CMD 418: Unit 2 - White Matter Tracts, Thalamus, Ventricles, Cerebrospinal Fluid, and Cebreovascular system

white matter tracts

myelinated fibers

• interhemispheric and intrahemispheric axonal connections

projection fibers

vertical ascending and descending fibers connecting cortex with brainstem and spinal cord

• corona radiata, internal capsule, sensory projection fibers, motor projection fibers

association

communication within hemisphere (intrahemispheric)

commissural

horizontal tracts between hemispheres (interhemispheric)

• corpus callosum

• largest commissural bundle (300-400 mil fibers)

corticospinal tracts

projection fibers then go from cortex to spine 

• originates in the motor cortex

corticobulbar tracts

projection fibers that connect the primary motor cortex to brainstem 

superior longitudinal fasciculus (arcuate fasciculus)

association pathway that connects frontal lobe to occipital lobe and temporal

• broca’s and wernicke’s

inferior longitudinal fasciculus 

heavily myelinated association pathway that connect temporal lobe to occipital

thalamus

sensory relay info station from brainstem to parts of the body 

part of neural circuitry

• circuitry of cerebral cortex, basal ganglia, thalamus, motor cortex

thalamus 

three thalamic functions

channeling, integration, regulation 

channeling 

projections of sensory info to specific cortical area

• pain, taste, temp, touch, vision, audition

integration

sensorimotor info before projecting to motor/premotor cortical areas

regulation

association areas and cortically mediated cognitive functions

thalamic physiology

bidirectional connections to specific cortical areas

• some nuclei with specific functions (higher mental, memory, sensorimotor)

thalamic nuclei: pulvinar function

language formulation, processing, lexical properties, reading, and writing

thalamic nuclei: pulvinar afferents 

primary and associated visual cortices, midbrain superior colliculus and reflex center

thalamic nuclei: pulvinar efferents 

angular & supramarginal gyri

thalamic nuclei: medial geniculate body function

relay center for audition

thalamic nuclei: medial geniculate body afferents

primary auditory cortices

damage to thalamus symptoms

central auditory processes

• auditory discrimination, understanding speech esp in background noise  

language

• aphasic symptoms, dysarthria, anomia

ventricles

produces CSF

• located underneath the cerebral cortex, some under subcortical structures 

lateral ventricles 

c-shaped on both the left and right of the brain 

• anterior, posterior (occipital) and inferior (temporal) horns 

• interventricular foramen - drainage to third ventricle 

third ventricle

space between two thalami

• cerebral aquedect - drainage to the fourth ventricle 

fourth ventricle 

pons and medulla in the brainstem 

• foramine of Luschka and megendie - csf drains into subarachnoid space surrounding the CNS

cerebrospinal fluid (csf)

storage and circulation in ventricles and produced by choroid plexus in ventricles 

CSF functions

mechanical cushion, protection from violent body mvnts, and removal of harmful waste 

ependymal cells 

line ventricles to keep CSF in ventricles 

CSF is absorbed through the

arachnoid granulations

after CSF is absorbed, it drains into the

superior saggital sinus (SSS)

• cavity along the longitudinal fissure

hydrocephalus 

disruption between production and absorption rates of CSF → intracranial pressure 

causes of hydrocephalus 

increased CSF production or impaired absorption and blocking of the draining to the SSS

sustained CSF pressure causes

ventricle enlargement and disproportionately small faces in infants 

arteries

supply oxygenated blood

• arterioles and capillaries

• buried deeper in the body

veins

return deoxygenated blood back to heart

• thinner than arteries

• more accessible

blood brain barrier 

first line of defense 

• functional in only CNS

• restriction of mvnt of harmful substances from blood to brain 

cerebrovascular supply

carotid artery, vertebral-basiliar arteries, circle of willis 

carotid system 

comes from the heart and then branches into 2 directions → external and internal carotids 

external carotid 

supplies blood outside the skull

• facial muscles, forehead, oral, and nasal cavities

internal carotid

supplies blood inside the skull

• carotid foramen in petrous bone

• branches to form the middle and anterior cerebral arteries

circle of willis

the connection of major arteries that supplies blood to the brain 

What artery is not part of the circle of willis?

MCA

anterior cerebral artery

medial surface of the frontal and parietal lobes

middle cerebral artery

lateral surface of frontal, temporal, parietal, and occipital 

posterior cerebral artery 

medial surface of occipital and temporal lobes 

central arteries distribute blood to

subcortical structures

anterior spinal artery

anterior/ventral two-thirds of spinal cord

posterior spinal artery

posterior/dorsal surface of spinal cord

venous sinus system

collection of deoxygenated blood

• veins empty into sinuses

• transportation back to heart

occlusive vascular pathology

thrombosis and embolism

thrombosis

narrowing of arterial wall which restricts bloodflow

thrombosis causes __% of strokes

60

embolism

plaque breaks away from thrombosis and blocks artery

an embolism causes __% of strokes

30

transient ischemic attack

mini stroke with a temporary artery blockage

hemorrhage

a bleed/rupture of blood vessels

hemorrhages cause __% of strokes

10

extra/subdural hematoma

like hitting your head

• trauma usually involved

subarachnoid hemorrhage

blood vessels under pia matter rupture which results with pressure on the brain

types of hemorrhages

extra/subdural hematoma, subarchanoid, aneurysm

arteriovenous malformations (AVM)

tangled dilated arteries and veins