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8/2/2019 2 the Brain 1 E-learning
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The Brain I
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The Brain
The part of CNS that lies within the skull & continues with spinalcord through foramen magnum
Nervous tissue divisions:
1. Central Nervous System:Brain & Spinal Cord
2. Peripheral Nervous System:
Peripheral nerves distributed throughout the body
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Major Parts of The Brain
Forebrain:CerebrumDiencephalon
Midbrain
(mesencephalon)
Hindbrain:PonsMedulla oblongataCerebellum
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Brain Stem
Mid brain
Pons
Medulla Oblongata
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Cerebrum
Largest part of brain
2 hemispheres: (Rt. & Lf.)
separated by a fissure
(longitudinal fissure)
extends over:
ant. & middle cranial fossae
tentorium cerebelli
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Internal Structure of Cerebrum
Outer Layer:
The Cerebral Cortex
Gray matter
folded from outside into:
gyri & sulci
Inner Layer:
white matter
What do gray & white mattersrefer to?
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External Aspect of Cerebrum
Folded into Gyri & Sulci
* surface area
Subdivided by sulci into lobes:
1. Frontal
2. Parietal
3. Occipital
4. Temporal
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Cerebral Lobes
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Main Cerebral Sulci
Central Sulcus:
separates ?
Located between 2 important gyri:
Precentral gyrus(which lobe?)
Postcentral gyrus(which lobe?)
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Precentral Gyrus
The primary motor area (large motor neurons)
Controls voluntary movement on opposite side of the body
Because:
Nerve fibers from precentral gyruscross over to other side within ???
Motor control in precentral gyrus is represented in an
inverted position
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Postcentral Gyrus
The primary sensory area (sensory nerve cells)
Receives inputs for:
pain, thermal sensation, touch & pressure (tickling)
Receives the sensations from opposite side of the body
Sites of cross over ??
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Main Cerebral Sulci
Central Sulcus
separates ?
Lateral Sulcus (separates?)
Parieto-occipital Sulcus
Calcarine Sulcus:
on medial surface of occipitallobe
communicates with ??
region of visual interpretation
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Main Functional Regions in Cerebrum
1. Motor area:
location?
2. Sensory area:
location?
3. Auditory area:interpretation of sound
location?
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4. Visual area:interpretation of visionmedial aspect of occipitallobe(post. pole of cerebrum)
5. Motor Speech area:(Brocas area)
Planning & production of
speech in a comprehensiveway
location?
6. Wernickes (Language) areainterprets the meaning ofspeech by recognizingspoken words
Location?
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Clinical: Brocas Aphasia
Difficulty in speech due to damage to brocas area
The person knows what he wants to say but cannot speak
expressive aphasia
non-fluent aphasia
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Diencephalon
Hidden by cerebrum
Consists of:
Thalamus
Hypothalamus
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Thalamus
Paired oval masses of gray matter (contains many nuclei)what are the brain nuclei ?
- Usually occupies 80% of diencephalon
Interthalamic connexion:
a bridge of gray matter joins the two halves of the thalamus
(in 70% of human brains)
Fxn:a major relay station for sensory pathways
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Hypothalamus
Contains special nerve cells that secrete several neurohormones
Most common:
1. hypothalamus-releasing hormones:
control pituitary gland secretions
2. vasopressin: (ADH)
secreted by: hypothalamus
stored in: ??
Fxn.: retention of water (kidneys)vasoconstriction bld. Pressure
Hypothalamus links 2 systems??
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Midbrain
Sup. Part of brain stem
Connects forebrain to hindbrain
Consists of 2 halves ant.:
Cerebral Peduncles
Each peduncle consists of:
ant. Part: crus cerebri
post. Part: tegmentum
middle part: substantia nigra
1 part posteriorly:
Tectum
*Contains the nuclei of which C.N.??
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