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Frontal Lobotomy
• ‘cure’ mental illness in 20th century
- •(1936 Egas Moniz): prefrontal “leukotomy”
- aka lobotomy— incisions that destoyed connections between
prefrontal region and rest of brain
•Egas Moniz receives Nobel Prize 1949
•before pharmacotherapy it was only “cure”
- •Early on used for depression, obsessive compulsive
- disorder, anxiety. ~40,000 done
- before Rx
•Walter Freeman (“The lobotomist”) and James Watts (USA)
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Some Preliminary
Brain Info
Gyri (Gyrus): Ridges
Sulci (Sulcus): Shallow grooves
Fissures: Deep grooves
Cerebrum:
- • largest
- part of the brain
- • controls
- higher mental functions
- • divided in
- L & R cerebral hemispheres
cortex = surface layer of gray matter
nuclei = deeper masses of gray matter
tracts = bundles of axons/white matter
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-
-
Major
parts of brain
Cerebrum, cerebellum
& brainstem
-
Neural
cortex
- surface
- layer of gray matter
-
Gray
matter
= neuron cell bodies, dendrites, and synapses
- –forms
- cortex over cerebrum and cerebellum
- –forms
- nuclei deep within brain
-
White matter
- bundles
- of axons that form tracts that connect parts of the brain & gray matter
-
Midsaggital (median) section of the brain
- Parieto-occipital sulcus only seen on this
- type of section
-
Neural tube is the
origin of brain
Enlarges into 3
primary brain vesicles
•Prosencephalon (forebrain)
•Mesencephalon (Midbrain)
•Rhombencephalon(hindbrain)
- Telencephalon:
- Becomes cerebrum
- Metencephalon:
- Forms cerebellum and pons
- Myelencephalon:
- Becomes medulla oblongata
- Note: Diencephalon
- and Mesencephalon persist
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Brain protection
& Support
Physical protection
2) Cranial Meninges (Dura/Arachnoid/Pia)
- 3) Cerebrospinal
- fluid (CSF)
Biochemical isolation
-
Skull
–Boneabsorbs most of impact
- Shell of car absorbs most of impact
-
cranial meninges
–Membranes anchor brain in place
–Seat belt keeps body from slamming into car
-
Cerebrospinal
Fluid (CSF)
–Fluid absorbs and disperses shock
–Airbag further cushions shock
-
Cranial
Meninges
3 layers: Dura, Arachnoid, Pia
Protect Brain from cranial trauma & continuous w/spinal meninges
- • Outer membrane
- Dura mater (endosteal layer)
- Dura mater (meningeal layer)
- Dural sinus: large collecting veins Between the layers
- •Middle membrane
- Arachnoid Mater (covers Pia)
- Subarachnoid space: CSF
- •Inner membrane
- Pia mater: fits like a glove entirely covers all brain surface goes into all fissures and sulci
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Dural
Folds
regions where dura mater dips down in between the brain regions.
3 folded inner layers of dura mater that extend into cranial cavity & stabilize and support brain contain collecting veins (dural sinuses)
-
dural sinuses
large venous sinuses that drain CSF and CNS blood into jugular vein
- 1)Falx Cerebri: contains Superior and
- Inferior sagittal sinus (Projects between cerebral hemispheres)
- 2) Tentorium Cerebelli (Separates cerebellum & cerebrum contains transverse Sinus)
- 3) Falx Cerebelli divides cerebellar hemispheres
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Cerebrospinal
Fluid
Fluid made by choroid plexus of ventricles
Made by specialized ependymal cells
Approximately 500 ml/day
- CSF is clear and colorless (150mL
- circulate)
- §Cushions and supports brain
- Brain weighs less suspended
§Transports nutrients, chemicals and wastes
CSF is absorbed into venous blood via arachnoid villi (granulations) drains to dural sinuses
-
Ventricles
- Lateral ventricles: Each cerebral hemisphere contains one large lateral ventricle;separated by
- a thin partition septa pellucidum
- Third ventricle: within diencephalon
- (thalamus on either side)
Interventricular foramina aka Foramen of Monroe) joins lateral vents. w/3rd
- Fourth ventricle: associated with pons and medulla oblongata; connected to 3rd ventricle by the cerebral aqueduct (of Sylvius) continuous
- with the spinal cord, and connected to the subarachnoid space by the lateral and medial aperture (foramen of Luschka and Magendie)
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Blood
Brain Barrier:
- Isolates CNS neural tissue from general
- circulation. BBB is formed by network of tight
- junctions between
- 1) Endothelial cells lining the CNS capillaries that have tight junctions between them (in contrast to periphery capillaries)
- 2) Astrocytes have foot processes that influence capillary permeability. Guardians of the BBB permeability
- Exceptions to BBB:
- •Not fully formed at birth
- •Parts of the hypothalamus
- •Capillaries of posterior pituitary and pineal glands
- •Breaks in BBB where blood has direct
- access: can monitor glucose, pH, and osmolarity
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Hydrocephalus
- –Too much CSF production or too little drainage decreased removal can result in extra fluid
- - Extra fluid compresses & distorts brain Causes ventricles to expand and put pressure on surrounding neural tissues
- - Can result from blockage of aqueduct or subarachnoid
- spaces
- - In infants cranial sutures have not fused so the skull enlarges to accommodate fluid
- •May cause retardation
- –In adults, ventricles expand
- •May damage neural tissue
- –Surgical treatmentà shunts
- –Drugs to decrease production of CSF e.g.Acetazolamide
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Brainstem
- “The stalk of the brain” relays messages between the spinal cord and brain; composed of Midbrain and Hindbrain.
- Medulla Oblongata/ Pons /Midbrain
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General Anatomy
Medulla Oblongata
Most inferior part of Brainstem: 3cm extension of spinal cord Pyramids and olives are visible on the surface
Ascending and descending nerve tracts
Nuclei of sensory and motor CNS (IX, X, Xl, Xll)
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Functions of Medulla
Oblongata
- 1)Allows brain and spinal cord to communicate
- 2)Coordinates complex autonomic reflexes
- 3)Controls visceral functions: heart, vasoconstriction vasodilation and breathing
- 4)non-vital reflexes i.e. coughing/sneezing swallwing/vomiting
- 3 groups of Nuclei in the Medulla
- 1.Autonomic nuclei that control visceral activities
- 2.Sensory and Motor Nuclei of Cranial Nerves
- 3.Relay stations along sensory and motor pathways
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MEDULLA OBLONGATA
Autonomic nuclei:
1.Gray matter. ‘Vital’ centers monitor CO2 levels and make appropriate adjustments
- Cardiovascular center: Cardiac (heart)
- and vasomotor (vessels)
- Respiratory rhythmicity center: Set “pace” as per input from pons.
- Receive input (ascending/sensory) from cranial nerves, cerebrum and brain stem = output (descending/motor) to regulate activity of
- peripheral systems (via tracts of white matter).
-
M O/
Myelencephalon
NUCLEUS
- 2. Sensory and motor nuclei: of 5 cranial
- nerves, V, IX-XII
4.Relay stations for sensory and motor:
- Nucleus Gracilis and Nucleus cuneatus pass somatosensory information to thalamus. Tracts
- leaving this area cross-over (decussate) to opposite side of spinal cord.
- Pyramids (Nucleus cuteatus & gracilis)
- Solitary nucleus: receives visceral
- sensory information,Sneezing, coughing,
- swallowing centers
- Olivary nucleus: information from
- somatic motor commands to cerebellar cortex
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Pons/
Metencephalon
- •Apneustic and pneumotaxic centers//respiratory centers
- The pons regulates rate and depth of breathing By adjusting respiratory rhythmicity centers of medulla
•Sensory and motor nuclei of 4 cranial nerves
•Relay stations: pons links cerebellum w/brain stem, cerebrum & spinal cord: i.e. sensory & motor to cerebellum
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Brainstem:
Midbrain /
Mesencephalon
Connects pons and cerebellum with cerebrum
- •Superior colliculus: visual reflex (turning from bright light)
- •Inferior collicullus: auditory reflex (turning toward sound)
- •Sensory and motor nuclei of 2 cranial nerves
- •Substantia nigra: Helps fine-tune
- voluntary motor activity “talks to the basal ganglia” (contain dopaminergic n.àParkinson’s d.)
- •Reticular Activating System
- –Helps maintain consciousness
- •Nucleus ruber: (red nucleus)
- - Involved in background muscle tone e.g. helps maintain posture
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Cerebellum “Little Brain”
- •Input & Output
- –Approximately 50 % of neurons in brain
- –Purkinje cell: dendrites receive up to 200,000 synapses
- –Folia = folds
–Vermis =“worm” separates halves
- 1) Adjusting Postural Muscles of Body:
- Coordinates rapid, automatic adjustments to maintain balance and equilibrium
- 2) Learning & Fine Tuning (conscious & subconscious movements): Compares motor commands with propriceptive information (position sense). Performs any adjustment to make the move smoother. Refines learned movement
- patterns
- Info.from proprioceptor/eyes/ears
- via brainstem.
- Fine tunes movement and makes it smoother with repetition
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Inner Brain Structures
Thalamus
- •Major relay station for all sensory stimuli except olfaction
- –Projects to primary somatic, gustatory, auditory and visual cortices in cerebrum
- –Filters many signals out
- Passes on only small portion of
- Arriving sensory information
- –Conscious awareness occurs in cortex
- Coordinates activities of basal nuclei, limbic system and cerebral cortex by relaying info between them
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Thalamus cont'
- Surrounds 3rd ventricle
- oval Mass of gray matter (like 2 eggs side by side)
- connected by intermediate mass (or interthalamic adhesion)
Sensory information from spinal cord synapses in thalamus and the thalamus edits and synchronizes information
- 23 nuclei in the thalamus:
- Major players on the path to the cerebrum:
- Medial geniculate nucleus: auditory information
- Lateral geniculate nucleus: visual information
- Other nuclei:
- Coordinates activities of basal nuclei (motor &
- learning), limbic system (emotion & motivation) and cerebral cortex (thinking, memory, language) by relaying info between them
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Diencephalon: Hypothalamus
- Coordinates activities of nervous & endocrine systems
- •Posterior & anterior pituitary
- Control of autonomic function
- Adjusts autonomic centers in pons and M.O. that
- regulate heart rate, blood pressure, digestion respiration.
•Subconscious control of skeletal muscle e.g. changes in facial expression that accompany rage
- •Regulates body temperature (via M.O.)
- •Circadian rhythms (day/night cycles)
- •Drives: Controls hunger and thirst centers
- •Feeding reflexes via mammaliary bodies
- –ie) chewing, swallowing, licking
- •Coordination between voluntary and
- involuntary functions
- –Thinking about a dangerous situation or stressful situation
- Will make hr & respir rate increase e.g. Just thinking of IBHS exams = b.p.
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Hippocampus
- Amygdala
- Parts of thalamus & hypothalamus
-
FCT
limbic system
- •Processing of memories
- i.e. memory storage and retrieval
- The hippocampus is important for transfer of immediate thoughts to long term memory stores
•Important for emotional states, motivational drives and associated behaviors.
• Input from many regions including olfactory
- Limbic System: links conscious intellectual functions of cerebral cortex with unconscious and
- autonomic brain stem functions.
- e.g. Fornix tract of
- white matter connects hippocampus with hypothalumus
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lymbic system associated diseases
Famous” Lesions:
1) Capgras (emotion)
2) Clive Wearing*
3) H.M. *
- •Damage hippocampus
- Can recall events from long ago but not hrs or
- Minutes ago
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Reticular
Activating System
- Group of nuclei scattered throughout
- brainstem. Nerve fibers connect hypothalamus, basal nuclei, cerebellum and cerebrum
- •Controls cyclic activities such as sleep-wake
- cycle
•Clusters of gray matter scattered throughout pons, midbrain and medulla
- •Regulate balance and posture
- –relays information from eyes and ears to cerebellum
- –gaze centers and central pattern generators
•Includes cardiac and vasomotor centers
- •Regulates sleep and conscious attention
- –injury leads to irreversible coma
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Learning Objectives
- •Review
- what brain structures the forebrain, midbrain and hindbrain develop into.
- •Review
- what brain structures the telencephalon, diencephalon, mesencephalon, metancephalon and myelencephalon develop into.
- •Understand
- and describe how the skull, meninges, CSF and BBB protect.
- •Describe
- structure and function of Blood/brain and blood/CSF-barrier.
- •Describe
- the structure, function & importance of the brainstem regions
- •Describe
- the structure, function and importance of the cerebellum.
- •Review
- the structure, function and importance of the diencephalon & limbic system
- •Review
- the terms gyrus, sulcus and fissures.
- •Where
- does CSF get made? Absorbed?
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