Neuro Lecture 2

• Supporting elements
• Form myelin
• Scavenger functions
• Guide migration of neurons
• Induction of and participation in the blood-brain barrier
• Nutritive functions

• Support
• Protection
• Nourishment
• Glial scar

Myelnation

Phagocytes of the CNS

Lines cavities of CNS

• Reception
• Analysis/Integration
• Conduction
• Transmission

Recovery of the neuron or reorgaization of undamaged neurons

• Metabolic center of neuron
• Nucleus or perikaryon

• Usually several per neuron
• Input units to cell
• Branch-like

• One per neuron
• Main conducting unit
• arsies from the axon hillock
• diameter 0.2-20 micrometers
• length up 1 meter

• Receives the Input
• Typically Dendrites & Cell Body

Basically proteins. Plasticity is affected by having more or less receptors

Microspecilizations which contain the post-synaptic density (PSD)

• Synaptic activity
• Profound spine loss is found in forms of mental retardation

A specialized portion of the axon where an action potential is initiated when the critical threshold is reached

• Receptive segment spreads signals passively to this region
• Begins at the cell body (axon hillock) and ends where the myelin sheath begins
• Potentials are summed and decision is made whether or not to fire (all-or-none)
• AKA - Tigger zone, initial segment, spike generating zone

• Information conducted from one location in the nervous system to another as action potentials (all or none) along the axon
• Typically the axon

• Each neuron has a spontaneous discharge frequency
• -Increasing information - an increase in discharge frequency
• -Decreasing information - decrease in discharge frequency

• Allows communication between neurons
• Typically the presynaptic terminal
• Contain volatge gated Ca2+ which release transmitter

• One-way
• Neurotransmitter release from presynaptic neuron
• Electrical response in post synpatic neuron

relay information from sensory receptors to CNS

Cross the midline, relay information to the Thalamus

Relay information to the cortex

Parallel processing for: sensory systems, input centers, information dispersion

• Axodendritic
• Axosomatic
• Axoaxonic

Amplification of weak signals

• Good for spatial discrimination
• Uses lateral inhibition that allows the body to pinpoint where the stimulus is located on the body.

Found in invertebrate autonomic nervous systems

First-order sensory neurons

2 order neurons in visual & olfactory systems

Largest class of cells in vertebrate nervous systems

• Sensory
• Motor
• Interneuron

• Process information locally
• rich dendritic arborization
• short axons

• Transmit information between distant locations within NS
• Long axons organized into tracts in SC and brain (2nd order neurons)

• Ischemic, traumatic, toxic, degenerative, abnormal development
• Damage to cell body or axon hillock causes cell death
• Neuronal death causes long-lasting or permanent loss of function

• Also known as Wallerian degeneration
• Distal portion of a damaged axon dies because it is disconnected from the cell body which it sustains it
• Causes denervation hypersensitivity (spasticity)
• Causes muscular atrophy

• Begins 2-3 days after injury
• Synaptic retraction
• Atrophy of presynaptic cell

• Collateral sprouting from intact neurons
• Reorganization (intact systems assume the lost function, neuroplasticity)
• Wallerian regeneration (functional connections with target cells may be re-established)

• Neurapraxia
• Axontmesis
• Neurotmesis

Due to ischemix block of neuronal conductivity and presents as a rapidly reversible loss of function (arm falling asleep)

Due to demyelination and presents as a loss of function that recovers after a few weeks following re-myelinization (Bell's palsy, Guillian-Barre)

Complete interruption of axon with loss of all function suberved by the cell, recovery of function may occur if Wallerian degernartion and regernation occur

Complete interruption of entire nerve fiber including cell membrane and myelin sheath, requires surgical re-attachment if recovery of function is to occur.

• Complication of axonotmesis or neurotmesis
• painful and non-painful

• Multiple Sclerosis
• Bell's palsy
• Guillian-Barre

• Biological factors (age and sex)
• Characterisics of Lesion (size, momentum)
• Experience (Environmental & training)

• Affect cortical depth
• Brain weight
• Dendritic branching,
• Spine development
• Enzyme activity

Protective

Improves recovery

• Usually an acquired autoimmune disorder
• Body produces antibodies that destroy acetylcholine receptors on the postsynaptic membrane at the myoneural junction
• Blocked receptors cause repetitive contractions to fail

• Double vision
• Difficulty chewing, swallowing and speaking
• Symptoms get worse with fatigue and use
• Ptosis (drooping eye lid)