Central nervous system
Composed of brain and spinal cord
Peripheral nervous system
conducts sensory and motor impulses to and from the skin, muscles, and other organs to spinal cord
What is the cranium occupied with?
80% brain tissue
10% blood supply
10% CSF
The most prominent and most easily palpable spinous process is?
C-7
Major regions of the brain
Cerebrum
Diencephalon
Brainstem
Cerebellum
How much glucose and oxygen does the brain use?
Glucose : 25%
Oxygen : 20%
What arteries supply blood to the brain?
Carotid and vertebral
A loss of blood flow from to the brain for ______ will result in unresponsiveness.
5-10 seconds
Cerebrum contains ___ if the brain’s total volume.
75%
Injury to cerebral cortex may result in?
Paresthesia, weakness, and paralysis of extremities
Function of frontal lobe
Voluntary motor action and personality
Function of parietal lobe
Controls somatic and voluntary sensory and motor function. Memory and emotions.
Function of occipital lobe
Processing visual information
Function of temporal lobe
Speech center, long-term memory, hearing, taste, and smell.
Function of cerebellum
Coordinates body movements. Maintenance of posture and equilibrium and the coordination of skilled movement.
Reticular activating system
Responsible for maintenance of consciousness, specifically one’s level of arousal.
Function of lower brainstem
HR, BP, and repsiration
Basal ganglia
Role of coordination of motor movements and posture
Midbrain
Lies immediately below the diencephalon and is the smallest region of the brainstem. Pupillary size and reactivity
Pins
Lies below the midbrain and above the medulla. Controls nerve fibers involved with sleep, respiration, and the medullary respiratory center.
Medulla
Continuous inferiorly with the spinal cord;
Medulla
Continuous inferiorly with the spinal cord and serves as a conduction pathway from ascending and descending nerve tracts. Coordinates HR, blood vessel diameter, breathing, swallowing, vomiting, coughing, and sneezing.
cauda equina
location where the spinal cord separates @ L2
Meninges
Protective layer that surround and enfold the entire CNS - specifically the brain and spinal cord.
Dura mater
covers the entire brain
Where are the meningeal arteries located?
Between the dura mater and skull
Arachnoid
Second meningeal layer. Contains blood vessels.
Pia matter
Third meningeal layer. Highly vascular that firmly adheres directly to the surface of the brain.
Tentorium
Separates the cerebral hemispheres from the cerebellum and brainstem
Somatic nervous system
Regulates or controls voluntary activities, including all coordinated muscular activities.
Primary function of cranial nerves
Special functions in head and face, including sight, smell, taste, hearing, and facial expression.
Two types of peripheral nerves
sensory and motor
Sensory nerves
Transmit sensory input from the body to CNS. i.e. touch, taste, heat, cold, and pain.
Motor nervces
Carry information from the CNS to muscles.
Connecting nerves
Short fibers that connect the sensory and motor which allow the cells on either end to exchange messages.
Which nerve network controls the arms and legs?
Arms : brachial plexus
Legs : lumbosacral plexus
Sympathetic nervous system
Controlled by hypothalamus.
Alpha receptor of SNS
Induce smooth muscle contraction in blood vessels and bronchioles
Beta receptor of SNS
Produces relaxation of smooth muscle in blood vessels and bronchioles. Chronotopic and inotropic effects on myocardial cells.
Chronotropic
Affecting HR
Inotropic
Affecting contractility
SNS is also responsible for
Sweating
Pupil dilation
Temperature regulation
Shunting blood from periphery to core during flight-or-fight
Spinal cord injuries at or above level ____ may disrupt flow of sympathetic communication.
T6
What would happen if there was a loss of sympathetic stimulation?
Disrupt homeostatsis and leave the body poorly equipped to deal with changes in its environment
Parasympathetic nervous system
Responsible for conserving energy and maintaining organ function.
What parasympathetic nerves supply the reproductive nerves, pelvis, and leg?
S2 through S4
Disruption of the lower parasympathetic nerves in the sacrum results in :
Loss of bowel/bladder tone and sexual function
Closed head injury is usually associated with blunt trauma and may result in :
Skull fx
Focal brain injuries
Diffuse brain injuries
Which can all be complicated by increased ICP
s/s of head injury
Lacerations, contusion, or hematomas to the scalp
Soft area or depression noted on palpation of the scalp
Visible skull fx or deformities
Battle sign or raccoon eyes
CSF rhinorrhea or otorrhea
s/s TBI
Pupillary abnormalities Period of unresponsiveness Confusion or disorientation Perseveration Amnesia Combativeness or other abnormal behavior Numbness of tingling in the extremities Loss of sensation and/or motor function Focal neurologic deficits Seizures Cushing triad Dizziness Visual disturbances Seeing "stars" N/V Posturing
When should you maintain a high index of suspicion of a frature?
Head appears deformed
Visible crack in the skull w/in a scalp laceration
Raccoon eyes
Battle sign
What are the four types of skull fractures?
Linear
Depressed
Basilar
Open
Linear skull fracture
Nondisplaced. Account for approximately 80% of skull fractures.
Depressed skull fracture
Result from high-energy direct trauma w/ a blunt object. Often have neurologic signs such as LOC.
What part of the skull is more susceptible to depressed skull fractures?
Frontal and parietal
Basilar skull fracture
High-energy trauma.
Extension of a linear fracture to the base of the skull.
Signs of basilar skull fractuer
CSF drainage from ears
Raccoon eyes
Battle sign
why does the absence of raccoon eyes and Battle sign does not r/o basilar skull fracture?
They may not appear until up to 24 hours following injury depending on the extent of the damage.
Open skull fracture
Severe forces applied to head and are often associated w/ multisystem trauma.
Two classifications of TBI
Primary injury and secondary injury
Primary injury
Injury to the brain and its associated structued that results instantaneously from impact to the head.
Secondary injury
Processes that increase the severity of a primary brain injury and negatively impact the outcome.
Potential causes of secondary injury
Cerebral edema Intracranial hemorrhage Increased ICP Cerebral ischemia Infection Hypoxia Hypotension
When can the secondary injury occur?
Few minutes to several days following initial head injury.
What happens when you hyperventilate a TBI patient?
Vessel size decreasing diminishing blood flow and oxygenation to deprived brain cells.
What happens when the brain is deprived of oxygen and CO2 levels increase?
The vessels dilate to bring more oxygenated blood to hypoxic tissue which, in turn, increased ICP, making it harder for blood to flow to swollen tissues.
What is the only indication for hyperventilation?
Signs of cerebral herniation
Signs of cerebral herniation
Unilateral dilated pupil that is unresponsive to light.
Decrease by 2 or more points in the GCS in a patient whose GCS score is less than 8.
What does appearance of clear or pink, watery CSG from the nose, the ear, or an open scalp wound indicate?
Dura and skull have been penetrated
Cushing triad
Increased BP
Decreased HR
Irregular respirations
Healthy adult ICP range
5 to 15 mmHg
Cerebral perfusion pressure
Pressure of blood flow through the brain. CPP = MAP - ICP
Minimum CPP require to adequately perfuse the brain is :
60 mmHg
What will happen if the CPP is less than 60 mmHG?
Cerebral ischemia will result causing potentially permanent neurologic impairment or even death.
Autoregulation
Body’s response to a decrease in CPP by increasing MAP, resulting in cerebral vasodilation and increased cerebral blood flow.
Early s/s of decreased ICP
Vomiting
HA
Altered LOC
Seizures
More-ominous, later: HTN Bradycardia Cushing triad Unilaterally unequal and nonreactive pupils Coma Posturing
Decorticate posturing
Character by flexion of the arms and extension of the legs.
Decerebrate posturing
Characterized by extension of the arms and legs
Clinical indications of mild elevation in ICP
Increased blood pressure Decreased HR Pupils still reactive Cheyne-Stokes respiration Attempts to localize and remove painful stimuli Vomiting HA Altered LOC Seizures
Cheyne-Stokes respiration
Respirations that are fast and then become slow w/ intervening periods of apnea
Clinical indications of moderate elevation in ICP
Widened pulse pressure and bradycardia
Pupils sluggish or nonreactive
Central neurogenic hyperventilation
Decerebrate posturing
What does a moderation elevation in ICP indicate?
Middle brainstem involvement
Central neurogenic hyperventilation
Deep, rapid respirations
Similar to Kussmaul but w/o acetone odor
Clinical indications of marked elevation in ICP
Unilaterally fixed and dilated pupil Biot respirations Flaccid response to painful stimuli Irregular pulse rate Fluctuating BP - hypotension common
Survival rate of each elevation level in ICP
Mild elevation : effects usually reversible w/ prompt and appropriate treatment
Moderate elevation : survival possible but often w/ some permanent neurologic deficit
Marked elevations : high mortality rate
Biot respirations
Irregular pattern, rate, and depth of breathing w/ intermittent periods of apnea
Focal brain injury
Specific, grossly observable brain injury
Examples of focal brain injuries
Cerebral contusion Epidural hematoma Subdural hematoma Intracerebral hematoma Subarachnoid hemorrhage
Cerebral contusion
Brain tissue is bruised and damaged in a specific area
Which area of the brain is most commonly affected by cerebral contusion?
Frontal lobe
Epidural hematoma
Accumulation of blood b/n the skull and dura mater
What is nearly always the result of an epidural hematoma?
Blow to the head that produces a linear fracture of the temporal lobe
Subdural hematoma
Accumulation of blood beneath the dura matter but outside the brain
What is a subdural hematoma typically from?
Rupture of the vein that bridge the cerebral cortex and dura
Classic presentation of epidural hematoma
LOC immediately following injury, which is then followed by a brief period of consciousness, after which the patient lapses back into unresponsiveness.
As ICP increases, pupil on the side of the hematoma becomes fixed and dilated.
Classifications of subdural hematomas
Acute : clinical signs develop w/in 48 hours following injury
Subacute : sings develop b/n 2 and 14 days after the injury
Chronic : symptoms may not appear for as long as 2 weeks
Which classification of subdural hematoma is more common in older adults, alcoholics, bleeding disease, and take anticoagulants?
Chronic subdural hematoma
Why are older patients and those with hx of alcohol use at higher risk for development of subdural hematoma?
Atrophy of the brain tissues increases the stretching of the bridging veins.
Common signs of subdural hematoma
Fluctuating LOC
Focal neurolgic signs
Slurred speech
Intracerebral hematoma
Bleeding w/in brain tissue itself. Occurs following penetrating injury to the head or rapid deceleration forces
Subarachnoid hemorrhage
Bleeding occurs into the subarachnoid space where the CSF circulates. Common causes include trauma or rupture of an aneurysm or arteriovenous malformation.
As bleeding into the subarachnoid space increases, the patient experiences s/s of increases ICP :
Decreased LOC Pupillary changes Posturing Vomiting Seizures
Diffuse brain injury
Any injury that affects the entire brain
Cerebral concussion is usually caused by “
Acceleration-deceleration forces
Concussion
Results in cerebral dysfunction that usually resolved spontaneously and rapidly w/o demonstrable physical damage to the brain or permanent neurologic impairment.
s/s of concussion
Dizziness Weakness Visual changes N/V Tinnitus Slurred speech Inability to focus
Severe concussion: Lack of coordination
Delay of motor functions
Inappropriate emotional responses
Diffuse axonal injury
Stretching, shearing, or tearing of nerve fibers w/ consequent axonal damage.
When does DAI most often?
High-speed, rapid acceleration-deceleration forces
