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PowerPoint® Lecture Slides
prepared by Leslie Hendon,
University of Alabama,
Birmingham
14
HUMAN
ANATOMY
fifth edition
MARIEB | MALLATT | WILHELM
PART 1
The
Peripheral
Nervous
System
Copyright © 2008 Pearson Education, Inc.,
publishing as Benjamin Cummings
The Peripheral Nervous System



Nervous structures outside the brain and spinal
cord
Nerves allow the CNS to receive information and
take action
Functional components of the PNS
 Sensory inputs and motor outputs
 Categorized as somatic or visceral
 Sensory inputs also classified as general or special
Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings
The Peripheral Nervous System

Autonomic nervous system (ANS)
 General visceral motor part of the PNS
 ANS has two divisions
 Parasympathetic
 Sympathetic
Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings
Functional Organization of the PNS
Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings
Figure 14.1
Basic Structural Components of the PNS


Sensory receptors – pick up stimuli from inside
or outside the body
Motor endings – axon terminals of motor neurons
 Innervate effectors (muscle fibers and glands)

Nerves and ganglia
 Nerves – bundles of peripheral axons
 Ganglia – clusters of peripheral neuronal cell
bodies
Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings
Basic Anatomical Scheme of the PNS
in the Region of a Spinal Nerve
Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings
Figure 14.2
Peripheral Sensory Receptors

Structures that pick up sensory stimuli
 Initiate signals in sensory axons
Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings
Peripheral Sensory Receptors

Two main categories of sensory receptors
 Free nerve endings of sensory neurons
 Monitor general sensory information
 Complete receptor cells – specialized epithelial
cells or small neurons
 Monitor most types of special sensory information
Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings
Peripheral Sensory Receptors


Wednesday
Sensory receptors also classified according to
 Location
 Type of stimulus detected
 Structure
Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings
Classification by Location

Exteroceptors – sensitive to stimuli arising from
outside the body
 Located at or near body surfaces
 Include receptors for touch, pressure, pain, and
temperature
Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings
Classification by Location

Interoceptors – (visceroceptors) receive stimuli
from internal viscera
 Monitor a variety of stimuli

Proprioceptors – monitor degree of stretch
 Located in musculoskeletal organs
Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings
Classification by Stimulus Detected


Mechanoreceptors – respond to mechanical
forces
Thermoreceptors – respond to temperature
changes
Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings
Classification by Stimulus Detected

Chemoreceptors
 Respond to chemicals in solution

Photoreceptors – respond to light
 Located in the eye

Nociceptors
 Respond to harmful stimuli that result in pain
Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings
Classification by Structure

General sensory receptors
 Widely distributed
 Nerve endings of sensory neurons monitor
 Touch
 Pressure
 Vibration
 Stretch
 Pain
 Temperature
 Proprioception
Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings
Classification by Structure

General sensory receptors are
 Divided into two groups
 Free nerve endings
 Encapsulated nerve endings
Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings
Free Nerve Endings



Abundant in epithelia and underlying connective
tissue
Respond to pain and temperature
Monitor affective senses
Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings
Free Nerve Endings

Two specialized types of free nerve endings
 Merkel discs – lie in the epidermis
 Slowly adapting receptors for light touch
 Hair follicle receptors – wrap around hair follicles
 Rapidly adapting receptors
Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings
Unencapsulated Nerve Endings
Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings
Table 14.1 (1 of 4)
Encapsulated Nerve Endings



Consist of one or more end fibers of sensory
neurons
Enclosed in connective tissue
Mechanoreceptors
 Include four main types
Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings
Encapsulated Nerve Endings

Meissner’s corpuscles
 Spiraling nerve ending surrounded by Schwann
cells
 Occur in the dermal papillae
 Rapidly adapting receptors for discriminative touch
 Occur in sensitive, hairless areas of the skin
Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings
Meissner’s Corpuscles
Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings
Table 14.1 (2 of 4)
Encapsulated Nerve Endings

Pacinian corpuscles
 Single nerve ending surrounded by layers of
flattened Schwann cells
 Occur in the hypodermis
 Sensitive to deep pressure – rapidly adapting
receptors
Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings
Encapsulated Nerve Endings

Ruffini’s corpuscles
 Located in the dermis and respond to pressure
 Monitor continuous pressure on the skin – adapt
slowly
Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings
Pacinian Corpuscles and Ruffini’s Corpuscles
Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings
Table 14.1 (3 of 4)
Encapsulated Nerve Endings

Proprioceptors
 Monitor stretch in locomotory organs
 Three types of proprioceptors
Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings
Three Types of Proprioceptors

Muscle spindles – measure the changing length of
a muscle
 Imbedded in the perimysium between muscle


fascicles
Golgi tendon organs – located near the muscletendon junction
 Monitor tension within tendons
Joint kinesthetic receptors
 Sensory nerve endings within the joint capsules
Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings
Proprioceptors
Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings
Table 14.1 (4 of 4)
Structure of Proprioceptors
Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings
Figure 14.4