1
Objectives for Nervous System
1. Explain the difference between the central nervous system & peripheral nervous system
2. Distinguish between the neurons & neuroglia cells & their function
3. Describe the Schwann cell in the peripheral nervous system
4. Discuss the membrane potential or action potential of membrane of nerve cells
5. Compare the difference between electrical & chemical synaptic transmission
6. Name the known neurotransmitters
7. Describe the neural reflex mechanism
8. Compare the sensory & motor pathways
9. Discuss the brain structure and sections
10. Explain the cerebral blood flow & blood brain barrier
11. State the manifestations noted in a deteriorating brain function
12. Differentiate the types of strokes
13. List 2 medical nervous system emergencies
14. Compare the types of traumatic brain bleeds
15. List 4 types of spinal cord injury and their presenting symptoms
16. State the cranial nerves in order
17. Compare the sympathetic & parasympathetic nervous systems
18. Describe the mechanisms of pain
19. Discuss how pain stimulation is transfer & processed
20. Compare the tactile, baroreceptors & proprioceptors for pain
21. Explain the final processing centers for pain stimuli
22. Discuss the process of smell & state what cranial nerve is involved
23. Explain the process of taste & list the cranial nerve involved
2
24. Explain the process of vision & state the cranial nerve involved
25. List the structures involved with vision
26. Explain the process of hearing
27. Discuss the structures involved with the process of hearing
28. Describe the vestibular system & explain its importance
3
Nervous System: Lecture 3
I. Nervous System (high metabolic need with 15% cardiac output & 20% oxygen) – NEITHER STORES
OR PRODUCES OXYGEN OR GLUCOSE
A. Organization – integration of both nervous (quick) & endocrine systems (slower)
1. Central Nervous System (CNS) – afferent & efferent divisions
a. Brain & spinal cord
b. Coordinates higher functions – sensory & motor
c. Controls and processes information
2. Peripheral Nervous System (PNS)
a. All neural tissue outside the CNS communicates to outside world
b. Relays information afferent to CNS and efferent to muscle/glands
c. Somatic nervous system (voluntary control) – SNS
1) Provides sensory & motor input muscles & glands
d. Autonomic nervous system (involuntary control) - ANS
1) Provides efferent motor stimulation to smooth muscles
of heart & glands
2) Division
a) Sympathetic- fight or flight, speeds up
b) Parasympathetic – counters, slows
B. Cells
1. Neurons= functional cells
a. Parts
1) Cell body (Soma)
a) Large nucleus with 1 or more nucleoli
b) Rough endoplasmic reticulum
c) DNA & RNA
d) Large amount ribosomes
e) Nissl bodies
(1) Spinal cord & brain tissue = gray color
2) Dendrites - receiver
a) Multi-branched extensions of nerve cell body
b) Conduct information toward cell body
c) Studded with synaptic terminals for communication
3) Axons – carrier
a) Long efferent processes from cell body
b) Cytoplasm of cell body fill axon
c) Proteins used synthesized by cell body
d) Axonal transport (rapid & slow)
4) Synaptic terminal (synaptic knobs) – communication site
b. Classification - functional
1) Sensory- afferent – information to CNS
a) Exteroceptors – provide information about external
Environment
4
b) Proprioceptors – monitor skeletal muscles and joint
position
c) Introceptors – monitor digestive, respiratory, CV,
deep sensation taste, pressure and pain, GU
5) Motor – efferent information- instructions from CNS to PNS
6) Interneurons – inside brain; analysis of sensory information &
motor response
c. Structural Classification
1) Multipolar – one or more dendrites; most common in CNS
motor neurons of skeletal
2) Unipolar – dendrite & axon continuous; sensory
3) Bipolar – 1 dendrite & 1 axon with soma in middle; rare
sight & hearing senses
2. Supporting Cells (Neuroglia or glial cells) = CNS & PNS – regulate environment
around neurons – smaller cells; more abundant than neuron;
can divide
a. Central Nervous System
1) Oligodendrocytes – myelin in CNS
a) Improve the speed of transmission
b) Nodes of Ranvier – gaps between myelin coverallow skipping
c) Myelin is lipid-rich
2) Astrocyte- largest & most numerous
a) Prominent in gray matter (rich in neuron cell bodies)
b) Transport of nutrients and wastes for CNS
c) Grab Ca & K
d) Repair tissue with scar called gliosis
3) Microglial – smallest and rare
a) Phagocytic cells from WBC
b) Protective function
c) Clean up crew
4) Ependymal – form lining of ventricular system
a) Choroid plexus = rich vascular network
(1) Cerebrospinal fluid produced
b. Peripheral Nervous System
1) Schwann Cells – cover for axon outside CNS
a) Increases speed of communication
b) Jelly roll fashion
c) Line up along neuronal process each own segment
d) Nodes of Ranvier
e) Surrounded by basement membrane & connective
tissue (endoneurium)
f) Fascicles- bundles nerves & blood vessels =
g) Perineurium – fascicles surrounded
h) Epineurial sheath – surround Perineurium
2) Satellite – surround & support neuron cell bodies in PNS
5
3. Functional Classification of Neurons (sensory, motor, interneuron)
a. Sensory (afferent division PNS) – receive information
1) External receptors – external environment information (touch)
2) Proprioceptors – monitor position & movement skeletal muscles
3) Visceral receptors (internal sensory) – monitor internal activities of
GI, GU, respiratory, CV, reproductive, taste, deep pressure
b. Motor
1) Somatic motor neurons – move skeletal muscle
2) Visceral motor neurons – move other like cardiac, smooth muscle,
glands, adipose tissue
c. Interneuron (association neurons) – CNS & Spinal cord interconnect
1) Higher function role
C. Communications or Neurophysiology
1. Membrane Potential
a. Stages
1) Resting – undisturbed
a) Outside = positive
b) Inside= negative
2) Depolarization – flow of electrically charged ions
a) Rapid inflow Na
b) Rapid outflow K
c) Local current moves impulse along
d) Graded potential – changes can’t spread far from site
stimulator
3) Repolarization – resting polarization re-established
a) Closure Na channels
b) Na/K pump returns to negative charge
b. Factors affecting resting potential
1) Cell membrane
2) Electrolytes
a) Sodium (Na) – extracellular high
b) Potassium (K) – intracellular high
c) Calcium (Ca)
d) Magnesium (Mg)
3) Channels (voltage gates)
4) Temperature
5) Chemicals
2.. Action Potentials – change in permeability of membrane
a. Skeletal muscles = contraction via synaptic terminal
b. Opening & closing of Na/K channels
c. All or nothing
d. Chain reaction along cells
1) Continuous propagation – slow, steady, forward movement
2) Unmyelinated axons = propagation
3) Myelinated = salutatory propagation – jumping & speed
6
e. Threshold – membrane depolarizes enough to have action potential
f. Refractory – membrane can’t respond no matter how strong stimuli
3. Synaptic transmission/communication
a. Electrical= passage of current- carrying ions = nerve impulses
1) Gap junctions
2) Quick passage
b. Chemical – most common & slower (Myasthenia Gravis)
1) Information transfer one neuron to effector cell
2) Transfer via neurotransmitters
3) Occurs over neuroeffector junction
a) Neuromuscular junction
b) Neuroglandular junction
4. Neurotransmitters (chemicals) – synaptic knob
a. Types
1) Acetylcholine (Ach) – cholinergic synapses
2) Norepinephrine (NE) – brain & ANS – adrenergic
3) Dopamine, gamma aminobutyric acid, serotonin – CNS
4) Nitric oxide & carbon monoxide - gases
b. Excitatory or inhibitory effects
1) Action neuron depends on balance between
2) If they were released at equal times would cancel each other
5. Neuronal Pool = group of interneurons with specific function
a. Divergence – information spreads from one neuron to many
1) Sensory bring to CNS – hot item= pain & reflex
b. Convergence – many give info to same postsynaptic neuron
1) Involuntary and voluntary control
c. Parallel processing – many pools get same info at same time
1) Makes possible sensory, motor, memory, speech
6. Nerve Plexuses – innervate large muscles by nerve trunks containing axons
from several spinal nerves = sensory & motor neurons
a. Cervical plexus – neck, thoracic, diaphragm
b. Brachial plexus – shoulder girdle & upper limb
c. Lumbar plexus – femoral, hip, skin over medial surface leg
d. Sacral plexus – gluteal – adductor & extensor hip & sciatic nerve –
knee, ankle, toes
7. Reflexes- automatic motor response to specific stimuli; rapid adjustments
involves sensory fibers deliver information from peripheral nerves
to CNS & motor fibers carry motor commands to peripheral effector; no
brain involvement; unconscious; protective;
a. Reflex arc – wiring ; negative feedback; receptor, sensory neuron, motor
neuron & effector included
1) Arrival & activation
2) Activation sensory neuron
3) Information processing
7
4) Activation motor neuron
5) Response of effector (muscle or gland)
b. Simple Reflex – sensory neuron synapse directly on motor neuron; quick
1) Stretch – automatic movement skeletal muscle length
a) Muscle spindles stimulate sensory neurons
that trigger motor response counters
b) Maintain posture & balance
c) Adjust muscle tone
d) Knee Jerk – unopposed contraction with stimulation;
example of stretch reflex
2) Damage
a) Absent = damage skeletal muscle, dorsal or ventral nerve
root, spinal nerve, spinal cord or brain
b) Hyperreflexia – severe spinal cord injury due to loss of motor
neuron connection with higher centers; areflexia to
hyperreflexia
c. Comples Reflexes – one interneuron between sensory neuron & motor
more delayed but more muscles involved
1) Withdrawal – moves stimulated part away from stimuli – pain
initiated also by touch or pressure receptor
a) Flexor – withdrawal reflex muscles of limb; yank
b) Reciprocal inhibition – prevent the opposing force
interneurons control the competition
(1 stimulated other is inhibited)
3) Spinal reflexes – higher center control with descending fibers
consistent, stereotyped triggered by external source
(descending tracts inhibit, fine tune, facilitate)
a) Babinski = toe fanning
1) High center or descending tracts injured appears
2) Infant positive due to immature synapses
b) Plantar = negative Babinski in adult
1) Damage to higher center or descending tract
causes return to positive reflex
D. Organization
1. Embryonic development = neural tube then segmented
a. Afferent become dorsal roots
b. Efferent become ventral roots
c. Longitudinal columns = afferent sensory neurons
in dorsal columns and efferent in ventral columns
e. Gray matter nerves arranged longitudinally in columns
2. Bilateral series of 11 cell columns
a. Four in dorsal root = sensory
b. Four in dorsal horn = sensory
8
c. Three in ventral horn = motor
E. Anatomy of System
1. Divisions
a. PNS
1) Ganglia – cluster of motor & sensory cell bodies
2) Nerves - bundles = spinal nerves
b. CNS
1) Centers
2) Tracts
3) Pathways (sensory & motor)
a) Sensory pathway (ascending) – monitor conditions in body
& external environment (1% reaches brain centers)
(1) Posterior column pathway = fine touch, pressure
vibration, position to cerebral cortex
(a) From spinal cord to medulla cross over
continue to thalamus to cortex
(b) Based on number of sensory receptor not
size of the site
(2) Spinothalamic pathway – poorly localized
sensations touch, pressure, pain, temperature
(3) Spinocerebellar pathway – proprioceptive
information muscles, bones, joints to cortex
b) Motor pathway – receive information from cortex commands
via SNS & ANS
(1) Efferent Division of PNS
(a) Somatic – voluntary control; direct over
skeletal muscles
(b) Autonomic nervous system –
unconscious control; control
over smooth muscle, cardiac muscle,
glands & fat cells
(2) Corticospinal pathway (pyramidal) conscious
skeletal muscle control begins
brain triangular shaped pyramidal
cells cerebral cortex synapse brain
stem to spinal cord to lower motor
neuron cross over opposite side body
L side controlled by R hemisphere = p 305
(3) Medial & Lateral pathways – indirect
(extrapyramidal) – subconscious
involuntary control muscle tone &
movement neck, trunk, limbs
coordinate learned movement
9
(a) Movements spread throughout brain
(brain stem, thalamus, basal nuclei of
cerebrum, & cerebellum)
[1] Drugs affect = Parkinson like
(Pheothiazines) – block
dopamine
(4) Cerebral palsy – voluntary motor responses due
to brain trauma, drug exposure, genetics, loss
O2 during delivery 5-10 minutes affects basal
ganglia, cortex, cerebellum, hippocampus,
thalamus = speech, motor skills, balance,
memory, learning abilities
2. Meninges – cover brain & spinal cord providing physical stability & shock
absorption to CNS tissue; blood vessels bring nutrients & O2
a. Covering
1) Dura mater- tough outer covering; fused to bone in brain not SC
a) Epidural space – between dura mater and arachnoid in SC
lymph fluid decrease friction
b) Subdural space – between dura mater & arachnoid
2) Arachnoid – squamous cells – space
a) Subarachnoid space – delicate web of collagen and
elastic fibers filled with CSF = transport and
shock absorber
3) Pia mater- delicate inner layer laced with blood vessels
a) Highly vascular
b. Blood Brain Barrier- astrocytes maintain and protect brain
1) Impermeable to many compounds
2) Lipid-soluble can cross not water-soluble
3) Facilitated diffusion
c. Spinal Cord Anatomy
1) Central canal – narrow internal passageway for CSF
a) Posterior median sulcus – groove
b) Anterior median sulcus – deeper groove
c) Adult central cord to L1 or L2
d) Cauda equine – long ventral & dorsal roots
2) Sections
a) Cervical (C1-8)
b) Thoracic (T1-12)
c) Lumbar (L1-5)
d) Sacral (S1-5)
10
e) Coccygeal (1)
3) Roots (spinal segment paired) – intravertebral foramen
a) Dorsal Root – sensory neurons information to cord
b) Ventral Root – motor neuron information away from cord
4) Horns
a) Posterior – sensory
(1) Lateral gray horn = visceral motor control
smooth muscle, cardiac, glands
b) Anterior – motor
5) Segments around horns
a) Posterior gray commissure
b) Anterior gray commissure
c) Posterior median sulcus
c) Anterior white commissure
6) Spinal Nerve – bound distal & ventral root = single nerve
a) Mixed nerves = sensory & motor mix
b) Outside cord
7) Matter
a) Gray – glial & neuron cells; H-shaped
b) White - large numbers of Myelinated & unmyelinated
axons
(1) Columns (regions)
(a) Posterior white columns
(b) Anterior white columns
(c) Anterior white commissure
(d) Lateral white columns
(2) Tracts – inside the columns (small carry between
segment cord; large between cord & brain)
(a) Ascending = sensory
(b) Descending = motor
8) Dermatome – sensory fibers sent to skin receptor from cord
a) Nerve fibers join network to supply sensory to skin =
1 dermatome
b) Map of dermatome – zone is served by corresponding pair
d. Brain (cerebrum, diencephalons, midbrain, pons,
medulla oblongata, cerebellum)
11
1) Cerebral hemispheres structure
a) Structure
(1) Cerebral cortex
(2) Gyri – elevated ridges external
(3) Sulci – gyri separated by shallow depressions
(4) Fissures – deeper grooves
(5) Lobes – defined regions
(6) Central sulcus lateral deep groove from longitudinal
fissure
(7) Corpus Collosum – link between hemispheres
(8) Longitudinal fissure – separates hemispheres
b) Motor & Sensory Areas
(1) Precentral gyrus – primary sensory cortex
(2) Primary sensory cortex – direct voluntary movement
by controlling somatic motor neuron brain & SC
(3) Postcentral gyrus of parietal loabe – primary
sensory cortex = sensory information touch,
pain pressure, temperature
(3) Visual cortex – occipital lobe = visual information
(4) Gustatory cortex – frontal lobe – taste
(5) Auditory cortex – temporal lobe = hearing
(6) Olfactory cortex – temporal lobe = taste
c) Association Areas
(1) Somatic motor association (pre-motor cortex) –
coordinated learned movements
(2) Visual Association
(3) Somatic sensory association – primary sensory
cortex = light touch
d) Processing Centers – higher order
(1) General Interpretive (Wernicke’s area) – sensory
association reception; integrates personality
damage = inability to tell meaning of words
Left hemisphere
(a) Aphasia – inability speak or read
(2) Speech Center (Broca’s) – edge of Premotor cortex;
Left hemisphere – motor formation words;
breathing patterns for speech
(3) Prefrontal Cortex – frontal lobe; coordinates info
from entire cortex; abstract thinking,
consequences, damage = anxiety, anger
inability to place events in order
12
(4) Memory – consolidation = short to long term
(a) Short Term – primary memory –
recall immediate
(b) Long Term – last longer (your name)
stored cortex
(c) Special memory – face recognition
words, voices = temporal &
occipital
(d) Damage = amnesia
auditory association = sounds
thalamic, limbic = memory stores
e) Specialization
(1) Right – sensory inputs, auditory, visual awareness,
creative abilities, spatial –temporal awareness
more negative emotions
(2) Left – speech, language, reasoning, analysis
communication actions
2) Diencephalon
a) Thalamus – info controller for cortex
(1) Paired, egg-shaped with 3rd ventricle between
(2) Relay for all senses except smell
(3) Screens, sorts, preprocesses sensory information
prior to sending to cortex
b) Hypothalamus – endocrine, hormones, emotions
autonomic functions, instincts, behavior
c) Pituitary – primary link nervous & endocrine systems
(1) Anterior lobe – releases to blood; controlled by
releasing factors made in hypothalamus
(2) Posterior lobe – receives from hypothalamus
d) Epithalamus – pineal gland
3) Cerebral Hemisphere lobes– intellectual functions
memory, complex motor function, sensations
(cerebrum), thought function
a) Frontal lobe – behavior anticipation &
consequences, expressive aphasia
b) Parietal lobe – determines meaningfulness of
sensory input; where things are
13
c) Temporal lobe- discriminating sounds; long
term memory, what or who stimulus is;
hallucinations occur here, receptive
aphasia
d) Occipital lobe – visual fields & bright lights;
colors, motion, depth perception,
patterns, location in space
4) Ventricular system – internal cavities filled with CSF (hallow)
a) Four ventricles (3rd & 4th largest)
b) Cerebrospinal fluid – cushioning
(1) Produced in choroids plexus
(2) Produce 500ml/day
(3) Total in ventricles at time 150ml
(4) Replaced every 8 hours
(5) Free exchange between CSF & interstitial
(6) Circulation Subarachnoid space to superior
sagittal sinus
c) Lateral ventricle
(1) 1 per hemisphere
(2) No direct communication between 2 hemisphere
(3) Interventricular foramen – communicates with 3rd
th
d) 4 ventricle in pons & medulla oblongata
(1) Mesencephalic aquaduct – connects 3 & 4
found in midbrain
5) Brain stem (midbrain, pons, medulla oblongata – relay station
processing, to or from cerebrum or cerebellum
a) Midbrain (mesencephalon)
(1) Process auditory & visual information – Colliculi
(a) Superior colliculi – eyes, head, neck reflex
to visual
(b) Inferior colliculi – reflex eyes, head, neck to
auditory
(2) Generate involuntary responses
(3) Consciousness = Reticular Formation (RAS)
involuntary functions = wakefulness
(4) Contains descending & ascending nerve fibers
(5) Cranial nerves = III & IV = eye movement
(6) Cerebral peduncles – ventrolateral surface
(a) Descending fibers to cerebellum via pons
(b) Descending fibers voluntary motor from
primary motor cortex
(7) Maintain muscle tone & posture by integration
information from cerebrum & cellebellum
14
giving voluntary motor commands –
affected by Dopamine
b) Pons – connects cerebellum to brain stem
(1) Tracts & relay
(2) Visceral motor control
(3) Involuntary control rate & depth of respiration
c) Medulla Oblongata – attaches to spinal cord
(1) Relay information sensory to thalamus
(2) Regulates automatic functions (HR, BP, RR,
digestive)
(3) Cardiovascular center – adjust HR & strength beat
(4) Respiratory center – pace for respiration
adjustment via pons
6) Cerebellum – posterior brain – automatic processing center
“Little Brain” = 2 lobes
a) Voluntary & involuntary movement – maintain balance
fine tunes
b) Bases on sensory information
c) Stored memories
d) Fine tune movement, balance, postural muscles
proprioception & adjustments for smoothness
e) Ataxia – balance disturbance
7) Basal Ganglia – purposeful motor activity, coordinates posture
neurotransmitter dopamine, fine motor
a) Deep brain structure between lateral ventricles & central
white matter cerebral hemispheres
(1) Several pairs of nuclei at base cerebral hemisphere
(2) Adjacent, below & surround thalamus
b) Subconscious control skeletal muscle & coordination
learned movement patterns; doesn’t initiate moves
adjusts pattern & rhythm
c) Caudate nucleus – head & curving tail follows lateral ventricle
muscle control & memory (feedback)
d) Lantiform nucleus = globus pallidus & lateral putamen
(1) Globus pallidus – incoming info
(2) Lateral putamen – rounded & involved with
motor control, movement & learning
(a) Connects to pallidus & nigra
(b) Outgoing info
e) Substantia nigra – planning & monitor movements
(1) Most basal
15
(2) Dominated by melanin
(3) Dopamine emissions
(4) Outgoing info
8) Limbic system – functional grouping
a) Olfactory cortex, basal nuclei, gyri, tracts- border of
cerebrum & diencephalon
b) Emotional states fear, rage, sexual arousal
c) Conscious intellect function – “want to do”
d) Long term memory store
e) Eating movements like chewing, licking, swallowing
Mamillary bodies of hypothalamus
f) Hippocampus – learning & long term memory
(1) Part cerebral cortex
(2) Moves information to long term memory
(3) Damage prevents new memory formation
(4) Encodes memories – emotional part
g) Amygdaloid body = limbic system (emotional sensor)
(1) Link the Limbic , cerebrum & sensory systems
(2) Learning, memory, emotions; threats
(3) Anxiety & stress = good & bad memory store
(4) Unconscious emotions send message to
hypothalamus for fight or flight response
h) Hypothalamus
i) Thalamus
j) Mamillary body
k) Limbic lobe
d. Cerebral blood flow
1) Cerebral Circulation Anterior – unilateral injury; large arteries=
thrombosis; small arteries = clot
a) Internal Carotid (large)
b) Anterior Cerebral (small)
(1) Feeds leg- leg motor strip
(2) Flat affect
(3) Mental impairment
c) Middle Cerebral (small)
(1) Feeds arm- arm motor strip
(2) Sensory impairment
(3) Aphasia
2) Cerebral Circulation Posterior – brain stem, bilateral injury –
bilateral visual deficits, memory
a) Vertebral Artery (large)
16
b) Basilar Artery (large)
3) Cerebral Regulation of blood flow
a) Venous outflow affected by positioning
b) Created by folds in dura
c) No valves
F. Injury to the System
1. Manifestations of deteriorating brain function
a. Signs & Symptoms
1) Respiratory
2) Level of response
3) Posturing
4) Pupils
5) Eye movement
6) Vital Signs
2. Medical Injury
a. Stroke (signs & symptoms) – FAST (face numbness or weakness, arm
numbness or weakness one side, speech – slurred, time 911)
1) Ischemic (thrombosis – artherscleosis; embolism – a-fib)
2) Hemorrhagic
3) Transient Ischemic Attacks (TIA) – stroke-like
a) Bifurcation of carotid
b) S&S – blurred vision = direct flow to eyes
4) Penumbra – tissue around infarct area; salvageable tissue
5) Lacunar stroke – infarction small vessels from HTN
little or no deficits; lots lacunar = dementia
6) Cryptogenic – no cause; no risks, negative CT/MRI
b. Seizure – abnormal electrical discharge brain neurons
c. Upper motor neuron injury – spastic paralysis; CNS loss
1) Multiple Sclerosis (demyelinating disease of CNS)
17
d. Lower motor neuron – flaccid paralysis; loss muscle & neural
e. Ischemic
f. Cerebral edema
g. Hydrocephalus
h. Brain death
i. Tumors
j. Parkinson’s
3. Nervous System
a. Infections
1) Meningitis
a) Bacterial- medical emergency and contagious
(1) Streptococcal, H influenza, Neissiera
meningitidis
b) Viral – less severe
2) Parasitic infections
3) Abscess – pus with in brain or spinal tissue
4) Encephalitis – acute infection with CNS involvement
vector carried- mosquitoes
b. Headache
1) Stress
2) Migraine
3) Cluster – unilateral, severe restless pain “tearing”, short
4. Trauma
a. Blunt
b. Penetrating
c. Bleeds
1) Subdural - venous
2) Epidural – arterial; LOC, then awake, then LOC
3) Intracerebral hemorrhage
d. Herniations
e. Diffuse
f. Focal
5. Spinal Cord
a. Concussion
b. Contusion
c. Compression
d. Laceration – tearing, slight damage but repairable
18
e. Transection
f. Incomplete transaction – parts cut but tracts intact
g. Cord hemorrhage – bleeding into tissues
h. Anterior cord syndrome – compression paralysis below lesion
with loss pain and temperature but vibratory & sensation there
i. Central cord- disruption of blood with paralysis greater upper limbs
j. Brown-Sequard syndrome – transaction of half cord with loss position,
movement, vibratory sense same side and loss temperature &
pain opposite
k. Cauda Equina- injury lumbar fracture = weakness and sensory loss
l. Spinal shock – injury from T 6 and above with loss reflexes, sensation ,
loss sphincter tone, bradycardia, hypotension
m. Paralysis
1) Monoplegia
2) Hemiplegia
3) Paraplegia
4) Quadriplegia
n. Herniated disc
II Peripheral Nervous System
A. Cranial Nerves
1. Olfactory – I = smell
2. Optic – II = vision;
3. Oculomotor III = eyelid & eyeball movement; 4 out 6 muscles move eyes
amount light taken in lens, & shape eye
4. Trochlear – IV = eye turns down & medially
5. Trigeminal – V = chewing, face & mouth touch & pain
6. Abducens – VI = eye turns laterally
7. Facial – VII = facial expressions, tears & saliva, taste
8. Vestibulocochlear – VIII = hearing & equilibrium
9 Glossopharyngeal IX = taste, senses carotid BP
10. Vagus = slows heart, aortic BP, taste, digestive organ stimulation
11. Accessory = swallowing, shoulder movement
12. Hypoglossal = tongue movement
B. Autonomic Nervous System (vital organs dual innervation of 2 systems)
1. Sympathetic
a. Divisions
1) Preganglionic, ganglionic, specialized neurons (neurotransmitter)
2) Ganglionic
b. Organized
1) Sympathetic Chain (T1 to L2) – fight or flight preparation
19
2) Collateral Ganglia- innervate abdominal area & reduces blood
3) Adrenal Medullae – release neurotransmitter epinephrine &
norepinephrine; longer duration
e. Receptors
1) Adrenergic
1) Alpha 1
2) Alpha 2
3) Beta 1
4) Beta 2
2) Dopaminergic
2. Parasympathetic – preganglionic & ganglionic neurons
a. Opposite effects than sympathetic except blood vessels
b. Acetylcholine is neurotransmitter
1) Receptors nicotinic & muscarinic (cholinergic receptors)
a) Nicotinic
b) Muscarinic
3. Dual innervation
C. Sensory & Motor Pathways
1. Sensory
a. Posterior Column Pathway
2. Motor Pathway
a. Corticospinal pathway – pyramidal system = conscious control skeletal
muscles
a. Medial & Lateral pathways – subconscious involuntary control muscle tone
& movement neck, trunk, limbs; learned movements
(extrapyramidal system) – spread through brain
1) Drugs
20
2) Cerebral palsy
D. Spinal Nerves
1. Divisions
a. Cervical
b. Throacic
c. Lumbar
d. Sacral
e. Coccygeal
2. Nerve plexuses
a. Cervical
b. Brachial
c. Lumbar
III. Sensory Function
A. Pain- unpleasant sensation with emotional, sensory & potential tissue damage
associations; perceptions vary between people (nociceptors = receptors)
1. Receptors found in surface skin, joint capsules, walls of blood vessels,
Periostea of bone
2. Theories
a. Gate control
b. Loesser’s Onion
c. Melzack’s Neuromatrix
3. Mechanisms
a. Fast pain
b. Slow pain
c. Referred pain
d. Visceral
e. Acute pain
f. Chronic
g. Cutaneous
4. Processing of pain –transmission to somatosensory cortex, perceived, sent
to limbic for emotions, to brain stem and ANS added
a. Pain awareness can decrease with changes in thalamus, reticular
activating, lower brain stem, spinal cord
5. Stimulation of nociceptors
a. Mechanical = pressure
21
b. Chemical – prostaglandins, histamines, H ions
c. Substance P – peptide release
B. Thermal
1.Receptors (thermoreceptors)
a. Cold
b. Warmth
c. Pain
2. Process along same path as pain stimuli
3. React quickly then stabilize quickly
C. Machanoreceptors (touch, pressure, position)
1. Tactile receptors (touch)
a. Types
1) Fine
2) Crude
b. Skin tactile receptors
1) Free nerve roots
2) Root hair plexus
3) Merkel’s disc
4) Meissner’s corpuscles
5) Pacinian corpuscles
6) Ruffini corpuscles
2. Baroreceptors (pressure)
a. Locations
1) Carotid sinus & aortic
2) Lungs
3) Stomach and digestive tract
4) Bladder
5) Colon
b. Consist free nerve endings in elastic tissue of location
3. Proprioceptors ( position)
a. Monitors joints, tendons, ligaments and muscle contraction
b. Process = subconscious
c. Terminology
1) Proprioception- awareness of posture, movement,
changes in equilibrium; aware weight & resistance
2) Kinesthesia – perceive weight or direction of movement
D. Chemical
1. Chemoreceptors (water & lipid soluble substances)
a. Found : Carotid & aortic bodies
E. Final Processing
1. Thalamus – level of consciousness
2. Somatosensory cortex – full meaning of stimuli; found in parietal lobe
22
3. Sensory homunculus – off thalamus; fine touch
4. Somatosensory association cortex – information given meaning with past
Learning input
5. Spinal cord – goes up to CNS via dorsal roots to medial lemniscuses to
thalamus in medulla
IV. Special senses
A. Smell (olfactory)
1. Location
2. Olfactory organs
a. Olfactory epithelium
b. Olfactory receptors – supporting cells & stem cells
c. Olfactory glands – produce mucus
3. Highly modified neuron – large volume receptors in small space
a. Smell occurs with dissolving of substance onto receptors
b. Action potential occurs
c. Information sent to CNS and smell interpreted from pattern of
receptor activity and past exposure
4. Pathway
a. Axon leaving olfactory epithelium penetrate ethmoid bone to reach
olfactory bulb
b. Axons leave bulb & travel olfactory tract to olfactory cortex in cerebrum,
hypothalamus, & limbic system = Emotions attached
(Do not go through the thalamus)
c. Strong emotional ties with smells
5. Cranial nerve olfactory (1)
B. Taste (gustatory)
1. Organs
a. Taste buds- lie along epithelial projections – papillae
b. Gustatory cells – sensory receptors
c. Taste hairs – microvilli
d. Taste pore – fluid
2. Follows olfactory sensation paths
3. Chemical dissolve, change membrane potential, leads to action potential
for sensory neuron
4. Taste sensations
a. Sweet
b. Salt
c. Sour
d. Bitter
5. Cranial nerves facial (Vii), glossopharyngeal (IX), vagus (X) – projected to
primary sensory cortex
6. Trigeminal nerve (V) – burning taste
23
7. Operates with olfactory – congestion hinders
C. Vision
1. Processing – information carried from optic globe to CNS to
primary & visual association cortices transmit signal to visual images
via optic nerve; ipsilateral transport ; visual cortex final discrimination –
cerebrum; thalamus switching station; midbrain controls pupils
a. Vision dependent on 3 pairs cranial nerves Oculomotor (II), Trochlear
(IV), Abducens (VI)
b. Perfusion – ophthalmic artery, central artery of retina, anterior & middle
cerebral artery, posterior cerebral artery
2.Accessory Structures
a. Eyelids (palpebrae) – wipers
b. Medial canthus & lateral canthus (attachments of lids)
c. Eyelash
d. Lacrimal caruncle – sebaceous glands – sleep dirt
e. Conjunctive – anterior eye; epithelium continuous with eyelid
f. Lacrimal gland – upper; watery, alkaline tear with antibacterial
g. Lacrimal canals – passageway out
h. Nasolacrimal duct – tears to nasal cavity
i. Muscles
1) Inferior rectus
2) Lateral rectus
3) Medial rectus
4) Superior rectus
5) Inferior oblique
6) Superior oblique
j. Orbital fat
3. Anatomy of Eye
a. Eyeball (optic globe)
1) Anterior cavity (anterior chamber & posterior chamber)
2) Posterior cavity – vitreous chamber = vitreous body
3) Outer cover = fibrous tunic
a) Sclera – “white eye”- fibrous connective tissue
(1) Muscle attachments
(2) Thickest posterior
b) Cornea – continuous with sclera; collagen fibers in
layer arrangement; limited healing
4) Vascular tunic
a) Provides blood & lymph
b) Aqueous humor provided – pressures 9-21
(1) Canal of Schlemm – passage for fluid
c) Controls shape
d) Regulates light control
e) Structures
(1) Iris – blood vessels, pigment cells, smooth
muscles for constrictions
(2) Pupil – opening ; controlled by ANS
24
5) Neural
a) Retinal
(1) Rods – light sensitive
(2) Cones – color, sharper, clearer
b) Macula lutea – yellow spot – light arrival
c) Fovea centralis – center macula lutea filled with cones
d) Optic disc – medial fovea; origin optic nerve; impulse
leaves from here and goes to brain
e) Blind spot – on disc with no photoreceptors
6) Lens – behind cornea & held in place with ligaments
a) Accommodation
(1) Myopia
(2) Presbyopia
b) Visual acuity
D. Auditory (interpret sounds) & Equilibrium (body position in space)
1. Anatomy of Ear
a. Division
1) External Ear
a) Pinna or auricle
b) External auditory canal
c) Ceruminous glands
d) Tympanum (tympanic membrane or eardrum)
2) Middle Ear- filled with air
a) Auditory tube ( Eustachian tube)– equalizing pressure
b) Bones – moves air like levers
(1) Malleus
(2) Incus
(3) Stapes
3) Inner Ear –
a) Membranous labyrinth – network canals
filled with fluid – endolymph
(1) Bony Labyrinth
(2) Perilymph (CSF) & Endolymph (K like
Intracellular) fills labyrinth
(3) Vestibule – pair sacs – linear acceleration
(Cranial nerve VIII)
(a) Saccule
(b) Utricle
(4) Semicircular canals – head rotation
(5) Cochlea “snail” – sense of hearing
(a) Round window
(b) Oval window
(c) Cochlea duct – houses
25
spiral organ of Corti
b) Receptors – hair cells – neurotransmitters
(1) Stereocilia – microvilli – displace & move hair
for neurotransmitter release
c) Organ of Corti – receptor of hearing
(1) Supporting cells & chochlea hairs
(1 row inner & 3 rows outer)
2. Hearing
a. Sound transmitter from tympanic membrane to middle ear bones to oval
window to periotic fluid in scala vestibule and tympani, sound
transduction is with the bending of the hairs in Corti, afferent fibers in
cochlea with CN VIII pass to primary auditory cortex in temporal lobe
to thalamus to auditory association cortex = meaningfulness of sound;
fibers cross so sound from both ears received
3. Equilibrium
a. Types
1) Dynamic = balance with sudden head movement
2) Static = posture & stability with no movement
b. Mechanisms involved
1) Vestibule
2) Semicircular canals
4. Problems
a. Infections
b. Tinnitus
c. Hearing loss (conductive, age, sensory)
d. Nystagmus
e. Vertigo
f. Motion sickness,
g. Meniere disease
h. Drugs
i. Tumors
j. Temporal bone fractures
E. Emotional responses
1. Desire/addiction – link between wanting & needing with dopamine major chemical
a. Uses limbic system
b. Reward system = dopamine = addiction
1) Chronic use = exhaustion requires more to get reward
2) Examples
a) Opiate system = pain & anxiety relief – heroine & morphine
lock receptor = euphoria
b) Cholinergic circuits – memory & learning
26
cocaine – noradrenergic – anxiety & stress blocks
c. Anticipation – part of reward system
2. Oxytocin – “good feeling” – sex, bonding, childbirth
3. Dopamine – “good feelings” – bonding
4. Expressions = independent & signals
a. Smiling
1) Heartfelt = emotions = mouth & eyes
2) Social – conscious areas with no eyes
b. Social beings – well developed frontal cortex
5. Thinking, Memories, Consciousness