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95 terms

The Peripheral Nervous System

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all neural structures outside the brain and spinal cord are known as...
The Peripheral Nervous System
The Peripheral Nervous System provides what?
They provide links to and from the external environment
Peripheral Nervous System includes what 4 things?
Includes sensory receptors, peripheral nerves, associated ganglia, and motor endings
Structures specialized to respond to stimuli are
Sensory Receptors
Activation of sensory receptors results in _____________ that trigger impulses to the CNS
Depolarizations
This receptor respond to touch, pressure, vibration, stretch, and itch
Mechanoreceptors
This receptor are sensitive to changes in temperature
Thermoreceptors
This receptor respond to light energy (e.g., retina)
Photoreceptors
This receptor respond to chemicals (e.g., smell, taste, changes in blood chemistry)
Chemoreceptors
These receptors are sensitive to pain-causing stimuli
Nociceptors
What are the three different receptor classes
-Exteroceptors
-Interoceptors
-Proprioceptors
This class of receptors respond to stimuli arising outside the body
Exteroceptors
This class of receptors respond to stimuli arising within the body
Interoceptors
This class of receptors are found near the body's surface
Exteroceptors
This receptor class respond to degree of stretch of the organs they occupy
Proprioceptors
This receptor class is found in internal viscera and blood vessels
Interoceptors
This class of receptors are sensitive to touch, pressure, pain, and temperature
Exteroceptors
This receptor class is sensitive to chemical changes, stretch, and temperature changes
Interoceptors
This receptor class is found in skeletal muscles, tendons, joints, ligaments, and connective tissue coverings of bones and muscles
Proprioceptors
This class of receptors constantly "advise" the brain of one's movements
Proprioceptors
Survival depends upon _________ and _________
sensation, perception
The awareness of changes in the internal and external environment is called
Sensation
The conscious interpretation of those stimuli is called
Perception
Cordlike organ of the PNS consisting of peripheral axons enclosed by connective tissue
Nerve
Connective tissue coverings include:
-Epineurium
-Perineurium
-Endoneurium
Coarse connective tissue that bundles fibers into fascicles
Perineurium
Tough fibrous sheath around a nerve
Epineurium
Loose connective tissue that surrounds axons
Endoneurium
4 Classification of nerves include:
• Sensory and motor divisions
• Sensory (afferent)
• Motor (efferent)
• Mixed
What is the most common type of nerve?
Mixed nerves
Carry impulses from CNS
Motor (efferent)
Carry impulse to the CNS
Sensory (afferent)
Sensory and motor fibers carry impulses to and from CNS
Mixed
The four types of mixed nerves are:
- Somatic afferent and somatic efferent - Visceral afferent and visceral efferent
Carry somatic and autonomic (visceral) impulses
Mixed Nerves
___________ originate from the brain or spinal column
Peripheral nerves
Damage to nerve tissue is serious because mature neurons are _______
Amitotic
A damaged nerve can only be repaired if the ________ remains intact
Soma
Regeneration involves coordinated activity among:
- Macrophages - remove debris
- Schwann cells - form regeneration tube and secrete growth factors
- Axons - regenerate damaged part
How many pairs of cranial nerves arise from the brain
Twelve
______ cranial nerves carry parasympathetic fibers that serve muscles and glands. They are:
Four;
(3) Oculomotor, (7) Facial, (9) Glossopharyngeal, (10) Vagus
T/F Cranial Nerves have sensory, motor, or both sensory and motor functions
True
Which cranial nerve functions solely by carrying afferent impulses for the sense of smell
Olfactory (1)
Which cranial nerve functions solely by carrying afferent impulses for vision
Optic (2)
Which cranial nerve functions in raising the eyelid, directing the eyeball, constricting the iris, and controlling lens shape
Oculomotor (3)
Which cranial nerve passes through the cribriform plate of the ethmoid bone
Olfactory (1)
Which cranial nerve arises from the retina of the eye and passes through the optic canals and converge at the optic chiasm
Optic (2)
Which cranial nerve have fibers extend from the ventral midbrain, pass through the superior orbital fissure, and go to the extrinsic eye muscles
Oculomotor (3)
Which cranial nerve which is primarily a motor nerve that directs the eyeball
Trochlear (4)
The fibers of this cranial nerve emerge from the dorsal midbrain and enter the orbits via the superior orbital fissures; innervate the superior oblique muscle
Trochlear (4)
What are the 3 divisions of the Trigeminal Nerve?
-ophthalmic (V1),
-maxillary (V2),
-mandibular (V3)
The fibers of this cranial nerve leave the inferior pons and enter the orbit via the superior orbital fissure
Abdcuens (6)
The fibers of this cranial nerve leave the pons, travel through the internal acoustic meatus, and emerge through the stylomastoid foramen to the lateral aspect of the face
Facial (7)
This cranial nerve conveys sensory impulses from various areas of the face (V1) and (V2), and supplies motor fibers (V3) for mastication
Trigeminal (5)
This cranial nerve is primarily a motor nerve innervating the lateral rectus muscle
Abdcuens (6)
Mixed cranial nerve with five major branches
• Motor functions include facial expression, and the transmittal of autonomic impulses to lacrimal and salivary glands
• Sensory function is taste from the anterior two-thirds of the tongue
Facial (7)
Fibers of this cranial nerve 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
Vestibulocochlear (8)
Two divisions of vestibulocochlear are:
-Cochlear (hearing)
-Vestibular (balance)
Fibers from this cranial nerve emerge from the medulla, leave the skull via the jugular foramen, and run to the throat
Glossopharyngeal (9)
The only cranial nerve that extends beyond the head and neck
Vagus (10)
Functions of this cranial nerve include equilibrium and hearing
Vesibulocochlear (8)
• Motor - innervates part of the tongue and pharynx, and provides motor fibers to the parotid salivary gland
• Sensory - fibers conduct taste and general sensory impulses from the tongue and pharynx
Which cranial nerve is it?
Glossopharyngeal (9)
• Most motor fibers are parasympathetic fibers to the heart, lungs, and visceral organs
• Its sensory function is in taste
Which cranial nerve is it?
Vagus (10)
The accessory nerve leaves the cranium via the ________ foramen
Jugular
This cranial nerve is formed from a cranial root emerging from the medulla and a spinal root arising from the superior region of the spinal cord
Accessory (11)
This cranial nerve innervates both extrinsic and intrinsic muscles of the tongue, which contribute to swallowing and speech
Hypoglossal (12)
This cranial nerve is primarily a motor nerve
- Supplies fibers to the larynx, pharynx, and soft palate
- Innervates the trapezius and sternocleidomastoid, which move the head and neck
Accessory (11)
______________ pairs of mixed nerves arise from the spinal cord and supply all parts of the body except the head
Thirty-one
Name the 31 pairs of mixed nerves:
- 8 cervical (C1-C8)
- 12 thoracic (T1-T12)
- 5 Lumbar (L1-L5)
- 5 Sacral (S1-S5)
- 1 Coccygeal (C0)
Each spinal nerve connects to the spinal cord via ____ _________ ______
Two medial roots
Each root forms a series of ________ that attach to the spinal cord
Rootlets
_________ ______ arise from the anterior horn and contain motor (efferent) fibers
Ventral roots
_________ _____ arise from sensory neurons in the dorsal root ganglion and contain sensory (afferent) fibers
Dorsal roots
All ventral rami except T2-T12 form interlacing nerve networks called _______.
Plexuses
Fibers travel to the periphery via several different routes are called...
Nerve Plexuses
Plexuses are found where?
-Cervical
-Brachial
-Lumbar
-Sacral regions
The major nerves of the lumbar plexus are the _______ and the _________.
Femoral and Obturator
Arises from L4-S4 and serves the buttock, lower limb, pelvic structures, and the perineum
sacral plexus
The longest and thickest nerve of the body is the
Sciatic
The sciatic is composed of what two nerves?
Tibial and fibular (peroneal) nerves
A __________ is the area of skin innervated by the cutaneous branches of a single spinal nerve
Dermatome
All spinal nerves except ____ participate in dermatomes
C1
any nerve serving a muscle that produces movement at a joint also innervates the joint itself and the skin over the joint is known as
Hilton's Law
A _______ is a rapid, predictable motor response to a stimulus
Reflex
Reflexes may:
- Be inborn (intrinsic) or learned (acquired)
- Involve only peripheral nerves and the spinal cord
- Involve higher brain centers as well
What are the five components of a reflex arc?
- Receptor - site of stimulus
- Sensory neuron - transmits the afferent impulse to the CNS
- Integration center - either monosynaptic or polysynaptic region within the CNS
- Motor neuron - conducts efferent impulses from the integration center to an effector
- Effector - muscle fiber or gland that responds to the efferent impulse
For skeletal muscles to perform normally:
- The Golgi tendon organs (proprioceptors) must constantly inform the brain as to the state of the muscle
- Stretch reflexes initiated by muscle spindles must maintain healthy muscle tone
Stretching the muscle activates what?
The muscle spindles
Excited Y motor neurons of the spindle cause the stretched muscle to _____________
Contract
________ impulses from the spindle result in inhibition of the antagonist.
Afferent
__________ is initiated by stimulating the lateral aspect of the sole of the foot
- The response is downward flexion of the toes
- Indirectly tests for proper corticospinal tract functioning
Plantar Reflex
___________ is the abnormal plantar reflex indicating corticospinal damage where the great toe dorsiflexes and the smaller toes fan laterally
Babinski's sign
Spinal nerves branch from the developing _______ ______ and ______ ________
- Supply motor and sensory function to developing muscles
spinal cord and neural crest cells
________ _________ innervate muscles of the head
Cranial nerves
Sensory receptors _________ with age and muscle tone lessens
atrophy