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Chapter 13:
Peripheral Nervous System
129
Anatomy
Undergraduate 2
12/01/2011

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Term
Peripheral Nervous System
Definition
all neural structures outside the brain and spinal cord
Term
PNS
Definition
includes sensory receptors, peripheral nerves, associated ganglia, and motor endings. Provides links to and from the external environment
Term
Sensory Receptors
Definition
Structures specialized to respond stimuli
Activation of sensory receptors results in depolarizations that trigger impulses to the CNS. The realization of these stiumli, sensation and perception, occur in the brain
Term
Receptor Classification by Stimulus Type
Definition
Mechanoreceptors, thermoreceptors, photreceptors, chemoreceptors, nociceptors
Term
Mechanoreceptors
Definition
responds to touch, pressure, vibration, stretch, and itch
Term
Thermoreceptors
Definition
sensitive to changes in temperature
Term
Photoreceptors
Definition
responds to light energy (e.g., retina)
Term
Chemoreceptors
Definition
responds to chemicals (e.g.,smell, taste, changes in blood chemistry)
Term
Nociceptors
Definition
sensitive to pain-causing stimuli
Term
Receptor Class by Location: Exteroceptors
Definition
Respond to stimuli arising outside the body. Found near the body surface. Sensitive to touch, pressure, pain, and temperature. Include the special sense organs
Term
Receptor Class by Location: Interoceptors
Definition
Respond to stimuli arising within the body. Found in internal viscera and blood vessels. Sensitive to chemical changes, stretch, and temperature changes
Term
Receptor Class by Location: Proprioceptors
Definition
Responds to degree of stretch of the organs they occupy. Found in skeletal muscles, tendons, joints, ligaments, and connective tissue coverings of bones and muscles. Constantly "advise" the brain of one's movements.
Term
Sensation
Definition
the awareness of changes in the internal and external environment
Term
Perception
Definition
the conscious interpretation of those stimuli
Term
Organization of the Somatosensory System: Input
Definition
Comes from exteroceptors, proprioceptors, and interoceptors
Term
Three main levels of neural integration in the somatosensory system
Definition
Receptor level, Circuit level, perceptual level
Term
Neural Integration: Receptor level
Definition
the sensor receptors
Term
Neural Integration: Circuit level
Definition
Ascending pathways
Term
Neural Integration: Perceptual level
Definition
neuronal circuits in the cerebral cortex
Term
Processing at the Receptor Level: Specificity
Definition
Stimulus energy must be specific to the receptor
Term
Processing at the Receptor Level: Receptive field
Definition
Receptive field must be stimulated
Term
Processing at the Receptor Level: Conversion
Definition
Stimulus energy must be converted into a graded potential
Term
Processing at the Receptor Level: Threshold
Definition
A generator potential in the associated sensory neuron must reach threshold
Term
Adaptation of Sensory Receptors: Cause
Definition
Adaptation occurs when sensory receptors are subjected to an unchanging stimulus. Receptor membranes become less responsive. Receptor potentials decline in frequency or stop
Term
Adaptation of Sensory Receptors: Quick adaptation
Definition
Receptors responding to pressure, touch, and smell adapt quickly
Term
Adaptation of Sensory Receptors: Slow Adaptation
Definition
Merkel's discs, Ruffini's corpuscles, and interoceptors that responds to chemical levels in the blood
Term
Adaptation of Sensory Receptors: Non-adaptive
Definition
Pain and proprioceptors do not exhibit adaptation
Term
Processing at the Circuit level
Definition
Chains of three neurons conduct sensory impulses upward to the brain
Term
Three types of neurons
Definition
First order, Second order, Third order
Term
First-order neurons
Definition
soma reside in dorsal root or cranial ganglia, and conduct impulses from the skin to the spinal cord or brain stem
Term
Second-Order Neurons
Definition
soma reside in the dorsal horn of the spinal cord or medually nuclei and transmit impulses to the thalamus or cerebellum
Term
Third-order neurons
Definition
located in the thalamus and conduct impulses to the somatosensory cortex of the cerebrum
Term
Processing at the perceptual level
Definition
The thalamus projects fibers to the somatosensory cortex and sensory association areas. First one modality is sent, then those considering than one. The result is an alternative, conscious image of the stimulus.
Term
Main Aspects of Sensory Perception
Definition
Perceptual detection, Magnitude estimation, Spatial discrimination, Feature abstraction, Quality discrimination, Pattern recognition
Term
Perceptual detection
Definition
detecting that a stimulus has occurred and requires summation
Term
Magnitude estimation
Definition
how much of a stimulus is acting
Term
Spatial discrimination
Definition
identifying the site or pattern of the stimulus
Term
Feature abstraction
Definition
used to identify a substance that has specific texture or shape
Term
Quality discrimination
Definition
the ability to identify submodalities of sensation (sweet or sour tastes)
Term
Pattern recognition
Definition
ability to recognize patterns in stimuli (melody, familiar faces)
Term
Nerve
Definition
cordlike organ of the PNS consisting of peripheral axons enclosed by connective tissue
Term
Structure of a nerve: Connective tissue coverings
Definition
Endoneurium, Perineurium, Epineurium
Term
Endoneurium
Definition
loose connective tissue that surrounds the axons
Term
Perineurium
Definition
coarse connective tissue that bundles fibers into fasicles
Term
Epineurium
Definition
tough fibrous sheath around a nerve
Term
Classification of Nerves
Definition
Sensory (afferent) and motor (efferent) divisions.
Term
Sensory (afferent) nerves
Definition
carry impulse to the CNS
Term
Motor (efferent) nerves
Definition
carry impulses from CNS
Term
Mixed nerves
Definition
sensory and motor fibers carry impulses to and from CNS; most common type of nerve
Term
Mixed Nerves
Definition
carry somatic and autonomic (visceral) impulses
Term
Four types of mixed nerves are...
Definition
Somatic afferent and somatic efferent
Visceral afferent and visceral efferent
Term
Peripheral nerve origination
Definition
brain or spinal column
Term
IF the soma of a damaged nerves remains intact...
Definition
damage can be repaired
Term
Regeneration of nerves involves coordinated activity among...
Definition
Macrophages - remove debris
Schwann cells - form regeneration tube and secrete growth factors
Axons - regeneration damaged part
Term
Cranial nerves: How many
Definition
12 from the brain
Term
Cranial nerves: functions
Definition
Both sensory and motor functions
Term
How many nerves carry parasympathetic fibers that serve muscles and glands?
Definition
4
Term
Cranial nerve I: Name, sensory function, motor function, Parasympathetic fibers
Definition
Olfactory, Smell, None, None
Term
Cranial nerve II: Name, sensory function, motor function, Parasympathetic fibers
Definition
Optic, Yes, None, None
Term
Cranial nerve III: Name, sensory function, motor function, Parasympathetic fibers
Definition
Oculomotor, None, Yes, Yes
Term
Cranial nerve IV: Name, sensory function, motor function, Parasympathetic fibers
Definition
Trochlear, None, Yes, No
Term
Cranial nerve V: Name, sensory function, motor function, Parasympathetic fibers
Definition
Trigeminal, General Sensation, Yes, None
Term
Cranial nerve VI: Name, sensory function, motor function, Parasympathetic fibers
Definition
Abducens, none, yes, none
Term
Cranial nerve VII: Name, sensory function, motor function, Parasympathetic fibers
Definition
Facial, Taste, Yes, Yes
Term
Cranial nerve VIII: Name, sensory function, motor function, Parasympathetic fibers
Definition
Vestibulocochlear, hearing and balance, Some, None
Term
Cranial nerve IX: Name, sensory function, motor function, Parasympathetic fibers
Definition
Glossopharyngeal, Taste, Yes, Yes
Term
Cranial nerve X: Name, sensory function, motor function, Parasympathetic fibers
Definition
Vagus, taste, Yes, Yes
Term
Cranial nerve XI: Name, sensory function, motor function, Parasympathetic fibers
Definition
Accessory, None, Yes, None
Term
Cranial nerve XII: Name, sensory function, motor function, Parasympathetic fibers
Definition
Hypoglossal, None, Yes, None
Term
Cranial Nerve I: Olfactory
Definition
Arises from the olfactory epithelium
Passes through the cribriform plate of the ethmoid bone
Fibers run through the olfactory bulb and terminate in the primary olfactory cortex
Functions solely by carrying afferent impulses for the sense of smell
Term
Cranial Nerve II: Optic
Definition
Arises from the retina of the eye.
Optic nerves pass through the optic canals and converge at the optic chiasm
They continue to the thalamus where they synapse
From there, the optic radiation fibers run to the visual cortex
Functions solely by carrying afferent impulses for vision
Term
Cranial Nerve III: Oculomtor
Definition
Fibers extend from the ventral midbrain, pass through the superior orbital fissure, and go the extrinsic eye muscles
Functions in raising the eyelid, directing the eyeball, constricting the iris, and controlling lens shape
Parasympathetic cell bodies are in the ciliary ganglia
Term
Cranial Nerve IV: Trochlear
Definition
Fibers emerge from the dorsal midbrain and enter the orbits via the superior orbital fissures; innervate the superior oblique muscle
Primarily a motor nerve that directs the eyeball
Term
Cranial Nerve V: Trigeminal - divisions
Definition
V1: Opthalmic
V2: Maxillary
V3: Mandibular
Term
Cranial Nerme V: Trigeminal
Definition
Fibers run from the face to the pons via the superior orbital fissure (V1), the foramen rotundum (V2), and the foramen ovale (V3)
Conveys sensory impulses from various areas of the face (V1) and (v2) and supplies motor fibers for mastication
Term
Cranial Nerve VI: Abducens
Definition
Fibers leave the inferior pons and enter the orbit via the superior orbital fissure. Primarily a motor nerve innervating the lateral rectus muscle
Term
Cranial Nerve VII: Facial
Definition
Fibers leave the pons, travel through the internal acoustic meatus, and emerge through the sylomastoid foramen to the lateral aspect of the face
Mixed nerve with five major branches
Term
Cranial Nerve VII: Facial - motor functions
Definition
Facial expression, transmittal of autonomic impulses to lacrimal and salivary glands
Term
Cranial Nerve VII: Facial - sensory functions
Definition
Taste from the anterior two-thirds of the tongue
Term
Cranial nerve VIII: Vestibulocochlear
Definition
Fibers arise from the hearing and equilibrium apparatus of the inner ear, pass through the internal acoustic meatus, and enter the brainstem at the pons-medulla border
Term
Cranial nerve VIII: Vestibulocochlear - divisions
Definition
Cochlear (hearing) and vestibular (balance)
Term
Cranial nerve VIII: Vestibulocochlear - functions
Definition
Solely sensory - equilibrium and hearing
Term
Cranial Nerve IX: Glossopharyngeal
Definition
Fibers emerge from the medulla, leave the skull via the jugular foramen, and run to the throat
Mixed nerve with motor and sensory functions
Term
Cranial Nerve IX: Glossopharyngeal - motor functions
Definition
innervates part of the tongue and pharynx, and provides motor fibers to the parotid salivary gland
Term
Cranial Nerve IX: Glossopharyngeal - sensory function
Definition
fibers conduct taste and general sensory impulses from the tongue and pharynx
Term
Cranial nerve X: Vagus
Definition
Only cranial nerve that extends beyond the head and neck
Fibers emerge from the medulla via the jugular foramen
A mixed nerve
Term
Cranial nerve X: Vagus - motor
Definition
parasympathetic fibers to the heart, lungs, and visceral organs
Term
Cranial nerve X: Vagus - sensory
Definition
in taste
Term
Cranial Nerve XI: Acessory
Definition
Formed from a cranial root emerging from the medulla and a spinal root arising from the superior region of the spinal cord
Spinal root passed upward into the cranium via the foramen magnum
Leaves the cranium via the jugular foramen
Term
Cranial Nerve XI: Acessory - motor functions
Definition
Supplies fibers to the larynx, pharynx, and soft palate
Innervate the trapezius and sternocleidomastoid which move the head and neck0
Term
Cranial Nerve XII: Hypoglossal
Definition
Fibers arise from the medulla and exit via the hypoglossal canal
Innervates both extrinsic and intrinsic muscle of the tongue which contribute to swallowing and speech
Term
Spinal Nerves
Definition
Thirty-one pairs of mixes nerves arise from the spinal cord and supply all parts of the body except the head. Named according to point of issue
Term
Spinal Nerves: Roots
Definition
Each spinal nerve connects to the spinal cord via two medial roots
Each root forms a series of rootlets that attach to the spinal cord
Term
Spinal Nerves: Ventral roots
Definition
Arise from the anterior horn and contain motor (efferent) fibers
Term
Spinal Nerves: Dorsal roots
Definition
Arise from sensory neurons in the dorsal root ganglion and contain sensory (afferent) fibers
Term
Spinal Nerves: Rami
Definition
Short spinal nerves branch into three or four mixed, distal rami (branches)
Term
Mixed, distal rami branches
Definition
Small dorsal ramus
Larger ventral ramus
Tiny meningeal branch
Rami communicantes at the base of the ventral rami in the thoracic region
Term
Nerve Plexuses: found where
Definition
All ventral rami except t2-t12 form interlacing nerve networks
Found in the cervical, brachial, lumbar, and sacral regions
Term
Nerve plexuses
Definition
Each resulting branch contains fibers from several spinal nerves
Fibers travel to the periphery via several different routes
Each muscle receives a nerve supply from more than one spinal nerve
Damage to one spinal segment cannot completely paralyze a muscle
Term
Spinal nerve Innervation: Back, Anterolateral Thorax, and Abdominal Wall
Definition
Back innervated by dorsal rami via several branches
The thorax is innervated by ventral rami t1-t12 as intercostal nerves
Intercostal nerves supply muscles of teh ribs, anterolateral thorax, and abdominal wall
Term
Cervical Plexus: Formed by
Definition
Ventral rami of C1-C4
Term
Cervical Plexus: branches are...
Definition
Cutaneaous nerves of the neck, ear, back of head, and shoulders
Term
Cervical Plexus: most important nerve
Definition
Phrenic nerve
Term
Phrenic nerve
Definition
major motor and sensory nerve of the diaphragm
Term
Brachial Plexus: Formed by...
Definition
C5-C8 and T1 (C4 and T2 may also contribute to this plexus)
Term
Brachial Plexus: function
Definition
gives rise to the nerves that innervate the upper limb
Term
Brachial plexus: branches
Definition
4 major branches
roots, trunks, divisions, cords
Term
Brachial plexus branches: Roots
Definition
Five ventral rami (C5-T1)
Term
Brachial plexus branches: Trunks
Definition
upper, middle, and lower, which forms divisions
Term
Brachial plexus branches: divisions
Definition
anterior and posterior serve the front and back of the limb
Term
Brachial plexus branches: cords
Definition
lateral, medial, and posterior fiber bundles
Term
Brachial plexus: nerves
Definition
Axillary, Musculocutaneous, Median, Ulnar, Radial
Term
Brachial plexus: Axillary nerve
Definition
innervates the deltoid and teres minor
Term
Brachial plexus: Musculocutaneous nerve
Definition
sends fibers to the biceps brachii and brachialis
Term
Brachial plexus: Median nerve
Definition
branches to most of the flexor muscles of the arm
Term
Brachial plexus: Ulnar nerve
Definition
supplies the flexor carpi ulnaris and part of the flexor digitorum profundus
Term
Brachial plexus: Radial nerve
Definition
innervates essentially all extensor muscles
Term
Lumbar plexus
Definition
Arises from L1-L4 and innervates the thigh and abdominal wall
Term
Lumbar plexus: major nerves
Definition
Femoral and the obturator
Term
Sacral Plexus
Definition
Arises from L4-S4 and serves the buttock, lower limb, pelvic structures
Term
Sacral Plexus: major nerve
Definition
sciatic nerve, the longest and thickest nerve of the body.
Term
Sciatic nerve
Definition
composed of two nerves: the tibial and the ocmmon fibular (peroneal) nerves
Term
Reflex
Definition
A rapid, predictable motor response to a stimulus.
May be inborn (intrinsic) or learned (acquired)
Involve only peripheral nerves and the spinal cord
Involve higher brain centers as well
Term
Reflex arc: Five components
Definition
Receptor, Sensory neuron, Integration Center, Motor neuron, Effector
Term
Reflex arc: Receptor
Definition
Site of stimulus
Term
Reflex arc: Sensory neuron
Definition
transmits the afferent impulse to the CNS
Term
Reflex arc: Integration center
Definition
either monosynaptic or polysnyaptic region within the CNS
Term
Reflex arc: Motor neuron
Definition
conducts efferent impulses from the integration center to an effector
Term
Reflex arc: Effector
Definition
muscle fiber or gland that responds to the efferent impulse
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