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Chapter 8
CNS
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ORGANIZATION OF NERVOUS SYSTEM
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The Nervous System
Central Nervous System (CNS)
Brain
Peripheral Nervous System (PNS)
Motor Neurons
Spinal Cord
Somatic Nervous System
Sympathetic
Sensory Neurons
Autonomic Nervous System
Parasympathetic
The Spinal Cord
Central
Canal
Dorsal
Root
Dorsal Root
Ganglion
Gray
Matter
White
Matter
Dorsal
Root
Peripheral
Nerve
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DEVELOPMENT OF THE BRAIN
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Embryonic Development
Forms as a tube!
Ectoderm (skin, nervous system): neural tube by day 20
Part of ectoderm where fusion occurs becomes neural crest
which then forms PNS ganglia.
by 4th week:
Forebrain, Midbrain, Hindbrain
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CNS
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Embryonic Development
(continued)
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TECHNIQUES
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Neurobiology:
Neurons trying to understand
themselves…!
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We have mapped many functions to
discrete parts of the brain.
Frontal
Lobe
The
Cerebral
Cortex
Parietal
Primary
Motor Primary
Lobe
Area Sensory
Area
Premotor
leg
Area
trunk
Sensory
arm
Association
Higher
Area
Intellectual
hand
Functions
Visual
face
Association
tongue
Area
Speech
Primary
Language
Motor
Visual
Comprehension
Area
Primary & Formation
Area
Auditory
Area
Memory
Temporal
Lobe
Occipital
Lobe
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Info comes from…
Surgeries
Accidents
Illness
Anatomy (autopsies)
Open brain studies
Animals
Live Imaging
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Imaging
CAT scans:
soft tissues
xrays
PET scans:
positron emitting fluid
glucose metabolism, blood flow.
MRI and fMRI
blood flow
magnets spin protons, radio waves are emitted
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Imaging
NOTE: PET and MRI look at blood flow…
what might they be missing?!
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PET
Stroke Damage
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Live imaging
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Electroencephalogram (EEG)
Summation of brain’s
electrical activity.
Used clinically to
diagnose epilepsy and
brain death.
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STRUCTURES OF THE BRAIN
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CNS
CNS = Brain plus spinal cord
- Gray matter consists of neuron cell bodies and
dendrites.
- White matter (myelin) consists of axon tracts.
- Ventricles
- CSF secreted by meninges, cushions brain
- Skull protects
- No pain sensors!
- Blood-brain barrier.
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CNS
Cell bodies in CNS: nuclei
Cell bodies in PNS: ganglia
Nerves: bundles of axons!
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Brain myths
We use only 10% of our brains.
It’s all downhill after a certain age.
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Brain facts
We are concious of only a small percentage of
what the brain knows!
It’s not the size, it’s the connections!
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Things you can do without a
brain…
Your gut has a “mind” of it’s own…
(enteric nervous system)
Reflex arcs.
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Brain
100 billion neurons.
10x more glial cells!
Weighs about 1.5 kg, uses 20% of blood flow.
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Brain
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Brain
Prosencephelon (Forebrain)
Telencephalon (cerebrum)
Diencephelon (thalamus, hypothalamus)
Mesencephalon (Midbrain)
Rhombencephalon (Hindbrain)
Metencephalon (pons, cerebellum)
Myencephalon (medulla)
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Brain
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BRAINS
Embryonic
Forebrain
Midbrain
Hindbrain
Shark
Goose
Human
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FOREBRAIN
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CEREBRUM
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Cerebrum
Telencephalon= cerebrum
Largest portion of brain (80% mass).
Responsible for cognitive mental functions.
Five lobes.
Cortex (2-4 mm of gray matter)
White matter and basal nuclei (gray)
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Cerebrum
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Cerebral Cortex
Cerebral cortex:
Characterized by numerous convolutions.
Elevated folds: gyri.
Depressed groves: sulci.
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Cerebral lobes
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Cerebrum
Central sulcus= between frontal and parietal lobes.
Frontal lobe:
precentral gyrus: motor neurons.
Parietal lobe:
Poscentral gyrus: somatesthetic sensation (cutaneous
touch, pain, heat, muscles and joints).
MAP of motor and of sensory control (homunculus)
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Cerebral Cortex
(continued)
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Cerebral Cortex
Temporal lobe:
auditory centers that receive sensory fibers from
cochlea.
Interpretation and association of auditory and visual
information.
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Cerebral Cortex
Occipital Lobe:
Primary area responsible for vision and
coordination of eye movements.
Insula:
Implicated in memory encoding.
Integration of sensory information with
visceral responses.
Coordinated cardiovascular response to
stress.
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Cerebrum
Basal Nuclei
gray matter located deep within white matter.
Corpus striatum
Functions in the refinement of voluntary movements.
Parkinson’s: degeneration of neurons that connect caudate
nucleus to substantia nigra of midbrain
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Cerebrum
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Language
Aphasia: speech and language disorder due to
head injuries and strokes.
Speech impediment: vocal cord or tongue injury.
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Language
Broca’s area:
articulation of speech.
Damage: slow to speak, comprehension is fine
Wernicke’s area:
language comprehension.
Damage: rapid speech, word salad
To read, hear words: visual, auditory -> Wernicke’s (concept of words)
To speak: Werknicke’s -> arcuate fasciculus -> Broca’s -> motor
Angular gyrus:
Center of integration of auditory, visual, and somatesthetic
information.
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Emotion and Motivation
Hypothalamus/ limbic
system.
Limbic system:
Includes amygdala and
hippocampus, (and
cingulate gyrus and fornix)
smell
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Emotion and Motivation
Rage, aggression:
Amygdala and hypothalamus.
Fear:
Amygdala and hypothalamus.
Feeding:
Hypothalamus (satiety centers).
Sexual drive and behavior:
Hypothalamus and limbic system.
Goal directed behavior (reward and punishment):
Hypothalamus and frontal cortex.
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Memory
Many structures, including:
Medial temporal lobe: Hippocampus
Prefrontal cortex
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Memory
Consolidation of short-term memory into longterm memory.
Requires activation of genes.
growth of dendritic spines.
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Long-Term Potentiation
synaptic learning.
Change in excitability.
Hippocampus (in medial temporal lobe)
Glutamate is NT.
NMDA receptors (Ca++ channels), postsynaptic
changes
NOS -> NO -> retrograde messenger->
presynaptic changes
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Diencephalon
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Thalamus
Thalamus:
Acts as relay center through which all sensory information
(except olfactory) passes to the cerebrum.
Lateral geniculate nuclei:
Relay visual information; stripes!
Medial geniculate nuclei:
Relay auditory information.
Epithalamus contains:
Choroid plexus where CSF is formed.
Pineal gland which secretes melatonin (circadian rhythms).
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Hypothalamus
Contains neural centers for hunger, thirst, and
body temperature.
Contributes to the regulation of sleep,
wakefulness, emotions, sexual arousal, anger,
fear, pain, and pleasure.
Stimulates hormonal release from anterior
pituitary.
Produces ADH and oxytocin.
Coordinates sympathetic and parasympathetic
reflexes.
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Pituitary Gland
Posterior pituitary:
Stores and releases ADH (vasopressin) and
oxytocin.
Hypothalamus produces releasing and
inhibiting hormones that are transported
to anterior pituitary.
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MIDBRAIN
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Midbrain
Visual, auditory reflexes
See out of corner of eye, move head; startle at a sound
Substantia nigra:
motor coordination, Parkinson’s
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HINDBRAIN
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Hindbrain
Hindbrain: connects spinal cord to rest
of brain.
Metencephalon:
Pons:
Connects other parts.
several nuclei associated with cranial
nerves
respiratory centers.
Cerebellum:
“little brain”
Receives input from proprioceptors
(joints, muscles, tendons).
Refinement/coordination of
movement.
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Hindbrain
Myelencephalon
Medulla (oblongata)
All descending and ascending fiber tracts
between spinal cord and brain pass
through it.
Vital centers: control of breathing, heart,
blood vessels.
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RAS
Reticular Activating System (reticular formation)
network of nuclei and nerve fibers within hindbrain
(medulla, pons), midbrain, forebrain (thalamus and
hypothalamus).
Maintains wakefulness and alertness
Turned off (by hypothalamus) to sleep
Anaesthesia, alcohol, tranquillizers
Coma
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Continue to engage the RAS and … onto lab!