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Organization of the CNS I. Phrenology. Review of the Nervous System. MAJOR FUNCTION: COMMUNICATION. Neuronal Morphology. The Neuronal Synapse. Glia – the Particular Role of Astrocytes. Astrocyte. Astrocytes Help Form the Blood Brain Barrier.

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Review of the

Nervous System

MAJOR FUNCTION:

COMMUNICATION






Astrocytes help form the blood brain barrier
Astrocytes Help Form the Blood Brain Barrier

  • Basal lamina of the astrocytes + the astrocytic endfeet produce help maintain the BBB.

  • Notice how astrocytes send processes to the external surface of the CNS where the endfeet form the glia limitans externa, which separate the pia mater from the nervous tissue.

  • Gap junctions and desmosomes join the endfeet to form a space between neurons and vascular endothelial cells (Fig. 2.2).



General orientation terms
General Orientation Terms

  • Rostral

  • Caudal

  • Posterior

  • Anterior

  • Dorsal

  • Ventral

  • Sagital

  • Horizontal

  • Coronal


Terms of

Orientation:


Planes of Section:

Horizontal

Transverse (Coronal)

Saggital


Major regions and landmarks
Major regions and landmarks

  • Six regions in the adult brain

    • Cerebrum

    • Diencephalon

    • Mesencephalon

    • Pons

    • Cerebellum

    • Medulla oblongata

  • Brain contains extensive areas of neural cortex

    • Layer of gray matter on the surface of the cerebellum and cerebrum






A spinal cord
A. Spinal Cord

  • Conduit for flow of information from PNS to CNS.

  • Participates directly in body movement control.

  • Processes sensory information from limbs, trunk, and internal organs.

  • Has segmental organization (most like primitive or early developmental NS).

  • Each segment has a pair of nerve roots.


B brainstem and cerebellum
B. Brainstem and Cerebellum

  • Brainstem = medulla + pons + midbrain.

  • ‘spinal cord’ for the head (sensory, motor control).

    -use of cranial nerves in place of spinal nerves.

    b. Transmission of information between brain and SC.

  • Regulation of arousal (via reticular formation at the core of brainstem).

  • Regulation of important visceral functions (e.g., bp and respiration).


Brain Stem:

Ventral Surface


Brain Stem:

Dorsal Surface


B brainstem and cerebellum1
B. Brainstem and Cerebellum

  • Cerebellum – regulation of movement, maintenance of posture and balance.

    -Works closely in concert with pons (derived from same embryonic brain division).


The cerebellum
The Cerebellum

  • Adjusts postural muscles and tunes on-going movements

  • Cerebellar hemispheres

    • Anterior and posterior lobes

    • Vermis

    • Flocculonodular lobe

  • Superior, middle and inferior cerebellar peduncles link cerebellum with brain stem, diencephalon, cerebrum, and spinal cord

    • Interconnects the two cerebellar hemispheres





C diencelphalon
C. Diencelphalon

  • Diencephalon – 2nd only to cerebrum as the most highly developed division.

  • Thalamus – key for transmitting information to cerebral hemispheres.

  • Hypothalamus – integrates functions of the ANS – controls endocrine hormone release from pit.


The thalamus
The Thalamus

  • Final relay point for ascending sensory information

  • Coordinates the activities of the cerebral cortex and basal nuclei


Thalamus
Thalamus

  • Part of diencephalon – relay nuclei through which sensory and motor information pass to and from the cortex.

  • E.g., in the 2 1° systems we have discussed:

    - from sc  1° sensory cortex

    - from 1° motor cortex  sc.

  • This is also the case for neural signals controlling other functions, such as learning and memory and emotions – and projecting to other parts of the cortex.

    A. Relay Nuclei have distinct roles, transmitting info from particular subcortical inputs to a specific portion of the cerebral cortex.






D cerebral hemispheres
D. Cerebral Hemispheres

  • These structures mediate the most complex and sophisticated human behaviors.

  • Cerebral cortex – highly convoluted to accommodate large surface area: gyri, sulci, fissures – deeper grooves – often separate major divisions.

    4 lobes:


Frontal
Frontal

  • Motor behavior

  • The 1° cortex at precentral gyrus.

    -nearby premotor areas

    -prefrontal asociation cortex

    -cingulate gyrus

    - important for reasoning and emotional control.


Parietal
Parietal

  • Sensory areas.

  • The 1° cortex at postcentral gyrus.

    -Superior parietal lobule

    -spatial perception, self-image

    -Inferior parietal lobule

    -integrating sensory information for speech and perception


Occipital
Occipital

  • The 1° cortex within calcarine fissure on medial surface.

  • Surrounding association cortex elaborates the sensory message so that we can see and integrate forms and colours.

  • Situated at the division of parietal and occipital lobes is an area important for recognizing faces.


Temporal
Temporal

  • Sensory functions, plus memory and emotions.

  • The 1° auditory cortex: on superior temporal gyrus – speech centre.

  • Much integration with nearby areas:

    -inferior temporal gyrus – perception of visual forms and colours.

    - works with nearby occipital.

    -temporal pole + medial temporal areas – mediate emotions along with nearby frontal cortical areas.


Ventricles of the brain
Ventricles of the Brain

  • Central passageway of the brain enlarges to form ventricles

    • Contain cerebrospinal fluid (CSF)



The cranial meninges
The Cranial Meninges

  • Continuous with the three layers of the spinal cord

  • Folds of dura mater help stabilize the position of the brain

    • Falx cerebri

    • Tentorium cerebelli

    • Falx cerebelli


Meninges of the cns
Meninges of the CNS

  • 3 layers:

  • Dura - thickest

  • Arachnoid – “spider-like”

  • Pia – delicate, adheres to surface.

  • Protective

  • Circulating function (contain blood vessels) – many veins and arteries in subarachnoid space.

    Dural sinuses are major venous areas carrying blood away from the brain.





The mesencephalon
The Mesencephalon

  • The tectum (roof) contains the corpora quadrigemina

    • Superior and inferior colliculi

  • The mesencephalon contains many nuclei

    • Red nucleus

    • Substantia nigra

    • Cerebral peduncles

    • RAS headquarters



The diencephalon is composed of
The Diencephalon is Composed of

  • Epithalamus

  • Hypothalamus

  • Thalamus


Internal capsule
Internal Capsule

  • White matter underling the cortex (seen as a band over the thalamus in sagital section).

  • Path of transmission of info immediate to and from the cortex.



Internal capsule2
Internal Capsule

  • In the following horizontal section, it lies between the thalamus and the caudate and other basal ganglia (putamen and globus pallidus).


The hypothalamus
The Hypothalamus

  • Controls somatic motor activities at the subconscious level

  • Controls autonomic function

  • Coordinates activities of the endocrine and nervous systems

  • Secretes hormones

  • Produces emotions and behavioral drives

  • Coordinates voluntary and autonomic functions

  • Regulates body temperature

  • Coordinates circadian cycles of activity





The basal nuclei
The Basal Nuclei

  • Caudate nucleus

  • Globus pallidus

  • Putamen

    • Control muscle tone and coordinate learned movement patterns





The cerebral cortex
The Cerebral Cortex

  • Surface contains gyri and sulci or fissures

    • Longitudinal fissure separates two cerebral hemispheres

    • Central sulcus separates frontal and parietal lobes

    • Temporal and occipital lobes also bounded by sulci


Laminar organization of the cerebral cortex
Laminar Organization of the Cerebral Cortex

  • All cortical regions are organized in layers.

  • Most cortical regions in humans are the most advanced form (neocortex, isocortex).

  • Allocortex – phylogeneticaly older, has fewer layers: 2 types:

    i. Paleocortex – sense of smell, emotions (olf bulb).

    ii. Archicortex – memories (hipp, 3 layers)


Laminar organization of the cerebral cortex1
Laminar Organization of the Cerebral Cortex

C. Brodmann’s Areas – Thickness of each of the 6 layers varies between these areas, which are also distinct functionally.

Areas that subserve sensation have a thick layer IV (thalamic n. project here)

1° motor areas have a thick layer V.




Association areas
Association areas

  • Control our ability to understand sensory information and coordinate a response

    • Somatic sensory association area

    • Visual association area

    • Somatic motor association area


General interpretive and speech areas
General Interpretive and Speech Areas

  • General interpretive area

    • Receives information from all sensory areas

    • Present only in left hemisphere

  • Speech center

    • Regulates patterns of breathing and vocalization


Cortex functions and hemispheric differences
Cortex Functions and Hemispheric Differences

  • Prefrontal cortex

    • Coordinates information from secondary and special association areas

    • Performs abstract intellectual functions

  • Hemispheric differences

    • Left hemisphere typically contains general interpretive and speech centers and is responsible for language based skills

    • Right hemisphere is typically responsible for spatial relationships and analyses



Focus cranial nerves
Focus: Cranial Nerves

  • 12 pairs of cranial nerves

    • Each attaches to the ventrolateral surface of the brainstem near the associated sensory or motor nuclei





The limbic system or motivational system includes
The Limbic System or Motivational System includes

  • Amygdaloid body

  • Cingulated gyrus

  • Parahippocampal gyrus

  • Hippocampus

  • Fornix

  • Functions of the limbic system involved emotions and behavioral drives


The cerebral cortex1
The Cerebral Cortex

  • Surface contains gyri and sulci or fissures

    • Longitudinal fissure separates two cerebral hemispheres

    • Central sulcus separates frontal and parietal lobes

    • Temporal and occipital lobes also bounded by sulci


White matter of the cerebrum
White Matter of the Cerebrum

  • Contains association fibers

  • Commissural fibers

  • Projection fibers


Association areas1
Association Areas

  • Control our ability to understand sensory information and coordinate a response

    • Somatic sensory association area

    • Visual association area

    • Somatic motor association area


General interpretive and speech areas1
General Interpretive and Speech Areas

  • General interpretive area

    • Receives information from all sensory areas

    • Present only in left hemisphere

  • Speech center

    • Regulates patterns of breathing and vocalization


Cortex functions and hemispheric differences1
Cortex Functions and Hemispheric Differences

  • Prefrontal cortex

    • Coordinates information from secondary and special association areas

    • Performs abstract intellectual functions

  • Hemispheric differences

    • Left hemisphere typically contains general interpretive and speech centers and is responsible for language based skills

    • Right hemisphere is typically responsible for spatial relationships and analyses


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