Neural Tissue

The nervous system includes all the neural tissue in the body.

Structure of the nervous system

The Nervous SystemThe Nervous System

Central Nervous SystemCentral Nervous System Peripheral Nervous Peripheral Nervous SystemSystem

BrainBrain Spinal CordSpinal Cord

SympatheticSympathetic ParasympathParasympatheticetic

SomaticSomatic AutonomicAutonomic

AfferentAfferent EfferentEfferent

Peripheral Nervous System

• Afferent - bring sensory

• Efferent - carry commands

Efferent DivisionSomatic - skeletal

muscle contractions (voluntary) & involuntary reflexes

Autonomic (visceral motor system) -Involuntary (smooth muscles, cardiac muscle & glandular secretions)

Autonomic Nervous System

• Parasympathetic - nonstressful

rest & digest

• Sympathetic –

• stressful

fight or flight

Neuron

Functional & Structural unit of the

nervous system

dendrites

Nissl bodies

nucleusnucleolus

neurofilaments

Initial segmentof axon

axon

mitochondria

dendritic spines

synapticterminals

telodendria

Golgi apparatus

axon hillock

telodendriaaxon

nucleus

perikaryondendrites

Multipolar Neuron

Vocabulary dendrites - typically highly branched,

carry messages

axon - propagates an electrical impulse away from the cell body

initial segment - base of an axon

Vocabulary cont.

axon hillock - thickened region

soma - cell body, houses organelles but lack centioles

telodendria - fine extensions off the axon

synaptic terminal - ends of the telodendria

Structural Classification of

Neurons

anaxonic neuron

bipolar neuron

unipolar neuron

multipolar neuron

Functional Classification of

Neurons

Sensory neurons (afferent) - from sensory receptorsto CNS

• somatic sensory neurons - monitor the outside world & our position in it

•visceral sensory neurons - monitor internal conditions & the status of the organs

Sensory receptors

proprioceptors

interoceptors

exteroceptors

Sensory Receptors

Further broken down into

Mechanoreceptors

Thermoreceptors

NociceptorsChemoreceptor

sOsmoreceptorsPhotoreceptors

Functional Classification of Neurons

Motor Neurons (efferent) - carry instructions

fromthe CNS to peripheral effectors

Functional Classification of

Neurons

Interneurons (association) - •outnumber all other types

•mostly in brain & spinal cord•situated between sensory & motor

neurons

Ependymal Cells

line the central canal & ventricles which house the brain & spinal cord,

creates a barrier between the

Cerebral Spinal Fluid (CSF) and the brain &

spinal cord

NeuroglialCells

Astrocytes

Maintain the blood-brain barrier

Create a 3-D framework for the CNS

Repair damaged nerve tissue

Guide neuron development Control the interstitial

environment

Oligodendrocytes

Form the myelin sheath along the length

of the axon myelin - increases the speed of

the action potential along the axon myelin sheath - membrane wrappingaround the axon internodes - area of the axon wrapped myelin (1 - 2 mm in length) nodes - small gaps (few micrometers) between internodes with no myelin white matter - CNS, areas withmyelinated axons, high lipid

content gray matter - areas containing

neuroncell bodies, dendrites &

unmyelinated axons

The Myelinated

Axon

Microglia

• least numerous

• cleanup by engulfing cellular debris, waste products & pathogens