SYTHNESIS OF NURSING/CRITICAL CARE- EXAM #3 STUDY GUIDE
CHAPTER 14: NEUROLOGY
Cerebral Circulation
• The brain receives about 750 mL of blood per minute, accounting for 15–20% of cardiac
output.
• Blood supply comes from two main arterial systems:
o Carotid arteries (anterior circulation)
o Vertebral arteries (posterior circulation)
• The common carotid arteries divide into:
o External carotid arteries → supply the face, scalp, and structures outside the skull
o Internal carotid arteries → branch into:
▪ Anterior cerebral artery (ACA) → supplies the frontal lobes and motor
cortex
▪ Middle cerebral artery (MCA) → supplies frontal, temporal, and parietal
lobes
▪ About 90% of strokes occur in the MCA
• The vertebral arteries arise from the subclavian arteries and enter through the foramen
magnum:
o Supply the spinal cord, medulla, and cerebellum
o Join at the pons to form the basilar artery
▪ Supplies cerebellum, pons, medulla, and inner ear
▪ Divides into posterior cerebral arteries (PCA) → supply occipital, medial,
and inferior temporal lobes
• These systems connect at the base of the brain via the circle of Willis, which helps
identify areas of vascular blockage.
Cerebral Metabolism
• The brain depends primarily on glucose for energy.
• Effects of low blood glucose:
o <70 mg/dL → confusion
o ≤40 mg/dL → seizures
o <20 mg/dL → cellular injury
• Continuous cerebral blood flow (CBF) is essential and maintained by autoregulation.
o If CBF decreases:
▪ Fluid shifts into cells → cerebral edema
▪ Aerobic metabolism shifts to anaerobic → acidosis and neurologic
impairment
• Anoxic brain injury begins after approximately 5 minutes, with permanent neuron
damage.
Chemical Regulation
• Cerebral vessels respond to chemical changes:
o PaCO₂ > 45 mmHg → vasodilation → ↑ CBF (most powerful regulator)
o Low PaCO₂ → vasoconstriction → ↓ CBF
o PaO₂ < 50 mmHg → vasodilation
▪ Less influence than CO₂
▪ Inadequate oxygen leads to anaerobic metabolism and lactic acid buildup
, o Increased hydrogen ions → vasodilation
Blood-Brain Barrier (BBB)
• Protects brain tissue from toxins and pathogens.
• Allows passage of small molecules (oxygen, glucose, CO₂, water).
• Larger substances are restricted unless conditions (infection, tumors) alter permeability.
Ventricular System & Cerebrospinal Fluid (CSF)
• The brain contains four ventricles filled with CSF.
• CSF production:
o Mainly by choroid plexus
o Rate: ~20 mL/hr (≈500 mL/day)
o Total volume: ~150 mL
• Functions:
o Cushioning
o Metabolic support
• Obstruction of flow leads to hydrocephalus.
Meninges
• Three protective layers:
o Dura mater → outermost, supportive
o Arachnoid mater → avascular, loosely covers CNS
o Pia mater → adheres closely, highly vascular
• Spaces:
o Epidural → between skull and dura
o Subdural → between dura and arachnoid
o Subarachnoid → contains CSF
Cerebrum
• Divided into two hemispheres, basal ganglia, and diencephalon.
• Corpus callosum connects hemispheres.
• Hemispheric dominance:
o Left → language and communication
o Right → spatial and nonverbal processing
• Lobe functions:
o Frontal → behavior, emotion control
o Occipital → vision
o Temporal (Wernicke’s area) → language comprehension
• Basal ganglia → fine motor control
Brainstem
• Controls essential life functions.
• Components:
o Midbrain → sensory relay, visual/auditory reflexes
o Pons & medulla → regulate breathing
o Medulla → heart rate, BP, reflexes (coughing, swallowing, vomiting)
Cerebellum
• Responsible for balance, coordination, and fine motor control.
• Damage leads to ataxia and balance problems.
Spinal Cord
• Extends from the medulla to L1 vertebra.
, • Contains 31 segments:
o 8 cervical, 12 thoracic, 5 lumbar, 5 sacral, 1 coccygeal
• Structure:
o Gray matter → central
o White matter → ascending (sensory) & descending (motor) pathways
Peripheral Nervous System (PNS)
• Includes:
o 12 cranial nerves
o 31 spinal nerves
• Autonomic Nervous System (ANS):
o Sympathetic (fight or flight)
▪ Releases norepinephrine
▪ ↑ HR, BP, contractility
▪ ↓ digestion
o Parasympathetic (rest and digest)
▪ Releases acetylcholine
▪ Restores baseline function
NEUROLOGICAL ASSESSMENT
Baseline Evaluation
• Mental status, orientation, responsiveness
• Glasgow Coma Scale (GCS):
o Range: 3–15
o ≤8 indicates coma and likely need for airway support
• Additional assessments:
o Speech/language
o Memory
o Cranial nerves
o Pupillary response (critical indicator)
▪ Normal size: 1.5–6 mm
Motor Function
• Strength graded on a 5-point scale
• Conditions:
o Hemiplegia → one side
o Paraplegia → lower limbs
o Quadriplegia → all limbs
• Arm drift test detects subtle weakness
• Posturing:
o Decorticate (flexor) → cortical damage
o Decerebrate (extensor) → brainstem damage
Reflexes
• Deep tendon reflexes (DTRs) graded 0–4+
• Superficial reflexes (corneal, gag, etc.)
• Pathological reflexes:
o Babinski sign → indicates upper motor neuron damage
Sensory Function
• Assessed through pain, temperature, and position sense
, • Dermatomes correspond to spinal nerve levels
Respiratory Assessment:
• should be assessed as a part of the neurological assessment, as changes in the respiratory
pattern can indicate neurological deterioration Increased Intracranial Pressure (ICP)
Increased Intracranial Pressure:
Monro-Kellie Doctrine
• The skull contains:
o Brain tissue
o Blood
o CSF
• Increase in one must be compensated by decrease in another
• Normal ICP: 0–15 mmHg
• Elevated ICP: ≥20 mmHg sustained
• Severe ICP elevation can cause brain herniation
Cerebral Perfusion Pressure (CPP)
• Formula:
o CPP = MAP − ICP
• Normal: 60–100 mmHg
• Maintain ≥70 mmHg in injury
Causes of Increased ICP
• Brain tissue swelling (edema)
o Cytotoxic → hypoxia
o Vasogenic → BBB disruption
• Increased blood volume
• Excess CSF (e.g., hydrocephalus, hemorrhage)
Assessment Findings of ICP
• Frequent neuro checks
• Changes in LOC
• Pupillary changes
• Vital signs
• Cushing’s triad (late sign!):
o Hypertension (widened pulse pressure)
o Bradycardia
o Irregular respirations
ICP Monitoring
• Indicated for GCS 3–8
• Types:
o Ventriculostomy → gold standard, allows CSF drainage
o Subarachnoid bolt → monitoring only
o Epidural sensor → least accurate
o Parenchymal monitor → highly accurate
Diagnostics
• ABGs (PaO₂, PaCO₂)
• CBC, CMP, coagulation labs
• CT scan (no contrast) → gold standard initially
• MRI, EEG, Doppler studies
CHAPTER 14: NEUROLOGY
Cerebral Circulation
• The brain receives about 750 mL of blood per minute, accounting for 15–20% of cardiac
output.
• Blood supply comes from two main arterial systems:
o Carotid arteries (anterior circulation)
o Vertebral arteries (posterior circulation)
• The common carotid arteries divide into:
o External carotid arteries → supply the face, scalp, and structures outside the skull
o Internal carotid arteries → branch into:
▪ Anterior cerebral artery (ACA) → supplies the frontal lobes and motor
cortex
▪ Middle cerebral artery (MCA) → supplies frontal, temporal, and parietal
lobes
▪ About 90% of strokes occur in the MCA
• The vertebral arteries arise from the subclavian arteries and enter through the foramen
magnum:
o Supply the spinal cord, medulla, and cerebellum
o Join at the pons to form the basilar artery
▪ Supplies cerebellum, pons, medulla, and inner ear
▪ Divides into posterior cerebral arteries (PCA) → supply occipital, medial,
and inferior temporal lobes
• These systems connect at the base of the brain via the circle of Willis, which helps
identify areas of vascular blockage.
Cerebral Metabolism
• The brain depends primarily on glucose for energy.
• Effects of low blood glucose:
o <70 mg/dL → confusion
o ≤40 mg/dL → seizures
o <20 mg/dL → cellular injury
• Continuous cerebral blood flow (CBF) is essential and maintained by autoregulation.
o If CBF decreases:
▪ Fluid shifts into cells → cerebral edema
▪ Aerobic metabolism shifts to anaerobic → acidosis and neurologic
impairment
• Anoxic brain injury begins after approximately 5 minutes, with permanent neuron
damage.
Chemical Regulation
• Cerebral vessels respond to chemical changes:
o PaCO₂ > 45 mmHg → vasodilation → ↑ CBF (most powerful regulator)
o Low PaCO₂ → vasoconstriction → ↓ CBF
o PaO₂ < 50 mmHg → vasodilation
▪ Less influence than CO₂
▪ Inadequate oxygen leads to anaerobic metabolism and lactic acid buildup
, o Increased hydrogen ions → vasodilation
Blood-Brain Barrier (BBB)
• Protects brain tissue from toxins and pathogens.
• Allows passage of small molecules (oxygen, glucose, CO₂, water).
• Larger substances are restricted unless conditions (infection, tumors) alter permeability.
Ventricular System & Cerebrospinal Fluid (CSF)
• The brain contains four ventricles filled with CSF.
• CSF production:
o Mainly by choroid plexus
o Rate: ~20 mL/hr (≈500 mL/day)
o Total volume: ~150 mL
• Functions:
o Cushioning
o Metabolic support
• Obstruction of flow leads to hydrocephalus.
Meninges
• Three protective layers:
o Dura mater → outermost, supportive
o Arachnoid mater → avascular, loosely covers CNS
o Pia mater → adheres closely, highly vascular
• Spaces:
o Epidural → between skull and dura
o Subdural → between dura and arachnoid
o Subarachnoid → contains CSF
Cerebrum
• Divided into two hemispheres, basal ganglia, and diencephalon.
• Corpus callosum connects hemispheres.
• Hemispheric dominance:
o Left → language and communication
o Right → spatial and nonverbal processing
• Lobe functions:
o Frontal → behavior, emotion control
o Occipital → vision
o Temporal (Wernicke’s area) → language comprehension
• Basal ganglia → fine motor control
Brainstem
• Controls essential life functions.
• Components:
o Midbrain → sensory relay, visual/auditory reflexes
o Pons & medulla → regulate breathing
o Medulla → heart rate, BP, reflexes (coughing, swallowing, vomiting)
Cerebellum
• Responsible for balance, coordination, and fine motor control.
• Damage leads to ataxia and balance problems.
Spinal Cord
• Extends from the medulla to L1 vertebra.
, • Contains 31 segments:
o 8 cervical, 12 thoracic, 5 lumbar, 5 sacral, 1 coccygeal
• Structure:
o Gray matter → central
o White matter → ascending (sensory) & descending (motor) pathways
Peripheral Nervous System (PNS)
• Includes:
o 12 cranial nerves
o 31 spinal nerves
• Autonomic Nervous System (ANS):
o Sympathetic (fight or flight)
▪ Releases norepinephrine
▪ ↑ HR, BP, contractility
▪ ↓ digestion
o Parasympathetic (rest and digest)
▪ Releases acetylcholine
▪ Restores baseline function
NEUROLOGICAL ASSESSMENT
Baseline Evaluation
• Mental status, orientation, responsiveness
• Glasgow Coma Scale (GCS):
o Range: 3–15
o ≤8 indicates coma and likely need for airway support
• Additional assessments:
o Speech/language
o Memory
o Cranial nerves
o Pupillary response (critical indicator)
▪ Normal size: 1.5–6 mm
Motor Function
• Strength graded on a 5-point scale
• Conditions:
o Hemiplegia → one side
o Paraplegia → lower limbs
o Quadriplegia → all limbs
• Arm drift test detects subtle weakness
• Posturing:
o Decorticate (flexor) → cortical damage
o Decerebrate (extensor) → brainstem damage
Reflexes
• Deep tendon reflexes (DTRs) graded 0–4+
• Superficial reflexes (corneal, gag, etc.)
• Pathological reflexes:
o Babinski sign → indicates upper motor neuron damage
Sensory Function
• Assessed through pain, temperature, and position sense
, • Dermatomes correspond to spinal nerve levels
Respiratory Assessment:
• should be assessed as a part of the neurological assessment, as changes in the respiratory
pattern can indicate neurological deterioration Increased Intracranial Pressure (ICP)
Increased Intracranial Pressure:
Monro-Kellie Doctrine
• The skull contains:
o Brain tissue
o Blood
o CSF
• Increase in one must be compensated by decrease in another
• Normal ICP: 0–15 mmHg
• Elevated ICP: ≥20 mmHg sustained
• Severe ICP elevation can cause brain herniation
Cerebral Perfusion Pressure (CPP)
• Formula:
o CPP = MAP − ICP
• Normal: 60–100 mmHg
• Maintain ≥70 mmHg in injury
Causes of Increased ICP
• Brain tissue swelling (edema)
o Cytotoxic → hypoxia
o Vasogenic → BBB disruption
• Increased blood volume
• Excess CSF (e.g., hydrocephalus, hemorrhage)
Assessment Findings of ICP
• Frequent neuro checks
• Changes in LOC
• Pupillary changes
• Vital signs
• Cushing’s triad (late sign!):
o Hypertension (widened pulse pressure)
o Bradycardia
o Irregular respirations
ICP Monitoring
• Indicated for GCS 3–8
• Types:
o Ventriculostomy → gold standard, allows CSF drainage
o Subarachnoid bolt → monitoring only
o Epidural sensor → least accurate
o Parenchymal monitor → highly accurate
Diagnostics
• ABGs (PaO₂, PaCO₂)
• CBC, CMP, coagulation labs
• CT scan (no contrast) → gold standard initially
• MRI, EEG, Doppler studies
