CH14: Brain & Cranial Nerves

major portions of the brain:

forebrain, cerebellum, brainstem

cerebrum

the ________ is the largest part of the brain

cerebral hemispheres

pair of half globes of cerebrum

gyri

thick folds on cerebrum surface

sulci

shallow grooves between gyri

longitudinal cerebral fissure

deep groove that separates cerebral hemispheres

diencephalon

include inner areas like thalamus and hypothalamus

cerebellum

second largest part of brain

separated from cerebrum by transverse cerebral fissure

brainstem

the bottom portion of the brain

brain development

-neurulation occurs within first 3 weeks

-brain begins as neural tube, neural folds fuse creating a hollow neural tube by day 26

-cerebrum grows rapidly, limited space causes it to curl posteriorly and inferiorly to encapsulate diencephalon and midbrain

meninges

-3 membranes surrounding brain and spinal cord

-protect the brain and provide structural framework for its arteries and veins

-outermost to innermost: dura mater, arachnoid mater, pia mater

dura mater

consists of outer periosteal layer and inner meningeal layer

dural sinuses

spaces located where periosteal and meningeal layer separate

meningitis

-inflammation of the meninges (serious in infancy and childhood)

-bacterial or viral invasion of CNS through nose and throat

-signs: high fever, stiff neck, drowsiness, intense headaches

-may progress to coma, then death

-diagnosed by examining CSF obtained by lumbar spinal tap

ventricles

fluid filled chambers

lateral

two _______ ventricles are located with one in each cerebral hemispheres

third

the _____ ventricle is the narrow medial space beneath the corpus callosum

fourth

the ______ ventricle is a small triangular chamber between the pons and cerebellum

cerebrospinal fluid (CSF)

-clear, colorless liquid that fills the ventricles, canals of the CNS and meninges

-production begins with filtration of blood plasma through capillaries of the brain

choroid plexus

spongy mass of blood capillaries on the floor of each ventricle

ependymal cells

neuroglia that line ventricles and cover choroid plexus; modify the filtrate

the flow of CSF

-continuously flows through the CNS

-driven by its own pressure, beating of ependymal cilia, and pulsations of the brain produced by each heartbeat

buoyancy

-function of CSF

-allows brain to attain considerable size without being impaired by its own weight

protection

-function of CSF

-protects brain from striking cranium when head is jolted

chemical stability

-function of CSF

-flow of CSF removes metabolic waste from nervous tissue

-homeostatically regulates chemical environment

2%; 15%

brain only contributes __% of adult body weight, but recieves __% of the blood because neurons have a high demand for ATP so contsant blood supply is critical

brain barrier system (BBS)

-regulates what substances can get from bloodstream into tissue fluid of the br