PATHO - Neuro

• Pain

  Is a complex experience with dynamic interactions between physical, cognitive, spiritual, emotional and environmental factors
• Pain


  "an unpleasant sensory and emotional experience associated with actual or potential tissue damage"
• Process of Nociception

  1. Transduction

  2. Transmission

  3. Perception

  4. Modulation
• Transduction

  • Activation of Nociceptors by noxious stimuli
  • Chemical: Bradykinin, serotonin, histamine, substance P, glutamate,
  • Mechanical: Pinching, cutting, stretching
  • Thermal: Hot, cold
• Transmission

  • A delta fibers (rapid, sharp, well-localized)
  • ^these are heavily myleniated
  • ^example: stabbing
  • C fibers (slow, dull, aching or burning, poorly localized)
  • ^these are not heavily myleniated
  • ^example: toothache
  • A beta fibers responsible for modulation which makes pain more tolerable by activating inhibitory interneurons (blocks transmission of pain)
• Perception and Modulation of Pain

  • Conscious awareness:
  • ^reticular limbic systems and cerebral cortex
  • ^interpretation influenced by cultural factors and life experiences
  • 
    
  • Modulation:
  • ^inhibitory neuromodulators and endogenous opioids
• Temperature

  Normal: 37 C, 98.6 F

  Measurements of core temperature:

  -Pulmonary artery thermistor

  -Tympanic membrane

  -Foley

  -Rectal

  -Oral

  -Infrared
• Thermoregulation


  • Mediated by hypothalamus, pituitary, and thyroid and their hormones: TRH, TSH, and thyroxine
  • Circadian rhythm (peaks about 6 pm)
  • Fluctuations with menstrual cycle, sharp rise just before ovulation
• Mechanisms of Heat Production and Loss

  • Heat production: metabolism, muscle contraction (including shivering), chemical thermogenesis
  • Heat loss: radiation, conduction, convection, evaporation; decreased muscle tone, increased ventilation, administration of cool fluids
• Fever

  Endogenous pyrogens (TNF-a, IL-1, IL-6) raise body temperature to kill microorganisms, decrease serum levels of iron, zinc and copper (minerals needed for bacterial replication), increasing lysosomal breakdown and auto destruction of cells preventing viral replication, phagocytosis is enhanced
• Hyperthermia

  • At 41 C (105.8 F), nerve damage, coagulation of cell proteins, and seizure can occur in adults, At 43 C (109.4 F), death occurs
• Hypothermia

  • At 35 C (95 F), a range of cardiac dysrhythmias occur, Atrial fibrillation is most common, Associated with a decrease in cardiac output
• Functions of Sleep

  • Conservation of energy
  • Restoration of tissues and growth
  • Thermoregulation
  • Regulation of emotions—sleep deprivation causes emotional disorders like irritability, anxiety, depression
  • Neural maturation
  • Memory and learning—information transfer between cerebral cortex and hippocampus
• Sleep


  Controlled by the suprachiasmatic nucleus (SCN) in the hypothalamus
• Sleep Architecture

  Stage 1 and REM > Stage 2 > Stage 3 > Stage 4

  This all together is 1 cycle of sleep and lasts about 75-90 minutes
• Sleep Characteristics of Infants and the Elderly

  • Adults sleep 7-8 hours, 4-5 cycles, with each cycle lasting 75-90 minutes
  • Infants sleep 16-17 hours per day, 50% REM, 50-60 minute cycles
  • For the elderly, total sleep time is decreased with increased sleep latency and poorer quality of sleep; sleep disorders increase the risk of morbidity and mortality
• Neurological Tools and Assessment

  • LOC, Pupillary Response, Posturing, ICP and CPP
• Neurological Disorders

  • Cerebral Vascular Accident (CVA) (Stroke)
  • Headaches
  • Seizures
  • Neurodegenerative disorders
  • Dementia
  • Brain Injury
• Level of Consciousness (LOC)

  Arousal and awareness of self and environment

  Oriented x3: person, time and place

  Response to painful stimuli:

  -withdraws (or swings at you appropriately), decorticate/decerebrate posturing
• Altered Levels of Consciousness

  • Metabolic
  • Psychogenic
  • Drug induced
• Pupillary Responses

  • Lack of pupil response to light indicates a brain-stem lesion
  • Eye movements correspond to cranial nerves 3 and 6
  • "Dolls head" Movement (Brainstem normal)
  • "Fixed pupils" (Brainstem not intact)
• Posturing

  • Decorticate posturing - damage to one or both corticospinal tracts ("Dead bug")
  • ^^ arms come in to center
  • ^^roughly 30% survive

  
  

  • Decerebrate posturing - upper brain stem damage
  • ^^ arms stay at sides and wrists flex out
  • ^^roughly 10% survive.
• Intracranial Pressure (ICP)

  • Cranial Cavity: 3 compartments (80% brain tissue, 10% CSF, 10% Blood), Encased in a nonexpendable skull
  • As pressure builds, brain tissue is subject to serious damage
  • NORMAL RANGES: Adults (supine) 5-15 mmHg, Children 3-7 mmHg, Infants 1.5-6 mmHg
• Monro-Kellie Hypothesis

  • "Increases in ICP within one compartment can be offset by a decreased volume in another compartment"
  • Compensation is limited by skull
  • Brain is able to compensate the most by compression, but brain compression may lead to rapid injury
• Increased Intracranial Pressure (ICP) Causes

  • Hemorrhage
  • Trauma
  • Infection
  • Severe hypertension
  • Brain tumor
  • Brain edema
• Increased Intracranial Pressure (ICP) Manifestations

  • Decreased level of consciousness, Lethargy, confusion, stupor, Cellular hypoxia, Brain injury & coma
• Cushing's Reflex


  • Occurs with severe, prolonged increases in ICP
  • Ischemia of vasomotor & cardiovascular centers in the medulla
  • Marked increase in MABP (270 mmHg)
  • Reflex slowing of heart rate
• Increased ICP Treatment

  • Stop bleeding (trauma, stroke)
  • Remove tumor
  • Osmotic Diuretic (mannitol)
  • Surgical drain, shunt to relieve pressure
• Cerebral Vascular Accident (CVA)


  • Also known as Stroke
  • Major source of mortality (#3)
  • 600,000/year,
  • Types:
  • ^ Transient Ischemic Attack (TIA)
  • ^ Ischemic
  • ^ Hemorrhagic
• Nociception = detection of pain by nociceptors
• Steps of pain:

  1. Noxious stimulus (i.e. needlestick)
  2. Transduction at peripheral nociceptor
  3. Transmission along 1st order neuron (goes towards spinal column)
  4. In the synapse at the dorsal horn of spine: 2nd order neuron crosses midline and ascends up the spinal cord (ascending tract)
  5. Signal arrives to thalamus
  6. In brain: periaqueductal gray matter modulates pain via descending tract
• Endogenous Opioids:

  Enkephalins

  Endorphins

  Dynorphins

  Endomorphins
• Making Beta Endorphins:

  1. POMC precursor cleaves into 3
  2. Gamma MSH
  3. ACTH
  4. and Beta-LPH
  5. Then Beta-LPH splits into:
  6. Beta endorphins
  7. and Gamma LPH, which later becomes Beta MSH
• Types of Pain

  • Nociceptive: traditional
  • Neuropathic: injury or malfunction of spinal cord and/or peripheral nerves
  • ^^Common causes are Diabetes and Chemo
  • ^^S/S: burning, tingling, shooting, stinging, pins and needles (paresthesia)
  • ^^Difficult to treat
  • Idiopathic: unknown origin
  • Referred: stimulus is in one area, but pain is perceived in a different one
  • Acute: beneficial, short term, self limited
  • Chronic: constant, no biological advantage (ex: fibromyalgia)
• Comparison of Acute and Chronic pain:

  • Experience
  • Source
  • Onset
  • Duration
  • Pain identification/differentiation
  • Clinical signs
  • Significance
  • Pattern
  • Course
  • Actions
  • Prognosis
• Neuromatrix Theory of Pain:

  Input from spinal cord, Signals from Brain centers, Memories, Emotions, Expectations, and Attention all cause Abnormal patterns of activity in the neuromatrix. The result is Pain
• Day and Night Cycles

  • Controlled by the suprachiasmatic nucleus (SCN) in the hypothalamus
• Changes in the Eye with Aging:

  CORNEA: increased astigmatism

  ANTERIOR CHAMBER: glaucoma (difficulty getting fluid out of eye)

  LENS: decreased color vision; and cataracts

  RETINA: increased minimal amount of light to see an objects
• Changes in Hearing with Aging:

  -Cochlear hair cell degeneration

  -Loss of auditory neurons

  -Degeneration of conductive membrane of the cochlea

  -Loss of cortical auditory neurons

  -Medication related:

  --Rapid IV Furosemide(LASIX): leads to electrolyte imbalance in hair cells and transient deafness

  --Gentamycin: auditory nerve damage, possibly permanent
• Changes in Smell and Taste with Aging:

  Decline in sensitivity to odors, usually after age 80

  Decline in olfaction may lead to diminished appetite

  Inability to smell toxic fumes or gases

  Higher concentrations of flavors required to stimulate taste

  Taste may be influenced by decreased secretion of saliva