A&p Chapter 14 Peripheral Nervous System

Front 1

Peripheral Nervous System (PNS)

Back 1

All parts of the NS except brain + spinal cord. Includes sensory receptors, peripheral nerves, associated ganglia, and motor endings. Provides links to and from the external environment.

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Ganglia

Back 2

Cluster/group of neuronal cell bodies outside of CNS

Front 3

Endoneurium

Back 3

Surrounds each axon

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Fascicles

Back 4

Are bundles of axons

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Perineureum

Back 5

Surrounds each fascicle

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Epineureum

Back 6

Surrounds the whole nerve

Front 7

Sensory receptors

Back 7

Are specialized to respond to changes in their enviornment called stimuli.

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Stimuli

Back 8

Changes in enviornment

Front 9

Define neuron

Back 9

A nerve cell

Front 10

Define nerve fiber

Back 10

An axon and its various sheaths
(In PNS, always have SC and often have myelin sheath)

Front 11

Define nerve

Back 11

Collection of nerve fibers and their specialized CT sheaths (epineurium, perineurium, endoneurium)

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Sensory receptors by stimulus:
Mechanoreceptors

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Touch, pressure, vibration, or stretch

Front 13

Sensory receptors by stimulus:
Thermoreceptors

Back 13

Temperature (internal or external)

Front 14

Sensory receptor by stimulus:
Photoreceptor

Back 14

Light (eyes-retina)

Front 15

Sensory receptor by stimulus:
Chemoreceptors

Back 15

Chemicals (blood ph, salt levels)

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Sensory receptor by stimulus:
Nociceptors

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Pain

Front 17

Sensory receptor by location:
Exteroreceptors

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Sensitive to external stimuli (pain, pressure, temperature, light)

Front 18

Sensory receptor by location:
Interoreceptors

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Responds to internal stimuli (chemicals, temperature, stretch)

Front 19

Sensory receptor by location:
Proprioceptors

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Responds to positon; found in muscles, tendons, joints, ligaments

(where body part is + state of connective tissue)

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Free or naked nerve endings

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Are present every where in body + responds primarily to pain + temperature

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Incapsulated dendritic endings:
Meissner's corpusles

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Are receptors for discrimminatory + light touch in hairless areas of body

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Incapsulated dendritic endings:
Pacinan or lamellated corpuscles

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Are stimulated when deep pressure is first applied

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Incapsulated dendritic endings:
Muscle spindles

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Detects when a muscle is being stretched + initiates reflex that resists stretch

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Incapsulated dendritic endings:
Golgi tendon organs

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Are stimulated when associated muscle stretches the tendon

Front 25

Incapsulated dendritic endings:
Joint kinesthetic receptors

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Monitors the stretch in articular capsules of synovial joints.

Front 26

Cranial nerves

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Emerges from brain

First 2 nerves sensory, rest are mixed

12 pairs

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Spinal nerves

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Emerges from spinal cord

31 pairs

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Cranial nerve I

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Olfactory

Front 29

Cranial nerve II

Back 29

Optic

Front 30

Cranial nerve III

Back 30

Oculomotor

Front 31

Cranial nerve IV

Back 31

Trochlear

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Cranial nerve V

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Trigeminal

Front 33

Cranial nerve VI

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Abducens

Front 34

Olfactory

Back 34

(Sensory) Receptors are in olfactory epithelium

Front 35

Olfactory damage:
Anosmia

Back 35

Fracture of ethmoid (perception of smell)

Actual damage to olfactory receptor (loss of smell)

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Optic

Back 36

(Sensory) Receptors in retina of eye

Front 37

Olfactory nerve passes through

Back 37

Cribriform plate of ethmoid to olfactory bulb

Front 38

Optic nerve passes through

Back 38

Optic foramen, partially crosses over at the optic chiasma

Front 39

Optic defect:
Anopsias

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Visual defects

Front 40

Oculomotor

Back 40

(Mixed) mainly motor nerves to 4 of the 6 eye muscles, eyelid, iris, and lens

Front 41

Oculomotor nerve passes through

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Superior orbital fissure of the ethmoid

Front 42

Oculomotor defect:
Ptosis

Back 42

Eyelids droop

Front 43

Oculomotor defect:
External strabismus

Back 43

Eyes rotate laterally, eyes don't move together - focusing becomes difficult

Front 44

Trochlear

Back 44

(Mixed) Mainly motor nerves to superior oblique muscle of eye

Front 45

Trochlear damage:

Back 45

Results in inability to rotate eye inferiolaterally

Front 46

Trigeminal

Back 46

(Mixed) Largest cranial nerve with 3 divisions

Front 47

Trigeminal:
V1 Opthalmic division

Back 47

Passes through the superior orbital fissure

Fibers come from nasal cavity, cornea, lacrimal gland

Tested by attempting to evoke corneal reflex

Front 48

Trigeminal:
V2 Maxillary divison

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Passes through foramen rotundum

Fibers from nasal cavity, palate, upper teeth, cheeks, lower eyelid

Tested with pin pricks + hot/cold objects

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Trigeminal:
V3 Mandibular divison

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Passes through the foramen ovale

To/from tongue lower teeth, chin

Tested by strength of jaw opening + closing, + lateral jaw movement

Front 50

Trigeminal damage:
Tic doulereux

Back 50

Inflammation of the trigeminal

Results in severe pain from slight stimuli

Partly treatable with drugs, in severe case nerve is severed

Front 51

Abducens

Back 51

(Mixed) Primarily motor to lateral rectus muscle of eye

Single muscle of eye

Front 52

Abducens defect:
Internal strabismus

Back 52

Eye cant move laterally

Front 53

Facial

Back 53

(Mixed) Somatic motor nerves run through internal acoustic meatus then stylomastoid foramen of temporal to muscls of facial expression, palate, tongue, salivary gland (sense of taste)

Front 54

Facial:
Parasympathetic motor nerves

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To lacrimal, nasal, salivary glands

Snesory nerves from anterior part of tongue

Front 55

Facial damage:
Bell's palsy

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Loss of taste, inability to tear, asymmetry of face

Paralysis of facial muscles, usually on 1 side, eyelid droops (results of herpes virus)

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Vestibulocochlear

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(Sensory) Cochlear divison transmits sound impulses

Vestibular division, equilibrium

Front 57

Vestibulocochlear damage:

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Deafness, dissiness, loss of balance, nausea

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Glossopharyngeal

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(Mixed) To/from pharnyx and part of tongue

Chemoreceptors for blood CO2 + O2 levels

Front 59

Glossopharyngeal damage:

Back 59

Damages gag and swallowing reflexes, impairment of taste

Front 60

Vagus

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(Mixed) Only cranial nerve that extends below neck

Autonomic regulation of heart, lungs, organs of abdominal cavity

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Vagus damage:

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Impaired peristalsis, difficult swallowing, death.

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Accessory

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(Mixed) Only cranial nerve that consists of cranial and spinal roo

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Accessory:
Cranial root

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Helps vagus control the muscles of the larynx and pharynx

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Accessory:
Spinal root

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Controls some of the major neck muscles

Front 65

Accessory damage:

Back 65

Causes head to turn to side, shoulder elevation becomes difficult

(Ask patient to move neck back)

Front 66

Hypoglossal

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(Mixed) Mostly motor to the tongue

Involved in speech + swallowing

Front 67

Hypoglossal damage:

Back 67

Inability to protrude tongue or tongue leaning to one side

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Spinal Nerve

Back 68

31 pairs - spinal nerves arise from spinal cord

Except for thoracics, ventral rami join together to form nerve plexuses

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Spinal nerve connects to spinal cord

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By dorsal + ventral root

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Rami

Back 70

Lie distal to + are lateral branches of spinal nerves that carry both motor + sensory nerves

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Dorsal rami

Back 71

Innevervated in back

Lie in point of origin from spinal column

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Ventral rami

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Only in thorax

Arranged in simple segmental pattern that corresponds to dorsal rami

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Cervical plexuses

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Formed by ventral rami of first four cranial nerve

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Brachial plexuses

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Stimulated partly in neck + axilla

Gives rise to virtually all nerves that inervate the upper limb

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Sacral + lumbar plexuses

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Overlap because many fibers of lumbar plexus contributes to sacral plexus via the lumbosacral trunk

The two plexuses are often referred as lumbosacral plexus

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Dermatones

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Area of skin innervated by cutaneous branches of single spinal nerve

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Hinton's law

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States that any nerve serving a muscle that produces movement at a joint also innervates the joint + skin over joint

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Somatic

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Conscious

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Visceral

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Internal organs

Front 80

Referred pain 1

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Some visceral afferent nerves ravel along the same pathways as the somatic nerves

The brain can interpret the impulses from the visceral nerves as being from skin + muscles

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Referred pain 2

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Heart is innervaed by T1-T5

Heart problems are mistakenly interpreted as coming from left arm

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Reflex

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Unlearned, rapid, predictable motor responses to stimulus + occur over highly specific neural pathways called reflex arcs

Response doesn't necessarily require brain

Front 83

Reflex arc process

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Receptor sends afferent impulses via sensory neuron to CNS.

The CNS, the integration center has neurons which recieve the information + stimulate a motor neuron to send an efferent impulse to effector (skeletal muscle)

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Reflexes can be

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Somatic (skeletal muscle) or autonomic

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Spinal reflexes

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Somatic reflexes mediated by spinal cord

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Reflex damage:

Back 86

Exaggerated, distorted, or absent reflexes indicate nervous system disorder

Front 87

Stretch reflexes

Back 87

Designed to prevent overstretching of muscles, connective tissues

Triggered by tapping on tendons attatched to muscles at elbow, wrist, knee + ankle joints

(Knee jerk)

Front 88

Stretch reflexes:
Monosynaptic process

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Muscle spindles detect slight stretch

Muscle spindle generates impulses to sensory neuron to posterior root of spinal nerve

Sensory neuron synapses with motor neuron in gray matter of spinal cord

Ach at NMJ triggers contraction of skeletal muscle

Front 89

Stretch reflex:
Knee jerk

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Stretches quadriceps as quickly as possible sends to dorsal root

(Sensory fiber goes in)

Designed to prevent overstretching or damage

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Flexor (withdrawl) reflex process

Back 90

Pain sensitive sensory neuron stimulated

Impulse propagates into spinal cord

Sensory neuron activated interneuron + signal sent to several segments

Several motor neurons activated + motor impulse propagates toward several NMJs

Ach released into synaptic cleft causes flexor muscles to contract, withdrawing body part from painful stimulus

Front 91

Stretch reflex diagnosis

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Absence or hypoactivity can indicate ventral horn signal or peripheral nerve damage,

diabetes mellitus,

nerosyphilis,

hyperactivity as seen in damage parts of corticospinal tract which sends inhibitory impulses.

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Diabetes mellitus

Back 92

Controls glucose levels

Front 93

Neurosyphilis

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STD

Front 94

Plantar relfexes

Back 94

A blunt object drawn along the sole of the foot normally causes curling of toes

Front 95

Plantar reflexes:
Babinski's sign

Back 95

1 degree motor cortex or corticospinal cord damage

Big toe dorsiflexes and the other toe fans laterally (normal in infants)

Front 96

Autonomic Nervous system

Back 96

Part of peripheral nervous system

COnsists of neurons that innervate involuntary muscle and glands

Also called:
Involuntary NS, General visceral NS

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Architecture of ANS

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Functional unit of ANS is almost always a two neuron chain

(CNS) Preganglionic neuron
(PNS) Postganglionic neuron
Effector organ

Front 98

Architecture of ANS:
Axons

Back 98

Axons tend to be relatively slow

Front 99

Architecture of ANS:
Preganglionic axon

Back 99

Thin and lightly myelinated axon

Front 100

Archiitecture of ANS:
Postganglionic axon

Back 100

Thinner and unmyelnated

Front 101

SNS

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Produces voluntary movements

Responds to consciously percieved sensory input

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ANS

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Produces involuntary movements (cardiac/smooth muscle + glands)

Responds to unconscious sensory input

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ANS reflex arcs

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Regulates activity of smotth, cardiac muscle + many glands

Continual flow of nerve impulses from autonomic sensory neurons in visceral organs + blood vessels propagates into integrating centers of CNS

Impulses in autonomic motor neurons propagate to various effector tissues

Can excite or inhibit activities of effector tissues

ANS activity is regulated by hypothalamus + brain stem of CNS

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Parasympathetic divison

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Most organs have dual innervation

Transmis opposing nerve impulses

Operates involuntary functions

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Norepinephrine (NE)

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speeds up or slows down

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Cholinergenic

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Neurons release acetylcholine

Front 107

Adrenergenic

Back 107

Neurons relase norepinephrine

Front 108

Presympathetic

Back 108

Starts at nerves (thoracolumbar location)

Front 109

Parasympathetic

Back 109

Starts at nerves (Craniosacral)

Normal body functions

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Blood vessels only have

Back 110

Parasympathetic NS

Front 111

Glycogenolysis

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Polysaccharide

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Lypolysis

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Breakdown of fats

Front 113

Sympathetic Division promotes

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"Fight or flight"

Allows more blood flow to heart + skeletal muscle

Speeds heart rate + strength of contraction

Promotes glycogenolysis, lipolysis

Stimulates arrector pilli muscles + sweat glands

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Effects of sympathetic NS are longer lasting than the effects of parasympathetic NS

Back 114

NE is inactivated more slowly than Ach

NE takes longer to exert its effect on postsynaptic cells

Adrenal medulla strengthens + helps maintain sympathetic effects

Front 115

Adrenal medulla

Back 115

Innervated by preganglionic neuron.

When sympathetic NS is activated, responds by releasing hormones, epinephrine + norepinephrine

Front 116

Adrenal medulla is actually a cluster of

Back 116

Modified postganglionic neurons.

Instead of releasing neurotransmitter NE to specific target,

It relases NE + epinephrine as hormones that circulate the blood. The effect is slower but longer lasting

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Sympathetic

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Dominates during "fight or flight" - extreme physical or emotional stress

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Parsympathetic

Back 118

Enhances rest + digest activities

Favors activities that support body functions that conserve + restore energy during rest + recovery

SLUDD: salivation, lacrimation, urination, digestion, defecation

Decreases: heart rate, diameter of airways, diameter of pupils.