Ch. 12
The Nervous System
and Nervous Tissue
Objectives
• Understand how the nervous system is divided
and the types of cells that are found in
nervous tissue
• Know the anatomy of a neuron and the
structural and functional types of neurons
• Understand what occurs at the synapse
The Nervous System
• Maintains internal coordination
– Sensory information
– Processing
– Response
• Two major subdivisions
– Central (CNS)
• Brain and spinal cord
– Peripheral (PNS)
• Nerves and ganglia
Divisions of Nervous System
legacy.owensboro.kctcs.edu
Divisions of Nervous System
• CNS
– brain and spinal cord
• PNS
– Cranial nerves
– Spinal nerves
– Sensory division
• Sensory information form environment to CNS
– Motor division
• Somatic
– Impulses to skeletal muscle
• Autonomic
– Impulses to cardiac and smooth muscle, glands
» Sympathetic
» parasympathetic
Neurons
• Communication cells of the nervous system
• Properties that allow communication
– Excitability
– Conductivity
– Secretion
• Three functional classes
– Afferent (sensory) neurons
– Interneurons (association neurons)
– Efferent (motor) neurons
Neuron Structure
• Soma – control center
– Chromatophilic (Nissl) bodies
– Neurofibrils
• Dendrites
– Receptive sites
– Conduct towards
• Axon Hillock
• Axon
– Impulse generators
– Conduct away
mindcreators.com
Synapse
• Site of neuronal communication
• Two types
– Axodendritic
– Axosomatic
• Synaptic cleft
– neurotransmitters
catalog.nucleusinc.com
Structural Classification
science.howstuffworks.com
Neuroglial Cells
• Four types of glial cells
– Astrocytes
• Synapse formation
– Brain derived trophic factor
• Nourish
• Regulation of neurotransmitters
• K+ regulation
– Oligodendrocytes
• myelination
– Microglia
• Immune protection
• Macrophages
– Ependymal cells
• Internal lining of CNS
• Production of CSF
• Two types of glial cells found
only in PNS
– Schwann cells
• Myelination
– Satellite cells
• Provide electrical insulation
around soma
• Chemical regulation
Myelination
nature.com
faculty.stcc.edu
Nerves
• Nerve
– Collection of nerve fibers in the PNS
• Nerve composed of multiple axons
• Epineurium
• Perineurium
– Fascicles
• endoneurium
web.uaccb.edu
Grey and White Matter of CNS
• Grey matter
– cell bodies, dendrites, unmyelinated axons,
neuroglia
• White matter
– Myelinated axons
histology.leeds.ac.uk
Reflex Arcs
• Reflex
– Rapid, autonomic motor responses to stimuli
– Somatic or visceral
• Monosynaptic
– Direct connection between afferent and efferent
neurons
• Polysynaptic
– One or more interneurons involved
Spinal Reflexes
Neuronal Circuits
• Diverging circuits
– Signal is passed to many pathways
• Converging circuits
– Various signals influence one neuron
• Reverberating circuit
– One neuron in a series sends feedback to a previous
neuron in the circuit
• Serial and Parallel processing
Disorders of the Nervous System
• Multiple Sclerosis
– Autoimmune attack of myelin on CNS axons
• Neuronal Regeneration
– Possible to regenerate axons of PNS
– Regeneration tubes