Download Chapter 14

Central Nervous
System
Portions of Chapters 13-14
pertaining to the brain
Protection CNS, fig 13.1, 14.4
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Connective Tissue:
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Skull bones
Vertebral column - spinal cord in vertebral
canal (created by vertebral foramina)
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Meninges - 3 layer CT: brain and spinal cord
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Sturdy shelter
Spinal continuous with cranial
Dura mater, arachnoid mater=meninx, pia mater
Vertebral ligaments-protect against spinal cord
displacement
CSF = cerebrospinal fluid
Fig. 13.01
Cranial & spinal meninges are
continuous
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Dura mater- “tough mother,” dense irregular CT
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Arachnoid mater- “spiderlike,” collagen, elastic
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 subarachnoid space (contains CSF)
Pia mater-“delicate” inner, thin transparent CT
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Most superficial
Forms sac at foramen magnum  2nd sacral
 subdural space
Adheres to brain and spinal cord
Contains b.v. supplying O2 and nutrients to cord
Spinal cord also covered by cushion of fat & CT
between dura mater & vert canal = epidural space
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CSF- produced by choroid plexus- capillary covered
by enpendymal cells (1 per ventricle)
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From blood plasma filtration & secretion
Clear, colorless liquid protects the brain & spinal cord from
chemical & physical injury
Homeostatic function:
 Chemical- enviroment for neuronal signaling
 Mechanical- shock absorb
 Circulation- exchange of nutrients and waste.
Continuous circulation thru cavities & subarachnoid space
O2, glucose, others from blood to neurons & neuroglia
 Proteins
 lactic acid
 Urea
 Na+, K+, Ca2+, Mg2+, Cl-, HCO3 WBC
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Tight junctions  CSF cannot leak
between capillary cells, must pass thru
ependymal cells: blood-CSF barrier
(selective to certain substances)
Dural sinuses- form an interconnected series
of channels in skull & lie between 2 layers of
the cranial dura mater
Brain developement, table 14.1
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Forebrain
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Midbrain
Hindbrain
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Diencephalon
 Thalamus, hypothalamus, epithalamus
Cerebrum
 Frontal, parietal, occipital, temporal, insula
Medulla oblongata, pons, cerebellum
*Brain stem = midbrain, medulla oblongata, pons
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(between spinal cord and diencephalon)
Diencephalon
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Thalamus- principal relay station for sensory
impulses:
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spinal cord, brainstem, cerebellum, & other parts of the
cerebrum  cerebral cortex thru the thalamus
crude perception of some sensations
essential role in the awareness and acquisition of
knowledge = cognition
Hypothalamus- controls many body activities &
one of the major regulators of homeostasis
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Has connection w/ pituitary gland
produces hormones
Cerebrum
Occupies most of the cranium
“seat of intelligence”
provides:
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ability to read, write, speak
make calculations
compose music
remember the past, plan future
imagine things that have never existed before
5 lobes:
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Frontal, parietal, occipital, temporal, insula
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Embryonic development- brain size  rapidly
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gray matter enlarges much faster than white matter
(deeper) resulting in cortical region rolling & folding
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Fissures =deepest grooves, (shallower = sulci)
Longitudinal fissure- most prominent
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Gyri = the ridges of folds
separating cerebrum into right and left hemispheres:
 hemispheres connected by a broad band of white
matter containing axons = corpus callosum
Gray matter- area in the CNS & ganglia:
nonmyelinated nerve tissue
White matter- aggregations or bundles of
myelinated axon in CNS
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Frontal lobe
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motor
premotor (learned motor activities of complex or
sequential nature)
frontal eye field (scanning movements of eye)
primary gustatory (taste)
Broca’s speech (speaking & understanding language)
**lateral cerebral sulcus separates frontal lobe from:
Temporal lobe
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primary auditory (interpret basics sounds: pitch & rhythm)
auditory association (is sound speech, music or noise?)
Wernicke’s (interprets meaning of speech by recognizing
spoken word)
Parietal lobe- separated from frontal lobe by
central sulcus. Areas:
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primary somatosensory: receives impulses from
somatic sensory receptors- touch, pain,
proprioception, and temperature
somatosensory association: integrate and interpret
sensations
common integrative: integrates sensory
interpretations from other association areas, allowing
one thought to be formed
Occipital lobe-
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primary visual (info about shape, color & movement
of the visual stimuli)
visual association (relates past and present visual
experiences).
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Insula- 5th part of the cerebrum
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cannot be seen on the surface of the brain,
within the lateral cerebral fissure, deep to the
parietal, frontal and temporal lobe
Sensory areas, motor areas
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Sensory areas- receive and interpret sensory
information
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Primary somatosensory area (behind central sulcus)
Primary visual area (posterior tip occipital lobe)
Primary auditory area
Primary gustatory area (base of postcentral gyrus)
Primary olfactory area (temporal lobe)
Motor areas- initiates movement
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Primary motor area (precentral gyrus)
Broca’s speech area (frontal lobe near lateral cerebral
sulcus)
Associative areas of cortex
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Consist of some sensory and motor areas
Deal with more complex integrative functions
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Memory, emotions, reasoning, will, judgment,
personality traits, intelligence
Are connected with one another by
association tracts
Brainstem
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Midbrain, medulla oblongata, pons
all parts contain
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tracts = white matter, bundle of nerve axons in CNS
nuclei = gray matter, unmyelinated nerve cell bodies-CNS
continuous with spinal cord
consists of:
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medulla- regulate various vital body functions
 White= sensory & ascending, gray= motor, descending
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Why do you think it is this way?
Rate & force of heartbeat
Diameter of blood vessels
Breathing rhythm,
Vomitting; coughing; sneezing; sensations of touch,
pressure & vibration; sense joint & muscle position
More brainstem
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pons- bridge between medulla & midbrain
 w/ medulla helps control breathing
midbrain-extends from pons to diencephalon
 reflex center for movement of eyes head and
neck in response to vision
 controls subconscious muscle activity
Cerebellum
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2nd largest part of the brain
Main function: evaluate how well movements
initiated by motor areas of cerebrum are carried
out
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Detect discrepancies & send feedback
governs coordination of skilled movements and
balance
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Equilibrium
Posture
Balance
Skilled activities: catching baseball, dancing, speaking
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Vermis- “worm”- central, constricted area
Cerebellar hemispheres- lateral lobes
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cerebellar cortex- superficial, gray matter in a
series of slender, parallel ridges called folia
deep to gray matter- arbor vitae = tracts (white)
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Each consists of lobes separated by deep & distinct
fissures:
 anterior & posterior lobes- govern subconscious &
controlled movements of skeletal muscles.
within white matter are cerebellar nuclei- nerve fibers
carrying impulses to other brain centers & spinal cord
attached to the midbrain by three pairs of
cerebellar peduncles= bundle of nerve fibers
Basal nuclei = basal ganglia
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Nuclei – collection of neuronal cell bodies
Receive input from cerebral cortex & provide output
to motor parts of cortex
Regulate initiation and termination of movements
Subconscious contraction of skeletal muscles
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Initiate & terminate some cognitive processes
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Automatic arm swings, laughing at jokes
Attention, memory, and planning
May act w/ limbic sys to regulate emotional behaviors
Basal nuclei (2)
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3 Basal nuclei
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Globus pallidus
Putamen
Caudate nucleus
Damage to Basal nuclei- may result in
uncontrollable shaking, muscular rigidity, and
involuntary muscle movements:
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Parkinson’s disease: degeneration of neurons between
substantia negra and putamen &caudate
Psychiatric disorders: OCD, schizophrenia, chronic
anxiety– thought to be basal nuclei to limbic system circuit
dysfunction
Limbic System, fig 14.14
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Encircling upper brainstem & corpus callosum
Ring of structures, inner cerebrum & floor of
diencephalon
Emotional brain- plays primary role in range of
emotions including:
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Pain, pleasure, docility, affection, and anger
Also involved in: olfactory and memory
Amygdala- ability to recognize or create facial
expression relating to emotion
Hippocampus- functions in memory
Injuries to the cortex
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Frontal lobe damage can lead to the loss of memory
& impairment of cognitive functioning (math problem
solving), loss of fine motor skills
Parietal lobe damage can cause right & left
confusion, difficulty writing, visual-spatial deficits
Temporal lobe damage can disturb word recognition
and memory of verbal material
Occipital lobe damage can impair visual pathways
Cranial nerves, table 14.4
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12 pairs, pass thru cranial foramina
Part of PNS
Numbered from anterior to posterior from
which arise from brain
Names designate distribution or function
2 are sensory nerves
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Olfactory and optic
Other 10= mixed nerves- contain axons of
both sensory and motor neurons
On Old Olympus' Towering Top A
Finn And German Viewed A Hop
I
II
III
IV
Olfactory- smell
Optic- vision
Oculomotor- muscle sense
(proprioception), movement of eyelid &
eyeball, accomadation of lens for near
vision, and constriction of pupil.
Trochlear- muscle sense (proprioception),
movement of eyeball
V
VI
VII
VIII
Trigeminal- conveys sensations for touch, pain,
temperature, and muscle sense (proprioception),
chewing.
Abducens- muscle sense, movement of eyeball
Facial- muscle sense, facial expression and
secretion of saliva and tears.
Vestibulocochlear- conveys impulses associated
w/ equilibrium, adjusts sensitivity of hair cells,
conveys impulses for hearing, may modify
function of hair cells by altering their
transmission and mechanical response to sound
IX
X
Glossopharyngeal- taste & somatic sensation,
muscle sense in swallowing muscles; monitor
bp; monitor O2 & CO2 in blood for reg breathing
rate & depth; elevates pharynx- swallowing &
speech; stimulates saliva secretion
Vagus- taste & somatic sensations from
epiglottis & pharynx; monitoring bp; monitor O2,
CO2 in blood for reg breathing rate and depth;
visceral organ sensations in thorax & abdomen;
swallowing, coughing, & voice production;
smooth muscle contract & relax in GI tract; slow
heart rate; secretion of digestive fluids
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Accessory- proprioception in muscle of
pharynx, larynx, soft palate; cranial
portion mediates swallowing movements;
spinal portion mediates movement of
head & shoulders.
Hypoglossal- proprioception for tongue
muscles, movement of tongue during
speech & swallowing
FYI
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Due to time constraints, the information on
the following slides will NOT be on the exam
but may be interesting information to you.
Brain waves & sleep, fig 14.17
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Brain waves- electrical signals that can be
recorded from skin of head due to electrical
activity of brain neurons
Electroencephalogram= EEG- to study
normal brain functions
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Changes during sleep
Diagnose epilepsy, tumors, metabolic
abnormalities, site of trauma, and degenerative
disease
Sleep
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Circadian rhythm- 24 hr sleep & awake cycle
suprachiasmic nucleus of hypothalamus
Cerebral cortex less active during most stages
RAS responsible for arousal
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Pain, touch, pressure, movement of limbs, bright light, buzz
of clock… olfactory not sufficient
Wakefulness= consciousness
Sleep= altered consciousness or partial
unconsciousness, exact functions- unclear
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Deprivation impairs attention, learning and performance
Learning and memory
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Learning- ability to acquire new information or skills
thru instruction or experience
Memory- process by which info acquired thru
learning is stored and retrieved
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Occurs in stages, over time
Plasticity- capability for change associated with
learning
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Change behavior in response to stimuli
Individual neurons synthesize different proteins or
sprouting new dendrites
Changes in strength of synaptic connections
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Immediate memory- ability to recall on going
experiences for a few seconds
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Perspective to present time
Where we are, what we are doing
Short-term memory- temporary ability to recall a few
pieces of info for seconds to minutes
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Unfamiliar telephone number -- get to phone
Involves hippocampus, mammilary bodies, 2 nuclei of
thalamus
More dependent upon electrical and chemical changes
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Long-term memory- more permanent
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short term may be transformed to long term
Lasts for days to years
Can be retrieved for use whenever needed
Reinforcement due to freq. retrieval = memory
consolidation
Motor skill memory stored in basal ganglia,
cerebellum, cerebral cortex
Estimated 1% of info that comes to our
consciousness goes to long term memory
Eventually forgotten (not a tape recorder!)
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details lost but explain in own words
Memory and conditions
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Anesthesia, coma, electroconvulsive therapy,
ischemia of brain all disrupt retention of newly
acquired info without disrupting long term memory
Amnesia- most recent memories return last, but
usually do not remember what happened the last 30
min before amnesia
Intense activity shows growth of new synaptic end
bulbs  with age possibly due to  use
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Opposite changes for inactive areas