11-The Brain 1 E-learning

8/2/2019 11-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:Anatomically:

1. Central Nervous System:

Brain & Spinal Cord2. Peripheral Nervous System:

Peripheral nerves distributed throughout the body( the cranial and spinal nerves which will form the peripheralnerves later on )

Functionally or physiologically :1. Somatic nervous system ( subdivided into sensory andmotor )2. Autonomic nervous system ( subdivided into sympatheticmainly by the sympathetic trunk and parasympatheticmainly by vagus nerve )


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Major Parts of The BrainForebrain:(prosencephalon)

Cerebrum

Diencephalon( two structureswithin the cephalon,the thalamus and thehypothalamus)

Midbrain(mesencephalon )

Hindbrain or tail brain:(rumbencephalon)Pons (means bridge,its brigdinghorizontally the twohalves of thecerebellum andvertically the upperparts of the brainwith the medullaoblongata and spinalcord below)

Medulla 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 )- Within the longitudinal fissue

you can find a duralreflection falx cerebri

extends over:ant. & middle cranial fossaetentorium cerebelli


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Internal Structure of CerebrumOuter Layer:

The Cerebral CortexGray matterfolded from outside into:gyri & sulci

Inner Layer:white matter

What do gray & white matters refer to?

Gray matter = nerve cells bodies, dendrites,unmyelinated axons

White matter = myelinated axons

- The myelin has a glistening white appearance


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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 the frontal from parietallobes

Parietooccipital Sulcus:

more prominent mediallyLateral Sulcus (Fissure):

Celvian Fissure separates the temporal from the

frontal and parietal lobes

Located between 2 important gyri:Precentral gyrus - frontal lobe

Postcentral gyrus - parietal lobe


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Precentral Gyrus

The primary motor area (large motor neurons)

Controls voluntary movement on opposite side of the bodyBecause:

Nerve fibers from precentral gyruscross over to other side within medulla oblongata

Decosation : crossing over

Motor control in precentral gyrus is represented in aninverted position


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Postcentral Gyrus

The primary sensory area (sensory nerve cells)

Receives inputs for:

pain, thermal sensation, touch & pressure (tickling)( General sensation )

Receives the sensations from opposite side of the body

Sites of cross over - two sites : 1- Spinal cord : general senstion 2- Medulla oblongata : fine sensation ( fine touch ) or vibration


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Main Cerebral Sulci

Central Sulcusseparates the frontal from

parietal lobesLateral Sulcus separates the temporal from the

frontal and parietal lobesParieto-occipital Sulcus

Calcarine Sulcus:on medial surface of occipitallobecommunicates with theparietooccipital sulcus( anteriorly )region of visual interpretation


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Main Functional Regions in Cerebrum

1. Motor area:location?Precentral gyrus

2. Sensory area:location?Postcentral gyrus

3. Auditory area:interpretation of soundlocation?In the middle of the

superior temporalgyrus


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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 ofspeech in a comprehensivewaylocation?

In the middle of inferior frontal gyrus

6. Wernickes (Language) area interprets the meaning ofspeech by recognizingspoken wordsLocation?

In the posterior part of the superior temporal gyrus


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Brocas area & Wernikes area are onlylocated in the dominant half of the cerebralhemispheres


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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 aphasiaagramatic 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 ? Islands of gray matter surrounded by white matter in the CNS : nucleus ( nuclei ) in the PNS : ganglion ( ganglia )

- Usually occupies 80% of diencephalonThe main function of the thalamus : its a major relay station for

sensory pathwaysInterthalamic 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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MidbrainSup. Part of brain stem

Connects forebrain to hindbrainConsists of 2 halves ant.:

Cerebral PedunclesEach peduncle consists of:ant. Part: crus cerebri

post. Part: tegmentum

middle part: substantia nigra(the black substance - containsmelanin )

1 part posteriorly:Tectum

*Contains the nuclei of which C.N.??


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Done by : Muad Al -Zoubi Best wishes

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11-The Brain 1 E-learning