The document discusses the central nervous system (CNS). The CNS consists of the brain and spinal cord. The CNS receives input from sensory neurons, directs motor neurons, and associates stimuli with responses through association neurons to maintain homeostasis. The human CNS allows for complex behaviors like learning, memory, emotions and self-awareness. The embryonic development of the CNS begins with the formation of the neural tube which becomes the CNS, while the neural crest forms the peripheral nervous system.
2. What is the CNS?
CNS Consists of
Brain
Spinal Cord
CNS
Receives input from Sensory Neurons
Directs activity of Motor Neurons
Associates motor response(s) with sensory
stimuli through Association Neurons to maintain
homeostasis
3. CNS in Vertebrates
CNS of all vertebrates are at least capable of very basic forms
of learning and memory
Human CNS capabilities allow for:
Behavioral modification based on experience
Perceptions
Learning and Memory
Emotions
Self-awareness
Direct motor activity
5. Embryonic Development of
the CNS
(for student reference)
Ectoderm is the initial embryonic tissue that develops into the nervous
system, the epidermis of skin as well as other structures (slide 4)
At 2 weeks of embryonic development the neural plate is formed (slide- 4)
A few days after the neural plate is formed, a groove is formed in the neural
plate; creating the neural groove (slide 4)
The part of the ectoderm where the fusion of the two ends of the neural groove
occurs creates a separate structure called the neural crest (slide 4)
Eventually, the neural tube will become the CNS and the neural crest will
develop into the ganglia of the peripheral nervous system (PNS) (slide 4)
By middle of week 4, since gestation, 3 distinct swellings are evident on the
anterior end of the neural tube which will form the brain (forebrain, midbrain, and
hindbrain) (slide 6)
During the 5th week, a five-regioned brain develops and specific structures begin
to form (slide 6)
6. Embryonic Development of
the CNS
Figure: http://faculty.irsc.edu/FACULTY/TFischer/AP1/AP%201%20resources.htm
8. CNS Composition
Gray matter
Consists of neuron cell bodies and dendrites
Present in the surface layer (cortex) of the brain
Present deeper within the brain (subcortical) in aggregations called nuclei
White matter
Consists of axon tracts
Underlie cortex and surround nuclei
Myelin Sheath give white matter the white color
Adult brain
Contains ~100 billion neurons
Weighs approximately 1.5 kg
Receives 20% of total per minute body blood flow
9. Cerebrum
The only structure of the
telencephalon
Accounts for 80% of brain’s mass
Primarily responsible for higher
mental functions
Consists of right and left hemispheres
(connected by corpus callosum)
Figure: Alan Hoffring/National Cancer Institute
10. Cerebral Cortex
Is the outer layer of the
cerebrum
Composed of 2-4 mm of
gray matter and underlying
white matter
Characterized by many
convolutions
Gyriare the elevated fold
of the convolutions
Sulciare the depressed
grooves of the
convolutions
11. Cerebral Cortex
Eachcerebral hemisphere is
subdivided by deep sulci or
fissures
Cerebral subdivisions:
Frontal lobe
Parietal lobe
Temporal lobe
Occipital lobe
Insula (insular lobe)
12. Cerebral Cortex
Frontal lobe
Anterior portion of each
cerebral hemisphere
Central Sulcus (fissure)
separates frontal lobe
from parietal lobe
Functions:
personality, higher
intellectual
processes, decision
making
13. Cerebral Cortex
Parietal lobe
Positioned superior to the
occipital lobe in both
hemispheres
Parieto-occipital sulcus
(fissure) separates parietal
lobe from the occipital lobe
Lateral sulcus or Sylvian
fissure separates the parietal
lobe from the temporal lobe
Functions: understanding
speech, formulating
words, interpretation of
textures and shapes
14. Cerebral Cortex
Occipital lobe
Is the rearmost and
posterior part of the
cerebral hemispheres
Functions: Focusing the
eye, correlation of visual
images, conscious
perception of vision
15. Cerebral Cortex
Temporal lobe
Bordered by parietal
lobe, frontal lobe, and
occipital lobe in both
hemispheres
Located beneath the
lateral sulcus (Sylvian
fissure)
Functions: processing of
sensory inputs, language
comprehension, memory
16. Cerebral Cortex
Insula
Situated deep within the
lateral sulcus
Functions:
Memory, integration of
cerebral activities
17. Motor and Sensory Areas
Precentralgyrus is
the motor area of the
brain
Postcentralgyrusis
the sensory area of
the brain
Homunculus map is
a representation of
the contralateral
sensory/motor side of
the body
Figure: http://med-review.blogspot.com/
18. Motor and Sensory Areas
The size of the mapped body region in the precentral (motor) gyrus is reflective
of the number of the motor innervations. For i.e. the largest areas in the motor
cortex represent body regions with largest number of motor innervations.
The size of the mapped body region in the postcentral (sensory) gyrus is
reflective of the density of receptors. For i.e. the largest areas in the sensory
cortex represent body regions with highest densities of receptors.
19. Language and Aphasiology
In the last
century, understanding of brain
function has been governed by
study methodologies such as
aphasiology
Aphasiologyis the study of
language impairment through
brain damage
20. Language and Aphasiology
Aphasiology research helped
define two loosely defined
brain regions in the left cortical
hemisphere:
Broca’s area
Function: speech
production
Wernicke’s area
Function: understanding
written and spoken
language
21. Language and Aphasiology
Broca and Wernicke’s areas
are connected by a fiber
tract called arcuate
fasciculus.
It appears that the words form
and are conceptualized in
the Wernicke’s area and
are communicated via
Broca’s area
22. Cerebral Lateralization
Each cerebral cortex
controls movement of the
contralateral (opposite)
side of the body
Somatesthetic sensation
from each side of the body
projects to the
contraletralpostcentralgyru
s
Right and left cerebral
hemispheres communicate
via a large fiber tract called
the corpus callosum
23. Cerebral Lateralization
Experiments have shown:
Right hemisphere has limited verbal ability
Right hemisphere is better at recognizing faces
Analytical and language abilities are characteristics of
the left hemisphere
Visuospatial ability is a characteristic of the right
hemisphere
24. Basal Nuclei
Are masses of gray
matter situated deep
within the white matter of
the cerebrum
Prominent structure is the
corpus striatum
(composed of caudate
nucleus and putamen)
Controls voluntary
movement
Figure: Brain E-Books brainmind.net
25. Thalamus
Situated between cerebral
cortex and midbrain
Functions as a relay
station to the cerebral
cortex for sensory (except
smell) signals
Is involved in regulation of
sleep and consciousness
Figure: Brain E-Books brainmind.net
26. Limbic System
Amygdala
Involved in memory and
emotional processing
Is part of the medial
temporal lobe and is
involved in consolidating
short-term memory into
long-term memory.
Note: When the
consolidation process is
over, long-term memory is
independent of the medial
temporal lobe
Septum
Involved in pleasure
27. Limbic System
Cingulate Cortex
Involved in pain and
visceral response
Hippocampus
Is a critical part of the
memory system
Is part of the medial
temporal lobe and is
involved in consolidating
short-term memory into
long-term memory
Fornix
Carries signals from
hippocampus to
hypothalamus
29. Emotion and Motivation
Brain regions of paramount importance in emotion and
motivation:
Hypothalamus
Limbic system
Experiments have shown the hypothalamus and limbic system to
be involved in the following feelings and behaviors:
Aggression
Stimulation of amygdala produces rage and
aggression
Lesions of amygdala results in docility (docile: easily
handled/taught)
30. Emotion and Motivation
Experiments have shown the hypothalamus and limbic system to be
involved in the following feelings and behaviors (con’t):
Fear
Produced by stimulation of amygdala and hypothalamus
Removal of limbic system results in absence of fear
Feeding
Hypothalamus contains both feeding center and satiety center
Stimulation of the feeding center will result in overeating
Stimulation of the satiety center results in stop of feeding
behavior
31. Emotion and Motivation
Experiments have shown the hypothalamus and limbic system to
be involved in the following feelings and behaviors (con’t):
Sex
Hypothalamus and limbic system are involved in sexual
drive and sexual behaviors
Goal-directed behavior (reward and punishment system)
Stimulation of certain parts of the hypothalamus can be
more rewarding than food or sex in motivating behavior.
Stimulation of other parts of the hypothalamus stimulate a
punishment system
32. Memory
Amnesia (loss of memory) found to result from:
Damage to the temporal lobe
Damage to the hippocampus
Damage to the caudate nucleus (i.e. Huntington’s
disease)
Damage to the dorsomedial thalamus (i.e. alcoholoics
suffering from Koraskoff’s syndrome with
thiamine/vitamin B1 deficiency)
33. Modern-day techniques for
studying brain function
Magnetoencephlography (MEG)
Measures brain activity through transmitted magnetic
fields produced by electrical currents in the brain
Electroencephlography (EEG)
Measures brain activity through direct measurement of
electrical activity of the brain
Able to discern REM sleep (Rapid-eye movement sleep
stage when dreams occur)
34. Modern-day techniques for
studying brain function
Four types of EEG patterns:
Alpha waves
Best recorded from parietal and occipital regions
Person is awake and relaxed with eyes closed
Frequency: 10-12 cycles/second
Child < 8 years old; Frequency : 4-7 cycles/second
Beta waves
Are strongest from the frontal lobes, especially the area
near precentralgyrus
Frequency: 13-25 cycles/second
35. Modern-day techniques for
studying brain function
Four types of EEG patterns (Con’t):
Theta waves
Emitted from the temporal and occipital lobes
Frequency: 5-8 cycles/second
Delta waves
Emitted in a general pattern from the cerebral cortex
Frequency: 1-5 cycles/second
36. Modern-day techniques for
studying brain function
Positron Emission Tomography (PET)
Is a functional neuroimaging technique that uses
injection of radioisotopes in the bloodstream to measure
brain activity
Functional Magnetic Resonance Imaging (fMRI)
Is a functional neuroimaging technique that measures
brain activity by measuring associated changes in blood
flow to any respective part of the brain or the brain as a
whole
39. Midbrain: Regions and
Functions
Corpora quadrigemina
Involved in visual reflex
Relay center for auditory information
Cerebral peduncles
Pair of structures composed of ascending and descending fiber
tracts
Red nucleus
Area of gray matter deep in the midbrain
Maintains connections with cerebrum and cerebellum
Involved in motor coordination
40. Midbrain: Regions and
Functions
Substantianigra
Part of the Nigrostriatal system
Nigrostriatal system projects from the substantianigra to the corpus
striatum of the basal nuclei
Nigrostriatal system is required of motor coordination
Degeneration of nigrostriatal fibers result in Parkinson’s Disease
41. Dopaminergic pathways
Mesolimbic dopamine
system
Reward pathway
Axons use dopamine as
a neurotransmitter
(dopaminergic axons)
Axons leave the
midbrain to the nucleus
accumbens and
prefrontal cortex
42. Dopaminergic pathways
Nigrostriatal dopamine
system
Motor control pathway
Axons use dopamine
as a neurotransmitter
(dopaminergic axons)
Axons leave the
substantianigra of the
midbrain and synapse
in the corpus striatum
44. Regions, Subregions, and
Functions
Metencephelon
Pons
Surface fibers connect to the
cerebellum
Deeper fibers are part of
motor and sensory tracts
passing from medulla
oblongata
Holds nuclei associated with
cranial nerves
Holds nuclei involved in
breathing regulation
Figure: http://www.knowabouthealth.com/normal-brain-communication-found-in-people-with-agenesis-of-the-corpus-callosum/8844/
45. Regions, Subregions, and
Functions
Metencephelon (con’t)
Cerebellum
Second largest structure of
the brain
Contains outer gray and
inner white matter (like
cerebrum)
Holds fibers that pass from
cerebellum, pass through the
red nucleus to the
thalamus, and then to motor
areas of the cerebral cortex
46. Regions, Subregions, and
Functions
Metencephelon (con’t)
Cerebellum (con’t)
Holds fiber tracts that
connect the cerebellum with
the pons, medulla
oblongata, and spinal cord
Recieves input from
proprioceptors
(joint,tendon, muscel
receptors)
Heavily involved in
coordination of movement
47. Hindbrain: Regions,
Subregions, and Functions
Myelencephalon
Composed of only the Medulla
Oblongata
Medulla Oblongata
Continuous between the pons
and the spinal cord
All ascending and descending
fiber tracts between spinal
cord and brain pass through
the medulla
Contains the pyramids where
decussation of fibers occur
Contains nuclei involved in
motor control, regulation of
breathing and cardiovascular
response
48. Reticular Formation
Complex network of nuclei
within:
medulla, pons, midbrain, thal
amus, and hypothalamus
Functions as a reticular
activating system (RAS)
Filters background stimuli
Regulates sleep-wake cycle
Regulates consciousness
and sleep
49. 60 Minute episode on fMRI
http://www.youtube.com/watch?v=8jc8URRxPIg
50. Spinal Cord
Runs in the
vertebral column
Made up of white
and gray matter
Gray matter is
centrally located
and surrounded
by white matter
(unlike the brain)
51. Spinal Cord
Gray matter forms
an H in the center
of the spinal cord
with two dorsal
horns and two
ventral horns
White matter is
made up of
ascending and
descending fiber
tracts
Fiber tracts are
arranged in 6
columns called
funiculi
52. Spinal Cord Tracts
Two types: Ascending and Descending Tracts
Terminology:
Ascending tract names start with a prefix spino- and end with
the brain region where the fibers first synapse (i.e.
spinothalamic)
Descending tract names start with a prefix reflecting the brain
region where the fibers start and ends with the suffix –spinal
(i.e. corticospinal)
53. Spinal Cord Tracts
Ascending Tracts
Fiber tracts that convey sensory information to the brain from receptors
throughout the body
Two types of information
Exteroceptive: Arise from external environment of the body (i.e.
pain, touch, temperature)
Proprioceptive: Arise from the internal environment of the body (i.e.
muscles, joints)
Usually, sensory information from the right side of the body end up in
the left hemisphere of the brain
Usually, sensory information from the left side of the body end up in the
right hemisphere of the brain
54. Spinal Cord Tracts
Ascending tracts (con’t)
Three types of neurons in
ascending pathways
1st order sensory neurons
2nd order neurons cross to the
opposite side (decussate) and
travel to higher level of CNS
3rd order neurons situated in the
thalamus and extends to
sensory regions of the cortex
55. Spinal Cord Tracts
Descending Tracts
Originate from the brain
Relay motor activity from the brain to the rest of the body
Two groups of fiber tracts
Corticospinal/pyramidal tracts : Motor tracts that descend without
synaptic interruption from cerebrum to spinal cord; Originate primarily
from motor cortex
Extrapyramidal tracts: Motor tract projections that carry autonomic
motor impulses (i.e. for speech and swallowing); Originate in the
midbrain and brain stem
56. Spinal Cord Tracts
Two groups of fiber
tracts
Corticospinal/pyramid
al tracts : Motor tracts
that descend without
synaptic interruption
from cerebrum to
spinal cord; Originate
primarily from motor
cortex
Extrapyramidal tracts:
Motor tract projections
that carry autonomic
motor impulses (i.e.
for speech and
swallowing); Originate
in the midbrain and
brain stem
57. Cranial and Spinal Nerves
CNS communicates with the body via nerves that exit
the CNS from:
Brain (Cranial nerves)
Spinal cord (Spinal nerves)
Cranial and Spinal nerves, and cell bodies outside the
CNS make up the PNS
58. Cranial and Spinal Nerves
Cranial Nerves
Count : 12 pairs
2 pairs arise from neuron cell bodies in the forebrain
10 pairs arise from the midbrain and hindbrain
Designated by Roman numerals, which reflect order of
position (numbered from front to the back of brain)
Names indicate the structure innervated by these nerves
(i.e. Facial)
Most cranial nerves are mixed nerves which indicates that
the nerve contains both sensory and motor fibers
60. Spinal Nerves
Fibers are packaged
together in the nerve
and separate near
the attachment of
nerve to spinal cord
Two “roots” to each
nerve:
Dorsal root
(sensory)
Ventral root (motor)
61. Reflex Arc
Stimulation of sensory
receptors evokes action
potentials that are conducted
into the spinal cord by sensory
neurons
A Sensory neuron synapses
with an association neuron
Association neuron synapses
with a somatic motor neuron
Somatic motor neuron then
conducts impulses out of the
spinal cord to the muscle and
stimulates a reflex contraction