Transcript Central Nervous System

Chapter 12
Embryonic Nervous System Development
 Ectoderm dorsal to the notocord
thickens to form the neural plate
 Invagination forms the neural
groove
 Fusing of neural folds completes
the neural tube as it lengthens (3rd
week)
 Anterior seals and expands = brain
 Posterior = spinal cord
 Spina bifida variations due to
 Neural crest cells migrate to
become PNS ganglia and glia; also
pigment cells
Embryonic Brain Development
Primary vesicle
system
Secondary vesicle
system
Adult brain structures
Ventricle
system
Lateral ventricles
3rd ventricle
Cerebral aqueduct
4th ventricle
Ventricles
 Interconnected tubular system
 Filled with CSF (ependymal cells)
 Apertures in 4th ventricle connect to subarachnoid space
Need to know:
• Lateral ventricles
• Septum pellucidum
• Interventricular foramen
• 3rd ventricle
• Cerebral aqueduct
• 4th ventricle
• Central canal
Cerebral Hemispheres
 Gyri
 Pre- & postcentral
 Sulci
 Central, pareito-occipital, &
lateral
 Fissures
 Longitudinal & transverse
 Lobes
 Frontal, parietal (2), temporal (2),
occipital, & insula
 Basic regions
 Cotex, white matter, & basal nuclei
Cerebral Cortex
 Gray matter composed of
interneurons
 3 Functional areas
 Motor areas
 Frontal eye field
 Sensory areas
 Olfactory cortex
 Association areas
 Posterior association
 Limbic association
 Demonstrates lateralization
 Left: math, speech, concrete
processing, logic
 Right: creativity, facial and
pattern recognition
 Contralateral control
Homunculus
 Entire body mapped within the
http://www.fizyka.umk.pl/~duch/ref/01/01-plastic/motorsomato.gif
brain = somatotopy
 Most neurons to areas w/ most precise
control or sensitivity
 Somatosensory version receives message
from sensors
 Spatial discrimination
 Motor version sends message to muscles
 Areas are adjacently mapped
 Contralateral control
http://www.pc.rhul.ac.uk/staff/J.Zanker/P
S1061/L6/homuncul.gif
Cerebral Cortex Damage
 Primary motor cortex
 Paralyzes voluntary muscles; reflexes intact
 Contralateral effects
 Premotor cortex
 Loss of motor skills; strength and ability unaffected
 Practice rewires
 Visual cortex
 Primary: functional blindness
 Association: can see, but not comprehend
 Language areas
 Broca’s: speech production
 Wernike’s: speech comprehension
Cerebral White Matter
 Communication between cerebral
areas and lower CNS
 Directional myelinated fibers
 Commissural fibers
 Connect hemispheres
 E.g. corpus callosum
 Association
 Connect parts of same hemisphere
 Adjacent gyri or different lobes
 Projection
 Enter or leave cerebral cortex
 Connect cortex to rest of NS, receptors,
& effectors
 E.g internal capsule & corona radiata
Basal Nuclei
 Input from all of cortex
 Project to premotor & prefrontal areas
via the thalamus
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Inhibits motor systems
Release = muscle mov’ts (action selection)
Start, stop, & monitor to limit excessive
mov’ts; multitasking

http://www.iupucanatomy.com/images/Picture%20943a.jpg
PD and HD
 Corpus striatum
 Caudate nucleus
 Lentiform nucleus
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Putamen
Globus pallidus
 Associated with subthalamic nuclei
and substantia nigra
http://www.colorado.edu/intphys/Class/IPHY3730/image/figure5-31.jpg
Diencephalon
 Thalamus
 Gray matter masses joined by the intermediate mass
 Regionally named specialty nuclei
http://academic.kellogg.cc.mi.us/herbrandsonc/bio201_McKinley/f15-15_diencephalon_c.jpg
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All afferents ‘relay’ through  sorts and edits
Mediates sensation, motor activities, arousal, learning and memory
 Hypothalamus
 Walls form infundibulum which attaches to pituitary gland
 Homeostatic control

ANS (visceral activities), emotion, body temp., food intake, water
balance/thirst, sleep, and endocrine control (releasing hormones)
 Epithalamus
 Pineal gland produces melatonin to regulate sleep-wake cycle
Brain Stem
 Brain stem organized like spinal cord
 Survival responses and cranial nerves (10 of 12)
 Midbrain
 Cerebral peduncles: pyramidal motor tracts
 Corpora quadrigemina
 Substantia nigra: melanin; voluntary initiation of mov’t
 Red nucleus: hemoglobin; coordinates motor mov’ts
 Pons
 Bridges cerebrum and cerebellum
 Respiratory centers assist breathing
 Medulla oblongata
 Decussation of pyramids
 Olives: sensory info about muscle and joint stretch to
cerebellum
 Cardiovascular and respiratory centers; emesis, hiccupping,
sneezing, and coughing
Cerebellum
 Anterior & posterior lobes
 Vermis connects 2 hemispheres of posterior
 Coordination, balance, & proprioception
 Ipsilateral input/output
 Learning patterned sequences
 Cerebellar processing
 Interprets intent of mov’t from cortex & proprioception from
sensors
 Determines best means of mov’t execution
 Sends plans to motor cortex to coordinate
 Damage results in clumsy, misguided mov’ts
Limbic System
 Emotional center
 Interactions with prefrontal lobes
 Coordinates sensory input with emotions
 Hippocampus
 Learning and memory
 Amygdala
 Fear and aggression
 Assess danger and elicits response to emotional stimuli
 Cingulate gyrus
 Associating memories to smells and pain
 Expression of emotions through gestures
 Focusing attention on emotionally significant events
http://universe-review.ca/I10-41-limbic.jpg
Reticular Formation
 Arousal and alertness due to
constant stimulation
 Studying w/ background noise
 Filters repetitive, familiar, and
weak stimuli
 99% sensory stimuli ignored
 LSD interrupts = overload
stimuli
 Coarse skeletal mov’t
 Inhibited by sleep centers
 Depressed by alcohol &
tranquilizers
http://www.daviddarling.info/images/reticular_formation.jpg
Meninges
 Covers and protects CNS
 3 layers (superficial to deep)
 Dura mater
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Periosteal layer attaches to skull
Meningeal layer form septa to anchor brain (sinuses too)
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Falx cerebri: longitudinal fissure (superior sagital sinus)
Falx cerebelli: vermis
Tentorium cerebelli: transverse fissure (transverse sinus)
 Arachnoid mater
 Doesn’t follow convolutions
 Serous fluid in subdural space above
 CSF in subarachnoid space below (arachnoid villi)
 Pia mater
 Connected to brain, follows all convolutions
 Meningitis
 General disease term
 Bacteria/virus invades CSF and inflames
Cerebrospinal Fluid
 Surrounds the brain & spinal
cord
 Buoyancy
 Supply for nutrients &
chemical signals
 Secreted by choroid plexus
 In all ventricles
 Lined with ependymal cells
 Selective barrier to ions and
removes wastes
 CSF pathway
Blood Brain Barrier
 Maintains stable environment for brain
 Allows selective permeability
 Nutrients in
 Wastes and toxins/dugs out
 Ineffective against fats, O2, and CO2
 Absent at 3rd and 4th ventricle
 Alcohol and other poisonings
 Metabolic activity monitoring
Spinal Cord Protection
 Within the vertebral foramen
 End L1/L2
 Lumbar puncture L3/L4 or L4/L5
 Epidural space
 Padding of veins and fat
 Dura mater
 Meningeal layer only
 Subdural space – histology only
 Arachnoid
 Subarachnoid space
 Extends beyond spinal
cord (S2)
 Pia mater
 Denticulate ligaments
External Anatomy
 Cervical and lumbar
enlargements
 Increased gray matter
 Conus medularis, cauda equina,
& filum terminale
 31 spinal nerve pairs
 Dorsal roots: sensory w/ganglia
 Ventral roots: motor
 Shingles attacks dorsal root
ganglia and cranial nerves
Internal Anatomy
 Anterior median fissure
 Posterior median sulcus
 Gray commissure
 Central canal
 Gray and white matter
 Anterior, posterior, and lateral
horns
 Ascending (sensory) and
descending (motor)
tracts