anatomy & physiology. right & left connected by large fiber tract: corpus callosum cover...
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The brainAnatomy & Physiology
Brain: unremarkable appearance ~ 3 lbs 4 major regions
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
1. Cerebral Hemisphere
Gyri, Sulci, & a Fissure
separates cerebral hemispheres other fissures separate brain into lobes
Longitudinal Fissure
spaces in brain filled with CSF
connected to subarachnoid space (around brain & spinal cord) and central canal of spinal cord
Ventricles of the Brain
parietal lobe posterior to central sulcus
receives impulses from sensory receptors (not special senses), interprets them◦pain recognition◦temperature◦light touch
Somatic Sensory Area
Humunculus
anterior to central sulcus in frontal lobe
major voluntary motor tract
Primary Motor Area
Humunculus
visual area
Occipital Lobe
auditory & olfactory areas
Temporal Lobe
Brocca’s Area: ability to speak◦@ base of precentral gyrus (usually only
on left side)◦injury inability to correctly vocalize
words
Frontal Lobe
Frontal Lobotomy
http://www.youtube.com/watch?v=_0aNILW6ILk
Frontal Lobotomy
http://www.youtube.com/watch?v=c6kRP41ygrI
Phineas Gage
anterior frontal lobe: higher intellectual reasoning
complex memories: frontal/ temporal lobe
all facets of speech: occipital/temporal/parietal lobes
Lobe Functions
Gray Matter of the Brain
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
Basal Nuclei
Parkinson’s Huntington’s
Imbalances in Basal Nuclei
2. Diencephalon
sits atop brain stem enclosed by cerebral hemispheres major parts:
◦Thalamus◦Hypothalamus◦Limbic system◦Epithalamus
Diencephalon
relay station for sensory impulses passing thru to sensory cortex
Thalamus
ANS center role in:
◦temperature control◦water balance◦metabolism
Hypothalamus
Limbic System: forms rim surrounding corpus callosum
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
Limbic System
~size of thumb in diameter & ~ 3 inches long
3 parts:1. midbrain2. pons3. medulla oblongata
Brain Stem
knots of capillaries w/in each ventricle
produce & secrete CSF (cerebral spinal fluid)
Choroid Plexus
smallest, uppermost part of brain stem
cerebral aquaduct: tiny canal that runs thru midbrain connecting 3rd & 4th ventricles
contains reflex centers for vision, hearing
Midbrain
Midbrain
“bridge” rounded structure that protrudes below midbrain
contains apneustic (produces deep, prolonged inspirations) & pneumotatic center (inhibits inspiration)
Pons
most inferior part of brain stem inferior border merges into spinal cord
centers: heart rate, BP, breathing, swallowing, vomiting
Medulla Oblongata
large, cauliflower-like projects dorsally from under occipital lobe
2 hemispheres convoluted surface provides precise timing for skeletal muscle activity
controls balance & equilibrium
Cerebellum
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)
Traumatic Brain Injuries
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
Cerebrovascular Accident(CVA)
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. hypertension2. hypercholesterolnemia3. heart disease4. narrowed carotid arteries5. hx of TIAs (transient ischemic attacks)6. diabetes7. smoking8. obesity9. 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
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
Sequelae of CVA
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
TIA
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
AD Pathology