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

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