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.

1. Central Nervous
System
(CNS)
Physiology 152 – Allied Health

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

4. Embryonic Development of
the CNS
Figure: http://faculty.washington.edu/chudler/dev.html

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

7. Overview: Brain Development
Sequence
Figure: http://faculty.washington.edu/chudler/dev.html

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

28. Hypothalamus
 Involved in:
 Reward processing
 Punishment
processing
 Regulates:
 Pituitary gland
 Blood pressure
 Hunger
 Thirst
 Metabolism
 Heart rate

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

37. Modern-day techniques for
studying brain function

38. Recap

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

43. Recap

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

59. Cranial and Spinal Nerves
 Spinal Nerves
 Count: 31 pairs
 Groups:
 8 cervical
 12 thoracic
 5 lumbar
 5 sacral
 1 coccygeal
 All are mixed Nerves

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

62. Textbook Reference
Human Physiology (6th edition) by Stuart Ira Fox