Nervous and Sensory System Vocabulary

Nervous System

CNS (Central Nervous System)

  • CNS = Brain + Spinal Cord

Structure of the Brain:

  • Cerebrum: Higher thinking, movement, sensation.
  • Cerebellum: Balance, coordination.
  • Brainstem: Vital functions (breathing, heart rate).
  • Spinal Cord: Connects brain to peripheral nerves.

Brainstem Breakdown:

  • Midbrain
  • Pons
  • Medulla Oblongata
    • Controls HR, breathing, vasomotor response.
    • Origin of cranial nerves III to XII.

Reflexes & Basic Life Functions:

  • Controls: Sneezing, coughing, swallowing
  • Reticular Formation: Filters sensory input, coordinates motor control.

Reticular Activating System (RAS)

  • Brainstem + Reticular Formation + Cerebral Cortex
  • Keeps you awake and alert
  • Injury here can lead to coma or sleep-wake disruptions.

Autonomic Nervous System (ANS) Integration

Sympathetic (Fight or Flight):

  • Increases HR, BP, dilates pupils.

Parasympathetic (Rest & Digest):

  • Decreases HR, increases digestion and salivation.

Located in:

  • Reticular formation
  • Hypothalamus
  • Brainstem and spinal cord

PNS (Peripheral Nervous System)

Components

  • Cranial Nerves (12 pairs)
  • Spinal Nerves (31 pairs)
  • Ganglia + branches

Nerve Fiber Types

  • Afferent = Toward CNS (sensory)
  • Efferent = Away from CNS (motor)

Functional Divisions

  • Somatic Nervous System: Voluntary movement
  • Autonomic Nervous System: Involuntary responses

Cranial Nerves Overview

  • I Olfactory – Smell

  • II Optic – Vision

  • VII Facial – Expression & Taste

  • Mnemonic for all 12 nerves: “Oh Oh Oh To Touch And Feel Very Green Vegetables, AH!”

Peripheral Nerve Anatomy

  • Axons → wrapped in myelin → grouped into fascicles → surrounded by connective tissue.
  • Myelin helps speed up nerve signals (like insulation on wires).

Neurologic Problems

Key Points

  • Stroke = Brain Attack – Time = Brain!
  • Increased ICP (Intracranial Pressure) is a life-threatening emergency.
  • Seizures ≠ Epilepsy unless they are recurring without cause.
  • TIA is a warning sign – treat it seriously!

Stroke (Cerebrovascular Accident – CVA)

What Is a Stroke?

  • Sudden interruption of blood flow to the brain
    • Ischemic (block) – 87%
    • Hemorrhagic (bleed)

Types of Strokes

  • Ischemic: Blocked artery, caused by thrombus or embolus
  • Hemorrhagic: Bleeding in brain tissue, caused by ruptured aneurysm or trauma
  • TIA (Transient Ischemic Attack): Mini-stroke, resolves in <24 hr, warning of future stroke

Key Symptoms (FAST)

  • Face drooping
  • Arm weakness
  • Speech difficulty
  • Time to call 911

Treatment & Nursing Priorities

  • CT scan STAT to rule out bleeding.
  • Ischemic → tPA within 3–4.5 hours.
  • Hemorrhagic → control BP, surgery if needed.
  • Monitor for ICP
  • Prevent aspiration (NPO until swallow eval)

Intracranial Pressure (ICP)

Skull Components

  • Brain (80%) + CSF (10%) + Blood (10%)
  • Monro-Kellie Doctrine: If one increases, the others must decrease to prevent pressure.

Early Signs of ↑ ICP

  • Headache
  • Nausea/vomiting
  • Restlessness
  • Blurred vision

Late Signs (Neuro Emergency)

  • Cushing's Triad:
    • ↑ Systolic BP (widened pulse pressure)
    • ↓ HR (bradycardia)
    • ↓ RR (irregular breathing)
  • Pupillary changes
  • Posturing (decorticate, decerebrate)
  • Coma

Nursing Care

  • Keep head midline
  • Elevate HOB 30°
  • No coughing, straining
  • Monitor neuro status frequently
  • Avoid hypotonic fluids! (can worsen cerebral edema)

Seizure Disorders

What Is a Seizure?

  • Sudden, uncontrolled electrical activity in the brain.

Types

  • Generalized: Entire brain; loss of consciousness
  • Tonic-clonic (grand mal): Stiffening + jerking
  • Absence (petit mal): Brief stare, mostly in kids
  • Focal: One hemisphere; may remain conscious
  • Status Epilepticus: Seizure >5 minutes or 2+ without recovery; medical emergency

Treatment

  • Benzodiazepines (Ativan) for active seizures
  • Anticonvulsants (phenytoin, levetiracetam) long-term
  • Seizure precautions: padded side rails, O2, suction ready

Nursing Tips

  • Turn patient on their side
  • Don’t restrain
  • Nothing in the mouth
  • Time the seizure
  • Document postictal (recovery) phase

Headaches

Migraine

  • Throbbing, unilateral, often with aura
  • Triggers: stress, chocolate, hormones
  • Treatment: triptans, NSAIDs, rest in dark room

Tension Headache

  • Band-like pressure, bilateral
  • Common with stress and poor posture

Cluster Headache

  • Intense stabbing pain, often around one eye
  • Occurs in “clusters” over weeks

Mnemonics

  • “CUSHING’S TRIAD”
    • Chewing slower (↓ HR)
    • Uncontrolled BP (↑ systolic)
    • Slow RR
    • It’s your brain’s last-ditch effort to survive pressure!

Ears and Sensory System

Key Points

  • The ear = hearing + balance
  • Hearing loss can be conductive or sensorineural.
  • Vertigo often comes from inner ear issues.
  • Safety is key with dizziness, tinnitus, or balance disorders.

Ear Anatomy & Function

3 Major Parts

  • Outer Ear: Auricle, auditory canal, collects sound
  • Middle Ear: Tympanic membrane, ossicles (malleus, incus, stapes) Transmits sound via vibration
  • Inner Ear: Cochlea, semicircular canals, hearing + balance

Key Structures

  • Cochlea = hearing (hair cells pick up sound waves)
  • Semicircular Canals = balance and spatial orientation
  • Eustachian Tube: connects middle ear to throat; equalizes pressure

Hearing Loss

Types of Hearing Loss

  • Conductive: Problem in outer/middle ear; sound can't reach cochlea (Earwax, fluid, otitis media)
  • Sensorineural: Damage to inner ear or nerve pathways (Noise exposure, aging, ototoxic meds)

Tests

  • Weber Test: tuning fork on forehead
    • Conductive: sound louder in affected ear
    • Sensorineural: sound louder in good ear
  • Rinne Test: compare bone vs. air conduction
    • Normal: air > bone
    • Conductive: bone > air

Balance & Dizziness

Vertigo vs. Dizziness

  • Vertigo = spinning sensation (Often inner ear cause like BPPV)
  • Dizziness = general unsteadiness

Meniere’s Disease

  • Inner ear disorder → excess fluid buildup
  • Triad: Vertigo, tinnitus, hearing loss
  • Risk for falls and injury!

Treatment

  • Diuretics, low-sodium diet, vestibular suppressants (meclizine)
  • Fall precautions!

Tinnitus

  • Ringing, buzzing, or roaring in the ears
  • Often from loud noise exposure or ototoxic meds
  • Can be permanent – protect your hearing!

Visual Connections

  • CN VIII (Vestibulocochlear): Hearing and balance
  • CN II (Optic): Vision
  • CN III, IV, VI: Eye movement
  • Damage can cause diplopia, nystagmus, or poor balance.

Memory Tips

  • Tinnitus Tip: “TINnitus sounds like a tin can buzzing in your ear!”
  • Weber/Rinne Quick Trick:
    • Weber = “W” is for Where does the sound go?
    • Rinne = “R” is for Right way (air > bone)

Nursing Priorities for Ear & Balance Disorders

  • Fall risk assessment
  • Turn head slowly
  • Dim lights if photophobia present
  • Hearing aids? Check batteries and fit
  • Speak clearly, don’t shout

Vision & Eye Disorders

Key Points

  • CN II (Optic Nerve) = Vision
  • CN III, IV, VI = Eye movement
  • Eye disorders can affect sight, safety, and independence.
  • Sudden vision loss = emergency!

Eye Anatomy Refresher

External Structures

  • Sclera: white part of the eye
  • Cornea: clear, dome-shaped front layer
  • Conjunctiva: thin membrane lining eyelids and eyeball

Internal Structures

  • Lens: Focuses light on the retina
  • Retina: Converts light to nerve impulses
  • Macula: Center of retina – sharp vision
  • Optic nerve (CN II): Carries vision signals to the brain
  • Aqueous humor: Fluid in front of lens (drainage issues = glaucoma)
  • Vitreous humor: Gel in eye that maintains shape

Cranial Nerves & the Eye

  • CN II (Optic): Vision (test with Snellen chart)
  • CN III (Oculomotor): Pupil constriction, eyelid elevation, most eye movement
  • CN IV (Trochlear): Downward eye movement
  • CN VI (Abducens): Lateral eye movement
  • Mnemonic: “LR6 SO4, all the rest are 3!”
    • Lateral Rectus – CN VI
    • Superior Oblique – CN IV
    • All other eye movements – CN III

Common Eye Conditions

Refractive Disorders

  • Myopia: Nearsighted
  • Hyperopia: Farsighted
  • Presbyopia: Age-related loss of near focus
  • Astigmatism: Irregular cornea shape
  • Corrected with glasses, contacts, or LASIK

Cataracts

  • Cloudy lens = blurry vision
  • Gradual onset, may see “halos” or glare
  • Surgery = lens replacement
  • Nursing Tip: Post-op: No straining, bending, lifting, or rubbing eye

Glaucoma

  • ↑ Intraocular Pressure (IOP) damages optic nerve
  • Types:
    • Open-angle (chronic) – slow, peripheral vision loss
    • Angle-closure (acute) – sudden pain, nausea, vision loss = emergency!
  • Treated with eye drops (beta-blockers, prostaglandins)
  • Check IOP regularly!

Macular Degeneration

  • Loss of central vision
  • Dry: Gradual; no cure
  • Wet: Sudden; treated with injections (anti-VEGF)
  • Leading cause of vision loss in older adults

Retinal Detachment

  • Separation of retina = EMERGENCY
  • Symptoms: floaters, flashes, curtain over vision
  • Surgery needed to repair

Eye Tests & Assessments

  • Snellen Chart: Visual acuity (distance)
  • Tonometry: Intraocular pressure (for glaucoma)
  • Pupil Reaction (PERRLA): CN III function
  • Visual Fields: Peripheral vision
  • Ophthalmoscope: Internal eye structures
  • PERRLA: Pupils Equal, Round, Reactive to Light and Accommodation

Memory Tricks

  • CN Eye Mnemonic: “Two, Three, Four, and Six see the tricks!”
    • CN II – See
    • CN III, IV, VI – Move the eyes
  • Pupil Response: “The pupils are the windows to the brain. If they’re unequal, unreactive, or sluggish — something’s wrong!”

Nursing Priorities for Vision Issues

  • Fall risk precautions
  • Educate on med adherence (especially eye drops)
  • Explain surgical prep/post-op (no rubbing, no lifting)
  • Protect eyes from trauma or light if dilated
  • Ensure accessibility tools for patients with low vision

Cranial Nerves

Quick List

  • I Olfactory – Smell like cookies! (Sensory)
  • II Optic – See the world like a superhero! (Sensory)
  • III Oculomotor – Move your eyeballs around (Motor)
  • IV Trochlear – Look at your nose with your eyes (Motor)
  • V Trigeminal – Feel your face and chew your food (Both)
  • VI Abducens – Look side to side like you're sneaking (Motor)
  • VII Facial – Smile, cry, and taste ice cream! (Both)
  • VIII Vestibulocochlear Hear music and balance like a gymnast (Sensory)
  • IX Glossopharyngeal Swallow your snacks and taste (Both)
  • X Vagus Talk, digest food, and keep calm (Both)
  • XI Accessory Shrug your shoulders like “I don’t know!” (Motor)
  • XII Hypoglossal Stick out your tongue! (Motor)

Mnemonic for NAMES

  • "Oh Oh Oh To Touch And Feel Very Green Vegetables AH Heaven"
    • Olfactory
    • Optic
    • Oculomotor
    • Trochlear
    • Trigeminal
    • Abducens
    • Facial
    • Vestibulocochlear
    • Glossopharyngeal
    • Vagus
    • Accessory
    • Hypoglossal

Mnemonic for FUNCTION

  • “Some Say Money Matters But My Brother Says Big Brains Matter Most”
  • Nerve # Function
    • 1 Sensory
    • 2 Sensory
    • 3 Motor
    • 4 Motor
    • 5 Both
    • 6 Motor
    • 7 Both
    • 8 Sensory
    • 9 Both
    • 10 Both
    • 11 Motor
    • 12 Motor

Bonus Round – Pretend!

  1. You just smelled a fresh-baked cookie… ➡ That’s Olfactory (I)!
  2. You look at it to make sure it's chocolate chip… ➡ Optic (II)
  3. Your eyes move to follow the cookie as Mom brings it… ➡ Oculomotor (III), Trochlear (IV), and Abducens (VI) all work together!
  4. You feel the cookie in your hand and chew it up… ➡ Trigeminal (V)
  5. You smile because it’s SO GOOD… ➡ Facial (VII)
  6. You hear your brother asking for a bite… ➡ Vestibulocochlear (VIII)
  7. You swallow the last bite and taste some frosting… ➡ Glossopharyngeal (IX)
  8. You talk and say, “That was yummy!” ➡ Vagus (X)
  9. You shrug when asked to share more… ➡ Accessory (XI)
  10. You stick out your tongue to tease… ➡ Hypoglossal (XII)

Practice Activity: Match the nerve to the action:

  1. Seeing stars - Optic (II)
  2. Tasting lemonade - Glossopharyngeal (IX)
  3. Balancing on one foot - Vestibulocochlear (VIII)
  4. Smiling - Facial (VII)
  5. Chewing a burger - Trigeminal (V)
  6. Shrugging shoulders - Accessory (XI)
  7. Smelling flowers - Olfactory (I)

Electrolyte Balance

Basics

  • Electrolytes = minerals that carry electrical charge.
  • Functions include:
    • Nerve conduction
    • Muscle contraction (especially the heart)
    • Fluid balance
    • Acid-base regulation

Major Electrolytes & Their Normal Ranges

  • Sodium (Na): 135–145 mEq/L, Fluid balance, nerve impulses
  • Potassium (K): 3.5–5.0 mEq/L, Cardiac & muscle contraction
  • Calcium (Ca²): 8.6–10.2 mg/dL, Muscle contraction, blood clotting
  • Magnesium (Mg²): 1.5–2.5 mEq/L, Nerve/muscle function, enzyme activity
  • Chloride (Cl): 96–106 mEq/L, Works with sodium
  • Phosphate (PO₄³): 2.5–4.5 mg/dL, Energy production, bone formation
  • Bicarbonate (HCO₃): 22–26 mEq/L , Acid-base buffering

Fluid Balance Essentials

  • ICF = Potassium
  • ECF = Sodium
  • Fluid loss = Electrolyte loss (e.g., vomiting, diarrhea)
  • 1 Liter = 1 Kg (2.2 lbs) → Best measure: Daily weights

Electrolyte Imbalances: Mnemonics & Signs

Hyponatremia → SALT LOSS

  • Stupor/coma
  • Anorexia
  • Lethargy
  • Tendon reflexes ↓
  • Limp muscles
  • Orthostatic hypotension
  • Seizures/headache
  • Stomach cramping

Hyperkalemia → MURDER

  • Muscle weakness
  • Urine changes
  • Respiratory distress
  • Decreased cardiac contractility
  • ECG changes
  • Reflexes hyper/absent

Nursing Priorities:

  • Monitor ECG
  • Replace or restrict as needed
  • Monitor labs & symptoms
  • Educate about foods rich in K, Ca², etc.

Hormones That Regulate Fluids & Electrolytes

  • ADH: Retains water
  • Aldosterone: Retains Na, excretes K
  • PTH: Increases Ca²
  • Calcitonin: Decreases Ca²
  • Vitamin D: Helps absorb Ca²
  • ANP/BNP: Reduces fluid volume (opposes RAAS)

Quick Lab Clues

  • ↑ Hematocrit, ↑ BUN = Dehydration
  • ↓ Hematocrit, ↓ BUN = Fluid overload
  • Urine output < 30 mL/hr = Kidney alert

Nursing Mnemonics

Hypovolemia → DRY

  • Dehydration signs
  • Reduced BP & urine
  • You feel dizzy & confused

Hypervolemia → FLOOD

  • Fluid overload
  • Lung sounds (crackles)
  • Overworked heart
  • Output (monitor closely)
  • Daily weights & diuretics