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Chapter 11
Brain Anatomy & Functions
1
Meninges
• Membranes
surrounding CNS
• Protect CNS
• Three layers
• Dura mater
• Outer layer
• Adheres to
cranial bones
• Tough
2
Meninges
• Arachnoid mater
• Thin, weblike
• Pia mater
• Inner layer
• Adhere directly to
brain
• Very thin
• Fibrous and
vascular
3
Meninges
• Spinal Cord
• Same three layers
• Provides protection
4
Ventricles
• Interconnected cavities
•Within cerebral
hemispheres and brain
stem
•Continuous with central
canal of spinal cord
• Filled with cerebrospinal
fluid (CSF)
5
Ventricles
• Lateral ventricles
•
Third ventricle
•
Fourth ventricle
•
Cerebral aqueduct
6
Ventricles
7
Cerebrospinal Fluid
• Secreted by choroid
plexus
• Circulates in
ventricles, central
canal of spinal cord,
and subarachnoid
space
• Completely
surrounds brain and
spinal cord between
the meninges
8
Cerebrospinal Fluid
• Clear liquid
• 80-150 ml in CNS
• Contains proteins,
glucose, and salts
• Nutritive and protective
• Shock absorber
• Helps maintain stable
ion concentrations in
CNS
9
Spinal Cord
• Slender column of
nervous tissue continuous
with brain
• Extends downward
through vertebral canal
• Begins at level of
foramen magnum &
terminates near first &
second lumbar
10
Cross Section of Spinal Cord
11
Functions of Spinal Cord
• Center for
spinal reflexes
• Conduit for
nerve impulses to
and from the
brain
12
Reflex Arcs
Reflexes – automatic, subconscious responses to stimuli
within or outside the body
13
Brain
14
Brain
Functions
Major Parts
• Interprets sensations
• Cerebrum
• Determines perception
• Two hemispheres
• Stores memory
• Basal nuclei
• Reasoning
• Diencephalon
• Makes decisions
• Brainstem
• Coordinates muscular
• Cerebellum
movements
• Regulates visceral activities
• Determines personality
15
Brain
16
Brain Development
Three Major Vesicles
1. Forebrain
2. Midbrain
3. Hindbrain
17
Brain Development
18
Cerebrum
• Looks like cap of
a mushroom
• Spread over
diencephalon
• 7/8 total mass
• Fills most of
cranium
19
Clinical Application: Cerebrum
• Result from displacement & distortion of
neurons at the moment of impact
• Concussion
• Abrupt but temporary loss of consciousness
following a blow to the head or the sudden
stopping of a moving head
• No visible bruising but post traumatic
amnesia may occur
20
Clinical Application: Cerebrum
• Contusion
• Visible bruising of the brain due to trauma
and blood leaking from microscopic vessels
• Pia mater is torn
• Results in unconsciousness for several
minutes to many hours
21
Clinical Application: Cerebrum
• Laceration
• Tearing of the brain, usually from skull
fractures or gunshot wound
• Large blood vessels bleed into the brain and
can cause cerebral hematoma, and increase
cranial pressure
22
Lobes of Cerebral Hemispheres
• Name of lobe
corresponds with
name of cranial
bone
• Frontal
• Parietal
• Temporal
• Occipital
• Insula
23
Functions of the Cerebrum
• Interpreting impulses
• Initiating voluntary movements
• Storing information as memory
• Retrieving stored information
• Reasoning
• Seat of intelligence and personality
24
Functional Regions of
Cerebral Cortex
Cerebral Cortex – thin layer of gray matter that
constitutes the outermost portion of cerebrum; contains
75% of all neurons in nervous system
25
Structure of Cerebrum
• Cerebral Cortex
• Surface of cerebrum
• Convolutions
• Folds in cerebrum
• Bumps or gyri
• Sulci
• Shallow grooves
• Fissures
• Deep grooves
26
Structure of Cerebrum
• Corpus callosum
• Connects cerebral
hemispheres
• Longitudinal fissure
• Separates
hemispheres
• Transverse fissure
• Separates cerebrum
from cerebellum
27
Sensory Areas
• Cutaneous
Sensory Area
• Parietal lobe
• Interprets
sensations on
skin
• Visual Area
• Medial
Occipital lobe
• Interprets
vision
28
Sensory Areas
• Primary
Gustatory
• Taste
• Near bases
of the
central sulci
• Primary
Olfactory
•
Smell
• Arise from
centers
deep within
the
cerebrum
29
Sensory Areas
• Auditory Area
•
Superior part
of temporal lobe
near lateral
cerebral sulcus
• Interprets
hearing
30
Sensory Areas
31
Association Areas
• Regions that are not primary motor or primary sensory areas
• Widespread throughout the cerebral cortex
• Analyze and interpret sensory experiences
• Provide memory, reasoning, verbalization, judgment, emotions
32
Association Areas
Frontal Lobe Association Areas
• Concentrating
• Planning
• Complex problem solving
Temporal Lobe Association Areas
• Interpret complex sensory
experiences
• Store memories of visual scenes,
music, and complex patterns
Parietal Lobe Association Areas
• Understanding speech
• Choosing words to express
thought
Occipital Lobe Association Areas
• Analyze and combine visual
images with other sensory
experiences
33
Hemisphere Dominance
• The left hemisphere is dominant is most individuals
• Dominant hemisphere
controls
• Speech
• Writing
• Reading
• Verbal skills
• Analytical skills
• Computational skills
• Nondominant hemisphere
controls
• Nonverbal tasks
• Motor tasks
• Understanding and
interpreting musical and
visual patterns
• Provides emotional and
intuitive thought processes
34
Hemisphere Differences
• Anatomical
• Frontal lobe of left hemisphere is smaller
• Left handed people
• Right parietal and occipital lobes are narrower
35
Hemisphere Differences
• Right Hemisphere
• Left handed
• Music and artistic
awareness
• Space and patter
perception
• imagination
• Left Hemisphere
• Right handed
• Numerical and
scientific skills
• Sign language and
reasoning
36
Memory
Short Term
• Working memory
• Closed neuronal circuit
• Circuit is stimulated
over and over
• When impulse flow
ceases, memory does also
• Unless it enters longterm memory via
memory consolidation
Long Term
• Changes structure or
function of neurons
• Enhances synaptic
transmission
37
Motor Areas
• Primary Motor Areas
• frontal lobes
• control voluntary muscles
• Broca’s Area
• anterior to primary motor
cortex
• usually in left hemisphere
• controls muscles needed for
speech
• Frontal Eye Field
• above Broca’s area
• controls voluntary
movements of eyes and
eyelids
38
Motor Areas
39
Functions of the Cerebral Lobes
40
Diencephalon
• Between cerebral hemispheres and above the brainstem
• Surrounds third ventricle
• Thalamus
• Hypothalamus
• Optic tracts
• Optic chiasma
• Infundibulum
• Posterior pituitary
• Mammillary bodies
• Pineal gland
41
Diencephalon
Thalamus
•Oval structure above midbrain
•Gateway for sensory impulses heading to cerebral cortex
• Receives all sensory impulses (except smell)
• Channels impulses to appropriate part of cerebral
cortex for interpretation
•Interpretation of pain, temperature, and pressure
42
Diencephalon
Hypothalamus
• Small portion inferior to thalamus
• Protected by sella turcica
• Maintains homeostasis by regulating visceral
activities
• Water concentrations
• Hormone concentrations
• Blood temperature
• Links nervous and endocrine systems
43
Diencephalon
• Homeostatic functions
• Regulates autonomic nervous system
• Reception & integration of sensory impulses from
viscera
• Mind over body (stress--heart rate increases)
• Rage & aggression
• Regulates body temperature
• Regulates food intake (hunger & full feelings)
• Thirst
• Sleep patterns
44
Diencephalon
Limbic System
Consists of
• portions of frontal lobe
• portions of temporal lobe
• hypothalamus
• thalamus
• basal nuclei
• other deep nuclei
Functions
• controls emotions
• produces feelings
• interprets sensory impulses
45
Brain Stem
Three Parts
1. Midbrain
2. Pons
3. Medulla Oblongata
46
Midbrain
•“Mesencephalon”
•Between diencephalon and
pons
• Contains bundles of fibers
that join lower parts of
brainstem and spinal cord
with higher part of brain
47
Midbrain
• Cerebral aqueduct
– Connects 3rd & 4th
ventricles of brain
•
Cerebral peduncles – bundles
of nerve fibers
– Motor pathway between
cerebrum & lower parts of
nervous system
•
Corpora quadrigemina –
centers for visual and
auditory reflexes
48
Pons
• Rounded bulge on underside
of brainstem
• Between medulla oblongata
and midbrain
• Helps regulate rate and depth
of breathing
• Relays nerve impulses to and
from medulla oblongata and
cerebellum
49
Medulla Oblongata
• Enlarged continuation of
spinal cord
• Conducts ascending and
descending impulses between
brain and spinal cord
• Contains 3 reflex centers
• Cardiac
•Heart rate & force of
contraction
• Vasomotor
•Controls diameter of
blood vessels
• Respiratory
•Controls breathing
patterns
50
Medulla Oblongata
• Contains various nonvital
reflex control centers
–
–
–
–
Coughing
Sneezing
Swallowing
Vomiting
51
Medulla Oblongata
• Reticular Formation
• Complex network of
nerve fibers scattered
throughout the brain stem
• Extends into the
diencephalon
• Connects to centers of
hypothalamus, basal nuclei,
cerebellum, and cerebrum
• Filters incoming sensory
information
• Arouses cerebral cortex
into state of wakefulness
52
Cerebellum
• Inferior to occipital lobes
• Posterior to pons and medulla
oblongata
• Two hemispheres
• Vermis connects hemispheres
• Cerebellar cortex
• Gray matter on surface
• Arbor vitae
• White matter inside
•Tree-like pattern
• Cerebellar peduncles
• nerve fiber tracts
53
Cerebellum
• Dentate nucleus
• Largest nucleus in
cerebellum
•
Integrates sensory
information concerning
position of body parts
• Coordinates skeletal muscle
activity
• Maintains posture
54
Cerebellum
• Damage results in
• Lack of muscle control
• Change of speech pattern
• Severe dizziness
• Disturbances of gait
(walking)
55
Life-Span Changes
• Brain cells begin to die before birth
• Over average lifetime, brain shrinks 10%
• Most cell death occurs in temporal lobes
• By age 90, frontal cortex has lost half its neurons
• Number of dendritic branches decreases
• Decreased levels of neurotransmitters
• Fading memory
• Slowed responses and reflexes
• Increased risk of falling
• Changes in sleep patterns that result in fewer sleeping hours
56
Clinical Application
Cerebral Injuries and Abnormalities
Cerebrovascular Accident
• Stroke
• Sudden interruption in blood
flow
• Brain tissues die
Cerebral Palsy
• Motor impairment at
birth
• Caused by blocked
cerebral blood vessels
during development
• Seizures
• Learning disabilities
57