Peripheral Nervous Flashcards
Nerves and Scattered Ganglia
Cranial Nerves (12)
Spinal Nerves (31)
Autonomic Nervous System
Sympathetic Nervous System
Parasympathetic Nervous System
Special Senses
- Eye (Vision)
- Ears (Hearing and Balance)
- Taste and Smell (Chemical Senses)
Generalized Sense:
Touch
Spinal Nerves
Axons
Schwann Cells
Connective Tissue
Connective Tissue
Endoneurium
Perineurium
Epineurium
- Bundle of nerve fibers attached to spinal cord
- All are classified as mixed nerves
SPINAL NERVES
sensory fibers
Dorsal root
motor fibers
Ventral root
- Group of nerve fibers from ventral rami of cervical, lumbar and sacral spinal nerves
- is a network of intersecting nerves that serve the same
part of the body
Plexuses
Plexuses
- I. Cervical Plexus
- II. Brachial Plexus
- III. Lumbar Plexus
- IV. Sacral Plexus
- Formed by the first 4 cervical nerves (C1, C2, C3, C4)
- This supplies the back and sides of the head and front of the neck with ordinary sensory fibers
- Most important branch is the phrenic nerve composed of motor fibers supplying the diaphragm
Cervical Plexus
- Lower 4 cervical nerves (C5, C6, C7, C8) and first thoracic (T1),
which supplies the skin and muscles of the upper limb - With branches like the radial, ulnar, and median nerves
- It passes above the first rib posterior to the clavicle and then enters the axilla.
Brachial Plexus
- From L1 to L4 spinal nerves
- Femoral nerve: supplies muscle and skin on the anterior aspect of the thigh
- Obrutator nerve: supplies muscles and skin of medial aspect of thigh
Lumbar Plexus
- From L4, L5, S1, S2 and S3 spinal nerves
- The largest branch is called as “Sciatic Nerve”
Sacral Plexus
T1 – T11 spinal nerves
Intercostal Nerves
T12 spinal nerves
Subcostal Nerves
- are 12 pairs of symmetrically arranged nerves attached to the brain
- serve functions such as smell, sight, eye movement, and feeling in the face.
Cranial Nerves
- Carry impulses towards the brain
- Cranial Nerves: I, II, VIII
Purely Sensory Nerves
- Carry impulses away from the brain
- Cranial Nerves: III, IV, VI, XI, XII
Purely Motor Nerves
- Carry both sensory and motor nerve fibers
- Cranial Nerves: V, VII, IX, X
Mixed Nerves
- Efferent peripheral nerve fibers distributed to smooth muscles, cardiac muscles and glands
Autonomic Nervous System
Autonomic Subdivisions
- Sympathetic
- Parasympathetic
- Also called as Thoracolumbar Division
- Actions are directed toward mobilizing the body’s energy for dealing with an increase in activity
Sympathetic Division
- Also called as Craniosacral Division
- Arises from the 3rd, 7th, 9th and 10th cranial nerves and from the 2nd, 3rd, and 4th sacral segments of the spinal cord
- Action of this division conserve body energies
Parasympathetic Division
- Injury to the brain due to involvement of its blood vessels
Cerebrovascular Accident (CVA / Stroke)
- Infection of the meninges
Meningitis
- Manifestations of an abnormal discharge of nerve impulses from some part of the brain
Seizure Disorders
- Increased in CSF pressure
Hydrocephalus
- Complete loss of voluntary motor function due to dysfunction of nervous system
Plegia
- Weakness of voluntary muscle activity due to dysfunction of nervous system
Paresis
- Caused by a virus that damages the anterior horn cells of the cord and the motor nuclei of the cranial nerves
Infantile paralysis (poliomyelitis)
Patchy demyelinization in multiple areas of the nervous system involving sensory and motor fibers followed by replacement of the myelin by scarlike plaques
Multiple Sclerosis
- Cavitation of the central canal of the spinal cord and excessive multiplication of neuroglia in the gray substance around it
Syringomyelia
- Injury to one half of the spinal cord and involving neuronal groups and nerve tracts
J. Brown-Sequard Syndrome
- disabling senile dementia, the loss of reasoning and ability to care for oneself
K. Alzheimer’s Disease
Outer fibrous layer
sclera and cornea
Middle vascular layer or uveal tract
Iris, Choroid and Ciliary Body
Inner nervous tissue layer
retina
- white of the eye forms the outermost layer of the eyeball
-Consists of a firm fibrous membrane that maintains the shape of the eye
-Gives attachment to the extrinsic muscles of the eye
Sclera
-as a clear transparent epithelial membrane
-Light rays pass through the cornea to reach the retina
cornea
- Lines the posterior five-sixths of the inner surface of the sclera.
- Very rich in blood vessels
- Deep chocolate brown in color.
- Light enters the eye through the pupil, stimulates the sensory receptors in the retina and is then absorbed by the choroid
Choroid
- The anterior continuation of the choroid consisting of ciliary muscle (smooth muscle fibers) and secretory epithelial cells.
- Acts like a sphincter
- Lens is attached to the ciliary body by radiating suspensory ligaments, like the spokes of a wheel
- Supplied by parasympathetic branches of the oculomotor nerve (3rd cranial nerve).
Ciliary Body
- Visible colored ring at the front of the eye lying behind the cornea and in front of the lens.
- Composed of pigment cells and two layers of smooth muscle fibers - one circular and the other radiating
- In the center is an aperture called the pupil.
- Parasympathetic stimulation constricts the pupil and sympathetic stimulation dilates it
Iris
- Highly elastic circular biconvex body, immediately behind the pupil.
*Thickness is controlled by the ciliary muscle through the suspensory ligament.
*Lens bends (refracts) light rays reflected by objects in front of the eye - only structure in the eye that can vary its refractory power, which is achieved by changing its thickness.
Lens
*Innermost lining of the eye
*Extremely delicate structure and well adapted for stimulation by light rays
*Composed of several layers of nerve cell bodies and their axons - sensory receptor cells, rods and cones
Retina
*Composed of several layers of nerve
cell bodies and their axons
sensory receptor cells, rods and cones
- Near the center of the posterior part is the macula lutea, or yellow spot -little depression called the fovea centralis, consisting of only cones
*small area of retina where the optic nerve leaves the eye is the optic disc or blind spot-no light sensitive cells
Retina
Chambers of the eye
- Anterior chamber
- Posterior chamber
Anterior chamber
▪Front of lens
▪Filled with aqueous humor
Posterior chamber
▪Behind lens
▪Contains vitreous humor
▪Skin, muscle, and connective tissue
▪Blinking
✓Prevents surface from drying out
✓Keeps foreign material out of eye
Eyelids
▪Eye sockets
▪Form a protective shell around the eyes
Eye orbits
Mucous membranes
▪Line inner surfaces of eyelids
Conjunctivas
▪Six per eye - move the eyeball
✓Superiorly
✓Inferiorly
✓Laterally
✓Medially
*Extrinsic eye muscles
Lacrimal apparatus
▪Lacrimal glands
▪Nasolacrimal ducts
▪Lacrimal glands
✓Lateral edge of eyeballs
✓Produce tears
▪Nasolacrimal ducts
✓Medial aspect of eyeballs
✓Drain tears into nose
cornea, lens, and fluids bend light to focus it on the retina
Refraction
impairment of distance vision
▪Eyeball is too long
▪Light focuses anterior to retina
▪ Snellen chart
▪Normal vision
* 20/20
Myopia
impairment of near vision
▪Eyeball is shorter
▪Light focused posterior to retina
▪Test using a handheld chart with various sizes of print
Hyperopia
▪ Impairment due to aging
▪Loss of lens elasticity
Presbyopia
▪ Distinguish shades of gray
▪ Testing
* Pelli-Robson contrast sensitivity chart
* Vistech Consultants vision contrast system
▪ Detect cataracts or retinal problems before sharpness is
impaired
Contrast sensitivity
▪ Color-blindness
* May be inherited
* More common in males
▪ Tests
* Ishihara color system
* Richmond pseudoisochromatic color test
▪ Difficulties may indicate retinal or optic nerve disease
Color vision
Lazy eye; one eye is not used regularly;
poor depth perception; often concurrent
with strabismus
Amblyopia
Cornea or lens has abnormal shape;
blurred images
Astigmatism
Opaque structures in lens prevent light
from passing through; vision fuzzy
Cataracts
Pink eye; highly contagious bacterial infection
Conjunctivitis
Common problem; decreased
production of oil in tears
Dry eye syndrome
Inversion of lower eyelid
Entropion
Increase in intraocular pressure due to
a buildup of aqueous humor in anterior
chamber
Glaucoma
Farsightedness
Hyperopia
Progressive disease; inadequate blood supply to
retina; most common cause of vision loss; affects people
over 50 years
Macular degeneration
Nearsightedness
Myopia
Rapid, involuntary eye movements
Nystagmus
Loss of lens elasticity; develops
with age
Presbyopia
Layers of retina separate; medical
emergency
Retinal detachment
Misalignment of eyes Crossed eyes; one or both eyes
turn inward Wall eye; one or both eyes turn outward
Strabismus
Many animals secrete odorous chemicals called
pheromones
▪the sensory nerves of smell
Olfactory receptors (Olfactory nerves /first cranial nerves)
respond to changes in chemical concentrations
✓Chemicals must be dissolved in mucus - located in the olfactory
organ
✓Stimulate the olfactory chemoreceptors
Chemoreceptors
concentrates volatile molecules in the roof of the nose- increases the number of olfactory receptors stimulated and thus perception of the smell.
Sniffing
*Inflammation of the nasal mucosa prevents odorous substances
from reaching the olfactory area of the nose, causing loss of the
sense of smell
▪The usual cause is a cold
anosmia
*Chemical can stimulate receptors for limited time
*Receptors fatigue and stop responding to chemical
* No longer smell odor
Sensory Adaptation
found in the papillae of the tongue
Taste buds contain chemoreceptor
Small sensory nerve endings of the glossopharyngeal,
facial and vagus nerves
cranial nerves VII, IX and X
where taste is perceived
Parietal lobe of the cerebral cortex
How many taste buds are located on the tongue soft plate, pharynx, and larynx
Nearly 10,000
A single, long microvillus, projects from each receptor cell to the surface through the taste pore
Gustatory Hair
About 12 very large, form a row at the back of the tongue each houses 100-300 taste buds
Vallate Papillae
are mushroom shaped and are scattered over the entire surface of the tongue containing about 5 taste buds each
Fungiform Papillae
are located in small trenches on the lateral margins of the tongue, ut most of their taste buds degenerates in early childhood
Foliate Papillae
The entire surface of the tongue has it and contains tactile receptors but no taste buds
Filiform Papillae
serves taste buds in the anterior 2/3 of the tongue
Facial (VII) nerve
serves taste buds in the posterior1/3 of the tongue
Glossopharyngeal (IX) nerve
Taste cells and supporting structures
- On taste buds
- Supporting structures fill in space
- Taste cells
*Chemoreceptors
*Chemicals in food and drink
must be dissolved in saliva to
activate
the process of hearing, is accomplished by the organs of the ear
Audition
which uses air to collect and channel sound waves
External Ear
which uses a bony system to amplify sound vibrations
Middle Ear
which generates action potentials to transmit sound and balance information to the brain
Internal Ear
serves taste buds in the throat and epiglottis
Vagus (X) nerve
*External ear
- Auricle (pinna)
- External auditory canal
*External ear
- Auricle (pinna)
- External auditory canal* Tympanic membrane
- Tympanic membrane
- Collects sound waves
Auricle (pinna)
- Guides sound wave to tympanic
membrane
External auditory canal
- Separates external canal and middle ear
- Vibrates when sound hits it
Tympanic membrane
- Middle ear
- Ear ossicles
- Eustachian tube
- Oval window
- Ear ossicles
- Malleus
- Incus
- Stapes
- Ossicles vibrate in response to vibration of tympanic membrane
Ear ossicles
- Connects middle ear to throat
- Equalizes pressure on eardrum
Eustachian tube
- Separates middle ear from inner ear
Oval window
labyrinth of communicating chambers
Inner ear
detect balance of the body
Semicircular canals
equilibrium
Vestibule
Hearing receptors
Cochlea
organ of hearing
Organ of Corti
- Startled by loud noises
- Recognize mother’s voice
Infants to 4 months
- Regularly follow sounds
- Babble at people
4 to 8 months
- Respond to the sound of their name
- Respond to “no
8 to 12 months
Effects of Aging to the Ears
*External ear larger / earlobe longer
*Cerumen dryer and prone to impaction
*Ear canal narrower
*Eardrum shrinks and appears dull and gray
* Ossicles do not move as freely
* Semicircular canals less sensitive to changes in position
– affects balance
`Effects of Aging to the Ears
*External ear larger / earlobe longer
*Cerumen dryer and prone to impaction
*Ear canal narrower
*Eardrum shrinks and appears dull and gray
* Ossicles do not move as freely
* Semicircular canals less sensitive to changes in position
– affects balance
`Effects of Aging to the Ears
*External ear larger / earlobe longer
*Cerumen dryer and prone to impaction
*Ear canal narrower
*Eardrum shrinks and appears dull and gray
* Ossicles do not move as freely
* Semicircular canals less sensitive to changes in position
– affects balance
Symptom of a disease, not a normal part
of aging
Hearing Loss
Hearing Loss
- Conductive hearing loss
- Sensorineural hearing loss
- Interruption in transmission to inner ear
- Causes
- Obstruction of ear canal
- Infection of middle ear
- Reduced movement of stirrup
Conductive hearing loss
- Sound waves not perceived by brain as sound
- Causes
- Hereditary
- Repeated exposure to loud noises/viral infections
- Side effect of medication
Sensorineural hearing loss
causes damage to sensitive cells in
cochlea
Noise pollution
Hearing tests
*Tuning forks
*Audiometer
differentiate between types of loss
Tuning forks
measures hearing acuity
Audiometer
Diagnostic testing
Tympanometry
- Measures the ability of the eardrums to move
- Detects diseases and abnormalities of the middle ear
Tympanometry
Build up of wax within external auditory canal
Cerumen impaction
Deafness
Hearing loss
Disturbance in equilibrium characterized by vertigo and
tinnitus
Ménière’s disease
Inflammation of the ear
Otitis
Swimmers’ ear
Otitis externa
Middle ear infection; common infection
Otitis media
Labyrinthitis; inner ear infection
Otitis interna
Immobilization of the stapes; common cause of conductive hearing loss
Otosclerosis
Hearing loss due to aging process
Presbycusis
