Nervous System Notes

The Nervous System

Overview

• Central Nervous System (CNS)
  • Brain and spinal cord
• Peripheral Nervous System (PNS)
  • Cranial and spinal nerves
  • Sensory neurons
  • Neuromuscular junctions

The Autonomic Nervous System

• Sympathetic and parasympathetic branches
• Motor and sensory innervation
• Part of the peripheral nervous system
• Involuntary control
• Sympathetic
  • Fight-or-flight response
  • Increases general level of activity in the body
• Parasympathetic
  • Dominates digestive system
  • Aids recovery after sympathetic activity

Fight or Flight vs. Rest and Digest

• Fight or Flight:
  • Dilate bronchi
  • Increase HR/BP/RR
  • Stop digestion/bladder function
• Rest and Digest:
  • Slow HR
  • Start digestion
  • Contract bladder

Cognition and Awareness

• Content of Thought
• Degree of Awakeness
• Glasgow Coma Scale (3-15)
• Time, place, self, situation
• Levels of consciousness:
  • Deep sleep, requires vigorous stimulation
  • Complete loss of cognition/consciousness
• Cognition: awareness of surroundings and ability to perform higher levels of thinking

Altered Cognition

Causes:

• hypoglycemia
• drug or alcohol overdose
• infection
• vascular dementia (cerebral vascular disease)
• respiratory failure
• medications
• traumatic brain injury (including bleeding)
• brain tumor
• psychological trauma

Signs and Symptoms:

• loss of alertness (lethargy, difficult to arouse)
• confusion or disorientation (inability to understand name, place, time, or context of a situation)
• memory loss (this could be short or long-term memory)
• loss of consciousness (unable to arouse even with pain or loud noise)
• inability to perform simple functions (e.g., using a pen, completing a math problem)
• poor regulation of emotion
• defects in thought or judgment

Neurotransmitters

• Synapse:
  • Presynaptic axon terminal
  • Vesicles contain neurotransmitter
  • Synaptic cleft
  • Postsynaptic receptor
• Neurotransmitter:
  • Released into synaptic cleft on stimulus
  • Postsynaptic neuron depolarizes, depending on neurotransmitters present

Key Neurotransmitters

• GABA (STOP)
• Serotonin
• Dopamine
• Acetylcholine
• Endorphins
• Norepinephrine
• Epinephrine
• Glutamine & Glutamate

Pain

Pain Scale

• 0-10 scale, ranging from "No Pain" to "Worst Pain Possible"
• Categories: No pain, Mild, Moderate, Severe, Very Severe, Worst Possible

Pain in the Brain

• Somatic sensory area in the cerebral cortex (parietal lobe)
  • Perception and localization of sensation
• Hypothalamus and limbic system
  • Emotional factors
  • Communication with other regions of the brain to integrate responses
• Reticular activating system (RAS)
  • Reticular formation in the brain stem
  • Awareness of incoming brain stimuli

Causes of Pain:

• Inflammation
• Infection
• Ischemia and tissue necrosis
• Stretching of tissue
• Stretching of tendons, ligaments, joint capsule
• Chemicals
• Burns
• Muscle spasm

Types of Pain:

• Somatic pain (soma = body)
  • From body tissues
  • Conducted by sensory fibers
• Visceral pain (viscera = internal organs)
  • Originates in internal organs
  • Conducted by sympathetic fibers
  • May be acute or chronic

Assessment of Pain

• Location of pain
• Descriptive terms
  • Aching, burning, sharp, throbbing, widespread, cramping, constant, periodic, unbearable, moderate
• Timing of pain
• Association with an activity
• Physical evidence of pain
  • Pallor and sweating
  • High blood pressure, tachycardia
  • Nausea and vomiting (may occur with acute pain)
  • Fainting and dizziness (may occur with acute pain)
  • Anxiety and fear (frequently evident in people with chest pain or trauma)
  • Clenched fists or rigid faces
  • Restlessness or constant motion
  • Guarding area (to prevent stimulation of receptors)

Referred Pain

• Source may be difficult to determine
• Pain may be perceived at a site distant from source
• Characteristic of visceral damage in the abdominal organs
• Example: Heart attack or ischemia in the heart

Phantom Pain

• Can follow an amputation
• Pain, itching, tingling
• Usually does not respond to common pain therapies
• May resolve within weeks to months
• Phenomenon not fully understood

Acute and Chronic Pain

Acute

• Usually sudden and severe, short-term
• Indicates tissue damage
• May be localized or generalized
• Initiates physiologic stress response
  • Increase blood pressure and heart rate; cool, pale, moist skin; increase respiratory rate; increase skeletal muscle tension
• Vomiting may occur
• Strong emotional response may occur

Chronic

• Occurs over extended time; may be recurrent
• Usually more difficult to treat than acute pain
• Often perceived to be generalized
• Individual may be fatigued, irritable, depressed
• Sleep disturbances common
• Specific cause may be less apparent
• Appetite may be affected (can lead to weight gain or loss)
• Affects ADLs

Neuropathic and Ischemic Pain

Neuropathic

• Originates in the peripheral nerves
• Infection or disease damages peripheral nerves
• Described as tingling, burning, or shooting; can be severe
• Often chronic
• Example: Diabetic Neuropathy

Ischemic

• Originates anywhere in the body
• Stimulus: sudden loss of blood flow that results in lack of oxygen to tissues and cells
• Described as aching, burning, prickling, or shooting, depending on location of the ischemia
• Acute
• Example: Myocardial infarction

Analgesic Drugs

• For Mild Pain:
  • ASA (Aspirin)
  • Acetaminophen
  • NSAIDs
  • Action: Decreases pain at peripheral site; all are antipyretic; ASA and NSAIDs are anti-inflammatory
  • Adverse Effects: ASA and NSAIDs have many adverse effects (nausea, gastric ulcers, bleeding, allergies)
• For Moderate Pain:
  • Codeine
  • Oxycodone
  • Percocet
  • Vicodin
  • Acts on central nervous system and affects perception; Narcotic (opium-often combined with ASA/acetaminophen; High dose may depress respiration
• For Severe Pain:
  • Morphine
  • Demerol
  • Methadone
  • Meperidine
  • Oxycodone
  • Acts on central nervous system; euphoria and sedation; Narcotic-Tolerance and addiction; High dose depresses respiration; nausea, constipation common.

Key Terms (Pain)

• PERCEPTION: Awareness of stimuli
• THRESHOLD: Level of stimulation required to elicit a pain response
• TOLERANCE: Ability to withstand pain
• ACUTE: Sudden onset, short duration
• CHRONIC: Long-term, persistent pain

Sensory Perception Problems

• Caused by anything that disrupts neurotransmitters and receptors resulting in changes in the information that reaches the brain
• Results may be an over stimulation or under stimulation of nerves

Over-Stimulation:

• Fibromyalgia: Over-stimulation of pain, pressure, and temperature receptors causing significant discomfort.
• Photophobia: Over-stimulation of the retinal nerve causing discomfort due to too much information being presented.
• Phonophobia: Over-stimulation of the auditory nerve causing discomfort due to too much information being presented.

Under-Stimulation:

• Neuropathy: Damage to a peripheral nerve causing inhibition of peripheral pain, pressure, and temperature receptors causing paresthesia. Diabetes, cardiovascular disease (peripheral), or surgery can be a common cause of this.
• Sensorineural hearing loss: Damage to an auditory nerve causing the inhibition of the translation and transfer of sound waves to the brain.
• Retinitis: Visual loss due to retinal inflammation causing inhibition of the translation and transfer of light to the brain. Cerebral vascular accidents (strokes) can also cause reduced vision.
• Spinal cord injury: Damage to the nerve trunk causing loss of sensation, pressure, or temperature below the level of injury (motor nerves preventing movement are also involved).
• Anosmia and/or ageusia: Loss of smell and/or taste caused by nerve inflammation or damage of nerves involved with those senses.

Neuropathy

Causes:

• Diabetic Peripheral Neuropathy: chronic elevated blood sugar damages nerve endings
• Neuropathy of Peripheral Vascular Disease: Poor perfusion to toes and fingertips cause hypoxic injury and nerve damage
• Neuropathy of trauma: never fibers are damaged during a traumatic event or surgery
• Others: excess alcohol use, viral illnesses, nutritional deficiencies, autoimmune conditions, malignancy

Most common causes:

• Trauma
• Poor glucose control
• Poor perfusion

Seizures

Causes:

• metabolic, congenital, genetic, perinatal, head trauma, infection, tumor, vascular disease, drug and alcohol abuse, high fever in children
• A change in permeability of the neuronal membrane: this can affect sodium and calcium channels within the neurons.
• Neurotransmitter imbalances: a defect in the inhibitory neuron.
• Reduced ability of neurons to exercise inhibitory control: by excitatory neurotransmitters over-powering inhibitory neurons (GABA).

Definition:

• Seizures: sudden, transient disruption in brain electrical activity. Caused by spontaneous, excessive discharge of neurons in the brain

Epilepsy (Seizure Disorders)

• recurrent seizures
• Diagnosis: someone experiences at least two unprovoked seizures occurring more than 24 hours apart.

Triggered by:

• loud noises, flashing lights, stress, changes in medication, hyperventilation (alkalosis)

Dangers:

• Respirations may be impaired, or the airway may be blocked by the tongue or vomits.
• Repeated or continuous seizures may cause hypoxia, hypotension, acidosis, or hypoglycemia, resulting in brain injury.
• Injuries associated with loss of consciousness

Diagnostic Tests (Seizures)

• Electroencephalogram (EEG): an electrical recording of the brain in real time while the patient is having a seizure
• Other tests: MRI, CT, PET (metabolic activity)

Types of Seizures: Generalized and Focal

Generalized Seizure:

• both hemispheres affected with loss of consciousness
  • Absence Seizure: brief loss of awareness, sometimes with facial movements, lasts 5-10 seconds with no memory of the episode
  • Tonic-clonic seizures: loss of consciousness with strong muscle contractions alternating with relaxation. Results in forceful jerky movements
  • Myoclonic seizures: quick uncontrollable muscle movement with no loss of consciousness, may affect one muscle or group of muscles or wider areas of the body

Partial Seizures:

• Focal Seizure: single area or or focal origin in the brain, may or may not involve loss of consciousness, repeated motor activity or sensation
• Status Epilepticus: recurrent or continuous seizures without recovery of consciousness

Phases of a Seizure:

• Prodromal: Nausea, irritability, muscle twitching
• Aura: visual or auditory sensation immediately preceding seizure
• Ictal: when the seizure happens
  • Tonic – muscle contraction and increased tone
  • Clonic – alternating contraction and relaxation
• Postictal: immediately after a seizure ends
  • Confusion, sore, EXHAUSTED
• Ictal = related to a seizure

Intracranial Pressure (ICP)

• Brain is encased in rigid, nonexpendable skull.
• Fluids, blood, and CSF are not compressible.
• Increase in fluid or additional mass causes increase in pressure in the brain
  • Ischemia and eventual infarction of brain tissue
• Increased ICP is common in many neurological problems.
  • Brain hemorrhage, trauma, cerebral edema, infection, tumors, abnormal circulation of CSF

Symptoms of Intracranial Dysregulation

• High brain pressure
  • Pain due to stretching of dura and blood vessels
  • Vomiting due to pressure on the emetic center in the medulla
  • Changes in level of consciousness due to pressure on the cerebral cortex
  • Increased blood pressure due to vasoconstriction due to cerebral ischemia
  • Slow pulse due to conpensation for increased blood pressure
  • Papilledema- swelling of optic disc
  • Fixed/dilated pupils due to pressure on Cranial Nerve III

Vital Signs with Increased Intracranial Pressure

• Cushing's Triad

  • Bradycardia
  • Increasing systolic blood pressure
  • Widened pulse pressure
  • Irregular respirations
    *What is Pulse Pressure?

• Pulse Pressure = Systolic - Diastolic

  • example: 120-80=40 (normal)
  • Wide Pulse Pressure- When there is a huge difference between the systolic and diastolic BP
  • Narrow Pulse Pressure- When there is not much of a difference between the systolic and diastolic BP

Interventions for increased ICP

• Ventriculostomy: a surgical procedure used to drain excess cerebrospinal fluid (CSF) from the ventricles of the brain.

Increased ICP - Herniation

• Increased pressure inside the skull pushes the brain stem through the foramen magnum

Dementia

• A progressive disease
  • Cortical brain function is decreased.
    • Impaired cognitive skills
    • Impaired thinking, judgment, and learning
    • Memory loss
    • Confusion
    • Behavioral and personality changes

Causes of dementia

• Vascular disease
• Infections (HIV, Creutzfeldt-Jakobs)
• Genetic disorders
• TBI
• Drug use, exposure to toxins
  *Alzheimer's Disease is the most common type of dementia

Other risk factors:

• Sedentary lifestyle
• Tobacco use
• Alcohol use
• Unhealthy diet
• Social isolation
• Mental inactivity

Alzheimer’s Disease

• NOT A NORMAL PART OF AGING, BUT INCREASED AGE IS GREATEST RISK FACTOR
• ACETYLCHOLINE decreases
• PLAQUES: amyloid beta protein and cell matter clump together
• TANGLES: tau protein becomes tangled
• HEAD INJURY (AD develops years later)
• GENETIC, FAMILY PATTERN
  • GENE MUTATIONS

Signs and Symptoms

• EARLY SIGNS
  • Memory Lapses
  • Increased difficulty performing tasks in work and social settings
  • Mood swings
  • Inability to concentrate
  • Impaired reasoning and judgment
• LATER SIGNS
  • Wandering
  • Unable to recognize family or self
  • Trouble controlling bowel and bladder
  • Needs assistance with ADLs
• LAST SIGNS
  • Inability to communicate
  • Requires full-time assistance
  • Failure of organ systems

Interventions

• Safe environment
• Decrease risk of falls and wandering
• Consistency of helpers
• Simplify and limit daily decisions
• Assist with ADLs, ensure they are eating and drinking
• Decreased stimulation
• Uninterrupted periods of sleep
• Promote dignity and quality of life

Vascular Disorders

• Transient Ischemic Attacks (TIAs)
• Cerebrovascular Accidents (CVAs)
• Cerebral Aneurysms

Transient Ischemic Attacks (TIAs)

• Result from temporary localized reduction of blood flow in the brain
• May occur singly or in a series

Due to:

• Partial occlusion of an artery
• Atherosclerosis
• Small embolus
• Vascular spasm
• Local loss of autoregulation

Signs and Symptoms

• Directly related to location of ischemia in the brain
• Intermittent short episodes of impaired function
  • e.g., muscle weakness in arm or leg
• Visual disturbances
• Numbness and paresthesia in face
• Transient aphasia or confusion may develop
• Repeated attacks may be a warning sign for obstruction related to atherosclerosis.

Cerebrovascular Accidents (CVAs) = stroke

• An infarction of brain tissue that results from lack of blood

Due to:

• Occlusion of a cerebral blood vessel
• Rupture of cerebral vessel
  *5 minutes of ischemia causes irreversible nerve cell damage.

Risk factors include:

• Diabetes
• Hypertension
• Systemic Lupus Erythematosus
• Atherosclerosis
• History of TIAs
• Obstructive sleep apnea
• Heart disease
• Smoking, sedentary lifestyle
• Combination of oral contraceptives and cigarette smoking
• Congenital malformation of blood vessels
• Increasing age
  *Infarction: death of tissue due to obstruction of blood supply

Signs and symptoms:

• Depend on the location of obstruction
• Size of artery involved
• Presence of collateral circulation may diminish size of affected area
• Lack of voluntary movement or sensation on opposite side of the body
  • Initially flaccid paralysis
  • Spastic paralysis develops weeks later
• NIH Stroke Scale (NIHSS)
  • Designed to assist with rapid diagnosis

Types of CVAs

• Ischemic: blot clot or blockage prevents blood flow to the brain
  • Thrombotic – blot clot (thrombus) forms in a blood vessel in the brain
    • Atherosclerosis
    • Coag disorders
  • Embolic – thrombus forms outside the brain and travels to the brain
    • Atherosclerosis, cardiac disease
• Hemorrhagic: Rupture of cerebral blood vessel
  • Least common type
  • Caused by
    • HTN
    • Drugs
    • Trauma
    • Coag disorders

Cerebral Aneurysm

• Localized weakness in the wall of an artery
  • Usually at the points of bifurcation on the circle of Willis
    • Berry aneurysms
• Often aggravated by hypertension
• Initially small and asymptomatic
• Slow bleed causes vascular type headache.
• Rupture leads to sudden fatal increase in ICP and death.

CVAs- Aneurysms Management

• Surgical treatment
  • If diagnosed before rupture
    • Clipping and tying off
    • Clipping may also be done after rupture
  • Substantial risk of rebleeding
  • Focused on reducing increased ICP and cerebral vasospasm
• Treatment for:
  • Clot-busting drugs
  • Surgical intervention
  • Glucocorticoids
  • Supportive treatment
  • Occupational and physical therapists; speech- language pathologists
  • Treat underlying problem to prevent recurrences
    *Rehabilitation begins immediately

Traumatic Brain Injury (TBI)

• Alteration in brain function or other evidence of brain pathology caused by external force
• Risk: 14 years or younger, 65 and older, males
• MVA’s and Falls
• Sports
• Mild concussion
• Classic concussion

Coup / Contrecoup

• "blow": brain crashes against skull
• "counter blow"

Parkinson Disease

• Complex motor disorder involving motor and neurologic symptoms
• Pathology largely unknown
• Cause: genetics, infection, trauma, atherosclerosis, toxins
• Resting tremor
• Rigidity
• Hypokinesia

Brain Death

• Damage to the point that it can never recover AND Cannot maintain body’s homeostasis
• Irreversible cessation of function of the entire brain
• No evidence of brain function
• EEG absent activity for 6-12 hours
• Brain begins autolysis