Neurons

The Cell, Nervous System

Basic but specialized structural/functional units of nervous system

Neurons

Fundamentals

• Specifically designed to signal chemically after electrical excitation
  • Single axon can carry only so much information
• Many different types of neurons in the body
  • Majority of the neuron is comprised of the dendrites
  • No uniform structure
• Fast and addressed
  • Fast : travels rapidly, begins and end abruptly
  • Addressed: provide highly discrete lines of communication
  • Utilizes neurotransmitter - diffuses quickly across the minute gap
  • Temporary (Fast) and spatially defined

Characteristics:

• Less abundant to Neuroglia
• Derived from Ectoderm
• Most specialized cells
• Established prenatally = NO Mitosis but have ability to regenerate
• Presence of chromatophilic substances Nissl bodies
• Presence of filamentous strands of protein (Neurofibrils)

Purpose/Function:

• Propagates the Action Potential in 3 ways
• 1)Periperty to brain - affarent: sensory
• 2)Brain to periphery - efferent: motor
• 3)Interneutorns involved in local circuits
  • Storing memory
  • Thinking
  • Regulating other organs/glands

Components/Anatomy:=

Micro

• Recepetors
• Dendrites - input and transmitting information
  • Dendritic spinules: greatly increase the surface area of dentrites
• Cell body/Perikaryon/Soma/Axon Hillock - integration
  • Made to receive information
  • Contains nucleus, ER and ribsomes
• Axon Hillock - enlargement at the beginning of the axon
  • Information is integrated
  • Connection btwn the cell body and the axon - nerve fiber that is specialized to carry an electrical message
• Axon - conduction
  • Vary in length, contains many mitochondria, microtubules and neutrofibrils
  • Collateral branches
• Myelin - insulation to make AP more efficient
  • Produced by:
    • 1)Oligendrocytes - CNS
    • 2)Schwann cells - PNS
      • MNEUMONIC: Mye CO-PS
        • <-- OC - oligo and central
        • --> PS - peripheral and schwann
• Nodes of Raniver - Critical for proper signal conduction
• Presynaptic terminals/Synaptic Bulb/Bouton Terminal - output
• Synaptic Cleft/Synapse -
  • Neurotransmitter releasd from the axon terminla traverses the synaptic cleft and binds to receptors on the second neuron

Macro

• Dendritic Zone

Types:

• Bipolar
• Pseudounipolar
• Multipolar neurons

Classifcation:

• Somatic sensory
• Somatic motor
• Visceral sensory
• Visceral motor

Concepts:

• Mitosis - or lack thereof
• Germ Layers
  • Ectoderm
• Structure of Afferent and Efferent Neurons
  • Afferent neurons have cell bodies closer to the dendrites
  • Efferent neurons have cell bodies is equidistant the dendrites and synaptic bouton

Micro - How It Works (Molecular Functions of Cell Membrane)

• Action Potential

Macro - How It Works (Anatomy and Function)

• • Input - Dendrites receive the synapses from presynaptic axon terminals of previous cells
  • Integration - Cell body combines inhibitory and excitatory synaptic inputs
  • Conduction - Axon propagates the action potentials
  • Output - Presynaptic axons trigger the release of neurotransmitters for further input

Building Concepts:

• Nervous Tissue
• Myelination

Terminology:

• Dendrites: branched processes that receive stimuli and conduct nerve impulses toward cell body
• Cell body/Perikaryon: contains Nucleus and specialized organelles and Microtubules
• Axon: cytoplasmic extension that conducts nerve impulses away from the Perikaryon/CB
• Presynaptic/Bouton Terminals/Synaptic Bulb - output
• Nerve Fiber: any process extending from the cell body of a neuron and the myelin sheath that surrounds it (axon or dendrite)

Links:

• Wikipedia