chapter 14

Cerebrum

Cerebrum

Most volume; right and left hemispheres; separated by longitudinal fissure

Cerebral hemispheres

Right and left hemispheres

Gyrus (gyri)

Surface fold

sulcus (sulci)

Indention

corpus callosum

Large bundle of axons (white matter) that links the 2 hemispheres

Rostral

Toward forehead (superior)

Caudal

Toward spinal cord (inferior)

Cerebellum

Inferior/caudal to cerebrum; rests in posterior fossa of skull

Diencephalon

Thalamus, Hypothalamus, Epithalamus; deep (in center) mostly hidden by cerebrum

Brainstem

Midbrain, pons, medulla oblongata

dural sinus

Enlarged veins between the periosteal and meningeal layers

dura folds

"seatbelts" for the brain meningeal layer folds inward, anchors brain

Superior sagittal sinus

an unpaired venous structure that originates at the junction of the frontal and ethmoid bone, directly posterior to the foramen cecum close to the crista galli

transverse sinus

runs laterally in a groove along the interior surface of the occipital bone

falx cerebri

in longitudinal fissure

Tentorium cerebelli

Between cerebrum & cerebelli

falx cerebelli

Between right and left halves of cerebellum

interventricular foramina

Connect them in the 3rd ventricle

Cerebral aqueduct

Connects it to the 4th ventricle

central canal

Extends into the spinal cord

choroid plexus

Masses of capillaries in the floors and walls of the ventricles

Ependymal cells

Line ventricles/canals and, thus, cover the choroid plexuses

arachnoid villi (granulations)

Reabsorb CSF -> superior sagittal sinus so it can be reabsorbed into the venous blood

Hydrocephalus

Water on the brain

Blood-CSF barrier

Tight junctions between ependymal cells covering choroid plexus capillaries

blood-brain barrier

Tight junctions between capillary endothelial cells; astrocytes -> tight junction formation

cerebral cortex

Gray matter, cerebral surface

Stellate cells

Round somas, short axon, dendrites in all directions

pyramidal cells

Tall and conical; only neurons with output from cortex; apical dendrite goes to brain surface; horizontal dendrites; axon goes to white matter

Basal nuclei

Masses of gray matter deep within the white matter of the cerebrum

limbic system

Gray matter structures around corpus callosum, medial side of both cerebral hemispheres

cerebellar cortex

Surface of cerebellum; cerebellum 10% of brain weight but 50% of brain neurons

Deep nuclei

Location of gray matter; in each cerebellar hemisphere

granule cells

Tiny, abundant neurons

Purkinje cells

Huge, globose neurons; dendrite forest

Reticular formation

Loose web of gray matter

arbor vitae

Axons connect cerebellum with spinal cord and rest of the brain (input and output)

association tracts

Connect regions within same hemisphere; long association fibers between lobes; short association fibers between gyri

Commissural tracts

Between cerebral hemispheres; mostly in corpus callosum; 2 hemispheres communicate

projection tracts

Vertical; between higher brain and lower brain/spinal cord

gracile and cuneate fasciculi

Pair of posterior ridges

Pyramids

Anterior ridges with nerve fibers from the corticospinal tract

corticospinal tract

Descending/Motor; carry signals from the cerebral cortex to skeletal muscles

Olives

Inferior olivary nucleus; relays info (from brain and cord) to cerebellum

Cerebellar peduncles

Stalks that connect cerebellum to medulla; contain tracts that transmit signals from spinal cord to cerebellum

Pons

Relays impulses between higher and lower brain regions

corpora quadrigemina

the four colliculi, two inferior and two superior, that sit on the quadrigeminal plate on the posterior surface of the midbrain

Red nucleus

High density of blood vessels; works with cerebellum for fine motor control

substantia nigra

Dark from melanin; produces dopamine, an inhibitory neurotransmitter; regulates body movement

cerebral crus

Contains corticospinal tracts

Diencephalon

Made up of the thalamus, hypothalamus, and epithalamus; deep (in center) mostly hidden by cerebrum

Thalamus

⅘ of diencephalon; 2 oval masses superior to brainstem

Hypothalamus

Maintains homeostasis

Pineal gland

Makes up most of the epithalamus

Melatonin

Secreted by pineal gland, increased secretion in the dark; used by some as a sleep aid

Vermis

Between hemispheres

Folia

Ridges, sulci between

sensory homunculus

Postcentral gyrus; size of homunculus' part corresponds to area of cortex assigned for it; face and hands have more sensory receptors and cortex

Somatotopy

Maps body area to Primary Motor Cortex

Agnosia

Inability to recognize familiar objects

Prosopagnosia

Can remember familiar faces, own face, in mirror

multimodal area

Integrate many sensory inputs

Central sulcus

Separates the frontal lobe from the parietal lobe, more specifically separates the primary motor cortex anteriorly from the primary somatosensory cortex posteriorly

precentral gyrus

is the anatomical location of the primary motor cortex, which is responsible for controlling voluntary motor movement on the body's contralateral side

postcentral gyrus

posterior to central sulcus; receives information from receptors for touch, pressure, stretch, movement, hot, cold, pain

Motor homunculus

Precentral gyrus; size of homunculus' part corresponds to area of cortex assigned for it; face and hands have more cortex (small motor units)

Dyskinesias

Movement disorders involving involuntary muscle movement

Huntington disease

Genetic, neurodegenerative disease that affects basal nuclei and cerebral cortex

Parkinson's disease

Substantia nigra not producing dopamine -> less inhibitory effect of dopamine on basal nuclei -> involuntary contractions

cerebral palsy

Loss of muscle coordination because of damage to motor areas of the cerebral cortex during fetal development, birth, or infancy

Ataxia

Lack of muscle control or coordination of voluntary movement; often involves problems with cerebellum; clumsy, awkward walking

Wernicke area

In temporal lobe, usually left; responsible for understanding and recognition of language; formulates phrases, plan of speech -> sends plan to broca area

Aphasia

Language deficit caused by lesions in hemisphere with wernicke and broca areas

Broca's area

In frontal lobe, same hemisphere as wernicke, usually left; plans muscle use to speak (-> 1 degree motor cortex -> larynx, tongue, lips, cheek)

Cognition

Mental process of acquiring knowledge and using it (understanding, reasoning, problem solving etc

)

contralateral neglect

Unaware of objects or body parts on the contralateral side

Learning

Memory

Mammillary nuclei connect to hippocampus and thalamus

explicit memory

Declarative memory, "words/numbers"

Implicit memory

Procedural memory (ability to tie one's shoes); emotional memory (fear of a wasp)

Amnesia

Defect in explicit memory

retrograde amnesia

Cannot recall info they once knew

Anterograde amnesia

Cannot store new info

Alzheimer disease

Atrophy of cerebral cortex, hippocampus and other brain regions

neurofibrillary tangles

Broken, twisted cytoskeleton in some neurons

Senile plaques (beta-amyloid)

Proteins that should be broken down but instead accumulate in extracellular space

EEG

Electrodes on scalp record surface electrical activity; useful for diagnosis and study of sleep disorders, metabolic problems, tumors, trauma, degenerative brain diseases

Sleep

Controlled by interaction between cerebral cortex, thalamus, hypothalamus, and reticular formation

Sleep paralysis

Inhibition of muscular activity (resembles coma but can be aroused by sensory stimulation)

circadian rhythms

Cycles that sleep is a part of (events reoccur at intervals of about 24 hours)

REM (paradoxical) sleep

Vitals increase, EEG like awake, harder to wake; about 5x a night, go back to stage 1-2

Orexins

Neuropeptides that stimulate wakefulness (Low in narcolepsy - excessive daytime sleepiness and fatigue)

Concepts

Place structures in appropriate brain area

Brain steum Medulla oblongata Pons Midbrain 2

Diencephalon Thalamas Hypothalamus Epithalamus 3

Cerebellum 4

Cerebrum Cortex

5 lobes Basal nuclei Limbic system

Describe the 3 meninges; how are they arranged differently from those around the spinal cord

Dura Mater-No epidural space, 2 layers of dura (periosteal and meningeal layer), only the meningeal layer continues into the vertebral canal Arachnoid Mater-Transparent, subdural space (between dura and arachnoid, only in some spaces)

Subarachnoid space (between arachnoid and pia, filled with CSF) Pia Mater-Microscopic, closely attached to the brain (follows sulci inward)