Nervous System Flashcards
The Brain
- Communication and control center of the body
- Receives, processes, and evaluates many kinds of input, decides on the response needed, and acts on that
- Controlled by:
- Involuntary activity- Autonomic nervous system
- Voluntary activity- Somatic nervous system
The Brain is Protected by:
- Skull
- Meninges
- Cerebrospinal Fluid (CSF)
Dura Mater
- Outer layer
- Tough, fibrous, double-layered membrane
- Forms the dural sinuses which collect venous blood and CSF for return to the general circulation
Arachnoid Mater
- Middle layer
- Loose, web like covering
Subarachnoid Space
- Contains CSF and cerebral arteries and veins
- Lies below the arachnoid
Subdural Space
- Potential space
- Normally empty, can fill with blood after an injury
Pia Mater
- Inner layer
- Delicate, connective tissue that adheres closely to all convulsions on the surface of the brain
- Contains many small blood vessels
Cerebrospinal Fluid
- Provides a cushion for the brain and spinal cord
- Clear, almost colourless liquid
- Formed in the ventricles in the brain and flows into the subarachnoid space
- Here it circulates the brain and spinal cord and eventually returns to venous blood
- To maintain normal pressures (ICP), it is important that equal amounts of CSF are produced and reabsorbed
Blood Brain Barrier
- Protective mechanism provided by relatively impermeable capillaries in the brain
- Cells are tightly joined together rather than possessing pores
- This barrier limits the passage of potentially damaging materials into the brain and controls the delicate balance of electrolytes, glucose, and proteins in the brain
Pons
Contain afferent (incoming) and efferent (outgoing) fibers
Medulla Oblongata
Vital control center that regulate respiratory and cardiovascular function (breathing and heart rate)
RAS (Reticular Activating System)
Determines the degree/arousal/awareness of cerebral cortex
Bronca’s Area
- Motor or expressive speech area
- Controls the output of words, verbal and written
- Located at the base of left frontal lobe
Wernicke’s Area
- Comprehends language received, both written and spoken
- Located at posterior temporal lobe
- Connective fibers to visual and auditory areas
Neurons
- Highly specialized cells that conduct impulses through the CNS and PNS
- Require glucose and oxygen for metabolism
Neurotransmitters
- Transmit impulses from cell to cell
Types: - Acetylcholine- chief neurotransmitter of PNS
- Epinepherine/Norepi- chief neurotransmitter of SNS. Causes vasoconstriction and increases HR. Stimulates alpha and beta receptors
ICP
Intracranial Pressure
Normally <15 mmHg
CPP
Cerebral Perfusion Pressure
Pressure needed to maintain blood flow to the brain
Normally 70-80 mmHg
MAP
Mean Arterial Pressure
70-100 mmHg
What happens when ICP=MAP
BLOOD FLOW STOPS
CPP= ?
MAP-ICP
Neurogenic Shock Symptoms
- Bradycardia
- Skin warm and dry
- No significant blood loss
- Paralysis and loss of spinal reflexes
Central Nervous System
Consists of brain and spinal cord
- Cerebrum: memory, emotion, problem solving, reasoning
- Cerebellum: movement, balance, general motor control
- Brainstem: breathing, blood pressure, eating
- Spinal cord: communication between brain and body, controls movement, sensation, and reflexes
Peripheral Nervous System
Somatic: controls voluntary movement and sensation in the skin, muscles, and joints. Responsible for relaying information from brain to skeletal muscles
Autonomic: controls automatic functions like heart rate, breathing, and digestion. Responsible for relaying information from brain to internal organs, allowing out body to function without conscious control
Sympathetic Nervous System
Part of the autonomic nervous system. Increases activity of the organs when your body activates its “fight-or-flight” response.
Parasympathetic Nervous System
Part of the autonomic nervous system. It helps relax your body after fight or flight situations.
Increased ICP
- Shifts CSF to spinal cavity to compensate, decreasing cerebral blood flow
- Effective until you become hypoxic - Hypoxia = arterial vasodilation in brain in attempt to improve blood supply = adds fluid volume
Signs and Symptoms of Increased ICP
- Severe headache
- Vomiting
- Papilledema
- Seizures
- Cushing’s reflex
- Decreased pulse
- Increased systolic BP with widening pulse pressure
- Irregular respirations
Cerebral Herniation Syndrome
- Brain swelling forces tissue down through the foramen mangnum
- Obstruction of blood flow
- Pressure on brain stem
Signs and Symptoms of Cerebral Herniation Syndrome
- Decreased LOC
- Coma
- Dilation of pupil on same side
- Paralysis on opposite side
- Decerebrate posturing
- Increased BP
- Bradycardia
Treatment of Cerebral Herniation Syndrome
HYPERVENTILATION 3:1
The only time you hyperventilate a patient
We need to decrease blood flow to the brain, it causes hypoxia and vasoconstriction but we have to preserve what is left
Concussion
Mild blow to the head causing sudden excessive movement of the brain
Signs and Symptoms of Concussion
- Period of unconsciousness or confusion
- Returns to normal
- Amnesia
- Headache
- Dizziness
- Tinnitus
- Nausea
Basilar Fractures
- Occur at base of skull
- Often accompanied by leaking of CSF through the nose and ears
- Occurs with blunt force trauma
Signs and Symptoms of Basilar Fractures
Diagnosed with dark discolouration around eyes and behind ears
Cerebral Contusion
- Bruised brain tissue with ruptured small blood vessels
- Usually from a blow to the head
- Brain swelling may be rapid and severe
Signs and Symptoms of Cerebral Contusion
- Prolonged unconsciousness
- Altered LOC
- Personality changes
- Profound confusion
- Persistent amnesia
- Abnormal behaviour
Depressed Skull Fractures
- Displacement of a piece of bone below level of the skull
- Compress brain tissue
- Blood supply to that area is impaired
- ICP often high
Diffuse Anoxal Injury
- Severe blunt trauma to the head
- Stretching, shearing, tearing of nerve fibers, from brain moving back and forth
- Generalized edema
- Subarachnoid bleeding with irritation to the surrounding tissues
Signs and Symptoms of Diffuse Anoxal Injury
- Seizure activity
- Coma
- Vomiting
- Herniation syndrome is possible
- Often results in permanent vegetative state
Anoxic Brain Injury
- Lack of oxygen to the cells
- Cardiac arrest, airway obstruction, drowning
- Spasm of cerebral arteries = perfusion is affected to the cortex
- 4-6 minutes of anoxia = irreversible
- Restoring BP and oxygen will not restore perfusion
Closed Head Injuries
- Skull is not fractured
- Brain tissue is injured from force
- Blood vessels may rupture
- Contrecoup injury- rebound of skull causes the brain to impact the opposite side of the skull
Epidural Hematoma
- Bleeding between the dura and skull
- Usually from a tear in the middle meningeal artery in temporal region
- Linear fracture = arterial bleed = quick onset and deadly outcome
Signs and Symptoms of Epidural Hematoma
- Head trauma
- Loss of consciousness
- Lucid interval then signs of ICP within minutes to hours
- Rapid death
Subdural Hematoma
- Between dura and arachnoid
- Associated with injury to underlying brain tissues
- Venous bleed = causes blood to accumulate slowly
- May be acute or sub-acute
-acute = 24 hours
- sub-acute = over a week - High risk- alcoholics and elderly on blood thinners
- Tear in the arachnoid can cause a loss of CSF into the subdural space = creates higher ICP
Signs and Symptoms of Subdural Hematoma
- Headache
- Changes in LOC
- Slurred speech
Subarachnoid Hemorrhage
- Between arachnoid and pia
- Associated with traumatic bleeding from blood vessels at base of brain
-Aneurysms - Initially localized but becomes diffuse secondary to meningeal irritation
Signs and Symptoms of Subarachnoid Hemorrhage
- Decreased LOC
- Pupil changes
- Posturing
- Vomiting
- Seizures
- Worst headache they ever had
- Prob has a history of HTN
Intracerebral Hemorrhage
- Bleeding in the brain tissue
- Frontal and temporal lobes are most common
- Blunt or penetrating trauma
Signs and Symptoms of Intracerebral Hemorrhage
- Altered LOC
- Similar pattern to CVA’s
- High mortality rates
Coma
- Deep state of unconsciousness
- Patient cannot be aroused by external stimuli
Causes of a Coma
- Structural: intracranial bleeding, head trauma, brain tumour
- Metabolic: anoxia, hypoglycemia, DKA, thiamin deficiency, kidney and liver failure
- Drugs
- Cardiovascular system: Hypertensive encephalopathy. Sudden raise in BP with headache, nausea, seizures. Seen in eclampsia. Shock, dysrhythmias, stroke
- Respiratory system: COPD, toxic inhalation
- Infection: Meningitis, sepsis
Cerebrovascular Accident
- Sudden alterations in LOC, sensation, and/or voluntary movement due to obstruction or rupture of an artery in the brain
- These effects may be permanent or temporary
- CVA, TIA, Stroke
Stroke and Intracranial Hemorrhage
Sudden interruption of blood flow to the brain that results in neurological deficit
Modifiable Risk Factors of Strokes
- High BP
- High cholesterol
- Cigarette smoking
- TIA
- Heart disease
- Diabetes mellitus
Non-modifiable Risk Factors of Strokes
- Age
- Gender
- Race
- Prior stroke
- Hereditary
- Hyper coagulopathy
- High RBC and sickle cell anemia
Pathophysiology of CVA’s
- Four major blood vessels
- Carotid (80% CBF)
- Vertebral arteries (20%) - Interconnected- circle of willis
- Collateral blood flow
- Scalp vessels, vessels of the dura and arachnoid - Occlusion results in infarct and ischemia
Cerebral Blood Flow
- Autoregulation of the cerebral vessels
- Constrict and dilate to maintain perfusion pressure
- Perfusion is regulated at the arteriolar level by levels of oxygen and glucose
- Ischemia and acidosis are vasodilators
- Sudden cessation of circulation from occlusion or hemorrhage cannot by readily corrected by auto-regulatory mechanisms
- Resulting ischemia leads to to neuronal dysfunction and death
Types of Strokes
- Ischemic Strokes
- Rarely lethal in the first hour
- 80-85% of strokes - Hemorrhagic strokes
- Rapidly fatal
- Less common
Ischemic Strokes
- Occlusion of an artery from plaque build up
- Often in carotids - Embolus causing sudden obstructions
- Thrombi may break off atheroma
- May be from tumors, air
Signs and Symptoms of Ischemic Strokes
- Hemiparesis or hemipalegia (contralateral)
- Numbness (contralateral) and facial drooping
- Aphasia
- Confusion or coma
- Convulsions
- Incontinence
- Diplopia (double vision)
- Dysarthria (slurred speech)
- Headache, dizziness
Thrombus vs. Embolus
Thrombus: blood clot
Embolus: obstruction of blood flow due to a mass of undissolved matter lodging in a vessel
Hemorrhagic Stroke
- Hemorrhage in cranial vault
- Epidural, subdural, subarachnoid
- Causes: cerebral aneurysms, AV malformations, HTN, stress or exertion, cocaine or other sympathomimetic drugs
Signs and Symptoms of Hemorrhagic Stroke
- Sudden onset accompanied by headache
- Nausea and vomiting
- Quick deterioration
- Hemorrhage = ICP = Coma
Cerebral Embolus
- Occlusion of an intracranial vessel from a fragment of a foreign substance
- Causes: atherosclerotic plaque
- Thrombi: valvular heart disease and A Fib
- Air embolism after thoracic surgery
- Fat embolism after long bone injury
- Gas embolus- diving injury
TIA
Transient Ischemic Attack
- Focal cerebral dysfunction - temporary reduction in blood flow
- Lasts minutes to hours (rarely more than 1-2 hours)
- Recovery in 24 hours
-Patient returns to normal, no permanent damage
- Indication of problems
- Obstruction related to atherosclerosis
- Can be from spasm of arteries
- Loss of auto-regulation
Signs and Symptoms of TIA
- Related to location of ischemia
- Weakness
- Paralysis
- Numbness of face
- Speech disturbances
- Result from a vascular disturbance
Seizure Disorders
- A temporary alteration in behaviour or consciousness caused by abnormal electrical activity at one or more groups of neurons in the brain
- Result of alterations in neuronal membrane permeability secondary to structural lesion or metabolic derangement
- Na and K enhances the ability or neurons to depolarize and emit an electrical charge = seizure
- Seizures are periods of sustained hyperactivity in the brain
- The nerve cells leave their normal activities and fire in massive, synchronized bursts
- Returns to normal in a few minutes
Generalized- Petit Mal
- Absence seizures
- Occur most often in children 4-12
- Lapse of consciousness
- No loss of posture
- No motor activity
- Maybe some isolated clonic activity
- Short duration, return to normal
Grand Mal: AKA Tonic-Clonic
- May be preceded with an aura
- Sudden onset with loss of organized muscle tone
Tonic Phase
- Extensor muscle tone activity
- Sometimes flexion
- Apnea
- Short duration
- Tongue biting
- Bladder incontinence
Clonic Phase
- Rigidity -> relaxation
- Convulsions
- 1-3 minutes
- Massive ANS discharge
- Hyperventilation, salivation, tachycardia
Postictal Phase
- Drowsiness or unconsciousness
- Lasts minutes to hours
- Followed by confusion and fatigue
- Transient neurological deficits
Status Epilepticus
- Prolonged seizure activity
- Reoccuring seizures before consciousness is regained
Simple Seizures
- Motor or sensory cortex
- Motor seizures clonic activity to one specific body part
- Sensory seizures- tingling, numbness, visual, auditory, or taste symptoms
- Generally, do not lose consciousness
- May lead to tonic-clonic
Jacksonian Seizure
- Seizure activity involving a brief alteration in movement, sensation or nerve function
- Generally do not lose consciousness
- Can be head twitching, word repeating, lip smacking, etc..
Complex Seizures
- Arise from focal seizures in temporal lobe (psychmotor)
- Manifest changes in behaviour
- Preceded by an aura
- Abnormal repetitive motor behaviour (automatisms)
- Period of amnesia
- Brief duration with return to normal
Syncope
- Fainting spell
- Usually positional with light-headedness
- Sudden onset, short duration
- Bradycardia with vagal stimulation
- May have a mini hypoxic seizure (not actually a seizure) because when you pass out you’re not breathing for a while
Tension Headaches
- Muscle contractions of face, neck, scalp
- Feels like tight band around head
- Result of stress, persistent noise, poor posture, eye strain
- Usually treated with analgesics
Migraines
- Severe incapacitating headaches
- Preceded by visual or GI disturbances
- Onset of intense throbbing pain
- Lasts 2-72 hours
- Often accompanied by nausea and vomiting
- Constriction and dilation of blood vessels
Sinus Headache
- Pain in forehead, nasal area and eyes
- Pressure behind the face- from build up of fluid in sinuses
Cluster headache
- Occur in bursts, short lasting but repeat for days or months
- Severe pain around one eye
- Tearing and nasal congestion
- Often caused by abnormalities in bodies biological clock (hypothalamus)
- AKA: histamine headaches
Brain Neoplasms- Tumors
- Malignant or benign
- Effects depend on size, location, rate of growth, hemorrhaging, edema
- Issues often arise from icreased ICP due to lack of space
Signs and Symptoms of Tumors
- Increased ICP signs
- Headache
- Vomiting
- Lethargy and irritability
- Personality changes
- Seizures
Brain Abscess
- Purulent material (pus) surrounded by a capsule
- Develops from bacterial infection from nasal cavity, middle ear, mastoid cells
- Also from surgery or penetrating trauma
- Infection = fever
- Expanding mass = nausea, vomiting, seizures, alterations in LOC, headaches
Muscular Dystrophy
- Inherited muscle disorder
- Slow progressive degeneration of muscle fibers
- Waste muscles is replaced by fat
- 12 years- few walk, few survive
- Death usually from pulmonary infections and heart failure
- No cure
Meningitis
- Infection, usually bacterial, of the meninges in the brain
- Microbes reach the brain via the blood
- Can result from head trauma or surgery
- Can be secondary to other infections
Signs and Symptoms of Meningitis
- Severe headache
- Back pain
- Nuchal rigidity (hyperextended, stiff neck)
- Vomiting
- Irritability and lethargy
- Fever and chills
- Rash
Kernig’s sign
Resistance to leg extension when hip is flexed 90 degrees
Brudzinski’s sign
Passive flexion of neck causes flexion of both legs/thighs
Multiple Sclerosis
- Progressive disease of the CNS
- Patches of myelin in the brain and spinal cord are destroyed
- This causes issues in nerve conduction and message impulse
- Autoimmune disease- body destroys foreign material, including myelin
- Scarring and nerve fibers damage
- No cure but there is medicine to help
Dystonia
- Local or diffuse alterations in muscle tone- from damage to neuron transmission to muscles
- Painful muscle spasms, unusual positions, strange movement patterns
Parkinson’s Disease
- Degeneration or damage to nerve cells in the basal ganglia (voluntary motor movements) of the brain
- Lack of dopamine- effects the nerve pathways that control muscle contraction
- Result- tense muscles, tremors, joint rigidity, slow movements
Central Pain Syndrome
- Damage or malfunction in the CNS- sensitization of the pain system
- Can be caused by infection or disease of the trigeminal nerve
- Car accidents
- Trauma
- Stroke
- Brief and very painful
Bell’s Palsy
- Paralysis/weakness of the facial muscles on one side of the face
- Due to inflammation of the facial nerve
- Viral often
- Usually one sided and temporary
- Eyelid and mouth droop
- Numbness and pain
- Taste impaired, sounds louder
Peripheral Neuropathy
- Damage or irritation to the axon or myelin sheath
- Interrupts nerve message impulses from the site to the brain
- Slows or blocks the nerve impulses
- Classifications- around the site and distribution damage
- Damage to sensory nerve fibers
- Numbness, tingling, cold, pain
- Starts at hands and feet -> central body
- Damage to motor nerve fibers: muscle weakness, wasting
- Damage to ANS: blurred vision, impaired or absent sweating, changes in BP, Gi disorders
Amyotrophic Lateral Sclerosis
- ALS- Lou Gehrig’s Disease
- Nerves that control muscular activity degenerate in brain and spinal cord
- Weakness in hands and arms
- Involuntary quivering
- Progress to all four limbs, respirations, and swallowing
- Death in 2-4 years- aspiration, pneumonia, starvation
Myoclonus
- Rapid and uncontrolled muscle contractions that occur at rest or during movement
- A symptom, not a disease
- May be a symptom of brain disorder or seizure disorder
Spina Bifida
- Congenital defect
- Part of the vertebra fails to develop
- Portion of the spinal cord exposed
- Most common in lower back
Polio
- Variable ranges of severity
- Unapparent infection
- Febrile illness without neurological effects
- Aseptic meningitis
- Paralytic disease
- Spread by feces, food transmission, airborne
- Fever, headache, sore throat, malaise
- Paralytic- pain, muscle involvement, brain stem -> inability to swallow or breath
Medications for Seizures
- Dilantain
- Valium
- Ativan
- Versed
