neuro: ch. 5 brain & enviro (cranium, ventricles, meninges)

Unique functions of the brain in relation to its local environment

• Skull

• Meninges

• Blood Vessels

• Cerebrospinal fluid (CSF)

• Ventricles

Foramen magnum

base of the skull

Where does the spinal cord transition to the medulla

cervicomedullary junction

Pyramidal decussation

lateral corticospinal tract crosses to other side of spinal cord

Foramen of the skull

foramen ovale and spinosum

Foramen ovale

mandibular branch of CN V

Foramen spinosum

middle meningeal artery

Fossa

compartments in base of skull

Fossa of the skull

anterior, middle, posterior

Meninges are layers of membranes surrounding the

CNS

Dura is composed of

tough, fibrous layers

What are the layers of the dura

periosteal and meningeal

Periosteal

outer layer

Meningeal

inner layer

Inner layer folds into cranial cavity to form

falx cerebri and tentorium cerebelli

Tentorial notch

opening in tentorium cerebelli

What passes through the tentorial notch

midbrain

The arachnoid layer looks

wispy, spidery

The arachnoid layer is adherent to

inner dura

CSF flows...

below arachnoid layer (subarachnoid space)

Pia mater adheres to the

brain surface

How many spaces are formed by the meninges

3 (1 actual, 2 potential)

Potential spaces ___ anatomical spaces, but will become a space if ____ occurs.

are not; hemorrhage

The epidural space is between the ___, containing the ___.

inner skull and dura; middle meningeal artery

What type of space is the epidural space

potential

The middle meningeal artery is a branch of the ___ and supplies the ___.

external carotid artery; dura

Subdural space is between

dura and arachnoid

What type of space is the subdural space

potential

____ cross over the subdural space to drain into the ____.

bridging veins; dura venous sinuses

Venous sinuses are ___ formed between the ___.

large channels formed between the two layers of dura

Venous sinuses drain venous blood and CSF into the ___ to reach the ___.

sigmoid sinuses; IJV

The subarachnoid space is between

arachnoid layer and pia

What type of space is the subarachnoid space?

actual

The subarachnoid space is filled with

CSF

The subarachnoid space contains

major arteries of the brain

Arachnoid trabeculea

fine filaments loosely connecting arachnoid to pia

Ventricles are ___ containing ___.

cavities; CSF

CSF assists with

buoyancy and chemical stability

There is/are ___ lateral ventricle/s within each hemisphere.

one

The third ventricle is within the

diencephalon

The fourth ventricle is surrounded by

pons and cerebellum

The horns of the lateral ventricles are named after

lobes and direction extending

Lateral ventricle horns

frontal, body, atrium, temporal, occipital

CSF leaves ventricular system via ___ in ___ ventricle to flow to the spinal cord.

foramina; fourth

Foramina in fourth ventricle

- Foramina of Luschka (lateral)

- Foramen of Magendie (midline)

CSF is reabsorbed by ___ into the ____.

arachnoid granulations/villa; venous sinuses

Cisterns

widened areas of subarachnoid space containing CSF

Perimesencephalic cisterns

Ambient

Quadrigeminal

Interpeduncular

Interpeduncular cistern is between

cerebral penducles

The quadrigeminal cistern is

superior and inferior colliculi

The ambient cistern is

lateral to the midbrain

Other cisterns

Prepontine

Cisterna magna (cerebellomedullary)

The lumbar cisterm contains the

cauda equina

What is the site of spinal/lumbar taps

lumbar cistern

BBB

blood brain barrier

Most capillaries allow free passage of substances due to ___ in the endothelial cells.

fenestrations

In the brain, capillary endothelial cells are joined at

their edges

Substances entering or exiting the brain must travel through ___, thus forming the ___.

capillary endothelial cells; BBB

What type of molecules can clear the barrier

fat-soluble, smaller molecules (diffusion through lipid bilayer)

___ monitors and restricts entry of ___ molecules.

BBB; water soluble and large

BBB requires ___ transport.

active

What cannot cross the BBB

most drugs, viruses, radioactive ions, and antibiotics

A blood-CSF barrier also exists between the

choroid plexus and CSF

Circumventricular organs

specialized brain regions where there is no BBB

Circumventricular organs allow the blood to be monitored so the brain can respond to

changes in the chemical environment of the rest of the body

Median eminence and neurohypophysis is involved in

regulation and release of pituitary hormones

Chemotactic trigger zone (area posterma)

senses toxins

The skull is a ___ space, so any space occupying lesion can cause brain tissue to ___.

rigid; exit the cranial vault

Elevated ICP can cause ___ cerebral perfusion and brain ischemia.

decreased

Normal ICP

15 mmHg

Cerebral perfusion pressure needs to be above

50 mmHg

s/s of elevated ICP

Small masses can be compensated for by a ___ in CSF and blood volume ___ rise in ICP

decrease; without

Brain herniation syndromes

*mass effect (due to tumor, edema, hemorrhage etc.) is severe enough to push intracranial structures from one compartment into another

Subfalcine herniation

cingulate gyrus herniates under falx cerebri

Subfalcine herniation can compress

ACA

Central herniation

central and downward displacement of brainstem

Central herniation involves which CN, and what can it lead to

CN VI; uncal herniation

Uncal (transtentorial) herniation

medial temporal lobe (uncus) through tentorial notch

Tonsilar herniation

cerebellar tonsils through foramen magnum

Severe head trauma includes

diffuse axonal shear injury, cerebral contusions, penetrating trauma, and intracranial hemorrages

All pts with neuro deficits

s/s of intracranual

What is a common first indication of subarachnoid hemorrhage or DVA

headache (HA)

Intracranial hemorrages is classified as

traumatic, nontraumatic

Epidural hematoma

Subdural hematoma

Chronic subdural hematoma

Acute subdural hematoma

Subarachnoid hemorrhage

Which type of subarachnoid hemorrhage is most common

traumatic

Intracerebral hemorrage

Types of intracerebral hemorrage

Contusions of cerebral hemispheres occure where ____ are immediately adjacent to ridges of the

Most common at

temporal and frontal lobe

Coup contrecoup injury

Non-traumatic intracerebral hemorrhage is caused by

HTN, brain tumors, secondary hemorrhage after ischemic infarction, vascular malformations (AVMs), coagulation abnormalities, infections, etc

What is the most common cause of non-traumatic intracerebral hemorrhage

HTN hemorrhage

Rebleeding

Identify the tentorial notch