the brain
Honors Anatomy & Physiology
for copying
Brain: unremarkable appearance
~ 3 lbs
4 major regions
1. Cerebral Hemisphere
• right & left connected by large fiber
tract: corpus callosum
• cover most of other 3 parts
• surface: elevated ridges = gyri separated
by shallow grooves = sulci
• Fissures deeper grooves separate
regions of brain
Longitudinal Fissure
• separates cerebral hemispheres
• other fissures separate brain into lobes
Ventricles of the Brain
• spaces in brain filled
with CSF
• connected to
subarachnoid space
(around brain &
spinal cord) and
central canal of
spinal cord
Somatic Sensory Area
• parietal lobe posterior to central sulcus
• receives impulses from sensory receptors
(not special senses), interprets them
– pain recognition
– temperature
– light touch
Primary Motor Area
• anterior to central sulcus in frontal lobe
• major voluntary motor tract
Occipital Lobe
• visual area
Temporal Lobe
• auditory & olfactory areas
Frontal Lobe
• Brocca’s Area: ability to speak
– @ base of precentral gyrus (usually only on
left side)
– injury  inability to correctly vocalize
words
Lobe Functions
• anterior frontal lobe: higher intellectual
reasoning
• complex memories: frontal/ temporal lobe
• all facets of speech:
occipital/temporal/parietal lobes
Gray Matter of the Brain
Basal Nuclei
• gray matter in brain that is NOT in
cerebral cortex
• functions: help regulate voluntary motor
activity by modifying instructions sent
to skeletal muscle by primary motor
cortex
2. Diencephalon
Diencephalon
• sits atop brain stem
• enclosed by cerebral hemispheres
• major parts:
– Thalamus
– Hypothalamus
– Limbic system
– Epithalamus
Thalamus
• relay station for sensory impulses
passing thru to sensory cortex
Hypothalamus
• ANS center
• role in:
– temperature control
– water balance
– metabolism
Limbic System: forms rim
surrounding corpus callosum
Limbic System
• regulates autonomic & endocrine
functions in response to emotional
stimuli (“reacting” brain vs. cerebral
cortex being “thinking” brain)
– set level of arousal
– motivation
– reinforcing behaviors
– rage, love, memory, empathy
Brain Stem
• ~size of thumb in diameter & ~ 3 inches
long
• 3 parts:
1. midbrain
2. pons
3. medulla oblongata
Choroid Plexus
• knots of capillaries w/in each ventricle
• produce & secrete CSF (cerebral spinal
fluid)
Midbrain
• smallest, uppermost part of brain stem
• cerebral aquaduct: tiny canal that runs
thru midbrain connecting 3rd & 4th
ventricles
• contains reflex centers for vision,
hearing
Pons
• “bridge”
• rounded structure that protrudes below
midbrain
• contains apneustic (produces deep,
prolonged inspirations) & pneumotatic
center (inhibits inspiration)
Medulla Oblongata
• most inferior part of brain stem
• inferior border merges into spinal cord
• centers: heart rate, BP, breathing,
swallowing, vomiting
Cerebellum
• large, cauliflower-like
• projects dorsally from under occipital
lobe
• 2 hemispheres
• convoluted surface
• provides precise timing for skeletal
muscle activity
• Controls balance & equilibrium
Traumatic Brain Injuries
• Head injuries are leading cause of
accidental death in USA.
• Concussion: dizziness, “see stars”, briefly
lose consciousness; No permanent brain
damage
• Contusion: result of marked tissue damage.
Cerebrum: may maintain consciousness
Brainstem: coma
• Cerebral Edema: swelling of brain due to
inflammatory response to injury/ initially
conscious neuro signs deteriorate (think
edema or hemorrhage)
Cerebrovascular Accident(CVA)
• stroke
• 3rd leading cause of death in USA
• occur when blood circulation to brain is
interrupted
– vessel could be blocked (temporary or
permanent) or hemorrhaging
CVA
• characterized by:
– abrupt onset of persisting neurological
symptoms that arise from destruction of
brain tissue
common causes:
– intracerebral hemorrhage
– emboli
– atherosclerosis of cerebral arteries
CVA Risk Factors
1.
2.
3.
4.
5.
6.
7.
8.
9.
hypertension
hypercholesterolnemia
heart disease
narrowed carotid arteries
hx of TIAs (transient ischemic attacks)
diabetes
smoking
obesity
excessive alcohol intake
CVA Treatments
• Thrombolytic:
– clot-dissolving drug: tissue plasminogen
activator (t-PA) greatly improved prognosis
for CVA
– aspirin (makes plts slippery  fewer clots)
– blood thinners
Sequelae of CVA
• Aphasia: from damage to left side
cerebrum where language centers are
• Motor Aphasia:
– damage to Broca’s area
– loss of ability to speak
• Sensory Aphasia:
– loss of ability to understand written or
spoken word
TIA
• Transient Ischemic Attack
• “mini-stroke”
• due to temporary restriction of blood
flow
• symptoms last 5 – 50 minutes
• “red flags” that warn impending & more
serious CVAs
Alzheimer Disease (AD)
most common type of dementia
>10% population > age 65
4th leading cause of death in US
characterized by progressive loss of
reasoning & ability to care for oneself
• cause of most cases unknown but…
•
•
•
•
– genetic factors
– environmental or lifestyle factors
– normal aging process