N332 - Module 7 + part of Module 8 (Brain and Spinal Cord Injuries; Shock) fully solved questions with 100% accurate solutions(Latest Update)

What is included in the central nervous system (CNS)?

Brain and spinal cord

What are the nervous system major divisions?

Central nervous system, Peripheral nervous system, and autonomic nervous system

What is the autonomic nervous system?

Mechanism used for compensation in the body when things go wrong in the body systems. Includes the sympathetic nervous system and parasympathetic nervous system

What are neurons?

-Basic units of the nervous system

-Transmits impulses ("messages")

-Motor neurons (efferent) - EXIT

-Sensory neurons (afferent) - ARRIVE

-Axons can be covered by myelin sheath

-Non-myelinated axons = gray matter

T or F: Motor neurons carry impulses from PNS to CNS

False. They carry impulses from CNS to PNS

T or F: Sensory neurons carry impulses from PNS towards CNS

True

What is the brain responsible for?

Directing the regulation and function of the nervous system and other body systems

What are the 3 main areas of the brain?

1. Forebrain

-Diencephalon

-Cerebrum

-Cerebral cortex

2. Cerebellum

3. Brainstem

-Midbrain

-Pons

-Medulla

What does the brainstem control?

Vital functions

T or F: When there is an injury to the brain stem there is a concern about vital functions

True

What is the skull formed by?

Cranial (frontal, ethmoid, sphenoid, occipital, parietal, temporal) and facial bones

What is the function of the skull?

Protecting the cranial vault contents

T or F: The skull is up to 6mm thick

True

T or F: the brain is flexible

False. It is non-flexible and complications can arise when the brain is swollen or needs to swell because the skull is not flexible

Is the internal surface of the skull base rough and irregular?

Yes. when there is injury the brain can rub against the irregular and rough surface

What injuries often leads to brain bleeds in head injuries?

Acceleration and deceleration injuries

What is the purpose of the meninges?

Protective covering of brain and spinal cord

What layers comprise the meninges?

-Pia Mater

-Arachnoid membrane

-Dura mater

Which meningeal layer is the innermost layer?

Pia mater

Which meningeal layer attaches to the brain and spinal cord?

Pia mater

What space is between the pia mater and arachnoid membrane?

Subarachnoid space which houses the CSF

Which meningeal layer is the middle layer?

Arachnoid membrane

Which space is between the arachnoid membrane and dura mater?

Subdural space

Which meningeal layer is the outermost layer?

Dura mater

Which space is between the dura mater and the skull?

Epidural space and extends down spinal cord

Which meningeal layer is the thickest and toughest layer?

Dura mater

Why is cerebral spinal fluid important?

-It provides cushioning to the brain for protection

-Produced by choroid plexus (125-150 ml at any one time; about 650 ml produced everyday; produced and reabsorbed)

-Circulates in subarachnoid space and through central canal of spinal cord

-contains water, protein, glucose, ions (Na, Cl, K)

What is the blood-brain barrier?

-Capillaries and cells tightly surrounding the brain

-Acts as a "filter" for the CNS

-Endothelial cells that line the brain vessels is selectively permeable

What is the function of the blood-brain barrier?

-controls exchange of O2, CO2, metabolites between blood and brain (prevent or slow)

-Keeps some substance in bloodstream out of cerebrospinal circulation and brain tissue

-Prevents large molecules into the brain (i.e., albumin, substances bound to albumin, many drugs (chemo, ABX))

What can pass through the blood-brain barriers?

-Oxygen

-Glucose

-CO2

-ETOH

-Anesthetics

-Water

How many sets of arteries supply the brain?

2 sets: Rt and Lt carotid arteries and Rt and Lt vertebral arteries

Do the Rt and Lt internal carotid arteries supply the anterior or posterior circulation of the brain?

Anterior circulation

Do the Rt and Lt vertebral arteries supply the anterior or posterior circulation of the brain?

Posterior circulation

What do the Rt and Lt internal carotid arteries split into?

Ophthalmic artery, middle carotid artery, and anterior carotid artery

T or F: venous blood drains via jugular veins

True

Which arteries form a ring at the base of the brain called the Circle of Willis?

Anterior, middle and posterior arteries

What does the ophthalmic artery supply in the brain?

Eyes

What does the middle carotid (MCA) artery supply?

Lateral cerebrum (hearing, upper body motor and sensory)

What does the anterior carotid artery supply?

Midline cerebrum (lower body motor and sensory)

What does the Rt and Lt vertebral arteries supply blood into?

Basilar artery

What does the basilar artery supply?

Posterior cerebrum (occipital lobe), brainstem and cerebellum

Where does the middle meningeal arteries enter the brain?

From above dura mater

When there is a fracture of the skull bone, what arteries are affected by the fractured bone?

Middle meningeal arteries

T or F: Fracture of the skull bone that affect the middle meningeal arteries results in bleeding that accumulates quickly

True

Where are bridging veins located?

Beneath the dura mater

Injury to the bridging veins results in what type of bleed?

Subdural hematoma

T or F: When there is injury to the bridging veins and a subdural hematoma results, bleeding accumulates slowly

True

Where do large arteries of the brain enter?

They enter the skull in the subarachnoid space

Injury to the brain impacting the large arteries results in what type of bleed?

Subarachnoid hemorrhage

When there is injury to the large arteries and a subarachnoid hemorrhage results, is it a slow bleed or a quick bleed?

Bleeding accumulates quickly

T or F: Symptoms of an arterial bleed present quickly, whereas symptoms of a venous bleed present slowly over weeks to months

True

What clinical effects might be present if the carotid artery is blocked?

Effects of the eyes, lateral cerebrum (hearing, upper body motor and sensory) and midline cerebrum (lower body motor and sensory)

What is the autonomic nervous system controlled by?

the reticular system in the brain stem

What does the autonomic nervous system regulate and control?

Regulates: cardiac and smooth muscle and glands

Controls: homeostasis

What are characteristics of the sympathetic nervous system if it is activated?

-Speeding up (increase metabolism)

-Fight or flight

-Increased HR, CO - Get blood where it is needed

-Decreased urine output - Urinating is not needed in times when SNS is activated

-Vasoconstricts vasculature - Move blood to vital organs

-Increased mental alertness

-Diaphoresis

-Dilated pupils

-Vasodilated coronary arteries - increases blood flow so the brain gets perfused

-Bronchodilation - bring more air in

-Decreased intestinal peristalsis - digestion is not needed in times when SNS is activates

-Increased releases of glucose by liver - increase of sugar stores to produce energy

What are characteristics of the parasympathetic nervous system if it is activated?

-Slowing down (decreased metabolism)

-Rest and digest

-Storage and maintenance of organs during rest periods

-Slows HR, CO

-Increased urine output

-Vasodilation of vasculature

-Decreased mental alertness

-Increased GI fluid secretion (stimulates GI system)

-Vasoconstriction of coronary arteries

-Bronchoconstriction

-Increased intestinal peristalsis

-Decreased release of glucose by liver

T or F: The brain does not have the ability to store essential nutrients

True

Because the brain does not have the ability to store essential nutrients, what it is dependent on to get its oxygen supply and perfusion?

Cerebral blood flow. the brain uses 20% of body's total O2 supply and it is dependent on this cerebral blood flow for energy

How do the cerebral arteries alter their own blood flow to maintain a constant pressure?

Autoregulation

How is autoregulation accomplished in the brain?

-Cerebral blood flow matches cerebral metabolic demand

-Vasodilation and vasoconstriction of cerebral arteries - responds to decrease and increase in blood supply

-When MAP is between 60-140mmHg

How does autoregulation of cerebral arteries fail?

When map is less than 60 (causes cerebral hypoxia) and greater than 140 (causes headaches, BBB disruption and edema)

What factors cause vasodilation (AKA increasing blood flow) of cerebral blood flow?

instances of:

-Hypotension (systemic) d/t low circulating blood volume - peripheral

-Increased CO2 (acidosis) - hypoxia, sedation, low RR, low O2 content

What factors cause vasoconstriction (AKA decrease blood flow) of cerebral blood flow?

Instances of:

-Hypertension (systemic)

-Decreased CO2 (alkalosis) - hyperventilation

T or F: When autoregulation fails, we depend on MAP for cerebral blood flow

True

What does hyperventilation cause in the brain?

Vasoconstriction because the person is blowing off CO2 and getting rid of CO2 in the body

T or F: CO2 is a potent vasodilator in the brain

True

What does hypoventilation cause in the brain?

Vasodilation because the person is holding in more CO2 in their body and the CO2 is vasodilating

What is the Munroe-Kellie Doctrine?

"As the volume of one component of the cranial vault triad expands, the volume of one or both of the other components must decrease to maintain a constant ICP"

What percentage does each component of the cranial vault triad take up?

Brain - 80%

Cerebral blood volume - 10%

Cerebrospinal fluid - 10%

What happens when there is an increase in brain mass caused by a tumor, making the brain matter take up 85% of the cranial vault?

There is either a decrease in either blood or CSF or both

What happens when there is a increase in blood flow to the brain, making cerebral blood volume 15%?

There is either a decrease in brain size or CSF or both

What happens if there is sustained increase in blood pressure in the brain?

Symptoms appear like headaches

What is intracranial pressure (ICP)?

The pressure exerted by the CSF within the ventricles of the brain

What is normal ICP?

0-15 mmHg

What is the threshold of ICP for treatment?

Sustained ICP of 22mmHg

What increases ICP?

-Cerebral edema d/t injury, HHS, SIADH, etc

-Hemorrhage/hematoma, mass

-Excess CSF (hydrocephalus)

-Increased cerebral blood flow d/t hypertension

-Increased intrathoracic pressure d/t tension pneumothorax, coughing excessively, deep suctioning, valsalva maneuver, bearing down, etc.

-Reduced cerebral venous drainage - brain veins are unable to drain blood out

-Superior vena cava syndrome - blood backing up in the brain because it goes to the brain but has difficulty leaving the brain

If ICP is rising, what should the body do to attempt to maintain perfusion to the brain?

-Reduce CSF by shunting CSF in spinal space to take it out of the cranial vault- first and most adaptable

-Shunt blood out of the skull to decrease blood flow and helps with ICP but does not keep the brain alive- second thing

T or F: Hemorrhagic strokes can increase ICP

True

What needs to be managed so that MAP pressure is high enough to control ICP in patients with a hemorrhagic stroke?

Blood pressure

What are the signs and symptoms of increased ICP?

-Headache

-Nausea and vomiting (nausea enter is in the medulla and with increased pressure it gets stimulated)

-Amnesia

-Behavioural changes: restlessness, irritability, confusion, impaired judgement

-Decreased LOC (this can be subtle at first but then progresses quickly), drowsiness

-Aphasia, changes in speech pattern/dysarthria

-Cranial nerve dysfunction

-Seizures

What late/terminal signs and symptoms of increased ICP indicate decompensation?

-Cushing triad: widening pulse pressure, irregular respirations, bradycardia

-Abnormal motor posturing: decerebrate; decorticate

-Unilateral or bilateral pupillary lack of reactivity ("fixed")

-Unilateral or bilateral pupillary dilation

What is Cushing's Triad?

A sign of late or terminal decompensation in increased ICP

Widening pulse pressure:

-Increased difference between SBP and DBP - because brain stem is no longer functioning

-Brain is herniating through the foramen magnum

Irregular respirations:

-Cheyne-stokes; slow and deep breaths followed by period of apnea

Bradycardia: low HR

What is the treatment of increased ICP?

-Shunts

-Burrholes

-Evacuation of blood/drains

-Craniectomy

What is the cerebral perfusion pressure?

Pressure gradient necessary to supply adequate amounts of blood to the brain. Measure of adequacy of cerebral blood flow

What is the normal cerebral perfusion pressure (CPP)?

60-100 mmHg

What happens when CPP is less than 60 mmHg?

It means that the arterial pressure cannot overcome increased pressure gradient to deliver O2 and nutrients to the brain

T or F: When ICP is higher your MAP needs to be higher than the ICP to perfuse blood to the brain

True

What is a normal MAP?

50-150 mmHg

What is the equation for calculating CPP?

CPP = MAP - ICP

MAP = (SBP) + (2xDBP)/ all over 3

IF:

ICP = 25 mmHg (normal 0-15 mmHg)

BP = 85/30 mmHg (normal 120/80 mmHg)

What is the CPP?

How is perfusion to the brain?

Calculate MAP first:

MAP = 85 + (2 x 30)/3 = 48.3

Then plug the MAP into the CPP equation:

CPP = MAP -ICP

CPP = 48.3 - 25 mmHg

CPP = 23.3

How is perfusion to the brain? Hypoperfused because CPP is less than 60-100mmHg

When autoregulation in the brain fails, perfusion becomes dependent on the:

a. BBB

B. CPP

c. MAP

d. CBF

C. MAP

What is included in the CNS assessment when you are not suspecting impairment?

-LOC (GCS)

-Vitals (brain stem controls vitals)

-Language and speech

-Cranial nerve status

-Pupils (PERRLA)

-Grip strength and extremity movement bilaterally

-Sensation

When the pupils are fixed, what does that mean?

There is not enough blood getting to the cranial nerves for the pupils to be reactive

What is the GCS?

Used to quantify consciousness and severity of head injury

What is the normal range of a GCS?

3-15

What does a score of 3 on the GCS indicate?

Death or heavily sedated

What does a score of less than 8 mean we have to do?

Think about intubating

Glasgow Coma Scale

Eye Opening:

Spontaneous - 4

To Voice - 3

To Pain - 2

None - 1

Best Verbal:

Oriented - 5

Confused - 4

Inappropriate Words - 3

Incomprehensible Sounds - 2

None - 1

Best Motor

Obeys Commands - 6

Localizes Pain - 5

Withdraws to Pain - 4

Flexion to Pain - 3 

Extension to Pain - 2

None - 1

What are examples of painful stimuli?

Nail bed pressure, pinching the trapezius muscle, sternal rub

What GCS score is a patient who is pulseless and apneic?

GCS of 3