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Principal Parts of the Brain. Cerebrum Diencephalon thalamus hypothalamus Cerebellum Brainstem midbrain pons medulla. Brain – midsagital section (photograph). Largest organ in the body at almost 3 lb. Brain functions in sensations, memory, emotions, decision making, behavior.

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principal parts of the brain
Principal Parts of the Brain
  • Cerebrum
  • Diencephalon
    • thalamus
    • hypothalamus
  • Cerebellum
  • Brainstem
    • midbrain
    • pons
    • medulla
brain midsagital section photograph
Brain – midsagital section(photograph)
  • Largest organ in the body at almost 3 lb.
  • Brain functions in sensations, memory, emotions, decision making, behavior
origins of ventricles
Origins of Ventricles
  • Neural tube encloses neurocoel space, which expands to form chambers (ventricles) lined with ependymal cells
csf flow
CSF flow
  • lateral ventricles (R and L)
  • inter-ventricular foramen
  • 3rd ventricle
  • cerebral aqueduct
  • 4th ventricle
  • median and lateral apertures
  • subarachnoid space

Arachnoid villi reabsorb CSF.


Why all this !$^%&*! trouble?

8 layers of protection of the brain and three related disorders
(8 layers of) Protection of the brainand three related disorders


Galea Aponeurotica



Dura Mater

Arachnoid mater

Pia mater

reabsorption of csf arachnoid villi
Reabsorption of CSF: Arachnoid Villi
  • Grapelike clusters (arachnoid granulations) penetrate inner (“endosteal”) layer of dura into venous blood of the venous sinus
  • 20 ml/hour

Reabsorption rate = Production rate

the cranial meninges review
The Cranial Meninges: Review
  • 3 layers:
    • dura mater
    • arachnoid mater
    • pia mater
  • Continuous with spinal meninges
  • Protects the brain from cranial trauma
pia mater
Pia Mater
  • Deepest layer composed of delicate connective tissue that clings tightly to the brain.
  • Contains tiny blood vessels that enter the brain tissue.
  • Attached to brain surface by astrocytes
arachnoid mater
Arachnoid mater:

middle meningeal layer isseparated from dura mater bythe “subdural space”

Subarachnoid space:

between arachnoid mater and pia mater

CSF and large blood vessels

web-like extensions span the space and secure it to the underlying pia mater

CSF gets into the subarachnoid space from 3 foramina (openings) in the roof of the 4th ventricle

Arachnoid Mater
dura mater
Dura Mater

Dura mater:

  • irregular connective tissue
  • inner fibrous layer (meningeal layer)
  • outer fibrous layer (endosteal layer) fused to periosteum
  • venous sinuses between 2 layers
the dural sinuses
The Dural Sinuses
  • Superior Sagital Sinus
  • Inferior Sagital Sinus
  • Straight Sinus
  • R and L Transverse Sinuses
  • R and L Sigmoid Sinuses

…. R and L jugular veins and back to heart.

dural folds
Dural Folds
  • falx cerebri
  • falx cerebelli
  • tentorium cerebelli

Figure 14–3b

dural folds1
Dural Folds
  • inner layer of dura mater (folded)
  • extend into cranial cavity
  • support brain
  • contain collecting veins (dural sinuses)
don t confuse the arachnoid villi of dural sinus with the choroid plexus of the ventricles
Don’t confuse the “arachnoid villi” of dural sinus with the “choroid plexus” of the ventricles!
review principal parts of the brain
Review: Principal Parts of the Brain
  • 750 to 2100 cc
  • about 98% of the body’s neural tissue
  • about 1.4 kg (3 lb)
endocrine preview pituitary gland
Endocrine Preview: Pituitary Gland
  • Connects to hypothalamus by thin double stalk (infundibulum)
    • venous connection (anterior pituitary)
    • axonal connection (posterior pituitary)
major regions and landmarks
Major Regions and Landmarks


3D Peel- Away of the Brain

Figure 14–1

lobes and fissures
Longitudinal fissure (green)

Frontal lobe

Central sulcus (yellow)

precentral & postcentral gyrus

Parietal lobe

Parieto-occipital sulcus

Occipital lobe

Lateral sulcus (blue)

Temporal lobe

Insula ?

Lobes and Fissures
gray vs white matter
Gray vs.White Matter
  • Gray matter
    • cell bodies, dendrites, unmyelinated axons
    • cortex and deep nuclei
  • White matter
    • primarily myelinated axons
    • X-Y-Z connections
projection fibers
Projection Fibers
  • Pass through diencephalon
  •  brain stem, cerebellum, and spinal cord
  • In lab: see the internal capsule
    • ascending and descending projection fibers
review cerebral white matter
Review: Cerebral White Matter
  • Projection fibers form descending & ascending tracts
  • Commissural fibers from one hemisphere to other
  • Association fibers between gyri in same hemisphere
association fibers
Association Fibers
  • within each hemisphere:
    • arcuate fibers:
      • are short fibers, connect 1 gyrus to another
    • longitudinal fasciculi:
      • longer bundles, connect frontal lobe to other lobes (in same hemisphere)
commissural fibers
Commissural Fibers
  • Bands of fibers connecting 2 hemispheres:
    • corpus callosum
    • anterior commissure
cortical motor areas
Cortical Motor Areas

Premotor cortex

Primary motor cortex

Frontal Eye Field

Broca’s Area

primary somatic motor cortex
Primary (Somatic) Motor Cortex
  • Located in precentral gyrus of the frontal lobe
  • “upper motor neurons” (pyramidal cells) may follow more than one pathway to “lower motor neuron” that controls contralateral skeletal muscles
    • corticospinal tracts
      • Old terminology – “pyramidal tract”
primary somatic motor cortex1


Primary (Somatic) Motor Cortex
  • Somatotopy
    • body map = “motor homunculus”
  • Strokes that are localized result in precise deficits.
    • cortex lesion contralateral side paralyzed
premotor cortex


Premotor Cortex
  • anterior to the primary motor cortex
  • planning of movements
  • “skills”
    • Learned motor patterns
  • Neurons project through corticospinal tract.
medical example
Medical Example
  • Stroke affecting the premotor cortex will cause loss of motor skills
  • Muscle strength and ability to perform individual movements are not hindered
  • If you damage the area controlling typing, you would not be able to type at the regular speed, but you could make the same movements. You would need to relearn the rhythmic movements.
broca s area
Broca’s Area
  • Speech production and articulation
  • anterior to the premotor area of frontal lobe
  • unilateral (usually the left hemisphere)
  • motor speech area
    • “planning” speech mechanics including direction of the tongue
medical example broca s aphasia
Medical Example:Broca’s Aphasia
  • A stroke to Broca’s area of the brain makes patients unable to speak.
    • They are still able to understand speech
    • …..frustrating!!!
    • Give them a pad and pencil; they can still write the words!
frontal eye field
Frontal Eye Field
  • Controls voluntary eye movements.
visual fields
Visual fields
  • Left occipital lobe receives visual images from right side of an object through impulses from nasal 1/2 of the right eye and temporal 1/2 of the left eye
  • Left occipital lobe sees right 1/2 of the world
  • Fibers from nasal 1/2 of each retina cross in optic chiasm
sensory association areas
Sensory Association Areas
  • Visual association area:
    • occipital lobe
    • interprets activity in primary visual cortex
  • Auditory association area:
    • temporal lobe
    • monitors auditory cortex
  • Somatic sensory association area:
    • interprets input to primary sensory cortex (e.g., recognizes and responds to touch)
somatosensory cortex
Somatosensory Cortex
  • anterior part of parietal lobe
  • somatotopy
    • spatial discrimination
somatic sensory association cortex
Somatic Sensory Association Cortex
  • posterior to the primary sensory cortex
  • Synthesizes multiple sensory inputs to create a complete comprehension of the object being felt.

Example: Touch a coin in your pocket; this area would help you identify a small coin as a dime

gustatory and vestibular cortex
Gustatory and Vestibular Cortex
  • Gustatory cortex
    • taste
    • parietal lobe
  • Vestibular cortex
    • Cranial Nerve VIII (8)
    • balance and equilibrium (position of head)
    • posterior part of the insula (deep to the temporal lobe)
olfactory cortex
Olfactory Cortex
  • Cranial Nerve I (1)
    • Receptors in the olfactory epithelium extend through the cribriform plate and send their info to the olfactory cortex.
    • frontal lobe above the orbits, medial temporal lobe
  • linked to “limbic system” for memory and emotion
limbic system
Limbic System
  • Emotional brain--intense pleasure & intense pain
    • Strong emotions increase efficiency of memory
    • arahippocampal & cingulate gyri & hippocampus
more cerebral functions later
More Cerebral Functions later
  • Start at the spinal cord and work our way back up to the cerebrum…

The Medulla Oblongata

  • Continuous with spinal cord
  • Controls visceral functions
    • Coordinates complex autonomicreflexes
  • Hard blow to the back of the head  fatal
nuclei in the medulla
Nuclei in the Medulla
  • Autonomic nuclei:visceral activities
  • Sensory and motor nuclei:cranial nerves
  • Relay stations:sensory and motor pathways

Figure 14–6b

medulla nuclei
Medulla Nuclei
  • Cardiovascular control center:
    • force and rate of heart contraction (can override the autorhythmic pacemaker cells of the heart)
  • Vasomotor center:
    • tone of vascular smooth muscle
  • Respiratory rhythmicity centers:
    • rate and depth of breathing
  • Additional Centers:
    • Emesis, coughing, choking, hiccupping, and sneezing
sensory and motor nuclei
Sensory and Motor Nuclei
  • Associated with 5 of 12 cranial nerves (VIII, IX, X, XI, XII)
  • Can you match their names to their basic functions?
relay stations
Relay Stations
  • Nucleus gracilis and nucleus cuneatus:
    • pass somaticsensory information to thalamus (lower and upper extremities, respectively)
  • Solitary nucleus:
    • receives visceralsensory information
  • Olivary nuclei (olives):
    • relay information about somatic motor commands (descending pathway)
    • Some somatic motor command do NOT cross here.
medulla decussation of the pyramids
Medulla: Decussation of the Pyramids
  • Lateral corticospinal tract (i.e., not all motor fibers) cross to the opposite side in the medulla.
the pons
The Pons
  • Link cerebellum to mesencephalon (midbrain), diencephalon, cerebrum, and spinal cord
  • somatic and visceral motor control

Figure 14–6c

the pons 4 groups
The Pons: 4 Groups
  • Sensory and motor nuclei of cranial nerves V, VI, VII, VIII
  • Nuclei involved with respiration:
    • apneustic center and pneumotaxic center
    • modify respiratory rhythmicity center activity
the pons 4 groups1
The Pons: 4 Groups
  • Nuclei and tracts:
    • process and relay information to and from cerebellum
  • Ascending, descending, and transverse tracts:
    • transverse fibers (axons)
      • link nuclei of pons with opposite cerebellar hemisphere