Lab Activity 14 The Brain Portland Community College BI 232

Lab Activity 14

The Brain

Portland Community CollegeBI 232

Brain Regions

• Cerebrum• Diencephalon

(thalamus, hypothalamus, pineal gland)

• Cerebellum• Brainstem (midbrain,

pons, medulla oblongata)

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Cerebrum

• Frontal lobe• Motor, speech (usually left lobe), personality

• Parietal lobe• Sensation (except smell), language

• Occipital lobe• Vision

• Temporal lobe• Hearing, smell, language

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Cerebral Cortex

• The superficial layer/rim of gray matter in the cerebral hemispheres• Gray matter

consists of cell bodies, dendrites, and unmyelinated axons.

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Sulci & Gyri

• Sulci: Shallow depressions of the cerebral cortex• Central sulcus is between the frontal and parietal

lobes• Lateral sulcus is between the parietal lobes and

temporal lobes.

• Fissures: Deep grooves• Longitudinal: separates cerebral hemispheres• Transverse: separates cerebrum form the

cerebellum• Gyri: The elevated ridges of the cerebral cortex

• Serve to increase the surface area

Sulci

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Transverse fissure

Longitudinal Fissure

TransverseFissure

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Lateral Sulcus

Central Sulcus

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Central SulcusPrecentral Gyrus: (frontal lobe) contains the primary motor area Postcentral Gyrus:

(parietal lobe) contains the primary somatosensory area.

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White Matter & Basal Nuclei

• White matter consists primarily of myelinated axons• Is beneath the gray matter cortex

• Notice how it is the opposite arrangement from the spinal cord (Spinal cord: white matter is on the outside and gray matter is on the inside.)

• Corpus callosum: Connects the right and left hemispheres

• Basal nuclei: Islands of gray matter within the white matter.• Function: Involved in the subconscious control of skeletal

muscle tone and the coordination of learned movement patterns

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White Matter & Basal Nuclei

White Matter

Basal Nuclei

Corpus Callosum

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Diencephalon

Structures

• Thalamus

• Hypothalamus

• Epithalamus

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Diencephalon: Epithalamus

• Superior to the third ventricle, contains the pineal gland

Pineal gland

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Diencephalon: Thalamus

• Relay station for sensory input

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Diencephalon: Hypothalamus

• Pituitary gland: Attaches to the hypothalamus via the infundibulum

• Mamillary bodies: Process olfactory sensations.

Pituitary gland (not in this picture) would be hanging here

Mamillary body

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Diencephalon: Hypothalamus

• Major Functions:1. Controls somatic motor activities at the

subconscious level2. Controls autonomic function3. Coordinates activities of the nervous and endocrine

systems4. Secretes hormones5. Produces emotions and behavioral drives6. Coordinates voluntary and autonomic functions7. Regulates body temperature8. Coordinates circadian cycles of activity

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Cerebellum

• Functions: • Coordination of

movements• Adjustment of

postural muscles

Vermis

Arbor Vita (white matter that looks like a leaf)

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3 Structures:• Midbrain

(mesencephalon)

• Pons

• Medulla oblongata

Brainstem

Corpora quadrigemina

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Pons

Medulla

Midbrain

Corpora quadrigemina

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Brainstem: Pons

• Functions:• Sensory and motor nuclei of Cranial nerves V,

VI, VII, and VIII• Respiratory control:

• Apneustic center and pneumotaxic center to modify the activity of the respiratory rhythmicity center in the medulla

• Nuclei and tracts that process and relay information to and from the cerebellum

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Brainstem: Midbrain

• Functions:• Connects pons to cerebellum• Superior colliculi: visual reflex centers• Inferior colliculi: auditory reflex centers

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Brain Meninges: Dura Mater

• Continuous with the spinal meninges

• Dura mater: An outer and inner fibrous connective tissue• Outer later is fused to the periosteum of the

cranial bones (no epidural space)

• Between the layers are tissue fluids, blood vessels and venous sinuses.• Venous sinuses are large collecting veins.• Venous sinuses drain into the internal jugular

veins

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Dural Folds

• The inner layer of dura mater that extends into the cranial cavity.

• Provide additional stabilization and support for the brain

• Contain the dural sinuses

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Dural Folds

• Falx cerebri projects between the cerebral hemispheres in the longitudinal fissure• Superior sagittal sinus & inferior sagittal sinus

• Tentorium cerebelli separates the cerebellar hemisphere from the cerebrum• Transverse sinus

• Falx cerebelli divides the cerebellar hemispheres

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Brain Meninges: Arachnoid & Pia Mater

• Arachnoid mater consists of the arachnoid membrane and fibers of the arachnoid trabeculae that attach to the pia mater

• Pia mater: attached to the surface of the brain, anchored by processes of astrocytes• Contains branches of cerebral blood vessels

that penetrate the surface of the brain.

• CSF is between these two membranes in the subarachnoid space

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Ventricles

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Brainstem: Medulla Oblongata

• Functions:• Center for the coordination of complex

autonomic reflexes (heart rate, respiratory rhythm, blood pressure)

• Control of visceral functions (vomiting, swallowing)

• Decussation of pyramids: a crossover point for the major motor tracts

Cranial nerves

• 12 pairs of cranial nerves

• Originate from the nervous tissue of the brain

• Some are mixed nerves while some are only sensory.

• We will learn more later

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Sheep Brain Dissection

• Follow instructions in book for the sheep brain dissection.

• When finished discard brain in the container provided.

Wash utensils and put back so other classes can use the materials.

• ID structures on the brain models for next week’s quiz.

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The End