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Phrenology


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(Taken from Kalat, 2007, p. 83)


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Nervous System

Central nervous system(CNS) Brain and Spinal Cord

Peripheral

(blue in figure) Cranial nerves, spinal

nerves, peripheral receptororgans

Autonomic (red in figure)

Control of visceral funcion

Sympathetic

Parasympathetic


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CNS

Two Cerebral hemispheresTwo Cerebral hemispheres

The brain stemDiencephalonDiencephalon

Mesencephalon (midbrain)Pons

Medulla Oblongata

Cerebellum


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Brain is protected by:

Skull Meninges

Cerebrospinal fluid (CSF)


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Meninges

Three layers

Dura mater Arachnoid

Pia mater

Diagrammatic representation of a section across the top of the

skull, showing the membranes of the brain, etc. (Greys769 Taken

from on-line Grays Anatomy; Modified from Testut.)


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Dura Mater (hard mother)

Continuous with the dura mater that covers the spinal

cord Tough, fibrous connective tissue Two layer

Superficial (outer) periosteal layer adheres to the skull Deep (inner) meningeal layer is in contact with the arachnoidmater

Meningeal veinscourse through the dura Dura punctured by Bridging veinsdrain underlying

neural tissue into sinuses Dural veinous sinusesform between layers

Drain blood and CSF and empty into jugular vein


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Three major reflections Between the cerebral

hemispheres Falx cerebri

Between the cerebellum and

the occipital lobe Tentorium cerebelli

Underneath the cerebral

hemispheres Falx cerebelli


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Arachnoid Mater

Spider-web likenonvascular membrane

In contact with the duramater above it, and theCSF-filled subarachnoid

cavity is below it.(subarachnoid cavityis filled with delicatearachnoid fibers

extending down to the piamater)


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Arachnoid granulations

protuberances (villi)through the meningeallayer of the dura

Locations of transfer ofsubarachnoid CSF toveneous system


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Pia Mater

Thin translucent layer

Adheres to the brain surface Location of the brain blood vessels

Together with the arachnoid are called the

pia-arachnoid membrane


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Epidural space (skull and dura mater)

Rupture of middle menigeal artery, or accumulation of arterialblood in the epidural space, is life-threatening

Subdural space (dura mater and arachnoid) Rupture of bridging veins, leading to subdural hemorrhage, or

accumulation of blood in space requires surgical intervention

Subarachnoid space (arachnoid and pia mater) Contains CSF and cerebral blood vessels Rupture of these vessels leads to subarachnoid hemorrhage

Condition may be due to Trauma

Congenital abnormalities (aneurysms) High Blood Pressure


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Cerebral Dural Venous Sinuses

Endothelial-lined channels, devoidof valves

located between the periosteal andmeningeal layers of the dura mater

Low-pressure return channels forvenous blood back to circulatorysystem

Superior Saggital Sinus

Inferior Saggital Sinus

Vein of Galen

Straight Sinus

InternalCerebral vein

Confluence ofSinuses(torcular

Herophili)


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Cerebral Dural Venous Sinuses

Confluence ofSinuses

Transverse Sinus

Sigmoid Sinus

Jugular vein

SuperiorPetrosal Sinus

InferiorPetrosal Sinus

Occipital SinusMarginal

sinusVeinous plexuses


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Lateral Surface

Principle landmarks

Sylvian fissure

Central sulcusdemarcate three of the four lobes

Parieto-occipital sulcus -> pre-

occipital notch demarcatesparietal and temporal lobedivisions from occipital lobe

Insula lies within the SylvianFissure

Temporal Lobe

Frontal LobeParietal Lobe

Occipital

Lobe


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Frontal Lobe

Primary Motor Area Relatively low levels of

stimulation ofprecentral gyrusproduce movement

Lesions in this regionproduce contralateralparalysis.

Most marked formuscles involved in finemotor movement

Motor Homonculus


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Frontal Lobe

Premotor Motor Area

Rostal of PrecentralSulcus

Important in initiating

motor plans andchanging motor plans


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Frontal Lobe

Brodmanns Area or

Frontal Eye Fields Between superior andinferior frontal gyri

Important for eyemovements


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Frontal Lobe

Brocas Area Bordered by the

inferior frontal sulcusand anterior horizontalRamus

In the left hemisphereis responsible forspeech

Lesions in this arearesult in aphasia


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Parietal Lobe

Primary sensory area

Delineated by thecentral and postcentralsulci

Stimulation producestingling and numbness

Similar contralateralrepresentation asprimary motor area.


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Temporal Lobe

Gyri ofHeschl

Wernickesarea

Perce

ptionof

color

andform


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Occipital Lobe

Visio

n


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Medial Surface

Corpus Collosum

Fibers which connect

the cerebralhemispheres

Divided into:

Rostrum (Head) Body

Knee

Splenium

Lesion disconnects thehemispheres

R

B

S

G


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AnteriorCommissure Fiber bundle

Connects: temporal lobes

olfactory structuresin each hemisphere

In humans, anteriorlimb = olfactory

posterior limb:visual and auditoryareas


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Surgery to cut the corpus collosum produces Split-brainpatients

Can perform familiar tasks bi-manually, but novel tasksare harder to coordinate Hands often work in opposition to one another.


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Patient saw the word sky in the

LVF and scraper in the RVF. With his right hand he drew what hecould see in his RVF (LH)

With his left hand:

Left hemisphere (LH) controlled itenough to draw a sky His RH controlled it enough to draw a

scraper. Neither could combine the words to

detect the emergent concept.

Similarly, hot in the LVF and dogin the RVF produced a picture of anoverheating dog, not a weiner in abun.


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Recovery

Corpus collosum doesnot heal.

Many alternative inter-hemispheric connectionsare present.

Left hemisphere learns to

control the right, butsubtle effects can still beobserved.

Patients also learn

strategies

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