in the human brain
1 x 10^11
100 billion
Size of a typical neuron
10 um (micrometer aka microns)
1 um = 10^(-6) m
How much of our brain do we use
- all of it
Brain’s power (watts) vs. body power
20 W
entire body 100 watts
uses 20% = energy intensive
Most common neurotransmitter
glutamate
also most important
Voltage inside neuron at rest + ions in neuro-electric activity
-65 mV
Na, K, Ca, Cl
Central nervous system
+ examples
all parts of the nervous system within bone
- spinal cord, brainstem, thalamus, cortex, etc.
Peripheral nervous system
all parts not within bone = peripheral nerves
3 components of the brainstem
- midbrain
- pons
- medulla
Spinal cord sections / dermatomes
- Cervical
- Thoracic
- Lumbar
- Sacral
Similarities between neurons and other cells
Enclosure
- lipid bilayer membrane
Organelles
- nucleus
- mitochondria
- etc.
Differences between neurons and other cells
Morphology
- dendrites
- axons
Electrically excitable
- action potentials
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)
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
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
- 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
- frontal lobe (cognition + language + movement)
- parietal lobe (touch + vision)
- occipital lobe (vision)
- 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+
