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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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slide3

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
slide11

Terms of

Orientation:

slide12

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).
slide20

Brain Stem:

Ventral Surface

slide21

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
ad