Transcript EEOB 235 Introductory Anatomy

Lecture 14 – Peripheral Nervous System
Peripheral Nervous System
carries information to and from CNS
components
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sensory receptors
motor endings
nerves
ganglia
Fig 14.2
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Sensory receptors
Lecture 14 – Peripheral Nervous System
classification systems
 based on location
exteroceptors
interoceptors
proprioceptors
 based on relevant stimulus
Mechanoreceptors detect physical deformation
Photoreceptors detect light
Chemoreceptors detect chemicals (nose and tongue)
Thermoreceptors detect temp
Nociceptors detect pain
 based on structure
free nerve endings
encapsulated nerve endings
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Lecture 14 – Peripheral Nervous System
Sensory receptors
types of receptors
 free nerve endings
abundant
stretch, pain, Temp
 Meissner’s corpuscles
Located in dermal papillae
light touch
 Pacinian corpuscles
close to hypodermis
deep pressure, vibration
 Ruffini’s corpuscles
dermis
prolonged pressure
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Lecture 14 – Peripheral Nervous System
Sensory receptors
types of receptors
 muscle spindles
wrap around intrafusal fibers
of skeletal muscle
detect rate and amount of
stretch on muscle
 Golgi tendon organs
muscle/tendon junction
detect tension
 joint kinesthetic receptors
sensory endings in joint capsules
similar to integument & Golgi
receptors
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Fig 14.4
Lecture 14 – Peripheral Nervous System
Peripheral motor endings
synapse at neuromuscular junctions
 1 axon terminal per fiber; > or = 1 fiber per neuron
 motor unit = neuron + muscle fibers
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Fig 10.10
Lecture 14 – Peripheral Nervous System
Peripheral motor endings
smooth muscle & glands
 innervation less direct than at NMJ
 swellings in visceral motor neuron terminals in
contact with or close to target
 response is slower than in skeletal muscle
** no direct innervation of cardiac muscle
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Lecture 14 – Peripheral Nervous System
Nerves
Cranial – details in lab
 can be sensory, motor,
or both (mixed)
 innervate (targets) head &
neck, abdomen (vagus nerve)
Spinal nerves
 31 pairs
 attach to cord by dorsal
and ventral roots (Fig 14.2)
 ventral rami form plexuses
Fig 14.6
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Lecture 14 – Peripheral Nervous System
Reflex pathways
rapid, involuntary motor responses
 somatic or visceral
pathway requires at least 2 neurons
receptor  sensory neuron  (CNS) 
motor neuron  effector/target
Monosynaptic reflex
sensory
neuron
Polysynaptic reflex
interneuron
motor
neuron
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