2 the Brain 1 E-learning

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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