Download Functional Classification of the Peripheral Nervous System

Essentials of Human Anatomy & Physiology
The Nervous System
Chapter 7
Nervous System Functions
1. Sensory input – gathered information
 Allows you to monitor changes occurring in
& outside of the body (changes = stimuli)
2. Integration
 Process and interpret the sensory input and
decide if action is needed
3. Motor output
 A response to integrated stimuli activates
muscles or glands
Structural Classification of the
Nervous System
 Central Nervous System (CNS)
 Brain
 Spinal cord
 Peripheral Nervous System (PNS)
 Nerves that extend from the brain and
spinal cord
Functional Classification of the
Peripheral Nervous System
 Sensory (afferent) division
 Nerve fibers that carry information to the
central nervous system
Functional Classification of the
Peripheral Nervous System
 Motor (efferent) division
 Nerve fibers that carry impulses away from
the central nervous system
Functional Classification of the
Peripheral Nervous System
 Motor (efferent) division
 Two subdivisions
 Somatic nervous system = Voluntary
 Autonomic nervous system = Involuntary
 Sympathetic
 Parasympathetic
Organization
of the
Nervous
System
Nervous Tissue: Support Cells
 Supporting Cells in the CNS
 Lumped together as neuroglia (AKAglia or glial cells)
 “Nerve glue”
 Includes many types of cells that
support, insulate, & protect the delicate
neurons
 Each type has specific functions
Nervous Tissue: Neurons
 Neurons = Nerve cells
 Cells specialized to transmit messages
 Nerve impulses
 Major regions of Neurons
 Cell body – Contains the nucleus and is
the metabolic center of the cell
 Processes – Fibers that extend from the
cell body (dendrites and axons)
Neuron Anatomy
 Cell body
 Nucleus
 Metabolic
Center
Neuron Anatomy
 Extensions
outside the cell
body
 Dendrites –
Conduct impulses
toward the cell
body
 Axons – Conduct
impulses Away
from the cell body
Axons and Nerve Impulses
 Axons end in axonal terminals
 Axon terminals contain vesicles that
contain neurotransmitters
 Axon terminals are separated from the
next neuron by a gap
 Synaptic cleft – just the space between
adjacent neurons
 Synapse – junction between neurons;
including the membranes of both neurons &
the space between them
Nerve Fiber Coverings
 Myelin





Covers nerve fibers
Whitish, fatty material
Waxy appearance
Protects & insulates the fibers
Increases the transmission
rate of nerve impulses
 Schwann cells – produce
myelin sheaths in jelly-roll like
fashion
 Nodes of Ranvier – gaps
in the myelin sheath along the
axon
Application of Neurons
• Multiple sclerosis (MS)
• Chronic, potentially debilitating disease that affects the central
nervous system, which is made up of the brain and spinal cord.
• Myelin sheath is destroyed- It hardens to a tissue called the
scleroses
• Transmitted nerve impulses are short-circuited
• Affected person loses control of his/her muscles and becomes
increasingly more disabled
• Autoimmune disease
• Protein component of the sheath is attacked
• No cure
• Interferon injections
•
• website
Hormone like substance released by some immune cells- provides relief
Multiple
Sclerosis
Neuron Cell Body Location
 Most neurons are found in the central
nervous system
 White matter- dense collections of
myelinated fibers
 Gray matter – unmyelinated fibers & cell
bodies
 Nuclei – clusters of cell bodies within the
white matter of the central nervous system
 Ganglia – collections of cell bodies
outside the central nervous system
(PNS)
Functional Classification of
Neurons
 Sensory (afferent) neurons
 Carry impulses from the sensory receptors
to the CNS
 Cutaneous sense organs (Vision,
hearing, equilibrium, taste & smell)
 Proprioceptors – detect stretch or tension
in skeletal muscles, tendons and joints
 Pain receptors
Functional Classification of
Neurons
Motor (efferent) neurons
 Carry impulses from the central nervous
system to the viscera and/or muscles and
glands
Interneurons (association neurons)
• Connect sensory and motor neurons in
neural pathways
Neuron Classification