Download Chapter 14

Principal Parts of the Brain
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Cerebrum
Diencephalon
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thalamus &
hypothalamus
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Chapter 14
The Brain and Cranial Nerves
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Largest organ in the body at almost 3 lb.
Brain functions in sensations, memory, emotions,
decision making, behavior
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Protective Coverings of the
Brain
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Bone, meninges & fluid
Meninges same as
around the spinal cord
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dura mater
arachnoid mater
pia mater
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Blood Supply to Brain
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Arterial blood supply is branches from circle of
Willis on base of brain (page 699)
Vessels on surface of brain----penetrate tissue
Uses 20% of our bodies oxygen & glucose needs
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blood flow to an area increases with activity in that
area
deprivation of O2 for 4 min does permanent injury
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at that time, lysosome release enzymes
Blood-brain barrier (BBB)
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protects cells from some toxins and pathogens
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proteins & antibiotics can not pass but alcohol & anesthetics do
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Cerebrospinal Fluid (CSF)
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80-150 ml (3-5oz)
Clear liquid containing glucose, proteins, &
ions
Functions
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mechanical protection
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chemical protection
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floats brain & softens impact with bony walls
optimal ionic concentrations for action potentials
circulation
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nutrients and waste products to and from
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Drainage of CSF from
Ventricles
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One median aperture & two lateral apertures allow
CSF to exit from the interior of the brain
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Reabsorption of CSF
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Reabsorbed through arachnoid villi
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grapelike clusters of arachnoid penetrate dural venous
sinus
20 ml/hour reabsorption rate = same as production
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Hydrocephalus
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Blockage of drainage of CSF (tumor,
inflammation, developmental
malformation, meningitis, hemorrhage
or injury
Continued production cause an increase
in pressure --- hydrocephalus
In newborn or fetus, the fontanels allow
this internal pressure to cause
expansion of the skull and damage to
the brain tissue
Neurosurgeon implants a drain shunting
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Medulla Oblongata
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Continuation of spinal cord
Nuclei of 5 cranial nerves
Cardiovascular center
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Respiratory center
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force & rate of heart beat
diameter of blood vessels
medullary rhythmicity area sets basic rhythm of
breathing
Information in & out of cerebellum
Reflex centers for coughing, sneezing, swallowing
etc
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XII = Hypoglossal Nerve
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Controls muscles of
tongue during
speech and
swallowing
Injury deviates
tongue to injured
side when protruded
Mixed, primarily
motor
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X = Vagus Nerve
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Receives sensations
from viscera
Controls cardiac
muscle and smooth
muscle of the viscera
Controls secretion of
digestive fluids
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IX = Glossopharyngeal Nerve
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Stylopharyngeus m.
(lifts throat during
swallowing)
Secretions of parotid
gland
Somatic sensations
& taste on posterior
1/3 of tongue
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Injury to the Medulla
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Hard blow to the back of the head may be fatal
Cranial nerve malfunctions on same side as injury
loss of sensation or paralysis of throat or tongue;
irregularities in breathing and heart rhythm
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Pons
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One inch long
White fiber tracts
ascend and descend
Pneumotaxic &
apneustic areas help
control breathing
Middle cerebellar
peduncles carry
sensory info to the
cerebellum
Cranial nerves 5 thru
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VII = Facial Nerve
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Motor portion
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facial muscles
salivary & nasal and
oral mucous glands
& tears
Sensory portion
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taste buds on
anterior 2/3’s of
tongue
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Midbrain
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One inch in length
Extends from pons
to diencephalon
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Cerebellum
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2 cerebellar hemispheres and vermis (central area)
Function
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correct voluntary muscle contraction and posture based
on sensory data from body about actual movements
sense of equilibrium
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Thalamus
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1 inch long mass of gray mater in each half of brain
(connected across the 3rd ventricle by intermediate
mass)
Relay station for sensory information on way to
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cortex
Thalamic Nuclei
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Nuclei have different roles
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relays auditory and visual impulses, taste and somatic
sensations
receives impulses from cerebellum or basal ganglia
anterior nucleus concerned with emotions, memory and
acquisition of knowledge (cognition)
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Hypothalamus
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Dozen or so nuclei in 4 major regions
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mammillary bodies are relay station for olfactory reflexes;
infundibulum suspends the pituitary gland
Major regulator of homeostasis
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receives somatic and visceral input, taste, smell & hearing
information; monitors osmotic pressure, temperature of
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blood
Functions of Hypothalamus
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Controls and integrates activities of the ANS
which regulates smooth, cardiac muscle and
glands
Synthesizes regulatory hormones that control
the anterior pituitary
Contains cell bodies of axons that end in
posterior pituitary where they secrete hormones
Regulates rage, aggression, pain, pleasure &
arousal
Feeding, thirst & satiety centers
Controls body temperature
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Epithalamus
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Pineal gland
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endocrine gland the
size of small pea
secretes melatonin
during darkness
promotes sleepiness
& sets biological
clock
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Subthalamus & CVO
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Circumventricular organs
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sites of entry of HIV virus into brain (dementia)
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Cerebrum
(Cerebral Hemispheres)
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Cerebral cortex is gray matter
overlying white matter
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2-4 mm thick containing billions
of cells
grew so quickly formed folds
(gyri) and grooves (sulci or fissures)
Longitudinal fissure separates left
& right cerebral hemispheres
Corpus callosum is band of white matter
connecting left and right cerebral hemispheres
Each hemisphere is subdivided into 4 lobes
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Lobes and
Fissures
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Longitudinal fissure
(green)
Frontal lobe
Central sulcus (yellow)
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precentral & postcentral
gyrus
Parietal lobe
Parieto-occipital sulcus
Occipital lobe
Lateral sulcus (blue)
Temporal lobe
Insula
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Basal Ganglia
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Control large automatic movements of skeletal muscles
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Limbic System
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Emotional brain--intense pleasure & intense
pain
Strong emotions increase efficiency of memory
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Brain Injuries
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Causes of damage
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Concussion---temporary loss of consciousness
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displacement or distortion of tissue at impact
increased intracranial pressure
infections
free radical damage after ischemia
headache, drowsiness, confusion, lack of
concentration
Contusion--bruising of brain (less than 5 min
unconsciousness but blood in CSF)
Laceration--tearing of brain (fracture or bullet)
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increased intracranial pressure from hematoma28
Aphasia
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Language areas are located in the left
cerebral hemisphere of most people
Inability to use or comprehend words =
aphasia
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nonfluent aphasia = inability to properly form
words
know what want to say but can not speak
 damage to Broca’s speech area
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fluent aphasia = faulty understanding of spoken
or written words
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faulty understanding of spoken or written words
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word deafness = an inability to understand spoken words
word blindness = an inability to understand written words
damage to common integrative area or auditory
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Hemispheric Lateralization
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Functional
specialization of each
hemisphere more
pronounced in men
Females have larger
connections between
2 sides
Damage to left side
produces aphasia
Damage to same area
on right side
produces speech with
little emotional
inflection
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Electroencephalogram (EEG)
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Brain waves are
millions of nerve action
potentials in cerebral
cortex
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diagnosis of brain
disorders (epilepsy)
brain death (absence of
activity in 2 EEGs 24
hours apart)
Alpha -- awake &
resting
Beta -- mental activity
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Theta -- emotional
II -- Optic Nerve
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Connects to retina
supplying vision
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I -- Olfactory Nerve
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Extends from
olfactory mucosa
of nasal cavity to
olfactory bulb
Sense of smell
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Dorsal View of Neural Groove
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Aging & the Nervous System
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Years 1 to 2
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rapid increase in size due to increase in
size of neurons, growth of neuroglia,
myelination & development of dendritic
branches
Early adulthood until death
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brain weight declines until only 93% by
age 80
number of synaptic contacts declines
processing of information diminishes
conduction velocity decreases
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Cerebrovascular Accident
(CVA)
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Third leading cause of death after heart
attacks and cancer
2 types of strokes
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Risk factors
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ischemic due to decreased blood flow
hemorrhagic due to rupture of blood vessel
high blood pressure, high cholesterol, heart
disease, diabetes, smoking, obesity, alcohol
Tissue plasminogen activator (t-PA) used
within 3 hours of onset will decrease
permanent disability
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Transient Ischemic Attack
(TIA)
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Episode of temporary cerebral dysfunction
Cause
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Symptoms
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impaired blood flow to the brain
dizziness, slurred speech, numbness, paralysis on
one side, double vision
reach maximum intensity almost immediately
persists for 5-10 minutes & leaves no deficits
Treatment is aspirin or anticoagulants; artery
bypass grafting or carotid endarterectomy
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Alzheimer Disease (AD)
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Dementia = loss of reasoning, ability to
read, write, talk, eat & walk
Afflicts 11% of population over 65
Loss of neurons that release acetylcholine
Plaques of abnormal proteins outside
neurons
Tangled protein filaments within neurons
Risk factors -- head injury, heredity
Beneficial effects of estrogen, vitamin E,
ibuprofen & ginko biloba
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