Neuroscience lecture 1

reticular theory

nerves communicate through a continuous nerve net championed by Camillo Golgi

Golgi Method

method to stain neurons; silver solution that randomly stains abt 1% of neurons in their entirety

• provided evidence for reticular theory

• made it so that surrounding structures don’t cloud image

neuron doctrine

discrete individual cells (Snatiago Ramon y Cajal)

Santiagi Ramon y Cajal

Father of modern neuroscience

• contributed to neuron doctrine & principle of dynamic polarity

• identified 2 main cells- neurons & glia

Neuron doctrine

principle that individual neurons are unites and signaling elements of the nervous system

• neurons are contiguous- discrete entities not a continuum

Neuron doctrine 1920

ross harrison shows neural processes (dendrites and axons) grow from cell body and axons extend to target neurons

Neuron doctrine 1953

Sanford Palay shows synapses & gaps between neurons

brainbow

developed by Lichtman & Sanes- process which stains individual neurons using genetically encoded fluorescent proteins

CNS

protected inside skull (skull & vertebral column)

• retina-myelate could be included depending on how you classify

PNS

extends beyond (exists entirely outside of) bony skull and vertebral column

sympathetic nervous system

fight or flight

parasympathetic nervous system

rest and digest

external stimuli

sensory & visceral

principle of dynamic polarity

Electrical signals within a neuron flow in 1 direction startingf at dendrites and ending at the terminal

Dendrites (e- flow)

input

soma (e- flow)

integration

axon (e- flow)

propagation

terminal (e- flow)

output

intracellular signaling

within neuron

intercellular signaling

between neurons or between neurons and their non-neuronal targets

Difference in organelles between neurons and regular cells

neurofilaments instead of microfilaments

synaptic vesicle

store and release neuro transmitter

mitochondria

concentrated in axon terminals- ATP required to release neurotransmitter

number of dendritic branches…

correlates w/ number of inputs

Spines

specialized locations for synapses that increase # of inputs locations

• highly plastic: can easily exchange in response to stimuli

• increase SA so more synapses

Axons

• propagate electrical signals between neurons

• form presynaptic terminal of synapses

• optimized for speed

how are axons optimized for speed

myelin and nodes of Ranvier

myelin

wraps axon like “insulation”- keeps electricity from escaping

nodes of ranvier

“breaks” myelin w/ concentrated channels; depolarized region

neuron structure

huge variability; structure determines function

sensory receptor neurons

transduce environmental signal into a neural signal (ex: rods, cones, olfactory receptors, taste bud, hair cell, pain, temp, and pressure sensors)

transduction

change sensory input to electrical signals

projection neurons

communicate w/ other neurons located in a different or distant CNS or PNS region

1. between brain areas

2. between brain, spinal cord, and sensory or motor structures

interneurons

communicate w/ other neurons located in same or nearby CNS region

• local connections within same brain area or spinal cord

2 types of interneurons

excitatory “GO”

inhibitory “stop”

glial cells

• glia- greek for glue (once thought that these cells held brain together)

• non-neural cells of nervous system

• support system for neurons

• more numerous than neurons

types of glia cells

astrocytes, ogliodendrocytes, schwan cells, microglia

cellular properties of glia

• have standard features of eukaryotic cells

• express glia fibrillary acid protein (GFAP) instead of neurofilaments

• antibodies to GFAP are used to mark glial cells

Astrocytes (astral- star like)

• restricted to CNS

• maintains extracellular environment required for neural signaling (esp. CA+2)

• can actively contribute to synaptic fxn

• could have role in memory and sleep

astrocyte “end feet”

interact w/ capillary endothelial cells to maintain tight junctions that comprise the “blood brain barrier”

olgiodendrocytes

CNS; myelinates several parts of several CNS axons

Schwann cell

PNS; myelinates one part of a single PNS axon

myelin

each individual glial cell lays down multiple layer of myelin (lipid membrane) to insulate myelinated axons

microglia

• scavenger cells that remove debris from sites of injury

• modulate inflammation, cell survival & cell death

• shape-shifting according function; very plastic

• protect against injury & help development